solar aa/aaa charger recommendations?

[disrup-sean]

Can anyone recommend a solution for solar charging lots of aa and aaa batteries on the playa? (I'm looking to provide greener power for the many EL wire/blinky bike lights and flashlights people in my camp are using. It works out to be hundreds of little alkalines in the trash. Madness! And thats just one tiny camp.. I'm thinking of building a "recharge camp" next year w/ goal: anyone can bring in spent rechargeable batteries to trade for charged ones)

For this year: there are a ton of small 4-battery solar chargers on EBay etc. But can anyone tell me:
-how long a particular one of these takes to charge (can i expect to charge more than 1 set per day per charger?)
-of any higher-volume charger to buy or build that effectively charges more than 4 aa's or aaa's at a time? (dont have much $$ to work with though)

Thanks

Sean

[diane o'thirst]

First of all, I think your "recharge camp" idea is brilliant.

I got an 8-cell charger off Ebay a few months ago but haven't used it yet. I'm putting it outside today to charge up a few AAA's for my EL wire. I'll keep you apprised of my findings.

[AntiM]

We use a very cheap solar recharger from That Chinese Import Store, and it has worked well enough for several years.

[disrup-sean]

[quote="AntiM"]We use a very cheap solar recharger from That Chinese Import Store, and it has worked well enough for several years.[/quote]

Thanks! But.. which import store? which charger? and, how many batteries can it charge in a day on the playa?

thanks

[AntiM]

Eh, Harbor freight, four? six? batteries a day, and I haven't seen it since last year, larry has it packed down in the power box so I can't look at it for sure.

[unjonharley]

A camp with a charging port great. My 120v charger will charge 4aaa 4aa 2 9v. It charges for 5hours and turns it's self off. This should give you an idea of time. Also I have a baby solor panel 3.4v, 6v, 9v. and 12v. It has a charger compartment for two aa. I can get the voltage but very little curent. To run a small amp I place the solor panel in line with the battery. This extends the battery life. Battery killers are the step down transformers. They will eat 40% of your amp hour just converting from say: 12v. to 3.4v. Any appliance with moving parts will eat your battery fast ie small disc player. The year I'm going to an Ipod style for imput.

[Token]

Rapid chargers from the RC Hobby industry are what would do the trick. Many to choose from however you must do some clever engineering to get many batteries charged at once.

Engineering problems:

1. AAA and AA cells cannot take more than 1A of current, either charge or discharge without overheating.
2. NiMH batteries are very sensitive to heat. These are the "high Capacity" rechargeable.

The regular consumer chargers for AA AAA batteries will not charge faster than 4 hours due to the above listed. You can charge faster but you must use advanced chargers that have rather nifty little computers on board to sense the condition of the battery and means to measure battery temperature.

Most Hobby chargers, the kind used for RC cars and planes, will charge 6 to 8 cells, at a rate of ~ 5A or even more. These rates are designed for C and Sub-C battery cells which are far more robust than the AA/AAA. You could however engineer this such that you are charging 5 banks of 6-8 AAs or 30 to 40 batteries at a time, provided they are all the same capacity, make and model.

Here is an example of such a charger:

http://duratrax.com/caraccys/dtxp4005.html

It costs ~ $50

Now, in order to feed this type of charger from a solar setup, you would likely need a marine 12V battery and probably a large 85W solar panel (i.e. 5A solar panel at 16V). You could use a smaller panel and limit the number of charges done per day.

The solar panel is where this gets very expensive. Expect to spend between $300 and $500 on this item.

You should check out the AEZ camp and see if anyone there has this worked out.