Indications for using battery heating (now the weather is getting colder)

[ukslim]

Does the bug affect cabin pre-heat, battery pre-heat or both?

I decided to do a battery pre-heat this morning. Started it 90 minutes before departure; app said it was on. Looked again 30 minutes before departure and app said it was off.

 

[Rolfe]

I don't know, I've never tried to pre-heat the battery. I thought the point of pre-heating the battery was to condition it to take a charge, so would you be doing it when the car is plugged in at home?

 

[gnutrino]

The driver's seat heater and passenger seat heater are the wrong way round in the app. To heat the driver's seat you have to select the passenger seat.

Just one of the joys of living in a RHD country when most of the rest of the world is LHD I assume. I blame the French.

 

[fnegroni]

I don't know, I've never tried to pre-heat the battery. I thought the point of pre-heating the battery was to condition it to take a charge, so would you be doing it when the car is plugged in at home?

When it’s at or below freezing it can prevent power delivery issues. I too wanted to test whether warming up the battery while connected to a granny charger was possible but the temperatures the last couple of days weren’t cold enough in the morning. I will try next time they fall down to below 5 degrees

 

[Rolfe]

I still haven't really figured out how to handle battery heating, but now the weather is getting colder (we've had frost here) I need to get to grips with it.

 

[Diggsy]

Is the battery preheating not simply to help with fast charging? That being the case, it doesn’t seem to make any sense for most of us who charge at home to have it activated.

 

[Rolfe]

I am not sure about that. I wonder about maybe starting a new thread about this. Should I split this one off?

OK, executive decision. I've made this into a new thread. Have at it.

 

[siteguru]

If you home charge the vast majority of the time, battery pre-heating isn't really worth it, certainly not for battery charge rate. You can improve efficiency when driving if the battery is heated, but you really need to be doing 20+ miles at a minimum (in one go) for the energy lost in heating to be a worthwhile investment, otherwise you'll end up using more energy than you would have by simply driving.

Notes caveats about driving style etc. ... this is probably the biggest influence to efficiency - miles/kWh

 

[Rolfe]

So if I'm going the 50 miles to Glasgow in the depths of winter, I should turn on battery heating? When should I do that? When I set off?

What about "intelligent battery heating" that we were all urged to turn off in the spring to improve our miles/KWh figures? How intelligent is it? Should we just be leaving it on in winter, or not when we're only doing short journeys?

 

[siteguru]

Battery heating whilst plugged in and charging I'd absolutely agree with. Beyond that, I don't think it's implemented well enough yet to be worthwhile.

 

[Rolfe]

What did you do last winter?

 

[lsb777]

I don't have my leased MG4 yet so I can't check, but it looks like there is an "i" next to the on/off switch for the battery heating. Can someone push and see if it gives any answers/help?

 

[siteguru]

What did you do last winter?

I just left intelligent battery heating off. I rarely did any trip where pre-heating the battery would give any benefit.

 

[MoDolph]

How intelligent is it?

My testing shows not very. I think it does the following but I need to wait until the weather is colder to confirm it:

If the battery temperature is <10 °C then it turns on until the battery temperature reaches 10 °C.

If you program a rapid charger into the satnav then it doesn't activate further heating.

 

[ukslim]

Ah OK. I was under the impression that low battery temperatures completely killed efficiency. And that this affects short journeys worst, since the journey's over before battery warms up -- so heating the battery in advance would be a good idea.

I guess I'll just observe my range and see whether the first part is true first!

I'm also a bit vague about how cold is cold enough to expect significant range degradation. 5°C? 0°C? -5°C? Or colder temperatures we rarely see in England?

 

[GarRo247]

I've seen a Tesla say it was heating the battery to improve range as part of it's preheating. I think in Canada they recommend heating the battery before driving. A cold battery would reduce the voltage a little and therefore horsepower too.

It's difficult to come up with an equation of when it is worthwhile. What if it takes 1kwh to heat the battery. Making that number up. How long are you going to have to drive for it to be worthwhile to make that 1kwh back in efficiency. If it improved efficiency by 10% you'd have to drive at least 70km to make back the power used to heat. And then on any sort of longer journey the battery is going to heat itself anyway as far as I know, so there is some distance after which you'd be up to temperature either way.

 

[the happy bunny]

On my Tesla (Model 3 with LFP batteries), the main reason for pre-heating is to draw power from the mains rather than depleting the car's own battery, to warm both the cabin and the battery itself.

LFP batteries perform quite inefficiently when they are cold, impacting their performance and regenerative braking capabilities (which further decreases efficiency).

So, performing preheating is a good way to mitigate the range drop experienced in colder weather.

Additionally, Tesla vehicles have a feature called 'battery preconditioning,' which is automatically activated when you're en route to a supercharger. The primary goal here is to warm the battery specifically to enhance the charging process. A warmer battery performs better during charging, improving the charging curve and allowing for a faster charge rate.

 

[Rolfe]

I presume that in our cars we can always turn battery heating on manually if we know we're heading for a rapid charger.

I'm not sure if the SE SR will let you pre-heat the battery using mains electricity just before you set off, if you've already charged to 100%. There's something funny going on there. Ideally, if you're plugged in to the charger, it would make sense to draw power from that to heat both the battery and the cabin just before you set off, but I don't think it lets you do that.

 

[siteguru]

I know you can manually start battery heating from the app too. (It's not obvious but it's under the Scheduled Charging link from the Charging Management page). No idea though if this works whilst you're charging on your home charge point.

 

[MoDolph]

I know you can manually start battery heating from the app too. (It's not obvious but it's under the Scheduled Charging link from the Charging Management page). No idea though if this works whilst you're charging on your home charge point.

It does activate the battery heating if the car is charging provided the battery temperature is below a certain threshold (10 °C I think).

When activated you see a reduction in the charging power shown in the app so this must be showing what is going into the battery.

If you try to activate it when the battery temperature is above the threshold it returns the message "Battery pack does not need to be heated"