Proper way to parallel two hybrid solar charger/inverters fro 120VAC 50amp rv

Worth noting this thread title mentions 120VAC 50-amp RV spec, which is North American territory — over here on UK narrowboats and off-grid setups we're dealing with 230VAC 50Hz, so some of the paralleling principles cross over but the specifics differ considerably.

That said, the fundamental rules for paralleling hybrid inverter/chargers are universal:

• Identical units — same firmware revision, not just same model
• Proper comms cable between units (Victron's VE.Bus for MultiPlus units, for example) — without this you're just hoping they sync, which they won't reliably
• Matched cable lengths to the battery, same cross-section, same lug crimps — any impedance mismatch causes one unit to carry disproportionate load
• Single configuration master controlling both via the comms bus

On my narrowboat I ran two Victron MultiPlus-II 3000s in parallel for a while before consolidating to a single larger unit. The paralleling worked but the setup is genuinely unforgiving — one firmware mismatch after an update had both units throwing fault codes until I realised what had happened.

For the RV application you're describing, what units are you actually considering? Brands like EG4 and Growatt have their own parallel protocols that aren't always well-documented. Some cheaper hybrid units claim parallel capability but the implementation is rough.

What's your battery bank chemistry and capacity? That affects whether paralleling even makes sense versus simply upsizing the inverter.

@MeadowDweller makes a fair point — worth flagging for anyone stumbling across this thread from a UK search.

When I was setting up my narrowboat system in Kent, I nearly bought into advice from American forums before realising the whole voltage architecture was different. Over here with 230VAC 50Hz, paralleling hybrid inverters like a pair of Victron MultiPlus-IIs requires proper VE.Bus daisy-chaining and configured master/slave roles through VictronConnect — not just wiring them together and hoping for the best.

The 50-amp 120VAC split-phase world the OP describes is genuinely a different beast. British setups running parallel inverters need synchronised AC output and matching battery bank configuration — I learnt that the expensive way with a Fogstar lithium build that threw BMS faults until I got the comms sorted properly.

Different problem sets entirely, despite sounding similar on the surface.

@MeadowDweller is right to flag this — worth being explicit for anyone arriving via Google. North American 120V/240V split-phase paralleling is a fundamentally different beast to what we're doing here.

For UK/EU parallel setups, Victron's Multi or Quattro units are the go-to — they support proper AC-coupled paralleling over VE.Bus with actual phase synchronisation rather than just hoping two inverters play nicely together. Running two mismatched units in parallel without that synchronisation is asking for circulating currents and magic smoke.

I run a single Quattro 5000 in my garden office setup and even that required careful attention to earthing and the transfer switch configuration to meet BS 7671. Paralleling doubles the complexity.

Anyone replicating North American YouTube tutorials using UK equipment really needs to verify the specific firmware and communication requirements — they're not interchangeable methodologies.

Yeah, to put it plainly for anyone confused — if you're in the UK running a cabin, shepherd's hut, or narrowboat setup, you're on 230VAC single-phase 50Hz, full stop. The North American split-phase 120/240V arrangement simply doesn't apply here.

If you're looking at paralleling inverter-chargers for a UK off-grid setup, Victron MultiPlus units are the obvious starting point — they're designed to parallel properly with the right configuration, though you'll need the VE.Bus cabling sorted and ideally someone who knows what they're doing with VEConfigure.

Paralleling generic hybrid units is a different matter entirely — most cheaper inverters aren't genuinely parallel-capable regardless of what the spec sheet claims. Found that out the hard way before switching to Victron kit.

Good shout from everyone flagging the voltage difference. Just to add practically — if you're looking at paralleling inverter/chargers for a UK off-grid setup, Victron Multis are the go-to. Their VE.Bus system handles parallel configs really cleanly, and you can stack them for extra kVA without much faff.

Done it myself with two Multiplus-II 48/3000s for the garden office — the key thing people miss is you must use identical firmware versions on both units, otherwise they'll argue with each other constantly.

Also worth noting — paralleling isn't always the answer. Sometimes a single larger unit is less headache. Depends whether you actually need the redundancy or just more watts.

Fogstar for the battery side if budget matters. Victron kit isn't cheap but the support and ecosystem genuinely justifies it for anything serious.