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GPS Navigation

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De la serie de Manuales de Montaña

Alimentación en montaña
Autodetención con piolet
Botiquín de excursión (borrador)
Guia de uso GPS Wikiloc para Android
Navegación con GPS
Principios NDR
Pilas, baterías y generación eléctrica en la montaña
Listas de compras de comida
Radios para la montaña
Rescate en grietas
Seguir un track en tu teléfono
Técnicas de cruce de ríos

This information was kindly provided by Jan Dudeck, the creator of the Greater Patagonian Trail

Introduction

Approximately 24 active GPS satellites orbit the earth roughly 20’000 km above ground. These GPS satellites transmit radio signals that are used by GPS devises to calculate the current position. The senders in the satellites are quite week; only 27 Watt are emitted by each satellite. At the user's receiver only one tenth of a million-billionth of a watt (100 attowatts) arrive. This makes the signal analysis and position calculation a slow and power-consuming process especially when starting up the GPS device.

When the GPS device is activated it listens for these week GPS signals. When receiving and recognizing the signals of at least 4 GPS satellites it calculates the current location. As more satellites are in range as more accurate the calculated location gets. After starting the GPS device, it can take several minutes till the current location is precisely displayed. While moving in open terrain with the GPS in standby the device can more easily track the location changes. Therefore, we normally do not switch off the GPS while moving as this facilitates a frequent and quick verification of the current position. We only switch the GPS off when taking a break and between pitching the tent and leaving in the morning to minimize power consumption.

Clouds, rain, vegetation and mountains between the GPS satellites and the GPS receiver damps the GPS signal making positioning less accurate, slower and increase the power consumption. In buildings the GPS signal is normally completely lost. If you never navigated with a GPS permit yourself some playtime at home before you rely on it in the outback. Following a track by GPS sounds easier than it actually is in confusing terrain. In the following I provide suggestions how to setup your GPS to correctly record your tracks, maximize battery life and facilitate its use on the trail.

Garmin Handheld GPS Device Setup

Setup of Track Recording on a Garmin eTrex30x

I recommend a Garmin handheld GPS device as the primary navigation device. The battery running time is annoying short while continuously recording tracks, you can’t change batteries when needed and it’s too fragile to be constantly carried exposed.

Recording of Tracks

When the GPS device is switched on and remains in standby it can record your track while moving. The additional power consumption of recording is insignificant as this feature only writes a few bytes every few seconds into the memory. Therefore recording tracks does not shorten the battery life. To setup recording go to the Main Menu, select Setup, and then Tracks. Recor¬ding your tracks and sharing them with the author is essential to keep the GPT route network updated. Therefore, this became part of the Terms and Conditions for Using the Hiker’s Manual and the Track Files. The tracks are recorded in the GPX file format. To view these tracks in Google Earth you must convert them into the KML or KMZ format. For this conversion use either Basecamp or one of the many free online tools. Several Garmin GPS devices store the recorded GMX files in the internal memory in the folders:

  • Garmin/GPX/Archive
  • Garmin/GPX/Current

My suggested track recording options are:

Suggested Track Recording Options for a Garmin eTrex30x
  • Record, Show On Map. This means that all your movements get saved and displayed on the GPS screen. This is very useful when backtracking i.e. after loosing the trail or to simply review at the end of the day what you hiked and paddled.
  • The Record Method Auto and the Recording Interval Normal generates a reasonable precise track without too many points.
  • Auto Archive Daily means that one track file is created for each day. This facilitates than handling and the analysis of tracks.
  • Choose a Colour that is easily distinguishable from other tracks and map features. I will try yellow next season.

Maximizing Battery Life

To maximize the battery life I suggest:

  • Use the GPS Satellite System only and not the Russian GLONASS in addition as this increases the standby power consumption by 30% without much benefit for hiking (GPS is sufficiently accurate). Also WAAS/EGNOS should be Off.
  • Select the actually used Battery Type (Alkaline, Lithium or Rechargeable NiMH) otherwise the display of the remaining power is incorrect. Note that the display of the remaining battery capacity is not particular reliable. It is not unusual that the display indicates for two days full batteries and then goes in one or two hours from full to empty.
Suggested System Setup to maximize battery life on a Garmin eTrex30x

In addition, the following display setup should be used to minimize power consumption:

  • Backlight Timeout 15 Seconds switches backlight automatically off.
  • Battery Save On causes the display to disappear after the Backlight Timeout setting. By pushing any button the display is reactivated. This option prolongs the battery life by about 40%.
  • The Backlight should remain Off whenever not needed i.e. during daytime. On several Garmin devices the backlight is controlled by briefly hitting the power button several times. This can accidentally activate the backlight when not needed. Therefore, make sure that backlight is not accidentally switched on during daytime.
Suggested Display Setup to maximize battery life on a Garmin eTrex30x

To better understand and optimize power consumption, I measured the actual power consumption of a Garmin eTrex30x under different conditions. The above suggested settings are partly based on these measurements.

Measured Power Consumption of GPS handheld device Power consumption of a Garmin eTrex30x (should be nearly identical for eTrex20x devices). Running time calculated for fully charged NiMH batteries with a 2000 mA capacity and an average voltage of 1.25 V. Low Power Alarm: When voltage drops below 1.2 V. GPS Off: When voltage drops below 1.1 V
Functions Percent Power in mW Current in mA Theoretical Running Time
GPS Standby in open terrain with clear view to sky 100% 125 mW 50 mA (40 h)
GPS Standby without clear view to sky i.e. inside building 140% 175 mW 70 mA (28 h)
GPS Standby + Recording 100% 125 mW 50 mA (40 h)
GPS Standby + GLONASS 130% 163 mW 65 mA (30 h)
GPS Standby + Recording + Screen Active 140% 175 mW 70 mA (28 h)
GPS Standby + Recording + Screen Active + Zooming/Moving 250% 313 mW 125 mA (16 h)
GPS Standby + Recording + Screen Active + 50% Backlight 200% 250 mW 100 mA (20 h)
GPS Standby + Recording + Screen Active + 100% Backlight 380% 475 mW 190 mA (10 h)

I do not fully trust the theo¬retical running time, but the measured power consumption provides a good estimate how different features affect the battery life. For the actual battery running time see the next table.

For planning purposes, I suggest calculating with the following typical battery life when using a Garmin eTrex30x or a similar device. These values are based on actual trail experience.

Typical battery life with GPS handheld device
Battery Type Typical Battery Life[1] Nominal Voltage Weight Comment
Rechargeable Battery Types
NiMH 2 to 3 days 1.2 V 2 x 25 g Lowest Long-Term-Cost. Suitable for recharging i.e. when carrying a solar panel or recharging in towns.
Not Rechargeable Battery Types
Alkaline 3 to 4 days 1.5 V 2 x 23 g Best Weight-Cost-Ratio especially when not carrying a solar panel. Not suitable for recharging.
Lithium 4 to 5 days 1.5 V 2 x 15 g Luxury Low-Weight-Option or emergency spares. Do not recharge as these batteries may explode.
Not Recommended Battery Types
Lithium-Ion - 3.7 V - DO NOT USE! AA sized 14500 Li-Ion batteries have a voltage of 3.7 V what may permanently damage the GPS.
Zinc-Carbon - 1.5 V - DO NOT USE! Zin-Carbon batteries have a much lower capacity, are not cold-resistant and may leak.

Carry enough spares and consider the use of a solar panel to recharge. If running low on power switch the GPS completely off while the route is clearly visible.

