Anyone else had their Daly BMS cut out randomly even when cells look balanced?

Been having a strange one with my 280Ah LiFePO4 pack (8 cells in 24v configuration) that I built up last autumn. Running a Daly 100A smart BMS and everything looks fine on the app — cells sitting nicely between 3.28v and 3.31v most of the time, no obvious drift. But every week or so the BMS just drops out completely. Whole pack goes dead, inverter shuts off, the lot. Reconnect the balance lead or give the main connector a wiggle and it comes back within a minute, no error codes, nothing logged.

I initially thought it might be a loose connection so I've gone back over every terminal with a torque wrench (8Nm on the cell busbars, 6Nm on the BMS lugs) and checked for any heat discolouration. Everything looks solid. It's a 3kW Victron Multiplus running the loads, pulling maybe 60-70A peak when the immersion kicks in, which should be well within the BMS rating. Ambient temp in the battery box is usually around 12-15°C so I don't think it's thermal either.

Has anyone seen this with the Daly smart range specifically? I'm wondering if it's a firmware wobble, a dodgy UART connection to the Bluetooth module, or something else entirely. Tempted to try the JK BMS that keeps getting recommended on here but wanted to see if there's a fix before I spend another £80.

Reply by Foggy:

@Ian1968 Classic Daly behaviour this — worth checking your temperature sensor connection if you've got one wired in. A dodgy or intermittent temp sensor reading can trigger a phantom protection cutout even when everything else looks healthy on the app. The app doesn't always flag it clearly either, which is the frustrating part.

Also, what's your load profile like when it cuts? I had almost identical symptoms on a similar pack and it turned out the BMS was seeing momentary current spikes that the app's polling rate was too slow to catch. Dropping my inverter's low battery cutoff helped mask it temporarily but the real fix was adding a small capacitor bank across the terminals to smooth things out.

What firmware version are you running on the Daly? Some earlier versions had known glitches worth updating past.

Reply by Nessa55:

@Ian1968 I had almost identical behaviour with my Daly 150A last winter. Worth checking your balance lead connections — even a slightly loose one on the middle cells can confuse the BMS into thinking there's an imbalance that isn't really there. Also, what's your charge current set to in the app? Daly's default overcurrent protection can be surprisingly aggressive and occasionally trips even when you're technically under the rated limit. Try dropping the protection threshold down a notch and see if the cutouts become less frequent. Mine turned out to be a combination of a slightly corroded balance connector AND the overcurrent sensitivity — sorted both and it's been rock solid since. Have you got the Daly PC software as well as the app? Sometimes it shows fault history that the phone app misses. 🙂

Reply by Jim1999:

@Ian1968 One thing I'd add that nobody's mentioned yet — check your cell interconnect busbars are properly torqued down. I had mystery cutouts on my own 24v pack last year and it turned out one busbar bolt had worked slightly loose over time. Under load the voltage drop across that dodgy connection was enough to confuse the BMS into thinking a cell was sagging badly.

Also worth having a look at your negative cable connection on the BMS itself. Daly units can be a bit sensitive to any resistance in that path.

Try putting a decent clamp meter on each cell group under a proper load — something that'll pull 40-50A — and see if any individual cell voltage drops away more than the others. That'll tell you pretty quickly whether it's a connection issue or a genuine weak cell. Good luck with it!

Reply by MandyPalmer56:

@Ian1968 Something worth looking at that hasn't been mentioned — check your BMS communication cable connections, particularly if you're using the UART port for the app. A loose or dodgy connection there can cause the BMS to throw protection trips that look completely random. Also, what's your load like when it cuts out? If you're running anything with a significant inrush current (inverter, pump, motor), the Daly can be quite sensitive to instantaneous overcurrent spikes even if your sustained draw is well within spec. Try logging the exact state of charge percentage when it trips — if it's consistently happening around the same SOC point, that narrows things down considerably. The Daly app's history log is actually decent for this if you haven't already had a poke around in there.