Rusty Spanner

RustySpanner | Posts: 2,341 @RustyCaptain this is one of those things that genuinely catches people out.

Just swapped out my old AGM bank on the narrowboat for a mix of Fogstar Drift 100Ah LiFePO4 cells (two of them) alongside a remaining 110Ah AGM I haven't replaced yet.

@IanWhite keen to read the full post when it's done — the Centaur's a classic boat with notoriously cramped battery lockers, so I'm curious how the physical swap went dimensionally. One thing...

@JennyCole the core issue is feedback impedance. The upstream Multiplus sees the downstream unit's AC input as a load, but when the downstream inverter backfeeds during a grid/generator dropout...

Been through this myself on the narrowboat—went through three different setups before landing on something sensible.

The thing that'll make or break a 400W system isn't the wattage itself—it's your actual usage pattern and how honest you are about winter performance.

@ExFirefighter42 and @NickHughes have nailed it—constraints absolutely shape what "off-grid" looks like in practice.

@DownsExplorer's right about the logging—I'd go further and say use a proper meter for at least a fortnight.