Pylontech + MPII: Effective charge voltage exceeding 52.4V and reaching 54.4V

Bit of an odd one this, and curious whether others running Pylontech with a Multiplus-II have seen similar.

On my narrowboat I've got a Multiplus-II 48/3000 paired with 4x Pylontech US3000C batteries and a couple of Victron SmartSolar MPPTs. The Pylontechs are supposed to top out at 52.4V, but I've occasionally logged the effective charge voltage nudging past that — sometimes touching 53.8–54V briefly before settling back down.

Not quite the 54.4V some are reporting, but close enough to make me pay attention.

From what I can work out, it seems to happen when:

• The MPPTs and the MPII are both pushing charge simultaneously
• ESS is doing something clever (or not so clever) in the background
• The BMS hasn't quite communicated fast enough to clamp things back

I've got mine set up with DVCC enabled and the Pylontech talking to a Cerbo GX via CAN bus, which should let the BMS dictate charge limits properly. And most of the time it does. But there's clearly some lag or edge case where voltage creeps up temporarily.

Has anyone pinned down whether this is a firmware issue, a DVCC config problem, or just the nature of how ESS coordinates multiple charge sources?

Worth noting for those of us off-grid or on boats — we don't always have a stable grid reference for ESS to anchor to, which might be making things worse compared to a typical house install.

Would be interested to hear what firmware versions people are running on both the MPII and the Cerbo when this crops up.

@YorkshireVanLifer classic Victron doing its "I know best" routine 😄

This is actually a known quirk — the MPII can temporarily push above the Pylontech's stated 52.4V during absorption if the DVA (Dynamic Voltage Algorithm) is doing its thing, or if you've got a slight calib

Interesting one — does this happen on solar charge cycles too, or specifically when the MPII is doing absorption from shore/generator power?

Asking because I've seen my Fogstar Drift cells behave differently depending on charge source. Wondering if the Pylontech BMS is actually requesting the higher voltage via CAN comms at certain SOC points, rather than the MPII freelancing on its own.

Have you checked what voltage the BMS is actually advertising in VRM? There's a difference between:

• CVL (charge voltage limit) — what the BMS tells the inverter it wants
• What the MPII actually delivers

If your CVL is showing 52.4V but the measured voltage creeps to 54.4V, that's a different problem than the BMS itself requesting 54.4V. Worth logging a few charge cycles on VRM and screenshotting the DVCC data.

Good timing on this thread — I saw almost identical behaviour when I first commissioned my cabin setup with a Multiplus-II 48/5000 and Pylontech stack.

What sorted it for me was making absolutely sure the DVCC settings in VenusOS were properly configured, with SVS (Shared Voltage Sense) enabled. Without that, the MPII was effectively flying blind on voltage and doing its own thing.

Also worth checking: are your CAN bus termination resistors correct? I had a dodgy connection once that caused the BMS comms to drop intermittently — the moment Pylontech stopped talking, the MPII fell back to its own charge profile and cheerfully climbed past 52.4V.

@JoeTurner to answer your question — in my experience it's more pronounced during AC-coupled absorption rather than solar, presumably because the MPII can throw more current at it faster.