dogman dan wrote: ↑
Dec 09, 2017 7:31 am
My two cents.
Nothing really wrong with the existing charging methods, provided the meanwells are set to the right voltage. (not overcharging) You might consider tuning them to very slightly undercharge the pack, if your needs don't require the entire capacity very often.
Using those 4s balance plugs, you can easily balance when you need to, using a very cheap RC 6s charger, or a discharging balancing device. An adapter can be made that plugs into the 4s plug, giving you another 5 pin 4s plug, and additional + and - wires to plug into an RC charger. Set charger to 2 amps, and the tiny wire can handle that fine. If you undercharged a tiny bit, the charger only needs a trickle to finish off and balance, so no need for big fat wires every 4 cells. You'd likely not need to balance all that often, doing it only when your pack has cells more than .05v off from each other.
Check your cells fairly often using a cellog 8, using those balance plugs. That's the human bms part.
If you decide to bms,, well, nothing whatsoever wrong with continuing the manual checks. Just wire it so you still have those plugs to check with a cellog.
When you are going to discharge 100%, figure out which cell is the lowest capacity by checking voltage when they are close to empty, like 10% or less left. ( like about 3.55v)Then put a cheap low voltage alarm on the plug that has that cell in it. Stop when the alarm goes off, and won't stop when you slow, or stop. You only need one on the worst cell. it will be the one that tells you when to stop, the others will still have some juice in them.
Use this alarm only when you need it, when the pack is nearly empty, leaving them in place all the time just makes their draw unbalance the pack. The alarm is just for limp home. Watching voltage of the whole pack will tell you when to start for home before you reach that limp home point.
As for safety, well, a "safe" battery with bms burned my house. Garage destroyed, house all smoked. It was a 9 month nightmare getting it all repaired.
So my shit, its never coming inside again, ever. The old kitchen stove that got ruined in the fire is now my battery storage place, in the back yard.