EV Charger on AC-Out and ESS

Been mulling this one over for a while and thought I'd throw it out here.

Running a Victron MultiPlus-II 48/5000 in my setup — Cerbo GX, Fogstar Drift lithium bank, ET340 on the grid tie — and I've been experimenting with hanging my EV charger off the AC-Out-1 rather than feeding it directly from the grid.

The logic being: let the ESS do its thing, prioritise solar, and have the car take whatever's left over without pulling from the DNO unnecessarily. Sounds elegant in theory.

In practice though, I keep running into the inverter's current limits acting as a ceiling. On a cloudy Pennine afternoon (so... most afternoons), the MultiPlus is juggling the house loads and the EV charger simultaneously, and it gets a bit twitchy. The ESS assistant seems to hesitate before deciding whether to throttle back or pull from grid.

A few questions I'm wrestling with:

• Has anyone successfully used Node-RED on Venus OS to dynamically cap the EV charger based on available solar headroom?
• Would an EVSE with proper OCPP support behave better than a basic tethered unit in this scenario?
• Is AC-Out-2 actually a cleaner solution here, so non-essential loads drop during low battery conditions automatically?

I think AC-Out-2 is the right answer but I'd lose the always-on convenience for the missus when she needs a quick top-up.

Anyone navigated similar compromises? Curious whether this is a configuration rabbit hole or a genuine limitation of the platform.

@PennineCamper looks like your post got cut off — what's the actual question? Curious where you're going with this though as I've been pondering something similar for my boat setup.

Are you asking whether it's safe to run an EV charger on AC-Out 1 vs AC-Out 2, or something around ESS mode prioritisation when the charger kicks in? The reason I ask is I've got a Victron MultiPlus-II 48/3000 and I'm trying to work out if my solar input can realistically handle a decent EV charge rate without the grid constantly cutting in to assist.

Also wondering if anyone's had issues with the ET340 metering going haywire when a big inductive load like an EV charger starts and stops — seems like it could confuse the ESS logic?

@PennineCamper yeah, finish the thought! Though I reckon I can guess where you're headed — you want to know if running an EV charger on AC-Out-1 will cause the MultiPlus to have a meltdown when the grid drops out, or whether ESS will gracefully limit charge rate to protect the battery bank.

Had exactly this scenario with my shepherd's hut build. I was pulling a small EV charger through the inverter and the MultiPlus handled it fine, but you absolutely need to set the AC input current limit sensibly in VEConfigure and lean on the DVCC current limiting to stop the Fogstar cells getting hammered.

The ET340 placement matters enormously here too — where exactly have you put it? That'll determine how ESS sees the load and whether it's factoring the charger draw into its grid setpoint calculations correctly.

@PennineCamper classic cut-off 😄 finish your thought!

But yeah I've been down this rabbit hole on my boat. AC-out EV charging with ESS is doable but there's a few gotchas depending on your grid code settings and whether you've got AC input current limits configured properly.

The MultiPlus-II will try to manage it but a sudden 7kW EVSE load can catch it off guard if your ESS assistant isn't tuned right — I had some nuisance tripping early on.

What's your battery capacity and grid connection situation? That changes the answer quite a bit. Also are you on 3-phase or single? The ET340 suggests maybe 3-phase but running a single MultiPlus-II...

Curious what you're actually trying to achieve — pure self-consumption, backup, or just cheaper overnight charging?

Really relevant thread for me — got a tiny house setup I'm planning and EV charging was on my list of questions too.

@BoatLouise did you find the MultiPlus struggled with the surge when the EVSE initialises? I've read the handshake between charger and vehicle can cause brief spikes even before actual charging load kicks in.

Also wondering — does ESS mode affect how the Multi handles AC-out loads when grid drops out? Presumably the EV charger just gets cut if you've got it set to not island, but what if you want it to island and the EV is mid-session?

Has anyone used a Victron Cerbo automation to shed the EV load first before the system hits its current limit? Feels like that'd be the clean solution rather than manually juggling amps.