Multiplus blijft stroom uit net halen, terwijl er zonne-energie voldoende is

Been running a similar ESS setup here and hit a frustrating issue I wanted to throw open to the group.

I've got two Multiplus-II 5kVA units running in parallel, Cerbo GX, a Carlo Gavazzi EM24 grid meter, and a decent lithium bank with a JK BMS. Solar production is clearly visible in VRM — sometimes pushing 3–4kW — but the system keeps drawing from the grid regardless. Batteries are at a healthy SOC, nothing's throttled, and yet the Multiplus seems almost reluctant to use what's available.

A few things I've already checked:

• ESS mode is set correctly (Optimise with BatteryLife)
• Grid setpoint is at 0W (or as close as I can get it)
• AC input current limit hasn't been accidentally cranked up
• BMS comms look healthy via the Cerbo

My hunch is it might be something around the BMS not asserting DVCC properly, or perhaps the grid meter response time causing the system to "prefer" grid as a buffer. The JK BMS is communicating over BMS-Can but I wonder if there's a configuration mismatch.

Has anyone else seen this with parallel Multiplus units specifically? I've read a few threads suggesting parallel configs can behave oddly with ESS charge/discharge limits. Fogstar cells on the battery side if that matters.

Would be good to hear from anyone who's cracked this — feels like it should be straightforward but clearly isn't.

@Taffy62 classic ESS "keep batteries at X%" governor being too aggressive — check your minimum SOC setting in Venus OS, because if it's set above your actual battery SOC the system deliberately pulls from grid even with solar screaming at it.

Also worth checking:

• Grid setpoint in ESS menu (should be ~50W, not 500W)
• EM24 comms — if Modbus is glitching, Cerbo loses grid visibility and defaults to import
• Are both Multiplus-II units on the same phase assistant firmware?

My motorhome parallel setup did something similar until I realised VRM was logging fine but the actual ESS assistant was running an older version on unit #2 — Victron's parallel config is fussier than they'd have you believe.

@Taffy62 worth checking your AC input current limit alongside what @FormerCop mentioned — if it's set too low, the ESS algorithm will actually blend grid and solar rather than prioritising solar exclusively, because the inverter can't ramp fast enough to cover transient loads without breaching that limit.

Also verify your EM24 is wired correctly for grid-parallel — I've seen installs where the meter was measuring on the wrong side of the consumer unit, causing the Cerbo to miscalculate import/export. Venus OS logs will show you exactly what the system thinks it's importing vs what your supplier meter records.

On my own narrowboat setup I run ESS with Optimised (with BatteryLife) disabled entirely, which gives far more predictable solar-first behaviour — might be worth toggling that off temporarily to isolate whether BatteryLife is the culprit.

Good shout from both above, but one thing nobody's mentioned yet — check your DVCC settings, specifically the SVS (Shared Voltage Sense) and SCS (Shared Current Sense) options.

If those aren't enabled properly across your parallel units, the Cerbo can get confused about actual battery state and pull from grid unnecessarily even when SOC looks fine on paper.

Also worth checking the ESS mode itself — Optimised with BatteryLife behaves very differently to Keep batteries charged or Optimised without BatteryLife. I had mine on the wrong mode for weeks and couldn't work out why the Multiplus kept importing during peak solar hours.

What firmware version are you on? There were some ESS scheduler bugs in older Venus OS builds that caused exactly this kind of behaviour.

@CableTieWarrior all solid points above, but on my boat setup I had something similar and it turned out to be the grid setpoint in ESS being set to feed a small amount from grid rather than zero. Even 50W feed-in from grid preference can confuse things when solar's abundant. Worth checking that figure in the ESS assistant — mine was defaulting to something odd after a firmware update. Also double-check your scheduled charging windows aren't accidentally active. Victron's interface buries that stuff and it'll override everything else regardless of SOC or solar availability.

Great points already from @CableTieWarrior and @MandyGrant — but one thing nobody's flagged yet is ESS mode scheduling.

If you've got a scheduled charge window active in the Cerbo, the Multiplus will stubbornly pull from grid during that window regardless of what the solar's doing. Caught me out badly last summer in the motorhome — couldn't work out why my Victron was ignoring glorious Welsh sunshine and hammering the hookup instead.

Check Settings → Scheduled Charge in VRM or the remote console and make sure you haven't got an accidental window enabled. Also worth verifying your minimum SOC setting under ESS — if battery is sitting just below that threshold, the system will prioritise grid to top it up before allowing solar to take over properly.