# Low power DC charging and battery heating



## mathias_c (8 mo ago)

Hello,

The problem of 7kW battery heating switching on when doing low power DC charging is already documented in video 



 .
To summarize, it shouldn't be neccessary to heat the battery if DC charging power remains low (under 50kW) but Tesla switches it on in all cases and it consume up to 7kW, leading to big charging inefficiencies.

I did the test using a personal 40kW DC charger on my model 3 2021 LR (Shanghai factory, Q4) and did some ScanMyTesla snapshots (attached). It should be normally still be considered as "low power" charging as it's around 0.5C (the battery capacity).
In the snapshot, can we can see that the car is heating the batteries up to 57-59 degrees Celsius. It is confirmed in the Tesla app with the orange heating icon symbol (looking like 3 sausages or bacon) that appears.
Doesn't such a temperature (57-59C), increase battery degradation ? (for Lithium NCA or NMC)
After the charging session, the car then increase the radiator fan speed to around 4600RPM to cool the battery and dissipate this wasted heat in the garage.

I have tried to enter service mode and disable battery heating manually but this didn't have an effect (I must make other attempts).
I was wondering also if it is better for the battery to do DC charging with a low State of Charge (less than 50%) rather than 50-90% ? (my guess is that charging from lower SoC is better as it's easier "to push" current when battery is at lower voltage)

Have you successfully been able to disable battery heating ? What's your view and experience on this ?

Low power DC charging in common in Europe (supermarkets,..) and also becomes available for private uses, this is unfortunate that this heating decrease charging efficiency considering soaring electricity prices and possibly degrade battery. This also block interesting applications to do low power DC charging (from solar panels for example) and avoid going the AC way.
I will have to stick to 11kW AC charging as much as possible.

Hopefully , Tesla will fix this one day and adjust parameters according to DC charging power....


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