Backpacking Solar Panel v2

[JWreno]

I carried a Suntastic 5 watt panel on 3 JMT trips and it did a good job keeping our Steripens and my iPhone and camera batteries charged. I had it secured to the top of my pack and it would slowly recharged devices as I hiked above the tree line. When we took breaks I would make sure the panel was sitting in full sun when possible.

I bought a Big Blue 14 watt panel last week. The panels and USB controller work great but I didn't like the 4 fold format. I removed all the fabric holding the Big Blue together and reconfigured it into a bifold version It now only wieghs 8.7 ounces compared to the original 12.7 ounces. I replaced the heavier fabric with some ripstop nylon and used some plastic pieces and adhesive to join each of two pairs of panels together to make it a bifold. I put some 3/16" shock cord loops around the perimeter of the panels so I can tie them off to the top of my pack when hiking.

I tested it yesterday under a full sun. I discharged the NiteCore NC10000 battery bank fully when charging other devices. I plugged it into the bifold 14 watt panel and it took 4.5 hours to fully charge the 36 watt-hour battery bank. I used a USB meter when charging it. It passed 38 watt-hours of solar energy when charging the battery bank. I saw a peak of 9.8 watts and it stayed above 9 watts until the last half hour or so when the battery bank was almost fully charged so the current was being throttled. My wife and I will each carry a NiteCore NC10000 battery bank and alternate each battery bank on the solar panel.

The BigBlue 14 watt panel can be purchased for $34 which is a bit less than the Suntastics 5 watt panel I bought more than a decade ago. I am glad to have a reasonable sized panel that provides better than an effective watt per ounce.

I like using the FarOut GaiaGPS apps and on my iPhone when hiking so it is good to have a way to keep the phone charged. We recharge the Steripens about every 5-7 days as needed. I have extra batteries for my Fuji X-H2 so I don't need to recharge it. My Kindle can go weeks without a charge with the Wifi turned off. It saves a lot of weight compared to paperback books. I have a Garmin Inreach Messenger and Garmin Fenix 7X watch that both can last for weeks without recharging so they can be recharged on resupply days.

[erutan]

Being above treeline I've never needed more than a 5W panel to keep two phones up indefinitely. I just use an Anker PowerCore II 6700 (not as weight efficient as the NB10000, but cheaper, lighter, and has all the capacity I need). The 4.3oz panel I used before isn't in service anymore (it started charging slowly due to water ingress after I left it out during a dayhike and it ended up raining, oops), but there's some decent solutions out there where you either sacrifice build quality or add some weight. https://www.sunnybag.com/products/sunny ... ini-aktion seems to be the more popular robust option with https://www.amazon.com/dp/B06Y655DJD/ on the other end.

https://www.reddit.com/r/Ultralight/com ... ls_with_a/ I made a thread on /u/ultralight recently, I'll copy and paste a few things out here.

Overview:

With a 4.3oz panel and an Anker PowerCore II 6700 stuck on the back with 15lb double sided sticky tape I was able to keep two iPhones up for 10 days, generally exiting the trip with both phones around 60-70% and the battery bank near full at around 8.5oz mostly above treeline in the Sierra Nevada (though perhaps not this summer lol). Having basically unlimited power is also nice for peace of mind if we do get delayed due to weather or an injury, and the bank was large enough to tide me over cloudy days.

My battery bank capacity is around 24Wh, so I'd normally get at least 8Wh a day (2 out of 6 ticks) just having it randomly on my pack most of the time, and would pull it really low if we were basecamping (we normally don't) and left it out in a sunny spot and could basically get a full charge on a mostly sunny day (1 to 6 ticks).

Some maths in reply to someone saying that just carrying 20000mah bank would likely be better than any solar setup I could come up with:

The Carbo 20000 is 77Wh for 10.42oz (taking the manufacturers rated capacity for the NB2000 and choosing the model that saves 0.4oz on case/what's around it).

My old 5W old solar panel + ~24Wh bank was 8.5oz. Subtract that power I start out with, and we're left with 53Wh (77-24) of power I'd need to get from the solar panel to match the 2oz heavier solution.

We're usually out for 9-10 day trips in the summer (biweekly 4 day work weeks for the season), but my pack is fully charged the first day, so let's cut that out and say it's 8-9 days. Our first trip of the season had wet snow until ~2am on day 7 and mixed rain days 8-9 - I forget what we exited with but we weren't thinking about power and it was fine. Most of the time in the Sierra I go from 3-4 dots on my bank to 5-6 at night (out of six), and if I'm basecamping I can get a full or near full 24W charge in but that's a rare case where we camp at the base of a basin and dayhike it then move on.

Over 9 days, I'd need 53/9 or 5.8Wh of power a day. Even with some loss charging into my bank, that'd be slightly over an hour of ideally positioned maximum charge (unlikely to impossible) or 3 hours at 40% efficiency, or 6 hours at 20% efficiency which seems to match up with me being able to generally get around 1/3 of my 24Wh bank charged (so generally around 8Wh though of course I could be on the high end of one dot going to the low end on another). Keep in mind I'll position the panel when we take lunch breaks, go off on a side hike / peak bag somewhere where we drop packs etc.

