Anyone else using a used EV battery pack as backup power? Sharing my Nissan Leaf experience so far

I picked up a 24kWh Nissan Leaf gen 1 battery pack off eBay about four months ago for £380. The cells tested at roughly 18kWh usable after degradation, which I'm genuinely happy with for the money. I've got it sat in my garage paired with a Victron Multiplus-II 5000VA and a 1,200W array on the roof. Day-to-day it's handling pretty much everything — lighting, fridge, laptop, the lot — without touching the grid from around April through September.

The trickiest bit was battery management. The Leaf pack doesn't come with an easy plug-and-play BMS for DIY installs, so I ended up using an Orion BMS Jr with a custom harness. Took me the best part of six weekends to get the cell groups balanced properly and talking nicely to the Victron over CANbus. There are worse ways to spend a winter, mind you.

What I'm curious about is what other people are doing for thermal management. My garage sits pretty steady but we had a cold snap in January where the pack dropped to about 4°C overnight, and the Victron wisely backed off the charge rate. I've since thrown a couple of 60W seedling heat mats under the pack on a thermostat, which seems to be doing the job. Has anyone built something more robust — proper insulated enclosure, active heating, anything like that? Also keen to hear if anyone's moved beyond Leaf packs onto BMW i3 or Tesla modules.

Tom1997 | 47 posts

@Roger1983 great project, really jealous of that price! I picked up a 30kWh Leaf pack (the 2016-ish "lizard" chemistry one) last year for £550 and it's been solid. One thing worth flagging for anyone following this thread - the Leaf packs have no active thermal management, so if you're in an uninsulated outbuilding keep an eye on temps during winter. Mine dropped to about 4°C in January and capacity noticeably suffered temporarily. Nothing dangerous, just worth knowing.

Also, what BMS are you running externally? The original Leaf BMS is obviously tied to the car's CAN bus which makes standalone use a bit fiddly. I ended up using a Daly 96V unit which works well enough, though I had to do some cell group voltage mapping first.

CotswoldVanLifer | 203 posts

@Roger1983 brilliant find at that price, genuinely impressive. I've been running a similar setup in my van for about eight months now using a salvaged 2013 Leaf pack - though mine's a bit rougher around the edges and I only squeeze about 14kWh usable out of it.

One thing worth mentioning that catches people out: the battery management system communication. Did you end up retaining the original Leaf BMS or are you running something like a JK BMS alongside it? I went the aftermarket route and honestly wish I hadn't initially - took me ages to get the cell balancing behaving properly.

Also curious what you're using for charge control on the input side? I'm currently on a Victron MPPT feeding mine and touch wood it's been solid, but always keen to hear what others are doing.

CarlCole97 | 89 posts

@Roger1983 that price is genuinely ridiculous — well done. I've been down a similar rabbit hole for my narrowboat build, though I went the Fogstar route in the end because I couldn't face the BMS headaches at the time.

The thing nobody warns you about with repurposed Leaf packs is the thermal management situation — or rather the lack of it on gen 1. Passive cooling is fine moored up in October, less fine crammed into a boat hull come July.

What are you using to monitor individual cell groups? That's where I'd be watching closely. A Victron Cerbo GX pulling data from a decent BMS makes a huge difference for catching a drifting cell before it becomes a proper problem rather than just a worry.

Keen to see how it holds through winter — the capacity drop in the cold will be the real test.

GeorgeSmith97 | 134 posts

@Roger1983 cracking project mate. One thing worth flagging if you haven't already sorted it — thermal management is something a lot of people overlook with the gen 1 Leaf packs. They're air-cooled (or rather, not really cooled at all properly), so if you're in an enclosed space and pushing decent charge/discharge rates, keep an eye on cell temps. I've got a pair of thermocouples running into a basic Arduino monitor on mine just for peace of mind.

Also curious what you're using for a BMS? I went with an Orion 2 and it's been rock solid, though pricey. There are cheaper Chinese options that people swear by but I've not personally tested them. Would love to hear what your cycle count is looking like after six months or so — these threads are gold for real-world data.

Nobby30 | 312 posts

@Roger1983 great project, 18kWh for £380 is hard to argue with! One thing I'd add that nobody's mentioned yet — keep an eye on cell balancing over time, especially with a degraded pack. The weaker cells tend to drift further from the rest as months go by, and if your BMS isn't catching it early enough you can end up with one module bottlenecking the whole pack. Worth doing a manual balance check every couple of months initially until you know how stable yours is. Also curious what you're using as your inverter/charger setup? I ran into a few compatibility headaches getting mine to play nicely with a Victron MultiPlus — took some fiddling with the charge voltage settings before I was confident leaving it unattended.