Free/cheap sources of 18650 cells for DIY packs

Mate, been pulling cells from old laptop batteries for years now. Most recycling centres won't take them, so you can often grab bags of dead laptops for next to nothing. Takes a bit of work to crack them open and test each cell, but you'll usually find 30-40% are still serviceable.

eBay's your friend too — search for "untested 18650 lot" and you'll find sellers shifting job lots cheap. Yeah, some'll be duds, but if you've got a decent charger (I use a Nitecore D4) you can sort the wheat from the chaff pretty quickly.

Fair warning though: old cells are a gamble. I've built packs from salvage that work brilliant in my caravan setup, but the capacity figures are anyone's guess. Fine for powering LED strips and USB kit, but I wouldn't trust them for anything critical.

Another route — phone repair shops sometimes have drawer fulls of old batteries they can't shift. Worth asking if they'd let you take them off their hands. Had good luck with that locally.

The thing I've learned is: cheap cells are cheap for a reason. Test everything with a proper tester, and don't cheap out on the BMS if you're building anything bigger than a small auxiliary pack. Had a mate's DIY pack go proper wrong because he skipped that bit.

What kind of capacity you after? Might help narrow down what's actually worth your time versus false economy. And if anyone else has sources round their area, keen to hear where you're sourcing from.

Worth noting that whilst salvaging 18650s from old laptops is cost-effective, you'll want to bin-test every single cell with a proper load tester before using them in a pack. I've had batches where 30-40% were genuinely dead or dangerous.

The real issue is consistency. Even cells from the same laptop batch will have wildly different capacity remaining. For a DIY LiFePO4 pack that you're relying on—especially if you're powering critical loads like fridges or heating—mixing aged cells creates real problems. You'll get voltage sag, uneven discharge, and potentially cell failure mid-winter.

If you're serious about it, factor in the cost of a decent cell analyser (Opus or Xtar). Otherwise you're essentially gambling with your system's reliability.

Better option: check eBay for bulk "untested" 18650 lots from battery recyclers. Usually £0.15-0.25 per cell, and you at least know they haven't been physically damaged during extraction.

I've been down this road with my van setup. Pulled about 200 cells from old Dell and HP batteries over two years. The tedious bit isn't cracking them open—it's the binning afterwards. @ZoeGrant's spot on there.

What caught me out initially was assuming "dead battery pack" meant dead cells. Often it's just one or two cells that've given up, and the rest are perfectly decent. I've got a cheap Fogstar tester now (about £15) which saves hours of manual checking.

Real talk though: the time cost nearly killed it for me. Working out cells at salvage prices, I was effectively earning about £3/hour. If you're genuinely skint, fine. But if you've got any spare cash, buying tested Renogy or similar used packs from eBay is sometimes quicker and not much pricier. The van's emergency setup can't afford dodgy cells halfway through winter.

That said, the learning curve was worth it. Understand cell chemistry properly now.

Doing the same with my shepherd's hut setup. Grabbed roughly 150 cells from a local computer repair shop who were chucking out dead packs. Mate was happy to offload them for a cuppa.

The key thing @ZoeGrant mentioned—testing is absolutely crucial. I use a basic Opus charger to capacity-test each cell before they go anywhere near my Victron setup. Found about 20% were genuinely knackered, rest ranged from 60-95% capacity.

Fair warning though: if you're mixing cells from different batches/ages, you'll need a proper BMS. Don't cheap out on that bit. Also keep a fire extinguisher nearby when charging untested salvage batches, just sensible.

The time investment's worth it if you're patient, but it's not a quick job.

Been salvaging from old packs for my tiny house battery bank too. @ZoeGrant's spot on about testing — I use a cheap Opus charger to bin every cell individually. Saves hassle later when you're mid-winter and a dud cell tanks your whole string.

Pro tip: befriend local computer repair shops and recycling yards. I've got a standing arrangement with a place near me — they ring when they've got a batch of dead laptops. The cells are usually in decent nick if the pack just failed due to a balance issue rather than age.

Only real downside is time investment. Cracking open batteries, testing, sorting by capacity — it's tedious. But if you're not paying for cells, it's hard to complain. I've built a 10kWh pack this way for under £200 in hardware costs.

Just chuck any that show <2500mAh or weird voltage readings. Not worth the fire risk, especially if you're doing EV charging or running critical cabin loads.

Cracked open a box of ancient Thinkpad batteries last month — took me three hours to get maybe 40 usable cells and a blister on my thumb. The real trick is finding the sweet spot between "free" and "not worth your time". My shepard's hut batteries are currently held together with prayers and what I thought were decent salvage cells, but they're drifting voltage like a moored boat.

