When charging a lipo:
- Is there a max current you should recharge at?
- Does the protection circuit on the lipo correct for the amount of current that should be going into the battery?
I'm looking at solar lipo chargers, I see the seeed studio lipo rider has a output current of 300mA. (Not sure if that's referring to the usb interface or the battery JST), but how do I know this will accurately/safely charge my 3.7v 270mA lipo.
Does anyone have a resource that's in laymen terms on lipo charging? Don't know why but the whole battery situation scares me a bit with safety concerns, as I feel like I've never been able to get my head completely around how to safely charge a lipo, despite products like the "seed lipo rider"
Best Answer
Generally you want to charge at "1C" or less unless your battery datasheet says otherwise; for a 270mAh lipo cell that's a max charge current of 270mA. Your protection circuit won't limit the charge current going into the battery- it would only open a FET to prevent charging in an overcurrent condition. You have to limit the charger current yourself. Many battery charger ICs will do this for you with a simple jumper or I2C register setting.
Packs usually come with a datasheet for the pack and a datasheet for the protection circuits. Both should be considered when setting up your charger. I just did this for the first time and set the limit on my Linear Tech (LTC3567) charger to a 100mA mode to be safe. It works like a champ and I don't need to worry about overcurrent on my pack (470mAh). Yes it takes a little longer to charge but that was okay for my design.
Sparkfun has some good charger examples (they are fairly cheap to buy if you want to go that route). Note that for this simple charger IC there is a "PROG" resistor that you can change to set your charge current limit.
Some of the RC forums/merchants have some decent reading on the subject. Here's one example: http://www.rogershobbycenter.com/lipoguide/