Battery heaters getting tested this week!

[S Davis]

Well it looks like my battery heaters in the back of my truck are going to get a workout this coming week. They are 25 watt silicone pads between thin aluminum and a computer fan for circulation on each battery. I can add another 25 watt silicone pad to each battery if needed.

 

[sunshine_eggo]

I can't see where your temperature sensor is located. With circulating heated air, there's a chance the air could warm the sensor vs. the battery. If you haven't done so already, I would insulate the sensor so air can't influence the temp reading.

Good looking install.

 

[S Davis]

Thanks, I am heating the air around the batteries so I do want air temp, there is nothing to pull heat directly from the cells they are suspended about 1.5” off the bottom of the box. I am running the air temp on at 4c off at 6c and with the circulation fan the whole box stays a fairly even temp.

 

[sunshine_eggo]

I wondered if that was the approach as it looked like you have a rubber mounted "floor" for the battery. As long as the box is never allowed to drop below freezing, I expect you'll always be good.

If the heating system is off (if powered by the truck, and it turns off when the truck is off), and the entire box+batteries is allowed to cool below freezing, I would be concerned that the air heating method could allow the temperature sensor to read a higher temperature at the surface while the core of the cell is still below freezing.

 

[S Davis]

You are right the heaters are always on so the batteries should never get below 4c. If they do it’s not that big an issue, I manually charge them at this point and have a battery switch on the DC/DC charge line from the truck. I can check cell temp before I hit them with a charge.

 

[S Davis]

Well it is now 15f and the heaters are keeping up.

 

[Mike Jordan]

Out of curiosity, what is the draw when the heater is on?

 

[S Davis]

Out of curiosity, what is the draw when the heater is on?

When both fans and heaters are on they draw about 5 amps per the DALY app, I am not sure that is right. The BMS will not register a draw lower than about 3 amps, have not been able to resolve with DALY.