I have a pile of used 18650 cells that came out of a propulsion battery. I'm toying with the idea of making up a small 12v nominal battery to supply some running lights, a cabin light (mix of led and incandescent) and, perhaps, a VHF for an hour or two once a week. It's a job that is taken care just fine by a lead acid battery at the moment. Still, I've got these cells that I'd like to do something useful with and a more portable battery would be nice.
Initial thoughts are to wire up 3s1p (10.8~12.6v) batteries with power and "balancer" leads in 18650 3 cell holders. (wiring: http://scriptasylum....peed/lipo.html)
The battery would be some number of the above in parallel in a box with a 3s controller (eg. http://www.ebay.com/...AAOSwBahVL1zU).
Each 3s1p battery would be charged either with an off the shelf r/c balanced charger or a balanced charger built up out of cell chargers (eg. tp4056). I suspect that slow charging is death for lipo but it's cheap and these are free cells so the tp4056 method is tempting.
1) is this an altogether bad idea?
2) I don't ~think~ that there's anything in circuit that would be harmed by 4s voltages. Would 4s be better? Maybe with a diode?
3) suggestions? Hints?