Charge batters vs. use batteries.

I understand the difference -- I have read a lot and still come away a bit mystified.

I have an arduino based project (technically ATTiny85) The arduino can run off "house power", but when that power is cut off; I need to to run from batteries.

There are two ways to charge them -- one a small solar cell which should be matched for a bit more than the load of the arduino; so it should make up for night time w/o solar. The 2nd way is to plug a pc into to download data.

From reading, I get mixed info on the "proper" way to do it. I plug into the arduino to get the info; that provides power to the power charger, which powers the batteries, ditto for the solar. But some have hinted "there's more to it" than just hooking it up in parallel.

Would someone give some guidance?

Thanks.

You have not said what sort of batteries you are planning to use - the voltage and the battery chemistry. Lead-acid batteries are the easiest. LiPos have a nasty enthusiasm for bursting into flames if misused.

...R

I have spent some time on a solar charge controller project, which is for an irrigation controller project. Anyway, I've seen my embedded projects lock up enough to know that I need a hardwired battery disconnect to prevent nuking the battery due to my bad software. I still have a lot of work to do on my project but have a look if you want. http://forum.arduino.cc/index.php?topic=296549.0

Thanks -- wel;l this is actually a 2 part project... one part, I plan on using a large battery (car) and solar panel or usb. The other is a handheld -- using lipo battery, solar or usb.

My thought was to "jump" the usb (for talking to the arduino) with a diode to 'feed' the solar charger card -- in theory I will still be able to talk the card, and feed from teh usb cable to charge it...

I just didn't know the best way to handle it -- seeed has a "lipo rider pro" but it's spendy with shipping...

Thanks for the link --i'll give a look over. Thank you borth for your replies.