Battery backup with SolArk or EG4 inverter and generator

Been looking into this setup for a while now and curious what others have found with these American inverters specifically around generator compatibility.

My main use case is EV charging — I want to be able to keep the car topped up even during outages without hammering a generator constantly. The idea being the battery bank absorbs the generator output efficiently, then the inverter handles the EV charger demand smoothly.

A few questions I keep coming back to:

• Generator frequency tolerance — both SolArk and EG4 seem designed around 60Hz systems primarily. Has anyone in the UK managed to sort the 50Hz compatibility properly, or is it a firmware rabbit hole?
• Battery recommendations — I've seen a lot of EG4 units paired with their own battery ecosystem, but wondering if anyone's running Fogstar or Pylontech packs with these inverters successfully
• Transfer switch behaviour — how seamless is the changeover when generator kicks in? Last thing I want is my EVSE resetting mid-charge

I realise most of these inverters are spec'd for the US market which makes me wonder if there's a genuine case for sticking with Victron here in the UK instead, even at the higher price point. The Victron ecosystem just seems far better documented for our grid standards.

Anyone running either of these setups in Britain? Particularly interested if you've got real-world generator runtime figures — whether a smaller 3kW generator can realistically charge a decent battery bank overnight for morning EV use.

Hey @MoorSeeker, interesting setup you're after! One thing worth flagging specifically with the SolArk and EG4 units — they're designed around 60Hz American grid standards, so you'll want to double-check your generator's frequency output and how the inverter handles 50Hz UK grid input. Some members have had success using these inverters off-grid entirely, bypassing the grid-tie complications altogether, which might actually suit your EV charging use case quite well.

For EV charging specifically, the surge capacity matters enormously — worth looking at what your peak draw will be and whether the inverter's generator input rating can keep up without the unit dropping into fault mode. What battery chemistry are you planning to pair with it?

@MoorSeeker the generator compatibility piece is genuinely where these American units get interesting — and occasionally frustrating. Running my garden office setup taught me that SolArk in particular is quite fussy about generator frequency stability. UK generators outputting a wobbly 50Hz will cause the inverter to disconnect repeatedly.

What sorted it for me was pairing with a decent inverter-generator rather than a conventional open-frame unit — the cleaner sine wave and tighter frequency regulation made the handshake much smoother.

Worth noting too: if EV charging is your priority, look hard at the SolArk's AC coupling limits under generator mode specifically. The peak draw from even a modest EVSE can cause grief that wouldn't show up during normal solar operation.

Victron's ecosystem handles all this more elegantly in my experience, but if you're committed to these units, the generator quality selection genuinely matters more than most people realise.

Bit of a red flag for me tbh — SolArk and EG4 are designed around 120V split-phase US grid standards. You'll be fighting the setup from day one trying to make them play nice with UK 230V single-phase generators and DNO regs.

Victron MultiPlus-II is the obvious answer if you want rock-solid generator integration here. Got one running in my static van alongside a Fogstar Drift battery — handles my Honda EU22i generator handoff without drama.

EV charging on top of that though... what's your target charge rate? Because your battery bank and inverter sizing needs serious thought before anything else. Most folk underestimate how quickly EV charging eats capacity.

What generator are you actually planning to use? That'll dictate a lot.

@ZFS_OffGrid raises the point I was going to make. These units are fundamentally engineered around North American electrical standards — 120/240V split-phase is baked into their architecture, not a setting you tweak.

For EV charging specifically in the UK, you're already dealing with 230V single-phase or 3-phase infrastructure. Bolting a SolArk or EG4 into that alongside a generator creates a compatibility headache that Victron Quattro or Multiplus-II simply doesn't have — they're designed for 230V 50Hz from the ground up.

Generator sync on the Victron units is also very well documented, with proper UPS-mode handover. Critical if you want uninterrupted charging sessions.

I run a Quattro in my static caravan setup and generator compatibility was seamless once PowerAssist was configured correctly.

Why specifically are you looking at the American brands? Price? Features? There might be a UK-native solution that ticks the same boxes.

@ZFS_OffGrid and @BayJason have already covered the voltage architecture issue well, so I won't retread that. What I'd add specifically around EV charging is that even if you do manage to run a SolArk or EG4 on a UK 230V single-phase setup with workarounds, you'll likely find the charge rates disappointing or inconsistent — particularly with Type 2 EVSE units that expect clean stable 230V. The inverter's internal frequency and voltage regulation behaviour under generator input can get a bit choppy, and some EVSE wallboxes are surprisingly fussy about that. Have you considered units like the Victron Quattro or Solis hybrid range instead? They're designed natively for 230V 50Hz and have solid generator passthrough logic. Might save you a fair few headaches. What generator are you planning to pair with this, out of curiosity?