Over 8 days I'd need 53/8 or 6.6Wh a day, which still seems well within my experience over many months of trail time (I joke we're non-contiguous thru-hikers since we do 9-10 days on trail, 4 off, from June-Sept barring excessive snow or smoke etc).

Over a 5 days one would need 10.3Wh, which seems like it'd be a bit much to bank on. But again that's comparing a 8.5oz solution to a 10.4oz one too. It also is mentally much nicer knowing I'll generally get 8-20Wh a day vs whittling down a 77Wh poor that's empty when it's empty.

Again being above treeline in the Sierra Nevada in summer is a fairly ideal condition - we're generally not in shade, solar power is strong (UV ratings hit 13-14 midday), days are long(ish), and the latitude is fairly low.

[JWreno]

I have the Carbo 20000 that I plan to use instead of the solar panel for trips with 3-7 day resupplies.

We are retiring July 2024 and will hike about 500 miles of the PCT for the rest of the season. We will do the rest of the PCT over the 2025-2026 years to complete it. Most of the time the resupplies are short enough that a panel won't be needed.

[CAMERONM]

Thanks for the summary of your solar experience. It does not appear that the weight to power ratio has changed so much in ten years. I stopped doing solar many years ago as I found it a bit "fiddly" with more components in a chain of devices and connections that could fail, and a few days of bad weather create anxiety. I also upped my powerbank to 10000 and sometimes 13000 as I find that the constant obsession with power is not worth the few ounces gained. I might reconsider solar in a long thru-hike situation, but otherwise it does not seem to pencil out well enough for me for 6-11 day trips.

[JWreno]

The Suntastics 5w panel was very useful on our 16 - 19 day trips where we resupplied at MTR. I still think there is an optimal 3-4 ounce panel that may be worth carrying even on shorter trips. We will be doing the 750 miles between Campo and Cottonwood pass in a couple of chunks in 2025-2026. Plenty of full sun days where a panel on the lid of the pack can put quite a bit of charge in a 10000 mAh battery.

I don't think SteriPen will be our primary water solution in Southern California because of the sketchier water sources. We may bring one Steripen for filtered water where we want to be sure viruses aren't an issue.

I plan on using the BeFree filters in the Sierra this year with a couple of Steripens as an option. I will probably carry a Sawyer in Southern California.

We will probably only have 1 phone turned on this summer on our 10-11 day trip. We will have a pair of Sony RX100 cameras and my Fuji XH2 so the phones won't be used as cameras. I plan on carrying the Fuji XH2 for much of the Sierra portion of the PCT over the next 2 summers. I may also carry it in the state of Washington. I doubt I will carry it for the Southern California or Northern California beyond the Sierras or in Oregon.

I carried a Canon 6D and 16-35mm f/4 lens on a compete SOBO JMT trip in 2014. My Fuji XH2 and Sigma 18-50mm f/2.8 zoom weigh about 33 ounces combined which is much less than my Canon setup.

We replaced our tents, my pack and my sleeping bag and dropped about 4 pounds of weight compared to previous JMT trips. There will be 2 or 3 of us depending on if my brother still wants to do all the PCT after this summer 10-11 day high Sierra trip. We will share stove and much common gear to reduce the need for compete gear independence. I am loaning my brother our excess gear so he only needs to worry about his clothing and food choices for the trip. If he decides the PCT is for him, he can buy any gear he wants for the following few years of PCT section hiking.

[erutan]

I used a 8.5oz solar + battery bank solution for 2 phones over 4 summers (with almost 3 months of trail time last summer)and it was fine even on trips with clouds. Our first trip last summer had a day of wet snow until 2pm (so reading in tent) and then 2 days of afternoon showers and we still had enough power. I find not having solar more stressful as we normally exit a 10 day trip with the battery bank mostly full so I never really worry about consumption / running out. I’ll get anywhere from 8-20Wh a day above treeline, whereas a 10.5oz UL powerbank is 77Wh.

Most of the time it’s just on my pack, I take it off and angle it if we’re stopped for a while but otherwise don’t think about it. 6-11 day trips are IMO ideal for solar - people doing long thru-hikes usually just recharge in town.

The only electronics we carry are phones and NU-25 headlamps (which I haven’t had to top off but could), though phones are used for photography, marking GPS points, a little reading, rare music etc. using low power & airplane mode (but not super dimming the screen) I usually use 20-40% of my phone battery a day, and start each day around 70-80% or so after charging in evening/morning. Catching up on battery bank charge after some cloudy days has never been an issue for me in the Sierra.

A NB10000 + light 5W panel would be an ounce or so lighter than a Carbo 20000. At that point it’s weight an extra 38.5Wh from the 20000 bank vs a usual 8-20Wh per day from the panel (partly cloudy days included, heavy overcast or solid rain excluded). Most rainy days I still get around 4W or so as it’s generally sporadic, though obviously during a monsoon etc it could be packed away all day.