Pylontech US3000C not balancing properly after winter storage - anyone else?

Had this exact issue with mine after leaving the static over winter. Two of the cells in the battery bank were sitting noticeably lower than the rest — took about 3-4 full charge/discharge cycles before things levelled out properly.

The Pylontech BMS does passive balancing only, which means it's slow — it can only bleed off charge from higher cells rather than actively redistributing it. After months of sitting in a partially discharged state in the cold, it's not surprising things drift a bit.

A few things that helped me:

• Charge slowly first — don't just hammer it at full current straight away
• Let it hit 100% and hold there for a couple of hours so the BMS has time to do its thing
• Check your Victron DVCC settings if you're running a Cerbo/CCGX — make sure SVS and SCS aren't fighting the battery's own voltage requests
• Worth checking the Pylontech console app if you haven't already, just to see the individual cell voltages rather than relying on aggregate SOC figures

One thing I would flag — if it's still badly unbalanced after 5+ cycles, that's worth digging into more seriously. Cold temperatures can permanently reduce capacity in lithium cells if they were stored at a very low SOC. What voltage were they sitting at when you came back to it?

Has anyone else noticed the US3000C seems worse for this than the older US2000B? Curious whether it's a cell chemistry thing or just confirmation bias on my part.

Yeah, seen this with Pylontechs before. The BMS goes into a sort of hibernation state during long storage and loses track of cell states — classic after a winter sitting idle.

Few things worth trying if @BayJason's 3-4 cycles doesn't fully sort it:

• Drop your charge voltage slightly (around 51.8V) for a few cycles, then bump it back up to full — forces gentler balancing
• Check your Victron DVCC settings if you're running one; sometimes the charge current is too aggressive post-storage for the BMS to keep up
• Pylontech's own BMS tool (via RS485/USB) lets you see individual cell voltages — worth checking if one cell is genuinely drifting vs just slow to report

Mine did something similar after sitting over January. Sorted itself by cycle 5 but I was watching it closely. If it's still showing >50mV spread after 6-7 cycles I'd be raising a warranty query.

Nothing wakes up a lazy Pylontech quite like a good old-fashioned "have you tried turning it off and on again" — my Victron kept throwing low SOC warnings at mine until I forced a full top-balance via the DVCC settings, sorted it in two cycles flat.

Good timing on this thread — dealing with something similar on my boat right now. Got a pair of US3000Cs that sat over winter and I'm noticing one module consistently reading about 50mV lower than the other at the top of charge.

Quick question for anyone who's been through this: does the balancing eventually sort itself out passively if you just leave it connected and cycling, or is it worth forcing it by holding the batteries at absorption voltage for an extended period?

Also — my Victron MPPT is set to the Pylontech recommended charge profile, but I've seen some people suggest tweaking the absorption time slightly to give the BMS more opportunity to balance. Is that safe or does it risk pushing outside what the BMS will tolerate?

Has anyone actually pulled data from the Pylontech console app to track how many cycles it takes to fully resolve?

Had this on the narrowboat last spring after a long winter layup. What worked for me was dropping the charge voltage right back to around 51V for a couple of cycles rather than letting the Victron MultiPlus push straight to absorption. Gives the weaker cells a chance to catch up without the BMS tripping everything out prematurely.

Worth checking the Pylontech's own app if you've got the console cable — you can see individual cell voltages and confirm whether it's genuine imbalance or just the BMS being confused about state of charge after sitting idle.

@OakSeeker on a boat you've also got the added complication of temperature variation in the bilge affecting cell behaviour. If yours were sitting cold all winter that'll compound the issue.

Mine sorted itself within a week of regular cycling once back in use.