Ev charger problem above 15 Amp

Bit of a niche one this, but wondering if anyone else has hit a wall with EV charging on an off-grid setup?

I've been mulling over whether to add an EV charger to my cabin setup — currently running a Victron Multiplus-II 48/5000 with a Fogstar Drift 10kWh battery bank — and I keep reading about people hitting current limits that seem to be more about the inverter struggling than any actual fault.

Specifically, what happens when you try to push above 15A from an inverter-based system? Is this a Victron EVCS thing, or does it crop up with other chargers too? My gut says the inverter's starting to sweat at that point, especially if there's any other load running simultaneously — kettle, lights, whatever.

A few questions for the hive mind:

• Has anyone successfully run an EV charger above 15A consistently from an off-grid inverter without it throwing a wobble?
• Is current limiting in the EVCS software the right approach, or does it need sorting at the Multiplus level via ESS settings?
• Does battery bank size/C-rate make a significant difference here, or is it purely an inverter headroom issue?

I'm not in any rush — the cabin isn't exactly hosting a Tesla fleet — but if I'm going to do this properly I'd rather understand the ceiling before I start throwing money at cables and hardware.

Anyone been down this rabbit hole already?

@Robbo the classic "works fine until it doesn't" scenario with EV chargers off-grid.

The core issue is that most EVSE units handshake with the car via the pilot signal and negotiate current dynamically — below roughly 15-16A many cars simply refuse to charge at all, or throw a fault rather than throttling back gracefully.

What inverter are you running? This matters enormously. My Victron Multiplus-II handles the inrush reasonably well, but cheaper inverters often can't sustain the startup surge a Type 2 charger demands, which causes the pilot negotiation to collapse mid-handshake.

A few options worth investigating:

• Ohme or Zappi — both support reduced-rate charging down to 6A
• Set your EVSE's DIP switches to 8A if it has them
• Victron's dynamic current limiting via ESS

What's your battery bank capacity? That changes the conversation considerably.

@Robbo this bit me hard when I was spec'ing up my van build. EV chargers are notoriously fussy about supply quality — they're looking for a rock-solid sine wave and stable frequency before they'll even handshake properly.

The 15A ceiling you're hitting is almost certainly your inverter going into current limiting rather than a charger fault. What inverter are you running? A Victron Multiplus will let you set the input current limit precisely, but cheaper units just throttle unpredictably and the EVSE interprets that as a fault.

Worth noting: most Type 2 EVSEs won't negotiate below 6A (1.4kW), so you need genuine headroom above that or the whole session collapses. For a cabin setup I'd be looking at a dedicated solar-to-EV controller rather than routing through your main inverter at all.

Great topic @Robbo. One thing worth adding that nobody's mentioned yet — have a look at whether your inverter supports a current limit setting, sometimes called "AC input current limit" or similar. Some of the better Victron and SMA units let you throttle the output so the EVSE never sees more than a set amperage, which can help trick it into behaving.

Also worth considering a proper EVSE rather than a basic granny charger — some like the Zappi or Ohme have more tolerance for fluctuating supply conditions and can ramp down gracefully rather than just tripping out.

What inverter are you running currently? That'd really help narrow down your options. Some older or cheaper units just genuinely can't maintain the waveform quality EVSEs expect, in which case you might be fighting a losing battle without an upgrade.

Great points from everyone above. One thing I'd add — have you looked at the Zappi charger by myenergi? It's got an eco mode specifically designed for variable/weak supplies and plays much nicer with off-grid setups than most mainstream EVSEs. That said, you'll still want to check your inverter's continuous output rating rather than its peak figure — manufacturers can be optimistic with those numbers. @CrispyRigger's point about inverter compatibility is spot on too. What inverter are you currently running @Robbo? That'll make a big difference to what's actually achievable. Some folk in similar situations also have luck simply throttling the charge rate right down to 6A overnight when battery bank is fully topped up from solar. Slower, but it works.