Anyone else keep a dedicated "emergency only" battery for home backup?

Been thinking about this after we had a 6-hour outage last winter. Our main motorhome setup (200Ah Fogstar lithium, Victron SmartSolar 100/30) carries us fine on the road, but at home we're just on the grid like everyone else.

I've been considering picking up a second smaller battery — maybe a 100Ah LiFePO4 — kept at around 50% SoC on a trickle charge, purely for emergencies. Run a few essentials off it: phone charging, router, a couple of LED lamps, maybe a small 12V coolbox for meds. Rough calculation puts that at maybe 20-30Ah per day, so a decent few days of light use.

The question is whether it's worth the faff of maintaining a separate dedicated unit, or whether people just rely on their main setup and shuffle gear around when needed. Anyone actually done this properly with an isolator switch or a dedicated Victron IP22 charger keeping it topped up? Curious what real-world setups look like rather than the theoretical stuff.

Taffy55 | 📍 Mid Wales | ⚡ Victron/BYD setup

@OldSailor78 snap - that exact scenario is what pushed me into sorting proper home backup too. Six hours is manageable but it makes you realise how unprepared you are when the freezer starts worrying you!

I've gone a slightly different route - rather than completely dedicated hardware, I've got my home battery (BYD 5kWh) configured with a reserved 20% SOC that the system simply won't touch for normal usage. Victron's ESS assistant handles it automatically. Feels like the best of both worlds - you're not leaving capacity sat idle permanently, but there's always something in reserve.

Living in Mid Wales, outages here can be proper lengthy ones, so that buffer gives real peace of mind. What sort of loads are you hoping to cover during an outage? That'd probably shape which approach makes more sense for your situation.

VanJulie | 📍 Afloat | ⚡ Boat setup

Been thinking about this a lot actually — on the boat I've got a dedicated "house bank" that I try not to raid below 30% for exactly this reason, it's almost self-enforcing.

For home backup though, does anyone find the self-discharge issue a problem if the battery just sits waiting? My concern would be a lithium sitting mostly idle for months and then not performing when you actually need it.

Is there a minimum maintenance charging setup people use — like a small trickle via a Victron MPPT and a single panel just to keep it topped? Or do most of you just rely on it being cycled regularly enough that it stays healthy anyway?

@OldSailor78 what's your thinking on keeping it genuinely "emergency only" versus letting it do some light daily work?