So I’m trying to reuse some lithium ion batteries (18650s). They’re wired into a 4S pack with a 4S BMS attached. The pack itself is working fine. My question is, how do I charge it? I’ve read all the datasheets and when on my bench top power supply I can see the current drop at 16V as time goes by I’m just curious as to what I can use that would monitor the charger automatically and not over charge.
You’re going to need a charger specifically designed to charge lithium ion batteries that are wired in series. We carry [this charger that could be used if you have the appropriate connectors available for it, (they are usually included on your RC battery pack) or you should be able to find a charger at a local RC hobby store that carries RC parts that should work.
[This web page might have some useful information for you too.](http://www.tjinguytech.com/charging-how-tos/balance-connectors)](SkyRC IMAX B6 V2 Professional Balance Charger / Discharger - PRT-16793 - SparkFun Electronics)