Best Way to Charge Batteries via Solar?

[Confederate]

I have a friend who will be visiting India this spring. She'll be in a place with no electricity and limited water supply. She wants a good flashlight and a solar recharger, though she'll be taking her own lithium batteries. She wants something that will be relatively light (no pun), dependable and resistant to heat. She also is looking into some other uses but is looking for general information at present.

There are plastic foldables available through DX and eBay, but she's also considering this 30 watt mono-crystalline device that looks like it might be a bit heavy to haul around. Anyway, all advice would be welcome. She presently wants to use a AA light like the L2D, but she might do better with a CR123A P3D for sheer runtime (not to mention battery cost).

I'd looked into small devices myself some time ago, but know little to nothing about the various technologies. The mono-crystalline makers/sellers spend a lot of time badmouthing the amorphous solar cells, but the biggest drawback to them is the cracking and peeling that might take place in a really hot, dry climate. Some of the chargers I've seen take anywhere from 1-2 days to charge 2-4 AA cells to 4-5 hours. Don't know if this can be improved upon or not. I also don't know what to tell her about any additional devices (converters, resistors, etc.) she might need as I am clueless on this topic.

Thanks.

 

[USM0083]

This looks pretty good, but a little costly.

http://store.sundancesolar.com/brsopo44wiba.html

 

[2000xlt]

http://www.21st-century-goods.com/page/21st/PROD/iSunSil

here is another, similar to the one in the link in the above post but less $$

 

[brandx]

I've lately been playing with sunlinq (12 W ?) solar panel and the UF-139 and Pila charger, both with 12V cigarette lighter adapters. From very limited trials, this seems to be fairly decent. I like the fold-up nature of the sunlinq.

 

[surfinsmiley]

I don`t know anything about them but I`ve seen a few people with Solar Back Packs cruising around Tokyo. They might be worth looking into.

 

[markus_i]

No direct response to your question, but I think you should check out the marine/boating sector. Long-distance sailors often use solar panels to recharge their batteries, and there's very little in terms of weather for electronics that is worse than what you'd get e.g. through an Atlantic crossing.
Your main problem probably will be to find something reliable in the low-voltage range, most panels (and electonics) are designed for charging 12V SLA batteries - and it will be hard to find a system that will reliably charge e.g. AA cells, mostly because end of charge determination gets hellishly complicated if you don't have a reliable power source (dU/dt becomes basically impossible, anything else except trickle charging will drastically reduce the battery lifetime, trickle charging takes forever). This might look better (theoretically) for Li cells, but I haven't yet seen a Li charger that doesn't require at least a reliable power source capable of 1C (and you'd still have to forget about CC charging).
After all, you might be better off (and need to pack less weight) with a multi-mode light (at least one battery conserving very low level mode - you don't need that much light in the dark) using primary Li cells and pack enough cells to last the length of your trip. Or alternatively a power light (only to be used when needed) and a generator light (shake, spin, whatever works). There was (is?) a single AA light with a single 5 mm LED in a rugged aluminium case, bright enough to find your way around in the dark - and a single AA lasted through 3 weeks of camping in .oz (the spare batteries were then employed in the CD player....).

Bye
Markus

 

[Lynx_Arc]

I wonder if you could just get a 12V SLA and use that to charge things from and basically recharge that from solar and plugin autos and the grid at times too if available.

 

[abvidledUK]

Don't forget the mechanical charging option, windy handle or pull string.

These even work when it's dark.

I'm sure Google or CPF will help out with links.

There's also the AA charger option.

 

[Bones]

PowerFilm offers a broad array of products, and they claim some are used by the military:

http://www.powerfilmsolar.com ... foldables/index.htm

http://www.powerfilmsolar.com .. rollables/index.htm

This plug 'n play charger combined with some Eneloops would be a simple and reliable option:

http://www.powerfilmsolar.com/products/military/foldable/index.htm

Eclipse Solar also makes some intriguing products:

http://www.eclipsesolargear.com/Products.asp

 

[baterija]

This plug 'n play charger combined with some Eneloops would be a simple and reliable option:

http://www.powerfilmsolar.com/products/military/foldable/index.htm

Nice one package setup that claims "Highly effective battery charging with breakthrough charging circuitry." Has a battery charged signal too. So it's not like most I have looked at previously where end of charge is determined by the sun setting or taking the batteries out. Wonder how smart it is.

Ni-Cd might be an idea with the "sunset timed" chargers to prevent overcharging.

 

[Confederate]

Thanks for the feedback. The PowerFilm solar units I'd think would be a little out of her price range, but they look perfect.

 

[Bones]

Nice one package setup that claims "Highly effective battery charging with breakthrough charging circuitry." Has a battery charged signal too. So it's not like most I have looked at previously where end of charge is determined by the sun setting or taking the batteries out. Wonder how smart it is.
...

The downside with all these devices is that it seems the only way to find out how good they really are is to buy and try them.

The upside is that even if the termination faulters at times, they don't put out enough power to cause significant harm to a sturdy cell like the Eneloop except over the very long term.

 

[Bones]

Thanks for the feedback. The PowerFilm solar units I'd think would be a little out of her price range, but they look perfect.

While the price of the larger sizes would make even Warren Buffet flinch, SunDanceSolar has this all-in-one from PowerFilm for 79.95:

http://store.sundancesolar.com/poaafosobach.html

Hardly a pittance, but it and a few Eneloops would offer your friend almost perpetual en'light'enment in India.

It would also offer the same comfort in an emergency when she returns.

 

[baterija]

The upside is that even if the termination faulters at times, they don't put out enough power to cause significant harm to a sturdy cell like the Eneloop except over the very long term.

Good point. You know I thought of something like that a while back when I was thinking about something like this and then somehow forgot.

 

[Bones]

The viability of the SteriPEN Solar Charger would depend on how much use your friend will require from her lights and the SteriPEN itself.

From the SteriPEN FAQs and Services page:

5. How long does it take to charge the Solar Charging Case using the solar panel?

It takes approximately 20 hours of direct sunlight which is typically 3-5 days.

The purifier does appear to be pretty efficient though, delivering 40-50 uses from a RCR123A according to the SteriPEN Battery Information page.

The SteriPen website doesn't have any views of the inside of the solar charger, but there's a reasonably good one at the PriceInsantity site.

It does have a tidy layout.