Note: The typical battery life is based on the experience of a few hikers (including me) that did not necessarily apply all the recommended power-saving settings, might not have used new healthy NiMH batteries or more sophisticated Garmin GPS devices with a higher power consumption. Therefore, the typical battery lift is rather conservative, and the actual battery life may exceed these values. I will update these numbers once I receive more feedbacks from other hikers that used eTrex20x or eTrex30x devices and applied all the recommended power-saving settings.

Optimizing GPS Displays

In the Setup menu under Page Sequence you can select displays that are useful for you i.e. the Map page, the Compass page, the Elevation Plot and many more. By hitting the back button you switch between your pre-select pages without selecting them every time in Main Menu.

Addition of Optional Pages on a Garmin eTrex30x

My pre-selected pages are:

Trip Computer and Sun and Moon Page of eTrex30x
  • Map: Shows the current location on the maps and permits zooming and panning to plan ahead. This is my most frequently used page.
  • Compass: You can select on the map a point an aim for this point using the Compass page. This is useful in cross country terrain and when packrafting in open water. If your device does not have a magnetic sensor (i.e. the eTrex20x comes without compass) then the orientation is only shown correctly while moving.
  • Elevation Plot: The elevation plot does not shrink mountains but shows you at least what you climbed and descended.
  • Trip Computer: You can select the values that you wish to get shown on this page. We tend to reset the counter daily to monitor our daily advance but you can keep the counter running if you love to see big numbers.
  • Sun and Moon: Knowing sunrise, sunset and moon status is useful to anticipate natural light and know your death-line for finding a suitable camp site. Also the calendar is handy when approaching a section end and planning your resupply trip.
  • Satellite: In dense forest satellite signal reception may be compromised. This page helps to understand the accuracy of the displayed location.

Several hikers who attempted to hike parts of the GPT had to abort and backtrack because they were unable to manage the track display, did not set up topographic maps correctly or run out of power on the trail. A proper learning and testing period before the adventure on the GPT could have prevented this.

So, reading GPS suggestions does not replace personal practice with your GPS device. A proper hike would be ideal but even testing in urban areas will be very helpful if you use your GPS with a playful attitude and test the different features and options. Be curious and not scared to change settings. Play! Have a stroll around your home with your GPS, record this track, download the GPX file from your device, convert it into a KMZ file and review your stroll on Google Earth!

Therefore, if you do not have a GPS yet, purchase one latest 3 month before you depart and practice. Setup your device yourself and don’t ask a nerdy friend to do it for you. Only if you learn to do it yourself, you will be able to understand and solve your GPS problems yourself when you have nobody around to ask.

Practical Considerations

Self made ribbon on backpack shoulder strap to carry the GPS in a location with unrestricted view to the sky. To secure the device against loss it remains hooked to the D-ring whenever moving.

The GPS device should be carried high up on the body within easy reach to facilitate frequent location checks. A mostly unrestricted view to the sky improves the GPS accuracy and minimizes the power consumption. Therefore it is not advisable to carry the GPS i.e. in a hip belt pocket. To quickly reach my GPS in a location with such a good reception I constantly carry it on top of my shoulder. For this I glued a belt clip to the GPS and stitched a ribbon to my backpack shoulder strap. In this location I can easily reach my GPS and to not loose the device I hook it up with a rubber strap to a D-ring on the shoulder strap.

When packrafting it is particular important to have the GPS within easy reach to not miss critical river exit points. Dangerous rapids and waterfalls may be ahead! When packrafting we also connect the GPS with a string to the packraft or the PFD (Personal Flotation Device). In addition, we attach a flotation device to the GPS as the GPS is heavier than water and sinks to the ground if it falls accidentally into the water. The plastic screen of a Garmin handheld GPS device is more robust than a typical smart phone glass screen but gets easily scratched. To maintain the screen in good condition I use a protective foil that can be replaced when worn.

Backup GPS Navigation Device

Relying on the Greater Patagonian Trail on a single electronic navigation device is negligent. A defect like a broken button can render the device useless. Should you lose your GPS on the trail you would not be the first one with this mishap. If your navigation device fails or get lost, you may try to backtrack relying only on your memory but if you are towards the end of a section with the food reserves depleted this is not an appropriate last resort. Also, some parts of route are too confusing to rely on memory. Therefore, I strongly recommend carrying in additional to a Garmin handheld GPS device a backup navigation device which can be a smartphone that is properly set up for navigation. Combining a Garmin handheld GPS with a smartphone is to my opinion the optimal navigation setup as this combines the advantages of each device to compensate the disadvantages of the other device. A smart phone with a large screen facilitates a proper review of the route before commencing a new section or each morning before departing, it can be linked to the InReach satellite communicator to read and type messages, it serves as a camera and much more. But the higher power consumption makes a smartphone less suitable for constant navigation and track recording. Make sure that also the power supply is redundant and that your navigation does not depend on a single piece of gear. The Garmin InReach Explorer is to my opinion not a suitable navigation device. The firmware makes it impossible to upload the GPT route network because the device has a build-in limit of only 25 tracks and 500 waypoints. We use our Garmin InReach Explorer exclusively for communication and to send our current position, so family and friends can follow our progress. I’m aware that three devices – a handheld GPS, a smartphone and an InReach satellite communicator – seams overkill to some hikers but the remoteness of many areas and the irregular route network make this combination of devices strongly advisable.

Satellite Communication Device

I highly recommend one of these satellite pagers:

Less suitable are:

The Garmin InReach relies on the Iridium satellite network, which has a consistently good coverage that gets better towards the poles. Therefore all Greater Patagonia is very well covered. This good coverage is archived by orbiting the roughly 70 to 80 active satellites over the poles and permanent inter-satellite-data-links. Read the Wikipedia article for more information.

The Globalstar satellite network used by the SPOT devises has a quite different constellation. The number of active satellites is smaller compared to the Iridium network; the satellites does not circle over the poles and have no inter-satellite-data-link but require a data-link to a ground station to send and receive data. This results in a reduced coverage and black-out periods in Patagonia that become worse towards the south. Read the Wikipedia article to the Globalstar system to better understand these differences. Also, some Globalstar devices (i.e. the SPOT Gen3) can only send but not receive information limiting their usefulness further.

In one season we carried a Globalstar SPOT and a Garmin InReach and clearly noticed the difference. While the InReach successfully send our position signal every 10 minutes the Spot had black-outs lasting several hours even with clear view to the sky. Therefore I do not trust the Globalstar coverage chart that claims that the entire Southern Cone is fully covered.

Based on this experience I consider a Garmin InReach substantially more reliable than a Globalstar SPOT but a SPOT is still substantially better than just a mobile phone.

A Garmin InReach devise comes with a price tag of 350 to 450 USD. In addition, you need a satellite data plan. Garmin offers affordable monthly plans that can be purchased for just the time required. We opted for the “RECREATION” plan that includes SOS service, 40 text message per month, position tracking in 10 minutes intervals and weather forecasts for 35 USD per month (plus a 25 USD annual fee). This plan allows that our families and friend can constantly see where we are (position tracking) and we can occasional send and receive text message and request weather forecasts which are quite reliable. A cheaper option is the “SAFETY” plan for 15 USD per month (plus 25 USD annual fee) that includes SOS service only and all data service is payed as used. See the Garmin InReach page for more details.

