Anyone else had their JK BMS throw a low voltage alarm even with cells balanced?

Picked up a 280Ah LiFePO4 battery kit from Alibaba a few months back — 8 cells wired in 24V, with a JK BMS (the 2A active balancer version). Been running it through a Victron SmartSolar 100/30 and a Multiplus 12/3000 (yes I know, mismatched voltages — long story, running it at 24V throughout now). Generally it's been solid, but last week I started getting low voltage alarms at around 24.8V even though all 8 cells were showing within about 8mV of each other on the JK app.

Thing is, 24.8V on a 24V LiFePO4 bank shouldn't be anywhere near the low voltage threshold — that's roughly 3.1V per cell which is fine for normal operation. I've got the BMS protection set to 2.85V per cell (22.8V pack) so it shouldn't be tripping anywhere near 24.8V. I checked the actual cell voltages on a multimeter and they matched what the app was showing, so it doesn't seem like a dodgy sensor reading.

Has anyone seen the JK do this? I'm wondering if there's a firmware glitch, or maybe the alarm threshold settings don't save properly after a power cycle. I did update the firmware via the app about a fortnight ago so that's my main suspect right now. Would be grateful for any thoughts before I start poking around in the settings again.

@Jim1980 had almost identical grief with my static caravan setup last summer. Quick question before you go down the rabbit hole — have you checked what voltage the JK is actually reporting per cell vs what a decent multimeter reads directly on the cell terminals?

Mine was throwing spurious low voltage alarms because the BMS sense wires had a dodgy crimp on cell 3. Looked fine visually but was giving the BMS a phantom low reading. Cell was actually fine.

Also worth asking: what's your low voltage alarm threshold set to in the JK app? Factory defaults can be surprisingly aggressive — mine was set to 2.8V which in a 24V string was basically screaming constantly during any decent load spike.

What's your actual cell delta showing in the app during the alarm event?

Watching this thread closely — I've got a JK BMS on my shepherd's hut build and had something similar happen last month.

One thing worth checking: what's your cell interconnect torque? I had a phantom low voltage alarm that turned out to be a slightly loose busbar connection on cell 3. The BMS was reading a false voltage drop under load rather than an actual low cell issue.

Also, are you monitoring individual cell voltages through the JK app during the alarm? That'll tell you pretty quickly whether it's a genuine weak cell or a connection/sensing issue.

@Jim1980 what does your cell delta look like when the alarm triggers — is one cell consistently lagging behind the others or is it random?

@Jim1980 had this exact thing on my camper van build. Check your cell internal resistance readings in the JK app — if one cell is spiking noticeably higher than the others under load, it'll drag that cell's voltage down fast enough to trip the alarm even when resting voltages look fine.

Also worth checking your busbars and cell terminal connections are properly torqued. Loose connections cause resistance issues that mimic a weak cell.

The 2A active balancer is decent but it only kicks in above a certain voltage differential — if the issue is resistance rather than capacity mismatch, balancing won't fix it.

I'd run a proper capacity test on each cell individually before assuming it's a BMS fault. Could just be a dud cell in the batch, sadly not unheard of with Alibaba kits.

@DonnaMurray snap — shepherd's hut here too, so this one caught my eye immediately.

What sorted it for me was realising the JK's low voltage cutoff was triggering on a single cell reading rather than the pack average. One of my cells had slightly higher internal resistance than the others, so under any meaningful load it would sag just enough to trip the alarm even whilst the others looked perfectly healthy.

I nudged the cell undervoltage protection down from 2.90V to 2.80V temporarily whilst I ran a few proper top-balance cycles with a bench power supply. After three full cycles the weakest cell tightened right up.

Worth checking your load at the point of alarm too — my immersion element was pulling the pack harder than I'd accounted for. The JK app's record function showed the exact moment everything went sideways.

@Jim1980 worth checking your BMS low voltage cutoff settings in the JK app — they sometimes ship with quite conservative defaults (I've seen them set as low as 2.8V per cell). If your protection voltage is set too close to your balance start voltage, you'll get phantom alarms even when the pack looks healthy.

Also double-check your cell sense wires are all making solid contact. I had a loose balance lead on cell 6 of my setup that was causing the BMS to read an artificially low voltage on that cell and trip the alarm. Tightened the connector and the problem disappeared overnight.

What's your actual per-cell voltage reading when the alarm triggers? That would help narrow it down considerably — could be a settings issue rather than anything wrong with the cells themselves.

@Jim1980 had something similar on my narrowboat setup — turned out to be a dodgy cell interconnect busbar causing a localised voltage drop that was fooling the BMS into thinking a cell was lower than it actually was.

Grabbed my multimeter and probed directly across each cell terminal (not the busbars) and found a 0.04V discrepancy between what the JK app was reporting and reality. Tightened everything down properly with a torque wrench and problem vanished overnight.

Worth checking your physical connections before diving deep into settings — especially with Alibaba kits where the busbars sometimes aren't torqued properly from factory. The JK BMS is reading what it sees at the sense wires, not necessarily true cell voltage if resistance is in the way! 🔧