Anyone tried those cheap 100Ah lithium batteries off eBay? Worth the risk?

So I went down this exact rabbit hole about 18 months ago when I was kitting out my shepherd's hut. Found a suspiciously attractive 100Ah listing, seller based "in the UK" but the warehouse was clearly Shenzhen with a Royal Mail sticker slapped on top.

Bought two. One arrived with a dented corner and the BMS gave up after about four months of regular cycling. The other one is still going somehow, touch wood. So... mixed bag doesn't even cover it.

The thing nobody tells you upfront is that the cell lottery is absolutely real. You might get grade A cells, you might get pulls from old EV packs, you might get something that was graded B in a factory in 2019. There's genuinely no way to know.

What I'd say now, having also gone on to buy Fogstar Drift cells for my garden office setup — the price difference feels massive until you factor in:

• Replacement costs if it fails
• Potential damage to your inverter or Victron kit
• The absolute faff of warranty claims with a disappearing eBay seller

That said, I don't think they're universally terrible. If you're using them for something low-stakes — a shed lighting circuit, maybe — the maths might still work out.

Anyone else been through this? Curious whether people have had better luck with specific sellers, or whether there's a sweet spot in the budget market I'm missing. The gap between "dodgy eBay" and "Fogstar/CATL proper" feels enormous — surely something decent exists in between?

@VivaraNomad been there. Bought a dodgy 100Ah off eBay for my cabin build — turned up with no BMS documentation, cells were clearly mismatched on capacity testing.

Lesson learned the hard way: if the listing doesn't name the cell manufacturer (CATL, EVE, etc.) just walk away.

Saved up another £80 and got a Fogstar Drift instead. Night and day difference — proper BMS, actual capacity, full UK warranty.

The maths people miss:

• Cheap battery fails in 18 months = money gone
• Decent battery lasts 8-10 years = genuine saving

Also worth checking the seller's return policy before buying. Most of these eBay jobs are "return to China" which costs a fortune.

Not saying every cheap option is rubbish, but I'd want to see real discharge curves, not just a marketing spec sheet.

@VivaroNomad @EmmaEdwards82 the "UK warehouse" thing kills me every time 😂 seller: "dispatched from Manchester!" — battery: arrives with Mandarin instructions and a faint smell of optimism

Seriously though, I've been down this road. Bought two "100Ah" cells that turned out

@VivaroNomad had exactly this dilemma when setting up my static caravan. Ended up going Fogstar Drift after bottling it on three different eBay listings 😅

The price difference felt painful at the time but honestly the peace of mind is worth it — especially when you're leaving the setup unattended overnight.

The thing nobody mentions with no-name cells is warranty support. When something goes wrong (and it does) you're on your own arguing with a seller who's already changed their account name.

Spent the extra, never looked back. Fogstar's been solid for 18 months now, zero issues.

@Fiona1974 made the right call — Fogstar Drift is genuinely excellent bang-for-buck and actually has a BMS you can trust.

The core issue with mystery eBay cells isn't just dodgy specs — it's cell matching. A proper 100Ah pack needs balanced cells from the same production batch. Random warehouse pulls are often B-grade rejects that'll diverge badly under load within months.

For EV charging loads specifically (which I run off my cabin array), you need a BMS that handles sustained high-current draw without throttling. Cheap packs almost universally lie about their continuous discharge ratings.

Worth knowing: Fogstar, Fogstar Draft, and even Renogy offer verifiable cycle ratings and actual warranty support. The price delta over eBay specials typically closes after you factor in one replacement purchase — which, statistically, you will be making.

Buy once, cry once. The maths don't lie.