Ordered one of these through ebay, got it in a couple weeks ago:
It’s an active balancer, started talking about them here:
Put it through some cycles and wanted to share my findings.
A bunch of numbers:
Tested on a 12s pack that was being fixed. Manually drained cells 5, 6, and 11 down to a voltage where bms balanding would NOT work (bms won’t go into balance charge if delta is ±0.075v or so).
- Starting voltages, out of balance cells in RED
- Drained pack down, variances have grown
- Attached balancer, LEDs on the balancer lights up when balancing, let it go until all lights turned off - resulting voltages
- Charge pack up again to about 50v, variance within 0.1v of max cell voltage
- Discharge pack down again, 0.15v drift seen in cells 5 and 6
- Charge it back up, seeing same figures as step 4
So what the hell’s going on.
Balancer compares cell’s voltage to its adjacent cells (not sure if higher or lower), and if voltage difference is 0.1v, it leeches charge from that adjacent cell until that variance comes under 0.1v. If that process drains the adjacent cells below 0.1v to its neighbor, it repeats the process. So there’s this cascading effect which is apparent when you see the LEDs light up.
You can see voltage variance between adjacent cells is never greater than 0.1v, but can be greater than that compared to the pack’s MAX cell voltage.
So far I’m kind of sold on these in place on bms.
But there some considerations before switching to these balancers.
- Balance’s quickly (rated at 1a balancing current)
- Stays cool at all times (bms gets above 250f during balancing), so can be attached directly to the battery
- Balances through all voltage ranges
- Easier installation (only needs B- and each cell’s balance leads)
- Always “bms bypassed”
- No bms max charging amperage limitations
- Max and min cell voltage difference can be high
- May lead to over charge
- No over / under charge protection, no over current protection
- Anything else you can think of?
I’m going to install this battery in one of my boards and put it into use, continue monitoring the pack and see if it’s a long term solution.