Anyone else using a second-hand EV battery as a home backup — what's your setup?

Been mulling this over for a while and finally pulled the trigger last month. Picked up a used Nissan Leaf Gen 1 battery (24 kWh pack, probably down to around 18–19 kWh usable given the degradation) off eBay for £380. Paired it with a Victron MultiPlus-II 3000VA inverter/charger and a 600W solar array on the garage roof. So far it's handling our overnight loads no bother — fridge, a few lights, router, the usual.

The fiddly bit was the BMS situation. The Leaf pack has its own onboard BMS but it doesn't talk nicely to the Victron out of the box. I ended up using a Batrium BM6 watchmon to bridge the gap and set charge/discharge limits properly. Not a plug-and-play job by any means — took me a good three weekends of head-scratching and a fair bit of help from the Endless-Sphere forum to get it stable.

What I'm really curious about is whether anyone's gone down a similar route with other EV donor packs — BMW i3, Renault Zoe, Tesla Model S modules, that sort of thing. Particularly interested in how people are handling thermal management in a UK garage environment, because I've not done anything clever there yet and I'm a bit nervous about the colder months coming in.

Got a Gen 2 Leaf pack myself (30 kWh, reckon ~22 kWh usable). Running it through a Victron Multiplus-II for the garden office and as whole-house backup.

Main thing I'd flag — the BMS situation is the real headache. Stock Leaf BMS doesn't play nicely with most inverters out of the box. Ended up using a Batrium BMS to properly manage cell-level monitoring. Worth every penny but adds cost.

Also worth checking individual module voltages before you commit — some second-hand packs have a couple of duff modules dragging everything down.

@GlenLover what inverter are you pairing yours with? That'll probably dictate how much faff you're in for with comms/integration.

Really interesting thread this. I went a slightly different route — picked up a Renault Zoe Z.E.40 pack (41 kWh nominal) from a breaker in Cambridgeshire for £800 last spring. Capacity tested at roughly 32 kWh usable which I'm well happy with for the price.

Main thing I'd flag that nobody's mentioned yet — thermal management. The Zoe pack has active liquid cooling built in, which is a proper advantage over the Leaf's passive setup, especially during summer charge cycles. Worth factoring in when choosing your donor vehicle.

I'm using a Growatt SPF 5000 inverter which has been rock solid.

@GlenLover — what BMS are you running with the Gen 1 pack? That's often the trickiest bit with Leaf packs given the cell-level monitoring. Happy to share notes if useful.

Great thread, this is exactly the kind of thing I've been experimenting with too. I went with a pair of BMW i3 60Ah modules (roughly 14 kWh usable after degradation) — easier to handle physically than a full Leaf pack, which was a big consideration for me working solo in a barn conversion.

One thing worth mentioning that nobody's touched on yet: cell balancing becomes really critical with these second-hand packs, especially after they've had an uneven previous life. I'm using a Daly BMS with active balancing and it's made a noticeable difference to the usable capacity versus my initial passive-only setup.

@GlenLover what BMS are you running on your Gen 1 pack? And has anyone had experience integrating these into a Home Assistant dashboard for monitoring? That's my current project and I'd love to compare notes.

Bit of a different angle from me — my EV battery isn't a home backup, it is the home. Got a second-hand Hyundai Ioniq pack fitted to the boat about eighteen months ago. The marine environment makes things interesting; moisture and vibration are constant concerns that you land-dwellers largely sidestep.

Went with a Victron Multiplus-II like @Dizzy70, paired with a Cerbo GX for monitoring — absolutely essential when the battery is tucked under the companionway steps where you can't easily eyeball it.

One thing I'd flag to everyone here: whatever your setup, proper cell-level BMS protection matters enormously with these repurposed packs. The original Leaf and Zoe BMSs aren't always reliable when pulled from their native environment — I spent good money learning that lesson.

Really enjoyed reading through everyone's setups here. I went with a Nissan Leaf Gen 2 40 kWh pack about eight months ago — similar starting point to @GlenLover but the newer chemistry holds up a bit better in my experience. Paired it with a Victron MultiPlus-II and a Batrium BMS which has been rock solid for monitoring individual cell groups.

One thing I'd flag that hasn't been mentioned — thermal management in winter. These packs weren't designed to sit in a cold garage doing slow home storage cycles. I lost noticeable capacity over last winter before I insulated the enclosure properly. Nothing dramatic but worth factoring in from the start rather than retrofitting like I did.

@Del — living in an Ioniq5 sounds brilliant in theory, how are you finding the real-world range impact from powering the home?

My angle's a bit more modest than @GlenLover's full home integration — I grabbed a Nissan Leaf Gen 1 24 kWh pack specifically for my garden office setup. Picked it up from a breaker in Yorkshire for around £400, degraded down to roughly 16 kWh usable.

Wired it through a Victron MultiPlus-II and it's been running the office — screens, lighting, a small heater — almost entirely off-grid since last spring. The part that surprised me was how stable the Victron BMS integration ended up being once I'd sorted the CAN bus communication properly. That took a few weekends of head-scratching, not going to lie.

Worth mentioning — the physical housing matters more than people think. These packs don't love damp, and a British garden shed is basically a humidity experiment. Proper ventilation and a decent enclosure saved me a lot of grief.

Really interesting thread this. I've been running a second-gen Leaf 40 kWh pack (similar to @Declan1985) for about six months now, but mine's purely grid-tied with a Victron MultiPlus-II handling the inverter duties. What I'd add that hasn't been mentioned — keep a close eye on the cell group voltage spread as temperatures drop heading into autumn. I noticed mine showing increased imbalance once it got consistently below 5°C in the garage. A bit of insulation round the pack sorted it. Nothing dramatic, but worth monitoring if you're in a colder part of the country.