What's everyone's go-to setup for emergency power when the main system fails completely?

So this happened to me last month — woke up in the static to a completely dead system. Victron MPPT had thrown a fault, batteries (two 100Ah Fogstar Drift LiFePO4s) were sitting at 2% and the inverter had shut itself off overnight. No solar input because we'd had four solid days of November grey in the Dales. Proper scramble to even boil a kettle.

I'd bodged together a backup using an old 30Ah AGM I had kicking about and a cheap 300W pure sine inverter from Amazon, but honestly it felt like a sticking plaster on a broken leg. Kept the phone charged and ran the router, that's about it. Made me realise I've never actually planned for this scenario, just assumed the main bank would always cover us.

Wondering what others are running as a genuine backup — talking dedicated small battery, a generator on standby, a EcoFlow or Jackery unit sat charged in a corner? I've got a Honda EU22i that lives in the shed but haven't wired it into anything properly. Is it worth running that through a transfer switch or just manually swapping over when needed? Curious what's considered best practice here rather than my usual "figure it out in a panic" approach.

Linda1972 | 847 posts | ⭐ Regular

Oh @DaleSpirit, that sick feeling when nothing comes on — been there! My backup-to-the-backup is a humble 40Ah AGM sat on a trickle charger in the shed, completely independent from the main system. Couple of 12V LED strips, a USB charging hub, and a small 12V compressor fridge wired directly to it. Nothing fancy but it keeps the essentials running while I sort out whatever's gone wrong with the main setup.

The key for me was keeping it entirely separate — different battery chemistry, different charging source (small dedicated panel), different wiring. When your main system goes down you really don't want your emergency backup tangled up in whatever caused the fault in the first place. Learned that the hard way!

What fault code was the Victron throwing? Might be a straightforward fix. 🙂

Keep a small dedicated emergency box that never gets touched — mine lives under the bed in the shepherd's hut.

Inside:

• Jackery Explorer 240 (always on a trickle charge via a tiny 50W panel)
• headtorch + spare batteries
• 12V USB power bank (Anker)

The Jackery runs my phone, a little LED strip and keeps the water pump going long enough to sort out what's actually gone wrong. Saved me twice now when my Victron SmartSolar threw a wobbly.

Key thing is keeping it completely separate from the main system — the temptation to integrate it is real but then it just fails alongside everything else.

@DaleSpirit what fault code was the MPPT throwing? Could be worth checking your battery cable connections first, loose terminal caused my last drama.

SolarJason | 1,203 posts | ⭐ Regular

The story that sticks with me: same scenario as @DaleSpirit, February 2022, -4°C outside. What saved me wasn't anything clever — it was a battered 40Ah AGM I'd nearly binned sitting in the corner of the outhouse, still holding charge from six months prior.

Now that old AGM is the emergency system. Completely isolated from everything. No BMS to throw a fault, no MPPT to confuse itself. Just lead acid doing what lead acid has done since 1859.

Paired it with a cheap Victron BMV to keep an eye on state of charge, and a small 240W pure sine inverter for anything critical.

The lesson I took: your backup shouldn't share any components with your primary system. The moment they overlap, one failure cascades into both.

JackieEdwards75 | 412 posts | ⭐ Member

Great thread @DaleSpirit — sorry you had that nightmare start to the day!

My absolute failsafe is a 40Ah lithium leisure battery on a completely separate circuit, charged via its own small solar panel and never touched for anything else. Keeps a 12V socket, a couple of USB ports, and one LED striplight running. Dead simple, no inverter drama.

What saved me last winter though was also having a 12V immersion element for hot water — not exciting but when everything else is down, a warm brew and a wash makes the whole situation feel less grim while you're diagnosing the main system!

Agree with @RobThompson about the dedicated box approach — isolation from the main system is key, otherwise when the main system fails it tends to take everything with it.