Seplos heating function not working?

I’ve been chatting to a Seplos engineer to try and understand how to make this work, and according to what I’ve been said, this should work.


I’ve placed temperature sensor 1 just above the heating pad, and temperature sensor 2 in a glass with ice
Temp 2 is 3°, so it should activate heating. However, temperature sensor 1 hasn’t gone up and measuring the voltage at the heating pad connectors shows ~ 0mV indicating it isn’t heating

Did you have any luck figuring this out? I've had the kid + temp sensors and just started laying things out. I noticed they published a video for the kid about the heating pads, complete with showing a bunch of different temp sensors underneath the cells, etc. But none of those were in the box and now Docan Amy is telling me that was just for making the video lol. My battery is going in an unconditioned shed in the middle of the U.P. of MI so this has to work.

beckkl said:

Did you have any luck figuring this out? I've had the kid + temp sensors and just started laying things out. I noticed they published a video for the kid about the heating pads, complete with showing a bunch of different temp sensors underneath the cells, etc. But none of those were in the box and now Docan Amy is telling me that was just for making the video lol. My battery is going in an unconditioned shed in the middle of the U.P. of MI so this has to work.

Click to expand...

Well, sort of. I placed the 4 sensors on the outside of the cells at mid height, two on each shelf, on the 2nd and 6th cells of each row.

I have set the low temperature protection very low (I think -10 deg C), this is because below this the BMS won’t charge but also won’t attempt to heat the battery, so it’s not really a condition I want to be in, I want to always be able to charge.
Then I set the low temperature alarm to 5 deg C; below this it will heat the battery when the charge starts; yes, it will still charging the battery straight away (without waiting for it to be at a safe temperature) but at a very low rate (5A) which I think it’s fine (0.02C for a 280Ah). After all, EV with LFP battery still charge at low temperatures, just very slowly.

Interesting. Yeah, gonna have to play with it. Right now the batteries will sit idle and disconnected most of the winter. The only time I would charge it is when I am up there, and likely from the generator. My concern is how long it will take to get them to temp. My SOK 12V 100AH with heaters take about 30 mins or so to get up to temp. I have a feeling this battery will take MUCH longer. The video they put out I think said it could raise the temp 4 deg C an hour, which would mean several hours for me depending on the time of year.

I have this data from the coldest day so far (-5 deg C).
I have 25mm polystyrene insulation around the battery and it's in an unheated garage.

As you can see, it starts charging at 11.30PM with the battery average temperature around 6deg; the inverter is sending about 10A to the battery, about half of it is going into the actual cells (seplos_bms_current), while the other half is sent to the heating pads.
After about 30 minutes the temperature has increased by 5deg, and at 12:34AM it starts charging at full power (but is still diverting some of that to the pads until 1:00AM), where you see that step in "seplos_battery_current". The fact that it still keeps heating after the "low temperature alarm" is cleared depends on the bms parameters, I have set "battery heating recovery" higher than "low temperature alarm recovery" for no specific reason.

Interesting. Going to have to get all this stuff dialed in before I schlep it up north. Thanks for the input.

FYI, I stumbled across this video on youtube. It looks like the under temperature protection will turn on the heating fet....... after 30 minutes