Anyone else finding Fogstar Drift cells need a full balancing cycle before first use?

Just taken delivery of a 4x280Ah LiFePO4 pack from Fogstar for my narrowboat build and noticed the cells arrived with quite different state of charge levels — one was sitting at 3.27V, another at 3.31V. Not massive but enough to make me wonder.

I've got a Daly Smart BMS wired up (150A, 4S config) and I'm planning to do a slow top-balance at 3.65V per cell before I assemble the pack properly. Curious whether others skip this step or consider it essential? I've read both camps online and it's confusing.

Also — does anyone know if the Victron MPPT charger absorption phase is aggressive enough to push passive balancing through the Daly, or is it worth grabbing an active balancer board as well? My solar array is only 400W so charge current will be fairly modest.

WS_VanLife | 847 posts

@RustySkipper completely normal with Drift cells in my experience — mine arrived with similar variance. What I'd suggest before even connecting your BMS is to do a slow top balance at the cell level. Get them all sitting at 3.65V individually using a bench power supply, let the current taper right down to near zero, then assemble your pack. The variance you're seeing (3.27 to 3.31V) is actually pretty modest compared to some batches people report, so you're not in bad shape. The bigger issue is if you skip this step and let your BMS try to sort it out — you'll end up chasing ghost capacity readings for weeks. Fogstar's support team are decent if you want reassurance, but honestly this is just standard LiFePO4 handling rather than anything specific to their cells.

ExPostie | 312 posts

Had the same with my Fogstar Drift 280s when I built the pack for my shepherd's hut last spring. The voltage spread was even wider than yours — think I had nearly 60mV difference across four cells.

I wouldn't rush straight into top-balancing though. Let them sit connected in parallel at around 3.65V for a good 24-48 hours before you even think about assembling the pack properly. Some people skip this and then wonder why their BMS is throwing balance warnings six months later.

What BMS are you running? If it's a Daly or similar with a narrow balance trigger threshold, it'll struggle to catch up if the cells start significantly apart. A JK or Seplos will handle it better but still — do the legwork upfront and save yourself the headache later.

HeathOllie | 1,203 posts

@RustySkipper worth noting that the voltage spread you're describing (roughly 40mV) is actually fairly modest for cells that have been sitting in a warehouse. The real issue isn't the resting voltage difference — it's that LiFePO4's flat discharge curve means a small voltage gap can represent a surprisingly significant capacity imbalance once you start cycling.

For my garden office build I top-balanced all four cells individually using a bench power supply set to 3.65V CC/CV before connecting the BMS. Brought each cell up independently, held them there until current dropped below ~100mA. First proper charge cycle after assembly the balance was near-perfect.

A decent active balancer BMS (I run Daly on my setup) will handle minor drift long-term, but that initial manual top-balance saves weeks of the BMS slowly working through the discrepancy.

CliffGazer | 156 posts

@RustySkipper one thing nobody's mentioned yet — top balancing vs bottom balancing matters here. For a boat application you almost certainly want top balance (charge all cells to 3.65V and hold there until current tapers off).

I did exactly this before commissioning my own marine pack and it made a substantial difference to how the BMS behaved during high-draw situations.

Worth double-checking your BMS balance leads are actually connected correctly before you start — I made a rather embarrassing error on my first attempt and wondered why nothing was happening for about two hours. Different cell numbering convention to what I expected.

Also — what BMS are you running? Some cheaper units have a balance current so low (like 30–50mA) that top balancing takes days at that cell spread. Victron-adjacent setups handle this far better in my experience.

SOC_Wizard | 89 posts

@CliffGazer good shout on the top vs bottom balancing distinction — that's caught me out before with my shepherd's hut setup.

One thing I'd add: what BMS are you running? I've found with Daly units the balancing current is often only 30–50mA, which means getting those cells properly topped off can take days at full charge, not hours. A proper active balancer wired in during the initial cycle makes a massive difference.

Also worth checking — did Fogstar include a cell datasheet with measured capacities? Mine varied by a few Ah between cells which affects how long the weaker ones need at absorption voltage before they're genuinely full.

48V_Pro | 2,847 posts

@RustySkipper I'd also suggest keeping an eye on your BMS passive balancer current during that first cycle — many budget BMS units only balance at 30–50mA which is painfully slow across a 280Ah cell. With a 40mV spread you're not in terrible shape, but if your BMS is only trickling away at that rate it could take several full cycles before things properly settle. Worth checking the spec sheet. If you're running a JK or similar active balancer you'll get there much quicker. Also, once you do get them balanced, log the voltage at rest after a full charge — gives you a useful baseline for spotting any cell drift further down the line, which matters especially on a narrowboat where you can't always keep a close eye on things. Good luck with the build! 🚢