Has anyone actually stress-tested a Daly BMS at high continuous discharge? Curious about thermal behaviour

I've been running a 280Ah LiFePO4 bank (4 x 100Ah EVE cells in parallel... yes I know, I'll do series-parallel eventually) in my Sprinter build for about eight months now. Got a Daly 100A Smart BMS on there and it's been mostly fine, but last weekend I pushed it harder than usual — running a 1500W inverter for a few hours to power tools on a job — and the BMS got noticeably warm. Not scorching, but warm enough that I didn't want to keep my hand on it.

According to Daly's specs the 100A unit is rated for exactly that continuous load, so I'm technically within limits. But I've read mixed things about how aggressively Daly protects itself thermally and whether it'll quietly throttle or just hard-cut you. Mine didn't cut out this time but I was watching it like a hawk on the Daly app the whole time. Cells stayed balanced, voltages looked sensible, lowest I saw was around 3.18V per cell under load.

Has anyone here properly thrashed one of these — maybe with a clamp meter logging actual current draw alongside the BMS readings — and seen where it starts to protest? Also wondering whether it's worth upgrading to a JK or Seplos unit with better thermal management, or if I'm overthinking a warm BMS on a hot day in a metal van.

MPPTFan | 847 posts

@ValleyCruiser interesting setup! I ran a Daly 100A on a similar EVE cell configuration for about six months and thermal behaviour was... acceptable but worth watching. The MOSFETs are the weak point under sustained high draws - I measured the heatsink plate hitting 58°C during a prolonged 85A discharge on a warm day with poor airflow. Daly's own thermal cutoff is fairly conservative which is reassuring, but the protection trips before the rated current in practice once things get toasty.

One thing worth doing - check the actual balance leads are properly seated. Mine had a slightly loose connection on cell 3 that caused phantom voltage readings under load. Took me weeks to track down.

What inverter are you running? That'll likely dictate whether 100A continuous is even realistic for your use case.

DODQueen | 312 posts

@ValleyCruiser I've pushed a Daly 100A pretty hard on my boat — sustained 80A draw running the inverter for cooking. The BMS itself got warm but never thermal shutdown on me. What did happen was the balance leads getting toasty where they met the board after a few months; worth inspecting those solder joints periodically.

One thing I'd flag: the Daly's overcurrent response is quite slow compared to something like a Victron Lynx Smart BMS. Fine for most use cases but if you're seeing any voltage sag under load, check whether it's actually the BMS creating resistance rather than your cells.

What's your continuous draw actually hitting? That changes the conversation quite a bit.

LauraGraham72 | 203 posts

@ValleyCruiser worth mentioning the heatsinking aspect if you haven't already looked into it. I've got a Daly 100A on my narrowboat and found that mounting it directly onto a small aluminium plate (I used a bit of 3mm scrap from a local fabricator) made a noticeable difference to how it handles sustained loads. Without it, the FETs were getting quite toasty above 70A continuous. Also keep an eye on your balance leads — I had one develop a slightly dodgy connection which confused the BMS into throttling unnecessarily. Took me ages to diagnose. The Smart version's Bluetooth monitoring is handy for spotting anomalies in real time rather than after the fact.

HMK_Sparks | 203 posts

On my static caravan setup I fitted a Daly 100A Smart and ran it hard during an EV charging experiment — pushing close to 90A continuous through a DC-DC arrangement. The BMS housing got noticeably warm but nothing alarming; maybe 45°C ambient measured with a cheap IR thermometer.

What I did notice was the Daly cutting out intermittently above 35°C ambient air temp, which I suspect was the over-temperature protection triggering on the internal MOSFET temp rather than the cell temp sensor. Worth checking whether your readings are from the cells or the BMS board itself — they can differ significantly.

Have you looked at the Daly Smart app data during your high draws @ValleyCruiser? The MOSFET temperature readout there is more useful than anything external.