Note that teh InReach Explorer is not really suitable to navigate on the GPT. The firmware makes it impossible to upload the GPT route network because the device has a build-in limit of only 25 tracks and 500 waypoints.

Batteries and Electrical Power Supply

The optimal power supply on a long-distance hike is a subject with opposing opinions and a wide range of products that promise the solution. I try to analyse this subject with Engineering methods based on actual measurements and calculations to challenge my own habits and no fall victim to false advertisements and myths.

Before I dive into detail a brief explanation of the used terms and units :

  • Voltage: Unit: Volt (V). If comparing different batteries and devices you should know the nominal Voltage. Non-rechargeable Alkaline and Lithium batteries provide approximately 1.5 V. Rechargeable NiMH batteries have a slightly lower voltage of about 1.2 V. Rechargeable Lithium-Ion batteries supply 3.7 V. All USB devises work with 5 V. This applies to USB power consumers and USB power banks with Lithium-Ion batteries. These power banks have electronics that steps up the voltage to 5 V. For more information see Table 113: See the battery and power bank specifications section.
  • Electrical Current: Unit: Ampere (A) or Milliampere (mA). 1000 mA equals 1 A.
  • Electrical Power Consumption: The commonly used unit for small electrical devices is Watt (W) or Milliwatt (mW). 1000 mW equals 1 W. For DC consumers the power consumption can be calculated by multiplying the supply voltage with the required electrical current. In example a GPS device that is powered with two AA NiMH batteries (2 x 1.25 V) and draws a current of 50 mA has a power consumption of 125 mW (or 0.125 W). Manufacturers sometimes provide the power consumption in Ampere (A) or Milliampere (mA) what is scientifically incorrect but not an issue if the voltage is known. The conversion between current (A) and power (W) is made by multiplying the current with the voltage.
  • Electrical Energy Consumption: The technical correct unit is Watthour (Wh). Note the difference between power and energy: power (W) is the rate of consumption while energy (Wh) is the accumulated consumption. So the energy consumption is the summed-up power consumption over a given time span. If you want to compare power and energy with hiking than power is like the speed and energy is like the distance covered.
  • Stored Electrical Energy: The technical correct unit is Watthour (Wh) but battery manufacturers often use Milliamperehour (mAh) to indicate the capacity of a battery. This is scientifically incorrect but when comparing batteries of the same type this works. But when comparing different battery types the unit mAh is misguiding. A Lithium-Ion battery with a capacity of 1000 mAh stores more energy than a 2000 mAh NiMH battery because the Voltage of a Lithium-Ion battery is higher. A Lithium-Ion battery with a 1000 mAh capacity contains roughly 3.7 Wh while a 2000 mAh NiMH battery contains only 2.4 Wh. Note that USB power banks are not rated based on the output voltage but based on the capacity of the internal Lithium-Ion battery.
  • Specific Stored Energy: The technical correct unit is Watthour per Kilogramm (Wh/kg). This number tells how much electrical energy is stored in relation to the weight of the battery or power pack. You can calculate the specific stored energy of a battery by dividing the stored electrical energy (Wh) by the weight of the battery (kg). As a hiker you obviously want this number to be high, to have as much as possible energy packed into as little as possible weight. But the battery chemistry puts physical limits to this. Understanding this helps to identify obviously false advertisements. I.e. if someone offers an AA NiMH battery with a capacity of 3500 mAh he scams. See the table about battery and power bank specifications for more detailed information.
  • Energy Transfer Efficiency: When charging an electrical device i.e. with a power bank some losses occur. A part of the energy will no end up in the charged device i.e. the smartphone battery but get lost in form of heat while charging. The common unit for efficiency is Percent. An energy transfer efficiency of 75% means that only ¾ of the stored electrical energy ends up in the charged battery. When charging a device from the grit in a town you do not need to worry about this, but when charging a device on the trail with a power pack this becomes relevant.
  • Effective Stored Electrical Energy: Unit: Watthour (Wh). This is the amount of the electrical energy of a power bank that ends up the in the charged device when considering the losses of the energy transfer process.
  • Generated Electrical Power: Unit: Watt (W). Today a wide range of outdoor gear promises a free recharge of your electrical consumers on the trail. Most common are solar panels but also water and wind turbines pushed on the market. The most weird gear I have seen is a stoves that promise to produce electrical energy using the thermoelectric effect. The power might be free but always comes with a weight penalty. Therefore the following is of importance:
  • Specific Power Generation: Unit': Watt per Kilogram (W/kg). This is the actual archived power output divided by the weight of the device. This number shows the difference between a gadget that just appears cool and an actual useful piece of gear.

Electrical Energy Consumption

The actual electrical energy consumption during a long-distance hike depends on the electronic consumers and their use. A Garmin handheld GPS device has a energy consumption of 1.5 Wh to 2.5 Wh per day if the previously recommended power saving settings are applied. One pair of AA batteries lasts therefore:

  • 2 x NiMH Rechargeable Batteries (2 x 2.2 - 3.0 Wh): 2 to 3 days
  • 2 x Alkaline Non-Rechargeable Batteries (2 x 3.0 - 4.2 Wh): 3 to 4 days
  • 2 x Lithium Non-Rechargeable Batteries (2 x 4.5 - 5.25 Wh): 4 to 5 days

The power consumption of a Garmin InReach Satellite Pager is quite low even in tracking mode. When using it in the “Extended Tracking” mode the device consumes approximately 1 Wh per day. In the “Extended Tracking” mode the device sends the current position every 10 minutes, but Bluetooth and GPS recording remains deactivated. And of cause, switching the device off while not moving is advisable to maximize the battery life. If an InReach is use in emergencies only then normally no battery power is consumed. This means recharging the InReach on the trail is not necessarily required and can be avoided by minimizing the use i.e. by extending the tracking interval to 1 hour or deactivating tracking completely. Below the capacity of the internal Lithium-Ion battery and the approximate running time with 10-minute tracking in the “Extended Tracking” mode:

  • InReach Mini with an internal 1250 mAh battery (4.6 Wh): Approximately 5 days
  • Newer InReach SE+ and Explorer+ models with an internal 2900 mAh battery (10.7 Wh): Approximately 10 days
  • Older InReach SE and Explorer models with an internal 2450 mAh battery (9.1 Wh): Approximately 10 days

The energy consumption of a smartphone is generally higher and varies substantially depending on the model and how it gets used. I assume that everyone knows that intense use can consume one full battery charge per day but keeping it in airplane mode with the GPS deactivated will make the internal battery last quite long. The internal Lithium-Ion batteries have depending on the model a capacity between 1’800 and a little over 3’000 mAh what corresponds with 7 to 12 Wh of stored energy. So, the smartphone energy consumption ranges from virtually 0 to about 12 Wh per day. This high variability makes it difficult to issue specific recommendations what recharge method is optimal.

If a smartphone is used as the primary navigation device, then the actual energy consumption should be carefully tested before the hike to have a good knowledge how many recharges are required on the longest planned sections. This test should measure the actual energy consumption of the smartphone with continuous track recording as this is part of the terms and condition for using the track files. In the following comparison with GPS devices I will assume a daily energy consumption of 5 Wh per day if the smartphone is as primary navigation device what corresponds to one full battery charge for about 2 hiking days. Note, that the actual energy consumption with continuous recording may be even higher. For this reason I use my smartphone only as a backup navigation device in specific circumstances when reviewing satellite images or a high screen resolution is required. A basic handheld GPS simply consumes much less energy than a smartphone and minimizes therefore the total weight.

