Multi RS Solar: Balancing 3 phases incorrectly during 'Keep batteries charged'

Seen something a bit odd with my Multi RS Solar lately and wondering if anyone else has had this.

Running a 3-phase setup in the static van site hookup — had it on Keep Batteries Charged mode overnight and noticed the phases were doing completely opposite things. One leg was pulling hard from the mains whilst another was simultaneously pushing back out. Felt like the inverter was fighting itself.

Checked the Victron Connect logs and sure enough, L1 was importing a decent chunk whilst L2 was exporting roughly the same amount back. Net effect on the battery was probably fine, but it's clearly not right — that's wasted energy and potentially some annoyed DNO questions if it keeps happening.

A few things I'm wondering:

• Is this a firmware issue or a config thing I've messed up?
• Does the Multi RS even balance phases properly in that mode, or is it treating each phase independently without looking at the overall picture?
• Anyone running ESS vs Keep Batteries Charged on 3-phase — noticed a difference?

My gut says it's the phase compensation settings somewhere in VE.Config but I've gone round in circles. Victron's documentation on 3-phase balancing isn't exactly crystal clear for off-grid/hybrid setups.

Worth noting my Cerbo GX firmware is fairly recent, updated it about a month ago — wondering if something shifted in that update.

Anyone dealt with this? Be good to know if it's a known quirk or something I need to dig into properly. Could be a setting I've overlooked but a fresh pair of eyes always helps on these things.

Hey @IslandCruiser, yes I've seen something similar on my 3-phase setup! In Keep Batteries Charged mode it does seem to struggle with phase balancing — I noticed one phase hogging most of the charge current whilst the others sat doing relatively little.

Worth checking a couple of things: firstly, make sure all three units have identical firmware — even a minor version mismatch can cause odd behaviour in the phase coordination. Secondly, double-check your VE.Bus cable connections between the units, as a dodgy cable can disrupt the master/slave communication.

Also, is your grid supply itself balanced? Sometimes what looks like a Multi issue is actually uneven incoming voltages confusing the system.

Have you raised it with Victron's community forum? They're usually quite responsive and it could be a firmware bug worth flagging. What firmware version are you running currently?

Seen this on my static caravan backup setup. The Multi RS Solar in 3-phase can struggle with phase balancing during Keep Batteries Charged because it's essentially treating each unit somewhat independently rather than coordinating load compensation properly.

Worth checking a few things:

• VE.Bus firmware — make sure all three units are on identical firmware versions, even a minor mismatch causes odd balancing behaviour
• In VEConfigure, check your AC input current limits are identical across all phases
• Some users report that switching briefly to Optimised with BatteryLife and back resolves a temporary sync issue

Also check the ESS Assistant settings if you're running that alongside. I had a situation where the phase compensation setting was set to individual phase rather than total of all phases — that'll cause exactly what you're describing.

VRM portal graphs will show you the per-phase current draw clearly if you need to confirm which phase is misbehaving.

Hey @IslandCruiser, interesting one this. Just to add something nobody's mentioned yet — have you checked whether your phase master/slave configuration is set correctly in VictronConnect? I had a similar quirk where the master unit was on L2 rather than L1, which caused some odd balancing behaviour particularly in Keep Batteries Charged mode. The master handles the overall charge logic and if it's not on the expected phase things can get a bit wonky.

Also worth checking your firmware version — there were some known phase balancing improvements in recent Multi RS Solar updates. Victron's changelog is worth a browse.

@LindaCross66 and @RetiredPlumber — curious whether your setups had any wiring asymmetry between phases? Sometimes unequal loads on standby can exaggerate the issue too. Would be useful to compare notes if you've got VRM data you can share.

Good shout from @Dave1984 on the phase synchronisation angle — that's often overlooked.

One thing nobody's touched on yet: check your ESS assistant version if you're running that alongside Keep Batteries Charged. I had a quirky interaction in my garden office 3-phase trial where an outdated assistant config was causing L2 to lag behind L1/L3 during absorption. Victron Connect showed balanced voltages but the actual charge currents per phase were noticeably skewed.

Worth pulling the VRM portal advanced graphs and plotting per-phase AC current over time — you'll see the imbalance clearly if it's there. Victron's CCGX/Cerbo logging is granular enough to catch it.

Also double-check your Multi RS firmware is on the latest stable release. There were some 3-phase balancing fixes pushed out in recent builds that specifically addressed Keep Batteries Charged behaviour.