Do you know how to make the heater film developing?How to solve the heating Pi film temperature unbalance? Large temperature differences can affect battery thermal management performance. Here below is the real case study how to solve this issue in our real experience.
1.functional analysis for heating film
the heater is putted between battery cooling plate and thermal pad, the main function is to heat up battery modules(4 modules). The temperature unbalance of all modules need to be within 10℃(heating from -20℃ to 15 ℃), heating rate less than 0.9℃/min. The heating film can be use for EV car or battery heater for truck.
2.first testing result
bad testing result. The temperature unbalance 16℃, totally unacceptable.
3.Root cause analysis for the heating film temp unbalance
We disassembly the thermal transfer film from battery pack, check it alone without battery module.
3.1.Check the heater film surface temperature unbalance
Apply on 220 AC, thermocouples used to see temperature distribution.
What we found: the highest temperature is on the middle, then the right zone, the lowest temperature is on the left zone. The failure mode is actually similar with battery module heating apply.
We cut the heating element(material is stainless steel) into equal piece, the same length, to check the electric resistance of heating element. The result is ok.
4. Failure analysis
1.Air around the heater film to absorb some heat which make the right & left zone temperature lower than middle zone.
2.The manifold of aluminum cooler on the left, heat go to manifold then to air, which make the left zone the lowest temperature.
5. Corrective action
1.Heater film design change.
Change the heating density distribution zone without change the total heating power.
2.Cooler manifold heat insulation
Apply heat insulation tap on cooler manifold to prevent heat leakage.
3.Adjust the heating film element pattern
6. Retest heating film in battery pack
Finally heating from -20℃ to 15℃, the max temperature is 9.5℃, heating rate is 0.76℃/min. Problem solved.
The heating film can be set to 12v,48v or 220v base on your electrical architecture voltage.