@PeakVanLifer's right about the computer repair shops — mine lets me root through their bin monthly for a cup of tea. Just remember you're basically playing Russian roulette with internal resistance and cycle count. A proper capacity tester (Opus or Xtar, not the quid shop specials) saves you months of frustration later. Worth spending the £30-40.

Also, your Victron BMV will absolutely rat you out if you've bodged together dodgy cells, so there's that.

Salvaging from old laptops works, but the real goldmine is power tool batteries — DeWalt, Makita, Bosch packs. Local builders often bin the older 18V NiCd stuff, and you can negotiate with trade suppliers who have dead stock gathering dust.

One thing nobody's mentioned yet: check with mobile phone repair shops. They've got drawers full of rejected battery packs from trade-ins. Condition varies wildly, but you'll find decent Samsung and LG cells if you sort through them.

Fair warning though — the labour-to-usable-cells ratio is brutal. I spent a weekend cracking open about 200 cells for my van conversion and got maybe 60 that tested good under load. The rest were marginal. Worth it if you're patient, but budget properly for a spot welder or quality tab connection gear. Cheap solder joints on high-discharge packs aren't worth the fire risk.

Also worth testing with a proper load tester, not just voltage. A Skyrc imax B6 or similar will save you building dodgy packs that fail under actual draw.

Ah, the power tool route @RayWatson81 mentions is brilliant — I've had decent luck with that myself. Picked up a knackered Makita pack from a mate's garage for a tenner, got about 12 good cells out of it.

The thing is, condition varies wildly. I've learned the hard way that just because a pack won't hold charge doesn't mean the cells are toast — sometimes it's dodgy internal wiring or a failed BMS. Worth checking voltage on individual cells before you spend three hours cracking open casings like @CamperCarl did.

For my boat setup, I've been supplementing cheap salvage with a few new Fogstar cells when I need consistency in a string. Mixed old and new cells in one pack is asking for trouble, but if you're building something with individual cell monitoring (which you should be anyway), salvage can work out decent value.

Fair warning though — testing takes forever. I use an old Nitecore D4, but honestly, a cheap multimeter and a spreadsheet will do the job if you've got patience. Keep the rejects for your spares box

Yeah, power tool route's solid but you've got to be careful with the age of the pack. I grabbed a job lot of old Makita 18V packs off eBay for about £20 last year — some cells were genuinely knackered, others tested fine. The problem is you never really know until you've cracked them open.

What I've found works better is hitting up local trade recyclers rather than the big municipal centres. There's a guy about 20 mins from me who shifts pallets of old cordless drills and impact drivers to folk like us. Usually £30-40 for a mixed bag of 5-6 packs, and the hit rate's much higher than laptop batteries.

For my EV charging setup, I ended up binning the salvage approach altogether and just bought a batch of Fogstar cells. Wasn't worth the hours of testing and binning dodgy ones when I needed consistent performance. But if you're just mucking about with a power wall or something less critical, the salvage game definitely works.

Dead UPS units are absolutely worth knowing about too. Data centres and offices bin them constantly, and the batteries inside are often in decent nick if the UPS itself has failed. I've scored several packs that way through local Facebook groups — people are usually just grateful someone's taking them off their hands.

The thing with both laptop and power tool salvage is condition checking though. I've built a couple of test rigs now (annoying but necessary) because you can't trust visual inspection alone. A cell that looks fine might be internally shot, and mixing dodgy cells into a pack is a recipe for thermal runaway.

@RayWatson81's right about tools though — they're more consistently built, and the casings are easier to crack open. Laptops can be a right faff with adhesive and screws in weird places.

Fair warning: if you're building larger packs, budget for a proper BMS and some decent monitoring. The penny-pinching stops being clever when you're dealing with lithium and limited space (learned that one the hard way in my garden office build).

Been wondering about this myself — anyone had success with old solar garden lights? Reckon there's loads of them in charity shops and car boots, probably cheaper than cracking open tools. Also, has anyone tested cells salvaged this way before putting them in a proper pack? Worried about capacity variance across a batch.

Salvage route's solid but test everything with a cheap multimeter before assembly — I've seen batches where 30% were already internal short. @ZFS_OffGrid's right about laptops though. Garden lights are mostly those rubbish LiPo pouch cells, avoid them. Focus on power tools and UPS units like @Louise1984 mentioned. Charge test in a 18650 charger with monitoring before trusting them in a pack.