Efficiency and Battery Heating

[nbenn]

Question I have from looking at forums from people discussing how to increase their miles per kwh.

Is it more cost efficient (less energy used in total) to just drive away cold (as long as you don't need the distance) rather than heating battery before driving each time?

Do you end up using more energy to heat battery in total than if you'd didn't heat the battery.

 

[Ian Key]

As has been discussed in the MG4 Range thread the only time you need to heat the battery is if you are doing a journey over 35 miles and it's below freezing.
Or you are short of time and are going to use a fast charger in which case preheat the battery for 30 minutes on your way to the charger.

 

[nbenn]

Great to know! Thanks. My MG4 is here next week and just trying to make sure I know what to do with it!

 

[Buster72]

As has been discussed in the MG4 Range thread the only time you need to heat the battery is if you are doing a journey over 35 miles and it's below freezing.
Or you are short of time and are going to use a fast charger in which case preheat the battery for 30 minutes on your way to the charger.

Can I ask what is the basis for the over 35 miles figure.

 

[Ian Key]

In the thread Battery Heating I did some rough calculations. Here they are to save you searching:

Doing some very rough calculations...

It was mentioned on last nights podcast that the heater for the battery uses 7kW/h
A video on YouTube shows the car being charged for 30 minutes before using a fast charger but that was for normal temperatures but during the recent cold snap it would probably take an hour.
Most drivers were getting 2m/kWh where as with a preheated battery it could be 3.5m/kWh. Or put another way unheated is 0.5 kW/mile increasing to 0.285 kW/mile when pre heated. An increase of 0.215 kW/mile.
To break even when preheating the battery for 1 hour it would take a journey of 32.6 miles.

No doubt someone will disagree with my calculations

 

[Buster72]

In the thread Battery Heating I did some rough calculations. Here they are to save you searching:

Thank you for this. And I now understand.