Battery heating

[Ian 2455]

Can anyone direct me as to the best way to utilise the battery heating on my 24 plate MG ZS EV? As the nights here in South Wales are already dipping down into the single digits, I use the battery heating function for when I am charging overnight but I was wondering if I should start to consider using the function prior to moving off in the morning as well?
Please keep all technical explanations at a level that a 1975 GCE O Level owner can understand...

 

[Robf]

Battery heating is to enable you to heat battery on cold days when you are approaching a rapid charger (20 mins before), otherwise I think best advice is to leave it off. Doubt it will help much at home charger.

 

[Lovemyev]

Pre heating the traction battery to the optimum temperature, prior to DC rapid charging, will help the car reach the highest possible charging rate / speed that it can on that day, on that charger.
But you have to factor in that using this facility, will reduce your remaining range.
So, if you are cutting it close to reach the rapid, then it may not be a good idea to use it.
When the car is plugged into a A/C home wall box and you select pre heating the battery, the wall box should engage and try to back fill the energy drawn from the traction battery.
But remember, if you are charging on cheaper “Off Peak” tariff and you are outside of the cheaper rate, then you will be paying a higher day rate that may out way any advantages of preheating the battery ??.
Myself, I have never used the battery preheat facility on our ZS EV.
More useful if you are rapid charging if you are in a big hurry IMO.

 

[RamseyLewis]

Hello. In the app there is a preheating schedule menu, and it says it's recommanded to pre-heat 1 hour before using the car. I've got a 4 hours roadtrip and i was wondering of I should do that before leaving in the morning, when the car is plugged (but charge ended). I'm trying to figure out this pre-heat things since almost 3 years and it seems there is no consensus on when to use it.

 

[Bubs]

The battery operates more effectively at the correct temperature. For both driving and for charging. Pre heating for an hour before hand can get your battery ready rather than while driving .

The confusing area, I find, is the question of if it is worth it to spend the energy to get to that temperature? Especially as we don't really get temperatures that are very low in the UK & Ireland.

I'd consider it if the car was plugged in and would use house power rather than battery power. And I had a long trip. But otherwise I leave it off.

 

[APMG]

Pretty sure battery heats at 7kW as well, so if you heat it for one hour you're perhaps being efficient driving but in fact just wasted 7kWh you could have used for some extra range.

Unless it's really in the minus Celsius for a long drive I'll no doubt ignore it.

 

[hmadsen]

Preheat is pretty simple to understand.

The battery can not take or deliver as much current when it is cold as when it is warmer.

So if you arrive at a supercharger with a stone cold battery, you might expect to get 90 kW but in reality you only get 30 kW (Charging heats up the battery, so it will probably rise in power (kW) after some time though).

If the car tried to accept 90 kW into cold batteries this would damage them.

The same can be true for driving, you can not draw as many amps from a cold battery, which in turn would mean that the acceleration is slower because of the low amps the car is allowed to draw from the batteries.

The third part is, when the car is doing regen braking. This also puts amps back into the battery and quite a few (Albeit very briefly).

I drive a Tesla and it has a telltale that means "Regen braking is limited". This one comes on if the car is unable to do full power regen as a warning, that one pedal driving might be limited and to remember to use the brakes instead.

This is always on, if I charge to 100 and in the summer it will turn off at about 95%

In winter with a stone cold battery I have had this one on, even if the SoC was below 60%, simply because a very cold battery will not ever be able to handle the current, the regen braking delivers to the batteries, even if it is not fully charged-

Of course, both the MG and a Tesla has software that limits the current into the battery, based on temperature and SoC so the battery will not be damaged (Probably mostly because MG or Tesla would have to replace the battery under warranty ).

I know that if I, on the Tesla app, set a departure time, it will heat the cabin if not plugged in, but if plugged in, it will heat both the cabin and the battery, to make the car has "full power" from the get go.

It also heats up the battery if navigating to a supercharger, the wildest I encountered was one morning, temperature was -11°C, I set a destination for a supercharger that was 100 miles away and it started heating as soon as I pulled out of the driveway (It says "Heating battery for supercharging" on the screen, when it has the battery heating on) and kept the heater on for the entire 1½ hours of driving.

 

[Ian 2455]

Very informative and well written. Thanks!