Anyone else running a cheap 100Ah LiFePO4 from Amazon — what's your actual real-world capacity?

Picked up one of those no-name 100Ah LiFePO4 batteries off Amazon back in March — think it was around £89, one of the ones with the built-in BMS and blue casing. Looked identical to about six other brands all clearly from the same factory. Figured at that price it was worth a punt for my shed setup running a few LED strips, a 12V fan, and charging phones overnight.

Been running it a few weeks now and I'm consistently pulling around 78–82Ah before the BMS cuts out, measured with a basic Bayite coulomb counter. Not terrible, but definitely not 100Ah. I half expected that, to be honest — I've seen people claim you're lucky to get 80% of rated capacity on these budget cells.

What I'm trying to work out is whether that's just the nature of cheap LiFePO4 or whether mine's particularly bad. Has anyone done a proper discharge test on one of these budget units? I've seen wildly different results posted elsewhere — some folk claiming 95Ah, others saying they barely got 70Ah out of theirs.

Also wondering if it's worth trying a top-balance on the cells — though cracking open a budget battery always feels like a bit of a gamble. Anyone gone down that road?

@MoorRoger those blue-cased ones are almost certainly all coming out of the same two or three factories in Shenzhen regardless of what name's printed on the front.

I've got a similar vintage one sat in my garden office setup. Tested it properly with a calibrated load — got 84Ah out of it at a 10A discharge rate down to 2.8V per cell cutoff. Not terrible honestly.

Worth noting: capacity tends to improve slightly over the first 20-30 cycles as the cells bed in. Mine gained maybe 3-4Ah across the first month.

The thing to actually watch is the BMS — those built-in units are often rated optimistically. Mine throttled hard above 40A draw even though it claimed 100A continuous. Running it through a Victron SmartShunt gives you much better visibility on what's actually happening versus what the battery "thinks" it's doing.

Got one of the same blue-cased units back in February — tested mine properly with a calibrated load tester and got a consistent 87Ah before the BMS cut off. Not bad for the money honestly. Worth noting though, I've seen these vary quite a bit unit to unit, so your mileage may differ. @MoorRoger what discharge rate were you testing at? I found mine loses noticeably more capacity if you push it hard — around 0.5C it drops to maybe 80Ah in my setup. For light van loads it's been perfectly decent, but I wouldn't rely on the full 100Ah figure for any critical calculations. Running two of them in parallel now and they've been stable for about four months. Fingers crossed they keep performing!

Ran one of those exact blue-cased units on my narrowboat for about eight months before upgrading to Fogstar Drift cells. Tested it properly with a calibrated load — genuine capacity was sitting around 78-82Ah depending on temperature. Cold mornings on the cut knocked it down noticeably, sometimes as low as 68Ah when we had that bitter snap in February.

The BMS was the real weak point — mine started throwing low-voltage disconnects at around 3.1V per cell rather than 2.8V, so it was quietly throttling usable capacity from both ends.

Not saying avoid them entirely — at £89 they're reasonable for low-drain static applications. But @MoorRoger I'd treat yours as a 75Ah battery in your planning calculations and you'll never be caught short.

Really interesting thread this. I've got two of those blue-cased units running my shed setup and did a proper discharge test last autumn using a DC electronic load. Got 87Ah from one and 91Ah from the other at a gentle 10A draw — so broadly consistent with what @Robbo41 found. Worth noting that ambient temperature makes a noticeable difference; I retested in January during a cold snap and dropped to around 79Ah on the better unit. Still decent value at that price point honestly, but I wouldn't rely on them for anything critical without building in a decent buffer. Anyone know if these typically improve slightly after the first few cycles, or have people found they degrade fairly quickly?

Has anyone actually stress-tested one of these under sustained high draw? I'm planning to run mine in a shepherd's hut setup and I'm less worried about raw capacity than whether the BMS throttles output when you're pulling, say, 30-40A continuously for a few hours.

@JimMoore — curious whether your shed discharge test was at a consistent C-rate or mixed loads? That seems to be where these budget units vary wildly compared to something like a Fogstar.

Also wondering if ambient temperature plays into this — my hut can get properly cold overnight in winter and I've read these no-name BMS units can cut out below 5°C without much warning. Anyone had that happen in practice?