Anyone else had grief with JK BMS active balancing kicking in too early?

Been running a 280Ah Eve LiFePO4 pack (4S) in my shed setup for about eight months now, paired with a JK BMS B2A8S20P with the 2A active balancer. Overall I'm dead chuffed with it, but I've noticed the balancing starts cutting in around 3.37–3.38V per cell, which feels way too low to me. At that voltage the cells are still sitting in the flat middle part of the charge curve where the SOC readings are basically meaningless and tiny voltage differences don't reflect any real imbalance in capacity.

The practical upshot is the balancer is running almost constantly during normal cycling, shifting current between cells that are probably only a millivolt or two apart in actual usable capacity. My worry is it's just generating heat and wear for no good reason, and possibly confusing my Victron Cerbo GX SOC calculations. I've had a poke around in the JK app and I can see the "Balance Start Voltage" parameter — currently left at the factory default — but I'm not confident what to set it to without making things worse.

Has anyone dialled this in properly on a JK with Eve or CATL cells? I was thinking somewhere around 3.45V so it only balances up near the top of the charge curve where the voltage actually tells you something useful. Keen to hear what settings others are running.

DontPanic44 | 📍 Yorkshire | ⚡ 24V LiFePO4 | Posts: 847

@LiFePO4Geek Yeah, had exactly this with my own JK setup. The default balancing trigger voltage is set quite low from the factory — think mine came in at 3.40V which meant it was trying to balance mid-discharge when the cells are still in that flat middle section of the curve where millivolt differences are basically meaningless noise.

Worth jumping into the JK app and bumping the "Balance Start Voltage" up to around 3.45V, maybe even 3.50V. That way it only kicks in when cells are actually approaching the top of the curve where balancing genuinely matters.

Also check your "Balance Trigger Voltage Difference" — I dropped mine to 5mV so it's not chasing shadows. Made a noticeable difference to unnecessary balancer cycling on mine.

Roger1983 | 📍 Somerset | ⚡ 48V LiFePO4 | Posts: 312

Worth checking your "Balance Start Voltage" setting in the JK app — mine was defaulting to something daft like 3.0V which meant the balancer was thrashing away constantly even mid-cycle. I bumped mine up to 3.45V and only balance in the top 20% or so of the charge curve where cell voltage spread actually matters for LiFePO4. The flat middle section of the discharge curve is so pancake-flat that balancing there achieves practically nothing anyway and just wastes energy churning it into heat. Also double-check your "Balance Delta Voltage" threshold — tightening that up so it only triggers when cells are genuinely diverging (say 5-8mV+) rather than reacting to normal measurement noise made a noticeable difference for me. @LiFePO4Geek what firmware version are you running?

JulieEvans | 📍 Shropshire | ⚡ 24V LiFePO4 | Posts: 156

Had this exact headache last spring! What sorted it for me was bumping the Balance Start Voltage up to around 3.40V so it only kicks in during the upper portion of the charge cycle where cell voltages actually mean something useful. Below that the readings are so flat on LiFePO4 that the balancer ends up chasing noise rather than genuine imbalance, and you can actually introduce more drift than you fix.

Also worth double-checking your cell delta trigger — mine was set absurdly low from the factory at something like 5mV. I moved it to 10-15mV and the unnecessary balancing activity dropped right off.

@Roger1983 makes a good point about the app settings generally — it's worth going through them methodically rather than just trusting the defaults, they're not always sensible out of the box.