Solar Chargers for Long Trips

Hi Perrin,

I have no personal experience with solar chargers but have looked into them.

These guys seem to carry quite a few:

solar chargers.

Dan

Another place to look is http://www.powerfilmsolar.com for both foldable and rollable and http://www.sundancesolar which retails powerfilm and brunton, give them a call and they can help you with your durability and application problems.
I have have one of the foldable chargers,which works fine but I’ve not tackled any huge treks with it.

Will you be constantly out in the wilds or will you be “hosteling”? If the latter, I would really just carry a lightweight 120/240 battery charger and a set of plugs. You can find very light weight versions of both. It’s just a lot easier charging batteries at night, when you are not doing anything but sleeping.

In contrast, having to stay put for 8 or 10 or 12 hours waiting for your solar panel to do its work can really crimp your traveling! Again, maybe this will work better in the wilds, but if you are in any human settlement, it’s not so easy to rig up the panel and just leave it there. Theft is always a possibility — and do you really want to be watching the thing (so to speak) while it’s charging?

I would like to be able to spend a few weeks at a time away from power sources and I agree that it is a problem boldly propping up an expensive charger in some random country. I won’t be able to use 120/240 chargers, most likely.

I want the ability to charge multiple devices though — this is pretty critical. The PDA, camera and Photobank all have their own different batteries, so I was thinking about getting 12V car charger plugins for each, and then plugging those into the solar panel. So unfortunately this rules out the AA / AAA charger solar panels.

Also, a panel that can be hung on my pack while I hike would be cool.

Thanks for the links, everyone. There are a lot of different options! Perhaps my biggest question is how big an array I need. I don’t know much about watts, volts and milliamps — what is sufficient for charging a 7.2V/720mAp Lithium ion battery? Will any charger do, or are some effectively useless because they would take days and days?

7.2vdc@720ma is 5.2 watts but you need a charger that trickles 720ma this puts you into about a 20 watt charger since a 10 only gives you 600ma and I don’t think anyone makes a 15. Powerfilm has a 20 watt foldable charger that weighs less than a pound, Brunton has a 26 watt that weighs 26 oz. You’ll also need an accessory connector for your devices.

Well, the Brunton Solar roll comes in 14W, 15V, 900mA and 9W, 15V, 600mA versions.

Does the solar panel’s milliamp rating need to surpass that of the battery? If it doesn’t, will it just charge slowly or not charge at all? If it just charges slowly, that might be ok, as this isn’t going to be a highspeed trip. That Solar Roll looks a bit too big to use while hiking though.

Perrin:

Sorry that I am not knowledgeable enough to really answer your question, but I would like to offer one caveat.

Be very careful reading the ads. I don’t remember the brand, but one light weight solar panel charger website touted how its “powerful” panel can fully charge a set of AA batteries in just 8 hours (wow, same as household AC circuits!). But after reading the finer print, I realized they meant fully charging 800 mA batteries! Most rechargeable AA’s nowadays are rated 2,500 mA — so “fully charge” really meant less than a third charged! As you know, even 2,500 mA batteries don’t last all that long…

Perrin-Multiply volts x amps to get watts. In your case you need a THEORECTICAL 5.184 watt solar charger output.

Portable solar chargers are rated in output watts assuming they have a clear sky and the sun directly overhead. For an average clear day with the sun moving across the horizon you will only get about 70% of the rated power (7.4 watts charger required). Light overcast skies will provide as little as 60% (8.6 watts charger required). Heavily overcast skies will provide as little as 30% (17.28 watts charger required).

I do multiple-month expeditions in Alaska with a similar equipment compliment to yours. Last year I used a Brunton Solaroll 14 and it was inadequate (significantly slower charge time than using 110 AC). This year I used a Brunton Solaris 26 and on the typical heavily overcast day it charged each device at about the same rate as a 110 AC.

I augment the solar charger with a Radio Shack 1 amp AC to DC converter (3.5 oz). This allows the same 12 volt power adapters to be used with line power or solar power.