The additional energy consumption of a flash light and a camera (if carried in addition to the smartphone) adds to this energy bill. Knowing your personal electrical energy consumption is important to correctly plan the required amount of batteries and to select the appropriate size of a power bank and/or power generation devices. Therefore I encourage every hiker that plans an adventure on the GPT to measure the actual power consumption of his devices before departing. The device running time with a full battery can be tested by selecting the to recommended power saving mode and simply monitor how long the device keeps running till the battery is depleted and the device faints out. This test verifies the actual capacity of the internal battery and the consumption of the device. When recharging the device, you can measure the power consumption by plugging an USB power monitor in between the USB charger and the tested device. These USB metering devices are cheep, simple to use and readily available online. An inexpensive recommendable USB power monitor is the PortaPow Dual USB Power Monitor.

If you run low on power or navigate with your backup navigation device you should completely switched off the handheld GPS or put the smartphone in airplane mode and deactivate GPS recording whenever the route is sufficiently visible.

Batteries and Power Banks

The most versatile way to carry electrical energy are batteries. The following table shows the characteristics of commonly used and recommendable battery types and USB power banks.

Battery and power bank specifications
Battery Type Stored Energy Weight Specific Stored Energy Nominal Voltage Actual Range Comment
Rechargeable AA Batteries
AA NiMH Battery 2.2 – 3.0 Wh 1’800 – 2’500 mAh 25 g 85 – 120 Wh/kg 1.2 V 1.4 – 1.1 V New quality NiMH batteries have a capacity of 2’000 – 2’500 mAh but over time and with frequent use this drops.
Non-Rechargeable AA Batteries
AA Alkaline Battery 3.0 – 4.2 Wh 2’000 – 2’800 mAh 23 g 130 – 180 Wh/kg 1.5 V 1.6 – 1.1 V Alkaline batteries are good for devices with a low power consumption (GPS).
AA Lithium Battery 4.5 – 5.25 Wh 3’000 – 3’500 mAh 15 g 300 – 350 Wh/kg 1.5 V 1.8 – 1.5 V Lithium batteries have the highest specific energy but are more costly.
Other Rechargeable Batteries and Power Banks
Lithium-Ion Battery Depending on size Depending on size Approximately 200 Wh/kg 3.7 V 4.1 – 3.7 V Most devices with build in batteries have Lithium-Ion batteries installed.
5000 mA Power Bank Nominal 18.5 Wh Effective 13 - 15 Wh 120 – 150 g Nominal 125 – 200 Wh/kg Effective 100 – 160 Wh/kg 5.0 V 5.0 V USB power banks are specified based on the capacity of the internal Lithium-Ion batteries (3.7 V) and not the output voltage (5.0 V) of the USB port.
10’000 mA Power Bank Nominal 37 Wh Effective 26 - 30 Wh 180 – 240 g Nominal 125 – 200 Wh/kg Effective 100 – 160 Wh/kg 5.0 V 5.0 V USB power banks are specified based on the capacity of the internal Lithium-Ion batteries (3.7 V) and not the output voltage (5.0 V) of the USB port.

Rechargeable NiMH Batteries

NiMH battery discharge curve. For GPS devices the discharge current is typical 0.1 A or less therefore the highest curve of the diagram is applicable. Image: lygte-info.dk

Be aware that the battery voltage depends on the charging state, the temperature and the load during use (consumer). When fully charged the voltage is slightly higher than the nominal voltage. During use the voltage drops. By measuring the voltage the battery state can be estimated. This is particular helpful when using rechargeable NiMH batteries. A fully charged NiMH battery provides 1.4 V at an ambient temperature of approx. 20 ºC (open-circuit voltage). At the beginning of the discharge cycle (first 10% of capacity) the voltage drops quickly to 1.3 V where the “plateau” starts. Once the plateau is reached the voltage slowly decreases during use to about 1.2 V (80% of capacity). When the battery is nearly empty the voltage drops again sharply (last 10% of capacity).

To maximize the life of rechargeable NiMH batteries the following should be observed:

  • For the GPS use pairs of batteries that you always charge and use together (best mark the batteries i.e. A1, A2, B1, B2, C1, C2, D1, D2 to easily identify pair A, B, C and D). Don’t mix a fully charged battery with a half-empty battery in the GPS. This makes your GPS faint quickly and may damage the batteries permanently (reverse-charging).
  • Don’t overcharge batteries. This is best done by charging two pairs of equally empty batteries together in the Goal Zero Guide 10 charger (With the Goal Zero device you must charge 4 batteries together otherwise this charger does not work. By combining 4 batteries with a similar discharge state the charger works more effective and the batteries suffer less.)
  • Don’t overheat batteries. Keep the batteries in a shady and ventilated location when charging. The gear pockets on the back of a solar panel is not suitable to hold the charger while charging.
  • Be aware, that poor copies of brand batteries are sold in dodgy places (eBay, street vendors, ...) that have often a much lower capacity than advertised. Therefore, get your NiMH batteries before your trip in a trustworthy location. I made good experiences with the eneloop NiMH batteries (2’000 mAh) and the four NiMH batteries that come with Goal Zero Guide 10 plus charger (2’300 mAh).
  • Be careful with high-capacity NiMH batteries that are rated with more than 2’000 mAh. These batteries are more sensible to over-charging or reverse-charging what can accidentally happen if two batteries with different discharge states are mixed in one device. I will test on my next investigation trip the eneloop Pro batteries with a rated capacity of 2’500 mAh. They are more fragile so let’s see how they behave in the field!

I fabricated a tiny ultra-light voltmeter from simple of-the-shelf electronics that I use on my hikes to monitor the state of my NiMH batteries. This helps to combine batteries of a similar discharge stage to recharge these batteries effectively without overcharging them.

Non-Rechargeable Alkaline Batteries

To be issued.

Non-Rechargeable Lithium Batteries

To be issued.

Rechargeable Lithium-Ion Batteries

To be issued.

USB Power Banks

The only lossless method to “recharge” a depleted device is changing batteries. This is one reason why I prefer a Garmin GPS device over smartphones. A battery change takes seconds and no electrical energy is lost.

In contrast, charging a smartphone or an InReach device with a USB power bank is not lossless. My measurements showed me that only 70% - 80% of the energy ends up in the charged battery and 20% - 30% of the energy is converted into useless heat during the energy transfer process. These losses are unavoidable due to the battery chemistry and the power consumption of the electronics in the power bank and the charged device. This means that a 10’000 mAh power bank with a rated capacity of 37 Wh equals 26 – 30 Wh in your smartphone and InReach. Therefore the effective specific stored energy of a USB power bank with Lithium-Ion batteries (100 – 160 Wh/kg) tends to be slightly lower than the specific stored energy of AA Alkaline batteries (130 – 180 Wh/kg) and not much better than NiMH batteries (75 – 120 Wh/kg). Non-rechargeable Lithium Batteries (300 – 350 Wh/kg) are clearly on top of the list when minimizing weight.

Note: I estimate that about one third of the losses (7% to 10%) occur in the power bank by stepping up the voltage from the internal Lithium-Ion battery (3.7 V) to the USB voltage (5.0 V). The remaining two third of the losses (13% to 20%) occur in the charged device when transforming the USB voltage (5.0 V) into the appropriate charging voltage (4.25 V) for the internal Lithium-Ion battery and by losses in the charged battery itself (internal battery resistance). The rule of thumb is: As warmer your devices become while charging as higher are the losses.

