wturber wrote: ↑
Feb 01, 2018 7:10 pm
Normally you want to start with all batteries at equal charge levels. Otherwise, the higher voltage batteries will discharge themselves into the lower voltage battery.
And they're going to try to do it as instantly as possible, so depending on cell resistance / etc it can be some very high currents--usually bad for the cells to be charged that way, but it depends on the cell specs, and the BMSes that are in there and what protections they have.
I'd recommend what others here have--just don't charge them all the way up in the first place, so you don't have to drain them down, or risk damaging them by too-rapid charging (when connecting unequal-voltage packs together in parallel).
It's possible your charger already has a voltage adjustment inside it that you can use to turn it down far enough.
ngant17 wrote: ↑
Feb 01, 2018 6:50 pm
That would give me 12Ahrs x 61.5 = 738 watts. Pretty close to optimum 750w with BBS02.
As Wturber notes, Watts (W) are not what you get in that calculation--you get Watt-hours (Wh). The "750w" of the motor systme is the typical power it might be able to run at.
The "738Wh" of the battery packs is the capacity (runtime) of the the batteries, and doesn't directly have anything to do with how many watts it can output. (though the "C-rate" of teh batteries, multiplied by their Ah, *does* tell you how many Amps (A) it can output, either peak or contuously depending on which one the given C-rate is for.
Also note that the fully-charged voltage of the pack is not used to calculate Wh; rather the average voltage of the pack is used for that.
So if the pack is typically around, say, 54v (you'd have to check what it actually is) at half-charge, then it's 12Ah * 54v = 648Wh.