Status of practical solar chargers?

Hi Kevin,

Probaly no help to you but I purchased a solar system a couple of year ago and after testing it it at home for a while I decided it was too much off a hassle to use on backpacking trips, I have used it car camping successfully.

On longer trips I carry 2 spare batteries for my phone and and two spare sets of AAA's for headlamp gps, I recently purchasd an Anker USB
charger that will charge my phone 3 or 4 times.

Cheers,

"- there are no lightweight solar chargers that you can just buy and have delivered. Lots of people just make their own.

– hiking while charging is near impossible as you spend too much time in the shade.

– charging takes too much time. 8-10 hours"

These three points are mostly false. The rest of it is: it depends.

Two weeks ago I bought a solar system over the counter at REI. You must define what you mean by lightweight (3 ounces or 3 pounds?), and you have to define how much power you need.

You can hike while charging, but that is mostly if the charger is hanging down off the back of your backpack while you are headed mostly north, and if you are mostly above treeline. A typical trip for me starts below treeline, but within one day I will be up at treeline or above, so I will have solar power before I need it. A friend of mine hikes for two months at a time in the Alps with a Goal Zero panel hanging off the backpack.

Charging takes too much time if you don't have the right system. My rule of thumb is that if I think I need 5 watts, I buy 10 watts. Except for a little weight, the only penalty might be that it charges too quickly. There are standard charge speeds or rates for most kinds of rechargeable batteries.

–B.G.–

Yeah. I wanted to clarify. I just need to charge my phone (which is my GPS, camera, etc)

And the biggest problem that I can see is that I only spend 20% of my time in the sun. So I guess 2 hours or so a day are in the sun.

There's usually and hour in the morning and another in the evening when I am at camp. So that's probably 4 hours of sunlight per day.

But in practice my phone lasts about 3 days so it seems like it would take 2 days to recharge it.

My goal is to be able to listen to more audio and watch more movies on my phone – which would require more power.

You will never find something that fits vague requirements. You need to know how much power your loads require. In the context of a rechargeable battery inside a device, that generally means voltage and amperage applied for X hours.

Most rechargeable batteries want to be charged over a time that is several times slower than the maximum output of the same battery. For a crude example, that means that if it takes 10 hours of use to drain the battery, it might take 40 hours to charge it back. Now, lots of batteries can go faster than that, but typically they have a limited number of charge cycles that they will last.

If you are out on shady trails a lot during the middle of the day, that is unfortunate since that is the best time to collect solar power (when the sun is highest in the sky).

My phone lasts for about 60-90 days on one charge. That is because I never turn it on except for an emergency. On AC-powered charging, it takes it only two hours to charge up. For a proper solar system, it should take about the same amount unless it was going to be shady.

–B.G.–

It depends on how battery dependent you are, but I minimize usage and can go pretty far between recharges. That might be a possible option for you or not, but it is something to think about.

Leaving the phone off most of the time and in airplane mode the rest of the time makes it last a long time and carrying one or more spare batteries would get me through longer trips than you propose.

I never need a spare battery for my light even on longish trips. I have 50 nights on my current batteries in my little eGear Pico light and suspect they just might go another 50 nights. I might run out of battery on an AT thru hike, but not on most trips. I just use it sparingly, like 5-15 seconds at a time and not all that frequently at that.

Yeah. I totally agree. This is what I have done in the past and my iPhone 4S lasted forever. My Samsung Galaxy SIII (Android) isn't lasting as long (so far) but I didn't have one of the power savings features enabled.

I want to change it up though and watch documentaries while I am in camp (lectures, presentations, etc).

That would require more power obviously.

…

I gave up on solar chargers after several admiittedly weak attempts (too cheap to spend big bucks on what seems to be unproven technology).
Besides, it always seems to cloudy around here. I bought a portable battery and have never looked back. I got one of these:
http://www.hypershop.com/HyperJuice-Mini-7200mAh-Battery-for-iPhone-iPad-iPod-USB-s/165.htm

No fuss.

So I ditched the iPhone and I have the Galaxy SIII now.

It's the PERFECT backpacking phone in theory – though I'm still working on decent battery life.

It has a removable battery!!! So I bought 4 of them :)

Having a backup battery when using GPS is really nice because you don't have to stress out about your battery dying since you have a spare.

Further. It has mini-SD so I bought a 64GB SD card which I store audiobooks and video on…

It's really a nice setup. That's why I want to try to use it more in the evenings when I a relaxing at camp.

The S3 is very nice but I notice a massive difference in call quality and coverage compared to my Work Dumb phone,

As the technology stands, for every trip I can plan in my head where I feel required to charge things, I keep falling on the reality that bringing extra batteries/power packs as the most convenient and lightest option.

I got some hope for the future innovations in thermoelectric devices that can charge from heat sources, like the PowerPot and BioLite. As it is though, they don't make a lot of sense for how I use stoves, as boiling a couple cups of water isn't likely going to give me much of a charge and I don't want to feed a twig fire for 2 hours or burn through all my gas to get my phone half charged.

