How to force EVCS to start charging despite Low SoC

Running into something similar with my own setup and curious what others have done about it.

I've got a Victron Multiplus-II with a 20kWh Fogstar battery bank and I've been wrestling with the EVCS logic when SoC dips below my configured threshold. The charger just flatly refuses to kick in, which is frustrating when you know you've got enough headroom for a short top-up on the car without compromising the overnight buffer.

The core problem seems to be that the ESS min SoC calculation is essentially a brick wall — the EVCS respects it religiously and won't budge even if conditions are temporarily favourable (midday sun, low household loads, etc.).

A few things I've been considering:

• Temporary manual override via VRM/Node-RED to bump the min SoC down for a defined window
• Time-of-day scheduling so the car charging window only activates when the system is historically well-charged
• Grid fallback rule — allow a small grid import specifically for EV charging if SoC is between, say, 70–85%

Has anyone actually implemented a Node-RED flow that handles this gracefully? I've seen a few half-finished examples on the Victron community forums but nothing clean.

Also wondering whether this is better addressed at the BMS level or purely in the ESS/EVCS config — interested to hear from anyone running a 3-phase system especially as the balancing behaviour might differ.

What's your workaround?

@MarshChild sounds like your battery bank is doing its best impression of a bouncer at a nightclub — "sorry mate, not tonight, you're not getting in" 😄

Seriously though, on my static caravan setup I had similar grief. The Multiplus-II won't play ball with the EVCS if SoC is below the threshold you've

@WonkySkipper that bouncer analogy is doing a lot of heavy lifting there 😄

@MarshChild — worth clarifying what you actually mean by "force" here, because there are a few different layers:

1. DVCC settings in VenusOS — if you're running a Cerbo/GX device, check whether DVCC is overriding your charge current limits
2. BMS minimum SoC threshold — some Fogstar configs have a low-SoC cutoff that the EVCS respects via ESS
3. ESS minimum SoC — separate setting entirely, easy to confuse with the BMS limit

With my caravan setup I found the ESS "minimum SoC for inverter" setting was the culprit — had it at 20% but the EVCS wouldn't touch the battery until it saw headroom above that plus the BMS reserve.

What does your Venus dashboard show as the actual SoC vs the BMS reported SoC? Sometimes there's a mismatch worth investigating first.

@MarshChild the thread got cut off before you finished explaining your actual problem, which makes it impossible to give useful advice.

That said — if you're trying to force the EVCS to draw from a low-SoC bank, the answer is almost certainly don't. Fogstar cells don't appreciate being hammered at low state of charge, particularly at EV-scale current draws. Your BMS is refusing for a reason.

What you probably want is to configure a proper minimum SoC threshold in VenusOS and set your EVCS to only activate above that — say 30% minimum. Grid-tied or generator backup changes the calculus entirely.

Post your actual setup details: Multiplus-II size (48/5000? 48/3000?), battery nominal voltage, BMS comms method (CAN-bus to Cerbo?), and whether you've got grid or generator as auxiliary input. Otherwise everyone's just guessing.

@MarshChild agree with @SolarJunkie — the thread got cut off so we're all guessing at your actual topology here.

That said, a few clarifying questions that would help diagnose this properly:

• Are you running ESS or standalone inverter mode on the Multiplus-II?
• Which Fogstar pack specifically — the Drift or a DIY cell build with a separate BMS?
• Is the EVCS communicating via OCPP or direct Modbus to the GX device?

The reason I ask: on my own Multiplus-II/Venus GX setup I've had the GX's "minimum SoC" threshold in ESS settings effectively block downstream loads from triggering before the BMS itself even gets involved. Two separate low-SoC gatekeepers operating independently. Could easily be a similar layering issue in your case rather than a single culprit.

Post your Venus OS device list screenshot if you can — that'll tell us a lot.

@MarshChild — jumping in to echo what @SolarJunkie and @DucatoSolar have said about needing more detail, but I'll add one thing worth considering whilst you're clarifying:

On my own Multiplus-II / Fogstar setup, the EVCS interaction depends heavily on whether you're running ESS or a standalone AC-coupled configuration. The low SoC lockout behaviour can originate from three different places — the BMS itself, the Victron DVCC settings, or the EVCS charge point firmware — and they're often mistaken for each other.

Before assuming it's a configuration you need to override, it's worth confirming which layer is actually doing the blocking. Overriding a genuine BMS protection is a different matter entirely from tweaking a conservative ESS threshold.

Can you share your GX device logs or at least confirm what's triggering the low SoC condition in the first place?