Anyone else had their Fogstar Drift 100Ah cells arrive with wildly different states of charge?

Picked up four 280Ah EVE cells from Fogstar last month for the van build — proper excited, great price, good reputation on here. Cracked the box open and whipped out the multimeter expecting them to be roughly balanced from the factory. Nope. Three were sitting around 3.27V and one was a rogue at 3.31V. Not catastrophic, but enough that my Daly BMS threw a fit during the first top-balance attempt and tripped the protection circuit before I'd even got going.

Spent a weekend doing a slow top-balance at 3.65V per cell using a bench power supply borrowed from a mate — got them all singing within about 5mV of each other before wiring the pack properly. First charge cycle on the Victron SmartSolar went smooth as you like after that. The Daly's been quiet ever since, sitting between 3.28V and 3.30V across all four during normal cycling.

Just wondering whether this is a known thing with Fogstar's current stock, or whether I drew the short straw. Did anyone else do a top-balance before first use as a matter of course, or just trust the cells and crack on? Tempted to say it should be mandatory but curious what the collective wisdom is here.

@EwanMurray This is completely normal and frankly expected with LiFePO4 cells shipped internationally. The manufacturers deliberately partial-discharge them to somewhere around 3.2–3.3V for transport safety regulations — lithium at full charge is classified differently for freight purposes.

What matters far more than arrival SoC is top-balancing before first use. Do not just slap them on a BMS and charge. Connect all four cells in parallel, bring them up slowly to 3.65V with a bench power supply (I used an adjustable lab PSU, current-limited to about 0.05C), and leave them there until current drops to near zero. That's your baseline.

My EVE 280Ah cells from a similar batch varied by nearly 80mV on arrival — after a proper top-balance they were within 3mV under load.

The Fogstar cells themselves have tested extremely well across the community. Don't panic, just balance properly first.

@EwanMurray Had the same with a batch of Fogstar Drift 100Ah cells I grabbed for my boat's emergency backup setup — two were sat around 3.27V, one was at 3.31V, and the last was barely 3.2V. Wasn't worried at all.

As @Paddy says it's normal, but what I'd add is don't rush the top balancing. I made the mistake first time round of pushing straight into capacity testing before a proper top balance at 3.65V. Ended up with skewed results that had me convinced one cell was duff — it wasn't.

Stick them all on a bench charger, get them to 3.65V individually, then sit them together with your BMS connected for 24–48 hours before doing anything else. Once they're genuinely balanced the cells should perform almost identically.

Worth the patience, trust me.

@EwanMurray Worth noting that before you even think about top-balancing, let those cells sit at room temperature for 24 hours if they've come in cold — LiFePO4 internal resistance behaves oddly when chilled and your readings will be all over the shop.

My EVE 280Ah batch from a similar supplier arrived with one cell sitting at 2.8V, rest around 3.2V. Looked alarming but after a slow charge to 3.45V per cell individually (I used a bench PSU with current limiting), they all settled beautifully and capacity tested within 2% of spec.

Do not just slam them all in parallel and hope the balancing sorts itself — if that low cell is genuinely sulphated rather than just discharged, you'll mask the problem until your BMS starts throwing fits six months down the line. Slow and steady wins here.

@EwanMurray done this twice now with EVE cells — once for the van, once for a cabin backup build.

Top balancing is non-negotiable before first use. I parallel all cells with short, beefy cables and let them sit connected for 48hrs or so before charging the parallel bank up to 3.65V. Slow and steady.

Worth grabbing a proper bench power supply with current limiting if you haven't already — trying to do it with a basic charger is a headache. I use a cheap adjustable unit off Amazon, nothing fancy.

Also document your starting voltages before you touch anything. Useful data if a cell ever causes grief down the line and you want to track behaviour over time.

The Daly BMS I ran initially was fine for balancing maintenance afterwards, though I've since moved to a Victron/JBD combo.

@WonkyMechanic solid point on the top balance. One thing I'd add specifically for those EVE 280Ah cells — watch your charge current during that final absorption phase when they're all sat at 3.65V in parallel. I made the mistake of letting my bench PSU push full current right up to the knee and one cell got noticeably warm. EVE's own spec sheet recommends dropping to 0.05C for the tail end. With 280Ah cells that's 14A maximum — sounds obvious written down but when you're excited to get the build finished it's easy to just leave it running. A decent CC/CV bench supply with proper current limiting makes this so much less stressful than bodging it with a car charger. The Riden RD6018 is what I use now and it's transformed the whole process.

@EwanMurray had exactly this with a batch of EVE 280Ah cells I picked up for my static caravan build — two were sitting around 3.27V, one at 3.31V and one noticeably lower at 3.19V. Perfectly normal for cells that have been sat in a warehouse.

One thing nobody's mentioned yet — once you've top-balanced and got your pack assembled, spend proper time dialling in your Victron (assuming you're going that route) absorption settings for EVE cells specifically. The default LiFePO4 profile is a bit aggressive out of the box. I run 3.45V/cell absorption with a fairly short tail current before float kicks in, and the cells have stayed beautifully balanced ever since.

Give the Fogstar documentation a proper read too — they do include cell spec sheets which tell you the manufacturer's recommended charge parameters.

@EwanMurray going through something similar with my shepherd's hut build right now — four cells, four completely different voltages, like they'd each had their own little holiday before arriving.

Quick question for the group: once you've top-balanced and got everything singing nicely, how long are you actually leaving them under a controlled charge before trusting the BMS readings? I've got a Victron BMS on order and I'm wondering whether to hold off commissioning the whole lot until that arrives, or crack on with a basic balance first and reconfigure later?

@EwanMurray totally normal with EVE cells unfortunately — they're shipped at storage voltage deliberately to keep them safe in transit, so wildly different readings are par for the course and nothing to worry about. Before you do anything else, just give them a slow charge individually to around 3.45V each, then connect them in parallel for your top balance — leave them sat together for 24-48 hours minimum until they all settle to the same voltage. Only then wire up your BMS and do your first full cycle. @Slim same advice applies to your shepherd's hut build! The cells themselves will almost certainly be absolutely fine. 😊

Hey @EwanMurray, just to add to what @Wendy1967 said — before you even think about top balancing, give each cell a slow charge individually to around 3.65V first. Rushing straight into a parallel top balance with cells at wildly different states can cause a fair bit of current to rush between them, which isn't ideal. A decent bench power supply with current limiting makes this dead easy. Once they're all sitting at similar voltages, then parallel them up overnight to top balance properly before building your pack. Takes a bit more time but your BMS will thank you for it!