EVCS starting with low solar

Anyone else had trouble with an EV charger trying to start up when solar's barely doing anything?

Running a Victron setup on my shepherd's hut site — Cerbo GX, couple of panels, Fogstar lithium bank. Just got an EVCS NS installed and updated to the latest firmware. Set it to Auto Mode so it should theoretically only charge when there's surplus available.

Problem is it seems to want to start the charging session even when generation is really low — like early morning or heavy cloud cover. Pulls the batteries down before solar can catch up. Not what I had in mind at all.

A few things I'm not sure about:

• Is there a minimum threshold I can set somewhere in the EVCS config, or does it pull that from the Cerbo?
• Does Auto Mode actually respect battery state of charge, or is it purely based on available PV watts?
• Anyone know if the Cerbo GX integration is doing what it's supposed to — mine says it's communicating but I'm not 100% convinced it's actually influencing charger behaviour

The Cerbo is on current firmware too so shouldn't be a compatibility thing. I've had a poke around the settings but it's a bit overwhelming and the documentation isn't exactly crystal clear for an off-grid scenario — most of it seems written assuming you're grid-tied with solar on top.

Would really appreciate if anyone's cracked this. Ideally I want it to not even attempt a charge unless batteries are above say 80% and there's decent surplus coming in.

@AnneWatson had exactly this on the narrowboat last spring. The EVCS kept attempting to initialise at dawn when the panels were producing maybe 40W between them — just enough to wake the system but nowhere near enough to actually sustain a charge session. Killed the batteries faster than you'd believe.

What sorted it for me was setting a minimum SOC threshold in the Cerbo GX before the charger was even allowed to request current. I think I've got mine at 65% now.

Also worth checking your minimum current setting on the charger itself — some units will keep retrying if they can't hit the floor amperage, and that retry loop is surprisingly hungry. The Victron ESS assistant can also help schedule charging windows if your site has any grid fallback at all.

@AnneWatson this is a classic issue with EV chargers — they often have a fairly high minimum startup draw that your panels simply can't meet at low irradiance.

A couple of things worth checking:

• Minimum SOC threshold — in your Cerbo GX, you can configure the EVCS not to activate below a set battery SOC (e.g. 60%). Stops it attempting to initialise on a half-empty bank at dawn.
• Scheduled charging — lock it to a midday window when your array is actually producing.

On my static caravan setup I also added a minimum grid/battery power condition in the Victron ESS assistant before allowing the charger to draw anything. Made a huge difference to nuisance tripping.

Worth checking what firmware your Cerbo is running too — there were some EVCS integration fixes in recent releases.

Sounds like the EVCS is basically trying to wake up before your system's had its morning coffee ☕

Worth checking whether your Victron setup supports minimum SOC thresholds before enabling the EV charger output — you can set rules in VRM or Node-RED so the charger circuit only gets power once your Fogstar bank is at, say, 50%+ and solar input is above a certain wattage.

I've done something similar on my garden office setup — had a inverter-hungry device causing chaos at low irradiance until I gated it properly through the Cerbo.

Does your EVCS integrate with the Cerbo directly via Modbus or are you running it as a dumb load? That changes your options considerably.

@AnneWatson the Victron ESS assistant has a "minimum SOC" threshold but what you actually want here is the grid setpoint / AC input current limit tied to your EVCS trigger conditions.

In VRM / Cerbo, look at the EVSE settings under "scheduled charging" or use Node-RED if you've got it enabled — you can write a simple automation that only enables the charger output once your battery SOC is above, say, 60% and PV yield is sustaining above a threshold wattage.

I did something similar on my van conversion's shore power circuit to stop parasitic loads kicking in at first light and hammering the cells before the panels were producing meaningfully.

Also worth checking your EVCS minimum activation current — some units won't even attempt a handshake below 6A, which on two panels in low light is borderline.