999zip999 said:
It should only be draining when the red led is on. The bms will balance at 55.2v. So ?
That's what I was thinking too. Draining as in, it hit a threshold, and it's bleeding it off to balance.
I guess the term "balance" is really loosely used. Balance in theory means all cell packs are exactly at the same voltage. But with the way these BMS seems to work, is that it's not the case it would seem. I think the cell packs, what it does is, they operate independently and when they hit that "threshold", the led turns on and it just bleeds off excess voltage/charge. This is independent of the other cell packs because they could still be charging. They certainly don't "receive" the bled off charge from the other cell pack.
So that's why in Ping's documentation, it mentions all LEDs would slowly and one by one turn on. They operate independently and hit the threshold separately. So in essence, the "true" balance only occurs when you have a charger voltage set high enough that everything hits HVC where the shunt resistors kick on and they are all bleeding the charge, waiting for the last few cells to catch up to them.
Truly, I think a real balancer is one where it is balancing on-the-fly simultaneously in real-time at any voltage. That means, anytime the BMS senses an imbalance by more than 1mV, it will just bleed off charge to the other cells and create equilibrium. But that wouldn't make sense on a passive balancing. Because if the balance function keeps bleeding like that, then the BMS would literally burn off the entire charge of the battery pack in 2 days just sitting there doing nothing because it kept bleeding off the voltage of each cell pack and trying to make it equalize. When in fact, it couldn't get it perfect, so it ended up bleeding off the entire battery pack through the resistor instead of bleeding it through to the other cells.
So going back, I think the term "balancing" with these BMS during full charge is not really accurate. What it really is doing it seems is that, it will just cap the cell voltages for each parallel P and bleed those charge, while waiting and allowing the other cells to "catch" up. And when they all catch up and hit max voltage, then that is when the charger shuts off. As in my case, that never happens because my charger voltage is not high enough to allow most of these packs to hit that bleeding threshold.
Perfect example is a 1S4P pack. If you charge a 1S4P pack which is 3.6V @ 10Ah (2.5Ah per cell), you don't need a balancer. Because as you charge 4.2V to the 1S4P, the cells will equalize each other in real-time, on-the-fly, you name it. That's "true" balancing in my opinion. In a series connection, it can't do that, so you have to rely on a circuit board BMS to either compare the voltages or bleed off when it hits a threshold.