Calculation examples:

  • Fully charging an InReach Mini with an internal 1’250 mAh (1.25 Ah) Lithium-Ion battery:
    • Stored Electrical Energy of internal battery: 1.25 Ah x 3.7 V = 4.6 Wh
    • Required power bank energy for recharging with a 75% Energy Transfer Efficiency: 4.6 Wh / 0.75 ≈ 6 Wh
    • This corresponds to 1’650 mAh of the nominal power bank capacity
  • Fully charging an iPhone 7 with an internal 1’960 mAh (1.96 Ah) Lithium-Ion battery:
    • Stored Electrical Energy of internal battery: 1.96 Ah x 3.7 V = 7.3 Wh
    • Required power bank energy for recharging with a 75% Energy Transfer Efficiency: 7.3 Wh / 0.75 ≈ 10 Wh
    • This corresponds to 2’650 mAh of the nominal power bank capacity

When using a USB power bank with Lithium-Ion batteries consider the following:

  • Select your power bank wisely. Compare weight and capacity before purchase. Stylish slim power banks may look nice but have typically a worse specific energy rating (more weight for the same capacity).
  • Avoid discharging Lithium-Ion completely. Better top up your smart phone and InReach when the remaining power drops below 25%. Lithium-Ion batteries do not suffer from a “memory-effect” like the obsolete Nickel-Cadmium batteries but dislike deep discharges. It is better to recharge a Lithium-Ion battery several times instead of fully discharging a battery and then recharging the battery completely.
  • I suspect that bringing the internal battery of a smartphone or an InReach all the way up to 100% results in more losses. There¬fore, if recharging such a device with a power bank on the trail, stop charging once reaching about 90% battery charge. Of cause, this does not apply when charging a device from the grit during a resupply stop in a town. Then get everything fully charged.
  • If using a power bank to recharge the InReach and a smartphone keep some reserve in the power bank to later choose depending on circumstances for what you need the energy more. Navigation or communication in case of an emergency.

The Goal Zero Guide 10 plus AA NiMH battery charger can also be used as a power bank but the efficiency is much lower compared to a power bank with Lithium-Ion batteries. For more information to this gadget see the section about USB AA NiMH Battery Charger.

USB Charger

Left: Standard in Chile (Type L, CEI 23-16 VII. Same as Italia and Uruguay) Center: Current Standard in Argentina (Type I, AS 3112. Same as Australia) Right: Older Standard in Argentina (Type C, Europlug) Image: Martín Lizondo

A USB charger is required to recharge the smartphone and the USB power bank during resupply town visits. In Chile and Argentina, the same voltage and grit frequency is used (220 V / 50 Hz) but both nations have different sockets. In Chile a USB charger with an Europlug works perfectly fine. For Argentina an additional Type I adapter may be useful.

To shorten charging time a high-power 2 A charger is preferable over a standard 1 A USB charger. The weight difference is not significant. A1 A USB charger weights typically 30 g. A 2 A charger can be as light as 36 g.

Solar Panels and Other Outdoor Power Generators

Generating electrical energy on the trail sounds cool and is a tempting option. In the following I will analyse 3 power generation devices and calculate the approximate break-even point from which carrying such a device becomes beneficial. The results of this analysis might surprise.

Solar Panels

A wide range of outdoor solar panels with USB outlets are available now. Testing them all is practically impossible, but I measured and compared about 10 devices from various manufactures in recent years. The following analysis is based on these performance measurements and not the often exaggerated manufacturer specifications. My first and most important lesson learned is: Don’t trust the advertised power output. Most of these numbers are exaggerated and I also noticed substantial variations between seemingly equal devices from the same manufacturer. I made my worst experience with the Goal Zero Nomad 7 Plus with a rated output power of 7 W. When delivered it supplied 1.5 to 2 W in bright sunlight with a perfect vertical alignment to the sun. After about 4 weeks on the trail it died completely (less than 0.1 W) presumable due to failed internal contacts (no external damage evident). Therefore, be sceptical and measure the actual performance of your solar panel before relying on it. This can be done easily with the previously recommended USB power monitor. Don’t trust blinking charging lights as these start blinking with a tiny trickle charge. Measure the actual charging current and trust only values that you measured yourself. To charge smartphones, AA NiMH batteries and power banks with solar power in a reasonable time a panel with a USB outlet and a power output of approximately 5 W is needed. Such a panel provides a charging current of 1 A when vertical alignment to the sun on a cloudless day and not too high ambient temperatures. It still supplies a few hundred mA under less favourable condition, i.e. when charging while hiking with the panel fixed to the backpack what normally results in a suboptimal alignment to the sun. Bigger solar panels make only sense if you have an unusual high power consumption i.e. when:

  • carrying and using a tablet on the trail,
  • relying on recharging in less favourable condition (areas with normally cloudy weather),
  • travelling in a bigger group with more power-hungry smartphones and cameras or
  • if you don’t need to care much about weight (packrafting with very little hiking).

Based on multiple tests I conclude that a good outdoor solar panel has a specific power generation of roughly 20 W/kg. So a panel with a 5 W power output weights around 250 g.

In addition to the solar panel a AA NiMH battery charger is required. I recommend the Goal Zero Guide 10 plus  device that weights 64 g. The bonus feature of this device is that it can also be used as a USB power bank by discharging AA NiMH batteries. But the Goal Zero charger comes with the disadvantage that it charges only 4 NiMH batteries together. Alternatively use the EBL USB Quick Charger . The advantage of the EBL charger is that it charges individual batteries (a single battery if you want) and that it charges faster if you have enough USB power (i.e. if you have up to 2 A USB input current in towns or with a bigger solar panel). But the EBL charger can not be used as a power bank. The weight of the EBL charger is with 68 g nearly identical. For more information to these the section about USB AA NiMH chargers USB AA NiMH Battery Charger. In addition, a sufficiently long Mini-USB cable is required. While charging, the batteries should not be “cooked” in the sunlight or the pocket on the back of the hot solar panel. There the batteries deteriorate quickly. To charge four NiMH batteries while hiking you need two additional NiMH batteries for your GPS. So you must carry at least six NiMH batteries to have also enough backup power for a series of cloudy and rainy days. So, a 5 W solar panel set with a charger, a cable and sufficient batteries weights at least 475 g:

  • 5 W solar panel: Approximately 250 g
  • AA battery charger: 65 g
  • Mini-USB cable: 10 g
  • 6 x AA NiMH batteries: 6 x 25 g = 150 g

This provides a good baseline to calculate the break-even point at which carrying a solar panel becomes beneficial. I do this by assembling hypothetical non-solar power supply sets of a similar weight. Only if all of these hypothetical sets would still be insufficient than a solar panel becomes beneficial.

  • Option 1: 20 Alkaline batteries (460 g). This hypothetical set provides roughly 30 days of power for the GPS device but no recharge for the smart phone or InReach.
  • Option 2: A 10’000 mAh USB Power Bank and 10 Alkaline batteries (Approximately 440 g). This hypothetical set provides roughly 15 days of power for the GPS device, two smartphone and two InReach Mini recharges.
  • Option 3: A 5’000 mAh USB Power Bank, 10 NiMH batteries and an AA NiMH battery charger with a cable (Approximately 460 g). This is a hypothetical set of someone that opts for rechargeable AA NiMH batteries instead of Alkaline batteries for environmental and/or cost reasons while recharging the AA NiMH batteries in towns only. This hypothetical set provides roughly 10 days of power for the GPS device, one smartphone and one InReach Mini recharge.

