Overcharging, BMS CCL not respected by Multiplus II when other chargers are active

Been scratching my head over this one myself. Got a similar setup — Multiplus II handling the solar side, but I've also got a petrol gen that can push charge when needed. Battery's got a solid BMS with CCL limits, but the Multiplus seems to ignore them when the gen's running.

My theory is it's a communication gap. The Multiplus reads the CCL from dbus-serialbattery, yeah, but only for its own charging circuit. Once you've got multiple charge sources active, it gets confused about who's responsible for respecting the limits. The gen charger doesn't know about the BMS restrictions, and the Multiplus doesn't coordinate between them properly.

I've been testing whether prioritising one charger at a time helps — basically programming the gen to only activate when solar's minimal. It's clunky but it works. The alternative I'm considering is a relay that shuts the gen charger down if the Multiplus detects the battery's hitting its CCL.

Has anyone else run into this? Wondering if it's a Venus config issue or genuinely a limitation of how multiple chargers talk to each other. My battery's LiFePO₄ and I'm paranoid about overcharging it, so I'm not keen on ignoring this.

Would be interested to hear how others are handling dual-charging scenarios without risking the pack.

Ah, the classic "too many cooks" scenario with your chargers. Multiplus II can be a bit stubborn about respecting external BMS limits when it's not the only voice in the room — especially if your genset charger isn't talking nicely to it.

Have you checked if VE.Can is properly configured between your Multiplus and BMS? Mine took a good hour of head-scratching before I realised the CCL wasn't actually being communicated. Also worth verifying your gen charger isn't just hammering voltage without honouring the charge current limit — cheap units absolutely do this.

What BMS are you running? Some play better with Victron's ecosystem than others. If it's not a Victron-native setup, you might need to manually set conservative charge limits and accept you'll never fully utilise that genset.

Spot on about the "too many cooks" issue. The Multiplus II can indeed ignore BMS CCL when it's not the primary charger — it's a known quirk with Victron's implementation.

What's your actual setup? Are you running the gen charger separately, or trying to sync them? If it's the latter, you'll want to look at:

• Assistant mode on the Multiplus — forces it to respect external charger priority
• VE.Bus BMS integration if you've got one — that'll enforce CCL across all chargers properly
• Check your ESS settings aren't overriding the BMS limits

I had similar grief with my motorhome setup until I realised the gen charger was maxing out whilst the Multiplus was still pushing hard. Ended up using a dedicated Victron MPPT for solar and letting a separate charger handle the gen input, with the BMS wired through a VE.Bus controller.

What's your battery spec and current charger configuration?