Pylontech US3000C not balancing properly after winter - worth recalibrating?

Been dealing with something similar after leaving my setup dormant for about 8 weeks over winter. My Pylontech US2000s came back looking a bit rough — one module was sitting noticeably lower than the others after a full charge cycle, which had me worried.

From what I've gathered, the Pylontechs do need a proper balance charge after extended storage. The recommended approach is to let them fully charge and then hold at absorption for a good while — the built-in BMS should eventually drag the cells back into line, but it can take several cycles rather than just one.

A few questions for anyone who's been through this:

• Did you find the imbalance sorted itself naturally after 3-4 cycles, or did you need to do anything manually?
• Is there any benefit to forcing a lower charge current during the rebalancing process, or does it not really matter?
• Anyone using a Victron Cerbo GX — are there any settings worth tweaking in Venus OS to help the process along?

I've read conflicting things about whether recalibrating via the Pylontech console cable is actually necessary or just overkill if the modules aren't dramatically out of balance. Mine are only about 8-10% apart, so I'm hoping passive balancing through normal use will sort it.

Would be good to hear from anyone running US3000Cs specifically, as I believe they have a slightly different BMS behaviour to the older US2000 range. Has anyone had persistent issues that didn't resolve on their own after a winter layup?

@LDVNomad had something similar happen with my boat setup after it sat unused over a winter stretch. One of my banks came back with a 0.08V spread across cells which the BMS wasn't happy about.

What worked for me was a slow, controlled full charge right up to absorption, then letting it sit at float for a good few hours before cycling it down and back up again. Did that twice and it pulled things back into reasonable balance.

Worth checking whether your Pylontechs are actually out of balance at cell level or just showing a state-of-charge discrepancy between modules — they're different problems. The Pylontech app (via the RS485 cable) will show you proper cell-level data rather than relying on the Victron display which can sometimes be misleading after a long dormant period.

@LDVNomad this is pretty common after extended dormancy — the cells self-discharge at slightly different rates and you end up with drift between modules.

What worked for me with my cabin setup was doing a few controlled full charge cycles through the Victron MPPT rather than just letting it top up passively. Basically force it to absorb properly at the right voltage ceiling and hold it there. The Pylontech BMS usually sorts itself out within 2-3 cycles once it's got enough data to work with.

Worth checking your DVCC settings in VenusOS if you're running a Cerbo — sometimes the charge parameters drift after firmware updates and it ends up never quite hitting proper absorption.

If it's still stubbornly unbalanced after 5 or 6 cycles then I'd be looking more closely at whether one module has a genuinely weak cell rather than just a calibration issue.

Classic Pylontech winter sulk — mine did exactly this after 6 weeks sat in the motorhome on the drive.

The bit nobody mentions: before you even think about recalibrating, check your inter-module comms cables are properly seated. A loose RS485 daisy-chain connection will make a perfectly healthy module look like it's dropped 15% — wasted two hours once convinced I had a dying cell when it was a £3 connector.

If cables are fine, do a slow full charge to 100% then let the Pylontech BMS sit at float for 4-6 hours — it does its own passive balancing during that window. Victron users, set absorption to hold longer than usual via VictronConnect.

@WingAndPrayer is right about the self-discharge variance, but most US2000/US3000 units recover fully without manual intervention if you're patient.

@FormerCop "winter sulk" is genuinely the most accurate diagnosis I've ever seen on here 😂

Can I ask a daft question nobody's addressed yet — does the order you bring the modules back online matter? I've got a similar setup in my van (Fogstar Drift cells but same principle applies) and after my 6-week