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Author Topic: Can I use this solar powered battery charger to recharge my AA batteries?  (Read 2309 times)
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How many AA batteries do you want to charge at once, and are the batteries NiMH types.
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Well, I am sure glad I asked you awesome folks here on the Arduino Forum about this. Thanks for the links and the info. For $3 I'll go with Doc's suggestion since the pre-made one online costs $14 + shipping. The purpose was to use something I already had laying around in order to reduce cost. Yes, 2500mah AA rechargeable batteries.

Let us know how the simple/cheap solution works. Sometimes there is more to the story.
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The 2450 mAh Nickel-Metal Hydride.

This is it right? http://www.ti.com/product/lm317

Doc, can you give me a link to where you would buy it from?

THanks in advance!
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I'm not Doc, but for the more common (and most uncommon) ICs both digikey and Jameco are decent sources.  Sure they'll be more expensive than you might be able to find on e-bay and electronics wholesalers(with some the term is used loosely); but they have an dependably acceptable level of quality for the products they sell (versus the hit-or-miss you often get by extreme bargin hunting), actual customer service (including basic stuff like datasheets and other documentation), and significantly faster delivery if you are in North America.  I also like to patronize the smaller online electronics vendors (like some of those listed on the Arduino Distributors list, but they of course have a more limited selection.
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I got a pack of 10 ordered off of eBay. Anyone have a diagram on how to wire the LM317? I'll have a hot wire and a neutral coming from the solar panel. How do I use these 3 legs on the LM317?
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I got a pack of 10 ordered off of eBay. Anyone have a diagram on how to wire the LM317? I'll have a hot wire and a neutral coming from the solar panel. How do I use these 3 legs on the LM317?

You could start with the datasheet: http://www.ti.com/product/lm317
There's lots of tutorials on the web, e.g. http://www.ladyada.net/library/equipt/diypsupp.html
When it comes to understanding batteries, the best source I've round is Battery University: http://batteryuniversity.com/ where you'll find useful info such as http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride
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Thank you for those links. I am going to read through them now.
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Something else to consider is the average level of insolation... in those northern latitudes there isn't a real bunch of available power in my experience a 10 watt panel does real well to put out 100 mA for more that 4 or 5 hours a day. I would like to change my suggestion and have Foolios buy a buck converter and use it to drop the voltage to 3 volts or so. That way there would be nearly 3A available to charge the batteries (10W/3V) and at that point have a serious charger. With that kind of current available you would have to monitor the batteries voltage. On a Ni-Mh battery the voltaf\ge under charge will climb to a given point and when the battery is nearly charged (Constant Current Charger) the terminal voltage will drop by a hundred mV or so... That's the point to change to trickle charge to "Top Off" the battery. The other great thing about the switcher is that 80 90% of the energy is available for the batteries. Buck mode regulators can be purchased for 2 - 3 dollars on Ebay... All Day Long.

Doc
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Something like this?
http://www.ebay.com/itm/DC-Blue-Voltmeter-Ammeter-4-5-24V-to-1-20V-2A-Voltage-Regulator-Buck-Converter-/271024606462?pt=LH_DefaultDomain_0&hash=item3f1a534cfe
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