Anyone else noticed Fogstar Drift cells running warmer than spec in summer?

Finally got round to logging proper temperature data on my narrowboat bank — four 100Ah Fogstar Drift LiFePO4 cells wired in series for a 12V/400Ah setup, managed by a Victron SmartShunt and a Daly BMS. Been running it since last spring with no real complaints.

This summer though, during sustained charging from a 400W Renogy panel array plus the alternator, I'm seeing cell temps nudging 38–40°C on the hottest afternoons. The Drift cells are rated to 45°C continuous, so technically still within spec, but it's closer to the limit than I'd like given they're tucked under the gunwale with limited airflow.

I've added a small 12V fan on a thermostat (kicks in at 35°C) which has helped knock a few degrees off, but wondering if anyone else running Fogstar cells — in a boat or cabin — has hit similar numbers and whether it's actually caused any long-term capacity fade. Supposedly LiFePO4 is more tolerant than other chemistries, but sustained heat still ages cells faster in my understanding.

Has anyone data-logged capacity over a full season and seen measurable degradation from summer heat?

Hey @HeathGazer, interesting one! I've got a similar setup on my static caravan and noticed the same thing last July during that hot spell. Worth checking whether your Daly BMS is actually throttling charge current when temps climb — mine wasn't doing it as aggressively as I'd expected. I ended up adding a small 12V fan pulling air across the cells which made a noticeable difference. Also, are your cells sitting directly on a metal surface? I found putting mine on a thin wooden board helped reduce conducted heat from the hull itself. What temperatures are you actually seeing on the cells? Mine were peaking around 38-40°C on really hot days which felt higher than I'd like but still within safe limits. Would be curious to see your logged data if you're willing to share it! 🙂

Mine ran so warm last August I started charging my phone off the residual heat 🔥

Jokes aside — I've got Drift cells in my shepherd's hut and noticed they peak a fair bit higher than spec when the sun's hammering down and the Victron's pushing a big charge current simultaneously. It's like a perfect storm of warmth.