Removing the battery for an Emergency?

Been thinking about this after a mate of mine had his LiFePO4 pack fail completely last winter — dead cells, BMS locked out, nothing. He's in a fairly remote spot in Wales and had zero backup plan. Got me wondering how many of us actually have a proper emergency fallback sorted.

In my setup I've got a small Fogstar 100Ah as a kind of "lifeboat" battery that stays on a trickle float separate from the main bank. If the main Victron system goes down for whatever reason, I can at least pull that smaller pack out and run essentials — phone, a lamp, maybe a small 12V fridge for a bit.

The question is really about accessibility though. Most of us bury our batteries in a cupboard or outbuilding and wire everything up properly — which is great until you need to disconnect something fast in an emergency. Are your terminals easy to get to? Do you have a manual isolator you can reach without digging through a load of cables?

Worth thinking about:

• A dedicated small emergency battery kept topped up
• A manual isolator that's actually accessible
• Even just a decent power bank rated for 12V output as a last resort

Curious whether anyone else has had a situation where their main bank failed and they had to improvise. Did you manage to partially disconnect and use part of the battery, or were you just stuffed?

Also — anyone running a completely separate small 12V circuit for absolute essentials that bypasses the main inverter entirely? Feels like that might be the sensible belt-and-braces approach.

@Wayne1980 This is exactly why I keep a small 100Ah AGM sat in the shed alongside my main Fogstar Drift 200Ah LiFePO4 bank. Not for daily use — purely an emergency fallback.

The critical thing people miss: if your BMS locks out, your Victron MPPT won't even see a battery to charge. You're completely dark. Having a bypass plan means physically being able to swap to the AGM, reconnect the inverter, and at least run basics.

Few practical points:

• Label your cables clearly — in a panic, colour coding saves you
• Keep the AGM on a trickle maintainer so it's actually charged when needed
• Document your wiring diagram somewhere waterproof, ideally laminated near the consumer unit

Your mate in Wales learned the expensive way. A £80 AGM backup is genuinely cheap insurance compared to a week without power in January.