Comparing the 5 W solar panel kid with these three non-solar options shows pretty clearly that the break even-point for a solar panel is far down the trail. Walking 10 to 15 days without resupplying is only required on the longest sections and a solar panel pays really off when exceeding this duration.

Conclusion 1: For someone that hikes light and fast a solar panel is rarely beneficial.

There are other motives that may make a solar panel beneficial: cost cutting, an unusual high power consumption on the trail, autarky and slowness. Minimizing costs: A overnight town-stop with a proper bed is something that most hikers enjoy but hikers with a tight budget might prefer to just buy food and return to the trail immediately. A solar panel eliminates the dependence on power sockets what helps to cut town time and no money must be spend on batteries.

Unusual high power consumption: Smartphone junkies will suffer on the GPT as there is little connectivity. But some hikers will probably still find reasons and opportunities to spend “quality time” with their smartphone on the trail. A solar panel helps covering the resulting power consumption. This applies also to hikers that carry and use a tablet computer on the trail.

Autarky and slowness: The primary range limitation when hiking is food; it’s the fuel for the body and we can carry only a certain amount in our backpacks. If someone gets extra food along the trail, he extends his range and postpones the moment at which me must eventually bail out to resupply. Resupplying at the section start or section end is often possible in the far north and in the south but from GPT05 to GPT12 and from section GPT19 to GPT21 hikers “normally” need to take a bus to get to a proper resupply town further away. Such a resupply trip can take up to 3 days. I used the word “normally” because there is a trick how to remain on the trail in this particular scenic and hiking-friendly area: purchase food from the arrieros, the native Pehuenche and settlers that live during the summer on the trail. There are also a few kiosks or mini shops in the tiny settlements on the trail that sell some basic supplies. At the right time you may also harvest piñones on sections GPT10 to GPT16 which provides plenty of free carbohydrates. So, in these areas food is easier to obtain than electricity. If you have a solar panel to recharge your electronics you can use these unplannable opportunities to get some additional food to remain longer on the trail. We frequently use such informal resupplies to stay 2 to 3 weeks on the trail, often with relaxing “zero” and “nero” days in company with residents on the trail. Our solar panel helped us to keep our electronics fully charged to not worry about remaining power. When being a guest at a puesto a solar has a bonus feature: you can offer to charge the mobile phones of your hosts.

Conclusion 2: A solar panel adds autonomy and permits slowing down if you get enough extra calories on the trail. Should you opt for a solar panel consider the following best practices and lessons learned:

  • Don’t buy a solar panel with a build-in battery (integrated power bank). This only seams handy but is not. While charging the battery inevitably overheats what quickly deteriorates the battery. Also, if just one of the two components deteriorates you have to scrap both.
  • I prefer foldable solar panels as they are more robust during transport. A single thin panel needs more care as it is easily crushed in the backpack. But a single panel without folds is easier to set up and to align to the sun. Choose whatever you find appropriate for you.
  • I know I repeat myself, but this is really important: Test your panel before relying on it! Rated values are normally exagger¬ated. You probably need to purchase a panel that is rated as 7 W or 10 W to get the recommended 5 W power output. Best use one of these tiny USB power monitors that indicate voltage and current to verify the actual performance after purchase.
  • Align your solar panel vertical to the sun when charging. To find the optimal angle tilt and rotate the panel to created the larges possible shade on the ground. The largest shadow means the most sun on the panel. When charging while hiking choose a suitable average position for the solar panel on the backpack.
  • While charging, connect the charged device(s) with a long enough cable to the solar panel to keeps your charged gadget(s) in a shady and ventilated location. Avoid placing the charged devices in the pockets on the back of the solar panel. These pockets might be useful to carry your charging gear while not using the panel but not when charging.
  • Carrying a USB power monitor on the trail is also handy to optimize the orientation of the panel to the sun and to check what is happening in suboptimal conditions i.e. cloudy weather. If you see that the charging current is unreasonable low don’t hazzle yourself with fruitless charging attempts. Many USB power monitors have two USB outlets. This makes the power monitor a handy “splitter” to charge two devices simultaneously from one USB outlet (i.e. in towns).
  • Some smartphones react oddly to variable charging currents. If the USB power output is temporary reduced these devices readjust to the reduced power output and continue charging with the reduced current even if the USB power output recovers to a higher level. If i.e. a cloud passes the solar power output drops and when the sunshine is back the smart phone uses only a fraction of the available power. This effect is particular annoying when charging while walking. The changing orien¬tation and the shade of trees along the trail inevitably results in a fluctuating power output.

A power monitor helps to recognize and to respond to this effect. If this happens simply unplug and replug the charged device. Smarter solar panels have build-in electronics that do this automatically.

  • Another barely known effect is the solar panel response to a partial shading. If i.e. 10% of the solar panel surface is covered the power output drops typically much more than just 10%. I tested solar panels that loose around 90% of the power output when 10% of the solar panel surface is in the shade. It needs a special solar panel configuration and a good electronics to minimize this effect. If you have a USB power monitor you can verify yourself how your panel reacts to partial shading.
  • Be aware that solar panels work best at lower temperatures. This makes a bright fresh morning the best time for charging. Just take make sure to tilt the solar panel enough to harvest the maximum amount of energy while the sun is low.

With my mixed experience I’m reluctant to recommend a specific item or brand. I made reasonable good experiences with solar panels sold by Anker but they only offer panels that are a bit bigger and heavier than actually needed. The Anker “15 W” solar panel has a maximum output of about 8 W and the weight is close to 400 g. A bit oversized for a group of two.

USB AA NiMH Battery Charger

Any outdoor power generator requires in addition a suitable AA NiMH charger to use the generated electrical energy in a handheld GPS device. In the previous chapter I briefly mentioned the Goal Zero Guide 10 plus  and the EBL USB Quick Charger . If you carry a Goal Zero Guide 10 plus AA NiMH battery charger with your power generation device calculate with the following charging and discharging efficiencies and currents:

  • Maximum USB charging current: 0.8 A (rated and measured)

Even if you have more power available the Goal Zero charger will not “draw” more than 0.8 A from the USB port. This corresponds to 4 W. Therefore, a solar panel bigger than 5 W is only beneficial in suboptimal conditions if used with this AA NiMH battery charger (charging while hiking or charging in cloudy weather). Fully charging 4 depleted NiMH batteries takes around 4 to 6 hours depending on the battery capacity. Note that the charging rate towards the end of the charging cycle is relatively low. Therefore I often stop the charging when the green light starts blinking fast.

  • Goal Zero Charging Efficiency: 65% to 70%

To fully charge 4 depleted AA NiMH batteries with a capacity of 2’000 mAh (4 x 2.4 Wh) roughly 14 to 15 Wh are required.

  • Goal Zero Power Bank Mode Efficiency: 60% to 75%

If using 4 fully charged AA NiMH batteries with a capacity of 2’000 mAh (4 x 2.4 Wh) roughly 6 to 7 Wh of USB power can be generated. If the charged USB device “draws” a lower current (0.5 A or less i.e. the InReach Mini) the energy transfer is more efficient (closer to 75%). Connecting bigger consumers (1 A or more like smartphones) makes the power bank mode of the Goal Zero charger rather inefficient (closer to 60%).

