Lipo Charger

ian field

Joined Oct 27, 2012
I have a couple 18650 cells that need to be charged .. Does anyone know a good charging circuit ??
My first go at lithium charging was the battery for a Nikon camera that I didn't have the charger for - the charging control from an E-cigarette did the job, but it look a long time. AFAIK: some E-cigs use a replaceable 18650 and you can buy the charger to go with the kit - but you have to shop around to avoid getting ripped off.

My own DIY charger started off as a very simple TL431 shunt regulator and current limiting resistor. This can be boosted by adding a PNP emitter follower in the manner of a Sziklai pair - its advisable to feed the battery via a Shottky-barrier diode in case the TL431 fails short circuit. The voltage has to be calibrated accurately and the SB diode Vf taken into account.

Either add a timed shutdown, or make sure you don't leave it charging more than 48h.