Power Assist, the two AC Inputs and Outputs

Been thinking about this a lot lately after rewiring my motorhome setup, so figured I'd throw it open for discussion.

Running a Victron Quattro (the single-phase 230V version obviously, not the American split-phase stuff you see discussed elsewhere), and I still sometimes second-guess myself on AC1 vs AC2 input priority.

My understanding:

• AC1 = your primary source (shore power, generator, etc.)
• AC2 = secondary/generator input with slightly different behaviour around Power Assist and transfer switching

The bit that tripped me up was Power Assist — where the Quattro tops up a limited AC source with battery power. Brilliant feature for when you're on a weak shore connection or a small genny, but the behaviour differs depending on which input you're using, and VEConfigure settings can make it feel a bit non-obvious.

Also worth mentioning — the AC Out 1 vs AC Out 2 split is something people overlook. AC Out 2 drops when you're on inverter only, which matters if you've got a fixed load you always want powered. Learned that one the hard way.

Anyone running a Quattro on a static caravan or boat with dual AC inputs actually configured? Curious whether you're using a generator on AC2 or doing something different entirely. Also whether anyone's experimented with the Power Assist threshold settings in VEConfigure — feels like there's a lot of headroom there that most of us never touch.

Happy to share my VEConfigure screenshots if useful.

@FellLover the dual AC input on the Quattro is where it gets genuinely clever. Ran mine on the boat for two seasons before moving it to the garden office.

AC Input 1 takes priority — grid or shore power in my case. AC Input 2 I had wired to a generator. The Quattro will seamlessly switch between them based on your programmed preference hierarchy.

The Power Assist piece is what separates it from a basic transfer switch — it'll supplement whichever AC input is active using battery power when the source gets overloaded. Set your input current limit low (say, 16A on a weak shore connection) and it'll top up the shortfall rather than tripping.

AC Output 1 stays live regardless — inverter takes over on grid loss. AC Output 2 only energises when AC input is present, useful for non-critical loads you want shedding during battery operation.

@FellLover had mine set up wrong for three weeks before realising the generator was on AC1 and shore power on AC2 — Victron's priority logic absolutely hates that arrangement, bit like me and Mondays.

@MrBodge73 that's a classic mistake — Victron's convention catches people out constantly.

Worth clarifying the AC input priority logic: AC1 is always preferred over AC2 when both are present. Most installations put shore power on AC1 and genny on AC2, but on a narrowboat I deliberately reversed this — generator on AC1 means it gets priority and the inverter doesn't try to supplement it unnecessarily during bulk charging.

The Power Assist function is where it gets genuinely useful: set your shore power input current limit low (say 16A on a weak marina pedestal), and the Quattro will pull deficit current from the battery bank rather than tripping the breaker. VE.Configure lets you tune the boost factor — I run mine at 2x, so a 16A input can effectively deliver up to 32A to loads briefly.

AC2 output also drops when on inverter — plan your critical loads accordingly.

@MrBodge73 😂 three weeks is rookie numbers, I had mine wired backwards for nearly two months on the shepherd's hut build before a mate pointed it out.

One thing worth flagging that nobody's mentioned yet — Power Assist is the real magic here. When your grid/shore input is current-limited (say a weak site hookup), the Quattro will top up from the battery to meet demand. Absolute lifesaver when I'm charging the EV and someone puts the kettle on simultaneously.

Key thing to set correctly is the input current limit in VRM/VictronConnect — get that wrong and you're either tripping the hookup or leaving battery capacity on the table.