  • Alkaline batteries should not be used to generate USB power with a Goal Zero Guide 10 due to an even lower efficiency caused by the poor Alkaline battery behaviour at a high discharge current. Efficiency is likely to be less than 40% so more than half of the energy is converted into useless heat.
  • Lithium batteries may be used as an emergency backup to generate USB power with a Goal Zero Guide 10. If using 4 Lithium batteries with a capacity of 3’000 mAh (4 x 4.5 Wh) approximately 11 to 13 Wh of USB power can be generated. Since Lithium batteries behave well at high discharge currents this conversion is reasonable efficient.

If carrying an EBL USB Quick Charger calculate with the following charging efficiencies and currents:

  • Maximum USB charging current: 2.1 A (rated) / 1.7 A (measured)

Fully charging 4 depleted NiMH batteries takes around 2 to 3.5 hours depending on the battery capacity.

  • EBL USB Quick Charger Charging Efficiency: Approximately 45%

To fully charge 4 depleted AA NiMH batteries with a capacity of 2’000 mAh (4 x 2.4 Wh) roughly 21 Wh are required.

Bio Lite CampStove

I recently stumbled in an outdoor shop over a piece of gear that also promises to charge electronics in the outdoors: the Bio Lite CampStove. This stove promises to produce electrical energy using the thermoelectric effect. All you need are small pieces of wood to recharge your gadgets while cooking with fire. Here the link.

This sounds cool? Certainly! But before getting excited let’s analyse it. The manufacturer specification states that the weight is 935 g and that the peak power output is 3 W. So, it would feel like a heavy stone in the backpack and when reading “peak power” I instantly know that I should not expect this output under normal conditions. So, let’s assume that an average power output of 2 W can be maintained over some time. 2 W out of 1 kg of gear means a specific power generation of 2 W/kg.

Compare it with a solar panel: A solar panel has 10 times the specific power output (20 W/kg). Therefore, a solar panel with the same power output would weight just 100 g and you do not need to throw constantly wood chips into it. I would go for the panel!

Let’s calculate how long it would take to charge a smartphone with a typical 2’000 mAh battery. 2’000 mAh corresponds to 7.4 Wh stored energy (you remember 2 Ah x 3.7 V = 7.4 Wh). If considering a charging efficiency of around 80% you need to produce at least 9 Wh of electrical energy to get if fully charged. With an average output of 2 W it would take 4 to 5 hours of keeping the stove running to recharge an empty smart phone. I would be annoyed!

A comparison with a power bank is even more embarrassing for the Bio Lite CampStove. A USB power bank of the same weight has an effective stored energy of up to 160 Wh. To produce the same amount of energy you need to run the Bio Lite CampStove somewhere around 100 h when assuming an average power output of 2 W and a charging efficiency of 80%.

If used 2 to 3 hours per day it produces only 4 to 6 Wh per day what would be barely be enough to keep a GPS and a InReach device running (considering the Goal Zero Charging Efficiency of 65% to 70%).

I can look at this piece of gear from whatever angle and I can’t see under what circumstances it provides a true benefit. Therefore, carrying the Bio Lite CampStove on a hike proves only the inability or unwillingness to analyse. So, for me this is a useless toy for adults that want to play the outdoor guy!

WaterLily Turbine

There is another power generator that recently pushed on the market: the WaterLily Turbine. The designers suggest using it in fast flowing rivers or hung up in a tree to harvest wind energy. Here the link.

According to the manufacturers specification the weight is 1.3 kg and the peak power output is 15 W. Again, peak power means that a bit less should be expected. I will assume an average power generation of 10 W for my analysis. With 1.3 kg it’s heavy but with approximately 10 W output it produces more than a trickle charge.

The specific power generation of the WaterLily Turbine is 8 W/kg. Much better than the Bio Lite CampStove (2 W/kg) but still inferior to solar panels (20 W/kg). Therefore there is no reason to carry this turbine in areas with enough sunshine. Solar panels come with the additional benefit that you can choose the size you actually need. This does not apply to the turbine; you can’t carry half the turbine if you just need half the power. The advantage of this turbine is that it works without constant attention like a solar panel and unlike like the Bio Lite CampStove that needs to be constantly feed with wood chips. So, someone can set it up when pitching camp and let it run over night hoping that it does not rain too heavy to find the turbine in the morning blocked by leaves and twigs or even flushed away.

If used every second night for 10 hours it produces 100 Wh per use or 50 Wh per day in average. Finding every night a spot with suitable conditions for this gear is not realistic and 50 Wh per day is still much more than a typical hiker or packrafter possibly needs. So in most cases it would be overkill.

Let’s compare this turbine with a power bank of the same weight. 1.3 kg of power banks store up to 200 Wh effective energy. This corresponds to running the turbine twice for 10 hours. That’s not bad but only useful if you really need a lot of electrical power. And I mean a lot! So the WaterLily Turbine is no complete non-sense like the Bio Lite CampStove. But carrying this turbine only pays of under very specific circumstances. It makes only sense in regions with insufficient sunshine. This might be the case when packrafting or seakayaking in the Patagonian fjords otherwise a solar panel is more effective and practical. And it is only beneficial on a rather long trip of a bigger group or for activities that require lots of electrical power i.e. when filming with (semi-)professional gear.

Conclusion

The previous analysis showed that there is no “one-size-fits-all-solution” but that hikers must make individual choices that match personal preferences and hiking habits. Also the chosen sections should be considered. Sunshine is frequent in the north (GPT01 to GPT15) and on the Argentine side (GPT23 to GPT26) making a solar panel more beneficial on these sections. In other areas someone might have bad luck and be pursuit by clouds and rain for a week or even more.

In the following I outline and compare fife power supply options for different hiking styles and budgets. Choose what fits best to you and fine-tune it to your necessities.

Navigation Equipment Options (Opt.: Optional)
Item Comment Luxury Ultra-Light Ultra-Light Economy Light Autarky & High-Power Smartphones Only
Navigation and Communication Devices
GPS Recommended Primary Navigation Device Yes Yes Yes Yes -
Smartphone Recommended Backup Navigation Device Yes Yes Yes Yes Yes
Backup Smartphone Second Backup Smartphone if no GPS used - - - - Yes
InReach Satellite Communication Device Yes Yes Yes Yes Yes
Power Generator
Solar Panel A solar panel with an actual 5 W power output is normally sufficient - - - Yes -
Batteries and Power Banks
AA Lithium Batteries Lithium batteries have the highest specific stored energy but are costly Yes Opt. Opt. Opt. -
AA Alkaline Batteries Alkaline batteries are cheaper and easier to find in small resupply towns - Yes Opt. - -
AA NiMH Batteries Rechargeable batteries minimize cost but slightly increase weight - - Yes Yes -
AA USB Charger Rechargeable batteries require a charger that may serve as power bank Opt. - Yes Yes -
USB Power Bank USB devices are best recharged with a Lithium-Ion power bank Opt. Yes Yes Opt. Yes
220 V USB Charger
USB Charger 220 V USB Charger with Europlug þ and Type L Adapter for Argentina Yes Yes Yes Yes Yes

Luxury Ultra-Light Option

Non-rechargeable Lithium batteries have a high specific energy compared to most other battery types including rechargeable Lithium-Ion batteries. Only 7.5 g of battery power are required to run a basic handheld GPS one full hiking day. This makes this option the lightest but also the most expensive option as Lithium batteries as costlier.

Be aware that Lithium batteries are normally not available in smaller towns in Chile and Argentina. In this case Alkaline batteries should be purchased. So, maintaining this luxury ultra-light strategy over the length of the GPT is difficult without a “bounce-box”.