The Brunton Solarolls have a mechanical design flaw in their jack design. After you have rolled and unrolled the Solaroll alot you will get an intermittent open circuit (power stops for 5-10 minutes at a time) on hot days. They also use old technology that is significantly less efficient than the Brunton Solaris line.

As Richard points out you need at least 125% of your needed ma just to break even with the charge rate on a good day.
I’ve only used folding chargers and have not had a problem with connections.

What happens if the Wattage is below what I need? Does it charge slower than normal wall-charging, or does it fail to charge fully?

I am looking at the Solio right now, because it has an internal battery to store the energy it gathers. The solar panel output is only 6V X 155mA, and the battery inside is 3.6V X 1600mA.

Would transfering the power from this battery to my example DSLR 7.2V 720mA Lithium battery fail to fully charge it, charge really slowly, or what?

If I get a charger than I can hang on my pack, I can just leave it out all the time and charge things up slowly. If I can’t hang it, I likely need a much stronger array to charge quickly.

Mostly… there could be some ramifications of not getting fully charge if the solar panel runs too far out on it’s V/A curve… but mostly it will simply charge slower.

I’ve used the Sunlinq (the smallest one as shown here: http://www.affordable-solar.com/sunlinq-6-watt-portable-flexible-solar-panel.htm) on a few trips – including a 5 day trip in the Central Cascades (think Seattle latitude!). A couple of hours on a sunny rock each day was enough to get the device (Combined PDA, Phone and GPS) back over 90% (from as low as 56%) charged. The terrain was too rough to try using it on the outside of my pack but I’ll try that later this week.

Perrin- Unlike a normal solar charger, 1) the Solio charges an internal battery from the sun and 2) then uses a variable voltage DC to DC converter to output from its internal battery to your device. The Solio’s internal battery wattage is approximately 3.6 * 1.6 = 5.76 watts. Your camera battery wattage is in the range of 7.2 * .72 = 5.18.

If the Solio wattage is below what you need to charge a device, the Solio will only partially charge your device but the charge rate should be the same as a wall charger.

Once the Solio internal battery is charged, it will then charge your camera battery at the same approximate rate as a wall charger.

With the Solio design you would want to keep in on your pack top all of the time and then use the Solio battery to charge your device battery in the evening.

Thanks for your technical help, everyone. I think I am more interested in smaller and lighter solar panels, rather than fast charge speed, as I won’t likely be out in the wilderness for more than a week at a time. I slow charge to just keep my devices going should work.

One last question, particularly to your last response Richard, or anyone who can answer: The Solio’s wattage is lower than that of my camera’s battery, so it won’t charge fully. Does this mean that the Solio will never charge it fully (having lower watts means it can’t fill a battery with higher watts) or will it just require charging and using up the Solio twice to get enough energy? If it’s the latter, I think I would be ok.

It is the latter; you will be OK.

Great, thanks for the tech advice everyone!

Has anyone had any really good or bad experiences with solar panels in the bush? Any good lightweight ones?

I used the Iowa Solar flexible panel for recharging cell phone and camera batteries. Was very pleased.

I don’t know what kind of pda you have, but if it is expandable via a compact flash slot for example, you might be able to add a small harddisk to your PDA and use it to offload your digital photos. Depending on how many pictures you take, you could also bring along several cheap memory cards. You might also bring along a separate battery pack with enough power for one week that charges your devices the same way a solar panel would. A good solar charger will be expensive, and not very light, so you might sitll come out ahead by simply carrying spare batteries.

Hi,

I realize I'm a couple of years late to this topic, but wanted to report back that the Sunlinq 12W folding panel worked like an absolute champ on a recent trip to Japan. It was in late March / early April and almost continually overcast. However, I was able to repeatedly recharge my cell phone (Nokia N95, fairly high capacity battery) from near zero to full charge within an hour or so under a very cloudy sky. I was personally impressed, didn't expect very good performance under cloud cover. Also, the unit folds down small, is light, durable, and packs well on ultralight trips.

Sam