Anyone else using old EV battery modules for home emergency backup?

Picked up a pair of Nissan Leaf Gen 2 modules off eBay last autumn — 8 cells per module, nominally 7.6kWh total once I'd balanced them properly. Spent a good few weeks building a plywood enclosure in the garage, wiring them in series/parallel to hit 48V, and bolting on a Victron SmartShunt to keep tabs on state of charge. First real test came during the storms in January when we lost grid power for about 11 hours — kept the fridge, router, and a few LED circuits running without breaking a sweat.

The trickiest part was cell balancing. These modules had been sitting in a breaker's yard for eight months, so voltage drift between cells was all over the shop — some at 3.6V, others down near 3.1V. Used a cheap active balancer off Amazon alongside a bench power supply to bring everything within 20mV before I dared put any meaningful load through them. Took three days of faffing, honestly, but the Victron data now shows rock-solid capacity curves.

BMS selection was the real headache. Ended up going with a Daly 100A 48V unit, which does the job, but I'm not entirely convinced it's logging cell-level data in a way I can pull into VRM. Anyone gone down the JK BMS route with salvaged EV cells? Curious whether the Bluetooth comms actually talks nicely to a Cerbo GX without too much grief.

Been down this road myself @TorJake! Got four Leaf Gen 1 modules sitting in my garage doing exactly the same job. Couple of things worth mentioning that caught me out early on — the Gen 1 cells degrade noticeably below about 10°C, so if your enclosure is in an unheated space you'll want to factor that into your usable capacity estimates. I've got a cheap temperature probe logging through a Raspberry Pi just to keep an eye on things.

Also worth checking your BMS settings carefully — I initially had mine configured for lithium-ion parameters rather than the Leaf's lithium-manganese chemistry and it was giving me daft readings.

What inverter are you running with yours? I'm currently on a Victron MultiPlus 12/3000 but wondering whether to upgrade. Curious what others are pairing these modules with.

Great thread this! @TorJake I went a slightly different route — grabbed a handful of BMW i3 modules from a breaker up near Warrington. Lovely cells, very consistent capacity and they balance up nicely. Been running mine through a Batrium BMS which honestly was the best money I spent on the whole build — gives me proper cell-level monitoring rather than just guessing.

One thing worth flagging for anyone starting out: do check your modules with a clamp meter under load before you commit to a layout. Had two cells in one module that looked fine on open circuit voltage but dropped badly once I put any decent draw on them. Would've caused no end of grief in the enclosure if I'd missed that.

How are you finding the thermal management side of things @TorJake? My garage gets properly Baltic in January and I'm wondering whether it's affecting capacity.