Hikers that put so much effort and money in minimizing weight will probably also minimize smartphone use to not carry a USB power bank or only a small one. Therefore it would not be a completely stupid idea to carry for emergencies a Goal Zero Guide 10 plus charger (64 g) as this device can be used with the Lithium batteries as a emergency USB power bank. Considering the expected transformation losses four Lithium batteries correspond roughly an effective stored energy of 12 Wh for the smartphone or the InReach. If i.e. the GPS fails the smartphone can be recharged at least once while being used for navigation. Or in case of an accident the InReach Mini can be recharged twice. This may eliminate the need to carry a USB power bank saving a few grams (A 5’000 mAh USB power bank weights at least 120 g and has an effective stored energy of 13 - 15 Wh).

Ultra-Light Option

Alkaline batteries are less costly and more easily available than Lithium batteries. Around 15 g of battery power are sufficient to run a Garmin eTrex20x or 30x one hiking day. Even on the longest sections this is still lighter than rechargeable NiMH batteries and a solar recharge kid. A pair of Lithium batteries might be carried as a backup if the amount of Alkaline batteries is calculated without much reserves. A USB power bank should be carried to recharge the smartphone (backup navigation device) and the InReach communication device. This option provides a good balance between minimizing weigh and minimizing cost. Add images.

Economy Light Option

Someone who dislikes non-rechargeable batteries for environmental reasons and prefers rechargeable batteries can use NiMH batteries and recharge these batteries during resupply town stops. To keep the GPS running 25 g of battery are required per hiking day. This is heavier than using Alkaline and Lithium batteries but less costly since no money is spend regularly on single-use batteries.

For a weight comparison two additional aspects need to be considered. First: a AA NiMH battery charger and a cable is require. And second: the amount of batteries is determined by the power demand of the longest section. If i.e. 12 batteries are required for the longest section (or combination of sections) than these 12 batteries need to be carried on all other sections as well even if not really needed. So the weight of this equipment options is set by the required maximum range and not by the actual length of each section.

Alternatively, a smaller set of rechargeable NiMH batteries (i.e. 4, 6 or 8 pieces) can be carried during the entire hike that is complemented only on for longer sections by a few Alkaline batteries to extend the range as needed.

A set of four Lithium batteries (4 x 15 g) might also be a wise backup. These Lithium batteries can either be used in the handheld GPS or in the Goal Zero Guide 10 to recharge USB devices in emergencies (smartphone, InReach). This can be an alternative to carrying a large power bank. Add images.

Autarky & High-Power Option

As analysed before a solar panel becomes only beneficial on very long hikes (two weeks or more between proper resupplies) and when a lot of electric power is required on the trail (intense smartphone use, tablet computer use). On sections shorter than two weeks it is normally lighter to carry just the right amount of batteries than adding a solar panel, an AA battery charger and sufficient rechargeable NiMH batteries to the gear. On the GPT several sections or combinations of sections are close to this break-even point but not clearly beyond. Therefore, it is worth considering this option, but it will not be the optimal choice for all hikers on the GPT.

A valid motive for carrying a solar panel on the GPT is the increased autarky that permits to slow down and a worriless use of electronic devices on the trail. But for hikers that want to be fast and light a solar panel rarely pays off.

Carrying a set of four Lithium batteries (4 x 15 g) is a wise complement to a solar power set. These Lithium batteries can be used in the handheld GPS i.e. if the solar panel fails or the sun disappears for more than a week behind clouds. In addition, these 4 Lithium batteries can be used in the Goal Zero Guide 10 to recharge USB devices in emergencies (smartphone, InReach). This can be an alternative to carrying a power bank. Add images.

Smartphones Only Option

Some hikers in recent years relied on smartphones only and did not carry a handheld GPS. Some managed to navigate the longer sections but deactivate GPS navigation and GPS recording whenever possible to make the smartphone battery and the power banks last long enough. Some smartphone users also struggled with the track file conversion and often lost a part of the track information in the conversion process. Based on these feedbacks I’m relucted to recommend this option.

Also, the higher power consumption of a smartphone eliminates the assumed weight benefit. A smartphone with GPS navigation and GPS recording activated consumes roughly 5 Wh per day. To have a range of 12 hiking days two 10’000 mAh power banks are required to recharge the smartphone every second day (at least 360 g in USB power banks). In comparison a handheld GPS consumes approximately 2 Wh per day so for the same 12-day period 8 Alkaline batteries are sufficient to keep the navigation device powered up (184 g in Alkaline batteries).

We start our smartphone occasionally to review satellite images when investigating new routes and to link it for a few minutes with the InReach to type messages and check the weather forecast. This preserves the battery to have the smartphone available as backup navigation device should the GPS fail.

Weight Comparison of Power Supply Options

Navigation Equipment Options (Weight per day)
Power Supply Option Device Consumption Cost per Day of Navigation Weight per Day of Navigation Additional Base Weight per Day of Range Additional Base Weight
Luxury Ultra-Light Option GPS & AA Lithium Batteries 2 AA: 4 – 5 days 1 – 3 EUR 7.5 g - -
Ultra-Light Option GPS & AA Alkaline Batteries 2 AA: 3 – 4 days 0.25 – 1 EUR 15 g - -
Economy Light Option GPS & AA NiMH Batteries 2 AA: 2 – 3 days - - 25 g 75 g
Autarky & High-Power Option GPS & AA NiMH Bat. & Solar Panel 2 AA: 2 – 3 days - - - At least 475 g
Smartphones Only Option Smartphones & USB Power Bank 1 smartphone charge: ≈ 2 days - - At least 30 g Backup Smartphone
Navigation Equipment Options (Weight depending on section length)
Power Supply Options With Non-Rechargeable Batteries 4 Days of Navigation 8 Days of Navigation 12 Days of Navigation 16 Days of Navigation 20 Days of Navigation
Luxury Ultra-Light Option GPS & AA Lithium Batteries (In addition, USB power bank for smartphone depending on habits and backup needs.) 30 g 2 x AA Lithium 60 g 4 x AA Lithium 90 g 6 x AA Lithium 120 g 8 x AA Lithium 150 g 10 x AA Lithium
Ultra-Light Option GPS & AA Alkaline Batteries (In addition, USB power bank for smartphone depending on habits and backup needs.) 92 g 4 x AA Alkaline 138 g 6 x AA Alkaline 184 g 8 x AA Alkaline 276 g 12 x AA Alkaline 322 g 14 x AA Alkaline
Navigation Equipment Option With Rechargeable Batteries 4 Days of Range 8 Days of Range 12 Days of Range 16 Days of Range 20 Days of Range
Economy Light Option GPS & AA NiMH Batteries (In addition, USB power bank for smartphone depending on habits and backup needs.) 175 g 4 x AA NiMH 275 g 8 x AA NiMH 375 g 12 x AA NiMH 475 g 16 x AA NiMH 575 g 20 x AA NiMH
Autarky & High-Power Option GPS & AA NiMH Bat. & Solar Panel At least 475 g At least 475 g At least 475 g At least 475 g At least 475 g
Smartphones Only Option Smartphones & USB Power Bank (In addition, a second backup smartphone required) At least 120 g 1 x 5’000 mAh At least 180 g 1 x 10’000 mAh At least 360 g 2 x 10’000 mAh At least 540 g 3 x 10’000 mAh At least 540 g 3 x 10’000 mAh