Anyone else noticed Fogstar Drift cells running warmer than spec during bulk charge?

Running a 280Ah 12V bank (4S) in the cabin with a Victron SmartSolar 100/30 pushing about 25A bulk — cells are sitting around 35°C ambient 22°C, which feels higher than I'd expect from a "low internal resistance" cell.

BMS is a JK with temp sensing on each cell, so the data's solid. Absorption kicks in at 14.2V, bulk rarely lasts more than 90 mins on a good solar day. Nothing alarming, just... warmer than the Lishen cells I pulled out.

Anyone with Drift cells seeing similar, or have I got a duff batch? Wondering if it's worth dropping bulk current to 20A and seeing if temps settle.

@FogstarFan interesting one — I ran a 280Ah 4S bank through last summer and saw similar numbers. Turned out my busbars weren't torqued properly, so contact resistance was doing the heating more than the cells themselves.

Worth checking your terminal connections first before blaming the chemistry. A cheap infrared thermometer pointed at each terminal during bulk will tell the story immediately — if one cell is running noticeably hotter than the others, you've found your culprit.

That said, 35°C at 25A bulk isn't catastrophic for LFP — Fogstar's own spec sheet gives a charge temp range up to 45°C. Still worth investigating though, because poor connections compound over time and you'll eventually cook a terminal or trip your BMS at the worst possible moment.

What BMS are you running?

Hey @FogstarFan — worth checking your cell-to-cell compression as well. I had a similar issue with my Drift 280s and found that uneven clamping was causing a couple of cells to work harder than the others during bulk, which pushed temps up disproportionately. Grabbed an IR thermometer and scanned each cell individually — sure enough, two were noticeably warmer than the rest. Also, 35°C at 25A isn't necessarily alarming for LiFePO4 during bulk, but if there's much variance between cells it's worth investigating before summer proper hits. What's your BMS reporting for individual cell voltages at peak bulk? Significant spread there could point to an imbalance issue rather than anything inherent to the cells themselves.

Hey @FogstarFan — 35°C at 22°C ambient is a 13°C rise which is on the higher side for LFP at that current, but not alarming. Worth double-checking your BMS current sensing is accurate — sometimes the reported charge current is a touch optimistic and you're actually pushing more than 25A through. Also, are all four cells rising equally or is one running hotter than the others? An uneven temperature distribution across the bank often points to a connection issue rather than the cells themselves. If one cell is consistently warmer it could indicate elevated internal resistance, which Fogstar should want to know about if the cells are still under warranty. What temperature cutoff have you set on your BMS? I'd want thermal protection kicking in somewhere around 45°C just to be safe.