I take an extra camera battery. $30 and it weighs less than an ounce. Easy as that.

I don't own a solar charger, but I have done considerable research. Was most impressed with the Solarmonkey Adventurer which measures 6.6 x 3.7 x 0.8 inches and weighs just 9.3oz. It can be ordered online for $130 from REI.

Still, you can carry quite a few batteries for 9.3oz. and how many batteries would you need between resupply points? I'm currently undecided on the benefit of carrying a solar charger.

Outdoor Gearlab Review
http://www.youtube.com/watch?v=MBAplV76vsM

Solarmonkey Advertisement
http://www.youtube.com/watch?v=hL7CD4A_WVE

"It has a removable battery!!! So I bought 4 of them :)"

So if you have 4 extra batteries why are you asking about solar chargers? 4 seems like it should last you 2-3 weeks?

“I also want something that I can just order online. I’m an engineer but I already have to many projects. I need something that just works.”

Since you are an engineer do the math. Amps in and amps out.

Here is a link you may not have read Solar for Backpacking?

Monocyrstalline panels are the most efficient and durable. Their weakness is that if just one of the cells is shaded it affects several cells and the output is significantly reduced. If one is hiking in the sun above tree line, you probably need to wear a wide brim hat, which can cast a shadow in the panel.

If I were to go solar on a trip, I would use the GoalZero stuff. Is it heavy? Heavy is relative. Fortunately I can hike without the need for any electronics that require a charging solution. If I was doing a multi-month trip, I would consider a smart phone or similar to stay in contact with my wife.

"Amps in and amps out."

Nick, it is a bit more complicated than that. A better rule would be this: Watt-hours in and watt-hours out.

Many of these solar thingies have the basic photovoltaic cell followed by an internal rechargeable battery and/or a buck-boost power converter. The photovoltaic cell can charge the rechargeable battery (or you might use some AC-powered charger to goose up the battery). The buck-boost converter will shift that typical battery voltage into some different voltage that your electronic device needs. One example is a PV cell that feeds a 12 volt battery, and then the converter produces 5 volts out of that to run out through a USB connector. The buck-boost converter can go the other way if the internal battery is low voltage and your electronics need a higher voltage.

Many small size PV cells are incredibly slow at recharging any battery, so they need to pump solar power for many hours to get the job done. However, we probably need to run some field tests in the desert near Palm Springs.

–B.G.–

"Many of these solar thingies have the basic photovoltaic cell followed by an internal rechargeable battery and/or a buck-boost power converter."

Yep, watts is probably a better measurement. The GoalZero Nomad has an open circuit voltage of 6.5-7 volts DC. 12 volt port is rated at 13-15 volts DC. I verified that at 14.97 volts. I also verified the USB port at 5V and the Guide 10 solar port at over 6V.

As far as being incredibly slow at recharging any battery… I guess that is the point :)

But it is a viable option for some people if they have the time and sun to charge their batteries.

Have a look at these guys: http://www.powerenz.com/store/index.php?_a=viewProd&productId=297

Most solar chargers have a small pannel, an internal battery,electronics, and then a protective case. Most of the weight of most solar chargers are in the internal battery and case. Basically they tack whatever linght that hits them and then stores it in the internal battery and then dumps all that charge into your device through a cable to your device.

If your device has its own battery and can charge through a USB cable then you don't need the internal battery. Then just make the pannel large enough so that you can get a full charge during lunch. Take a look at this MYOG project:

http://www.extremtextil.de/catalog/Fabrics/coated:::21_22.html?

Basically he took a flexable solare pannel which included a power connector and stripped it down to its minimum weigh He started out at about 8oz and then after dumping the extra stuff and stripping of heavy items he didn't need he was down to 3.8oz. He then made his own DC to DC converter to get the solar voltage down to what his phone could handle. It ended up weighing 5oz and on his grand canyon trip was able to keep the partially charged for several days even through he only got about 40 minutes a day of charging. On his 4 day he got 1.5 hours of charging in and that got him a full charge.

The OP wanted an off-the-shelf solution. With the GoalZero Nomad 7 USB and Guide 10 ports, he could charge his USB batteries and also store electricity in a battery pack for those trips where is rains for a few days. A pretty versatile solution.

"With the GoalZero Nomad 7 USB and Guide 10 ports"

Yup. I don't currently need the +5V output, but it might be handy some day. The +12V output is handy today. There are some other good products if all you need is +5V or else only +12V.

Nick, I guess you can see the light.

–B.G.–

The Nomad 7 can charge 4 AA batteries in the Guide 10 in about 2-4 hours of sun. For 2-3 day trips, I'd take a rechargeable battery pack which would weigh less. For anything longer or where I want to really want to use my smartphone a lot, I'd take my solar panel.

At the Zion Trail Ragnar, I was able to check out an almost identical solar charge system as Goal Zero (which I currently own). They appear to be similar in quality, style but lighter and much cheaper. Check them out!

http://www.suntrapsolutions.com/shop/st7-solar-panel/