How do you pre heat the battery

[lsb777]

I don't have scientific proof but can only provide an opinion based on recent experience. Mid-February I drove from Brighton area to Liverpool. I left home at 4am and ensured that the home charging finished at that time. I also set the battery pre-heating to come on and also finish at 4am (I think I set it for 90 mins). I didn't set the cabin pre-heating as weather was not icy and I'm happy with the heated seat & s/wheel initially, but did have the HVAC running at fan speed 1 and 23c once I got going. I arrived at Tesla Banbury with 33% battery, so approx 3.29mls/kWh for 135 miles at mostly motorway speed. Based on this alone, it would seem that the pre-heating did help to ensure I started with a warmer battery giving better range than ABRP expected.

There is some logic to using the function in that we all know that EV batteries dislike the cold weather (so a pre-warmed battery should perform better) and batteries do not take rapid charging as effectively when the battery is not at optimum temperature (hence companies like Tesla pre-conditioning their batteries prior to supercharging). Somewhere on the net there's bound to be an experiment to see how much battery is lost by pre-conditioning the battery in the miles before rapid charging, compared to how much longer you may have to wait at the rapid charger and not get the speed you were expecting to see.

 

[tsedge]

As I understand it:

• Warmer battery == longer range, this is principally why EVs have a shorter range in the winter.
• Warmer battery == faster rapid charging, significantly quicker when warm.
• Long journey == battery gets warm after a few hours anyway, so no need to pre-heat battery if charging after several hours.
• Short journey == cost of pre-heating battery won't be recouped, so no point doing it.
• Long journey with early stop for rapid charging == preheating will probably be worth it to speed up the charging and extend the range for the second part.
• At home plugged in == might as well pre-heat battery if you want to.

Like others, when I turned off intelligent battery heating being always on, my range went up and I've left it off.

 

[fnegroni]

i would add to the above: if you expect maximum performance from the motor, you must enable intelligent battery heating and ideally pre heat the battery: primary example, mg4 xpower taken for a quick blast in winter.

I monitor the battery temperature and the LFP battery pack doesn’t warm up greatly while driving even for long periods unfortunately. So if it’s very cold outside (at or below freezing) I either preheat the battery if I’m doing several short journeys over a few hours time span, or don’t pre heat the battery but enable the intelligent battery heater at the start of a long journey

 

[siteguru]

I wonder if pack self-heating is a function of reduction in cell voltage? (As well as current draw). If yes then that could explain why the NMC pack does self-heat whereas the LFP pack doesn't (to any great extent).

 

[tsedge]

Yes, the NMC definitely does self-heat well, so probably the advice for LFP owners should be to use the intelligent heating more often than for us.

 

[Rolfe]

I suppose I could turn the intelligent battery heating back on and see what happens. It would be interesting to see if my range could get any worse than it is already, with repeated evening trips to a village three miles away, and back, with cabin pre-heating.

 

[fnegroni]

I suppose I could turn the intelligent battery heating back on and see what happens. It would be interesting to see if my range could get any worse than it is already, with repeated evening trips to a village three miles away, and back, with cabin pre-heating.

It will definitely get worse with intelligent battery heating. Pre heating the battery is the better option of the two in that case, if you need the battery to be heated. If you take it easy you don’t need to do either on short trips. Heck, on trips of around 1 mile or two and less than 10 minutes I don’t put the HVAC on either as it’s an absolute waste.

 

[Rolfe]

I just turned it on this evening, prior to putting the car on charge. I'm doing a long trip on Thursday. But I'm wondering what good it's likely to do. Am I right in assuming that the car will heat the battery anyway if not doing so would be likely to cause damage or shorten its life?

 

[Tig170]

LFP user here : not really found a use for this, can get 86 kW when battery lower than ~40%, but as soon as above 90% ish - down to 10-20% ish. Not really found a use for battery heating either at home or via DC rapid charging.

 

[fnegroni]

I just turned it on this evening, prior to putting the car on charge. I'm doing a long trip on Thursday. But I'm wondering what good it's likely to do. Am I right in assuming that the car will heat the battery anyway if not doing so would be likely to cause damage or shorten its life?

You mean you pre-heated the battery or you enabled intelligent battery heating?

 

[hharzel]

I keep the battery heater on whenever it's below 1-2°C and also preheat for at least half an hour, unless it's less than -10°C, then I preheat for one hour. With cabin heater on, yes it will more than double the consumption for the SE without a heat pump. AFAIK, LFP is much more tolerant of high count of charging cycles than lithium plating, which is the primary battery wear mechanism in colder environments - that along with the fact that I cannot completely turn off recuperation, I'm not taking any risks with battery life.

I don't care about performance and acceleration, I just like my tools to last and as for the car, I don't expect less than 10 years.

As I side note, last week the weather was rather mild (a few degrees celsius above zero) so I decided to drive without both cabin and battery heater using only heated seats and steering wheel. I was reminded on how efficient the car could be with 14-15kWh/100km consumption, so the car is obviously an excellent choice for warmer places. Unfortunately here in Finland it's nearly 150 days of freezing hell, so I have to admit the LFP version wasn't the best choice and if I were aware of leasing options at the purchasing time, I would have waited for Trophy/Luxury.

 

[tsedge]

I just turned it on this evening, prior to putting the car on charge. I'm doing a long trip on Thursday. But I'm wondering what good it's likely to do. Am I right in assuming that the car will heat the battery anyway if not doing so would be likely to cause damage or shorten its life?

There is no question of damage or life shortening here. The car will not let that happen.

 

[tsedge]

You mean you pre-heated the battery or you enabled intelligent battery heating?

Yes, the two are separate functions - one off manual preheat vs the car choosing when to apply it.

 

[Rolfe]

You mean you pre-heated the battery or you enabled intelligent battery heating?

I enabled intelligent battery heating, wondering what difference that will make to the long trip tomorrow.

 

[Rolfe]

There is no question of damage or life shortening here. The car will not let that happen.

That's what I was assuming/hoping.

 

[siteguru]

This seems to be on topic:

 

[fnegroni]

I enabled intelligent battery heating, wondering what difference that will make to the long trip tomorrow.

It will only make a difference when you start the car. Not while charging it.

It probably won’t make much of a difference in terms of efficiency if you drive economically or if you don’t plan to super rapid charge.

It should though make a difference on the regen.

It will possibly give you a few extra miles though: maybe 5 or 6 depending on the temperature and how much regen you have.

 

[tsedge]

This seems to be on topic:

The video is a useful explanation but his advice isn't suitable for all.

For example:

• He doesn't mention that a warmer battery will give more range: this is not a small effect, this is principally why winter range decreases so much.
• With a plastic undertray below the battery, the wind doesn't have a significant effect on battery temperature: it stays hot for a long time.
• I find a long drive DOES warm the battery well on my Trophy LR, I get very high charge rates well over 100kW if I charge after a 2-3 hour drive even in winter. Apparently the LFP is different, however.

His explanations help but he is oversimplifying the advice - find out what your car does and what it benefits from.

NB: MG should make it much clearer and give us more control over battery heating.

 

[Rolfe]

I'm still confused. I appreciate that the car will look after the battery and turn on the heating if that is needed to preserve battery health, without me needing to do anything about it. So far so good.

Pre-heating. I can't pre-heat using mains electricity unless I carefully time the charge to be finishing the balance just as I want to drive off, and I don't know how I'd possibly do that, given that I don't know by how much the battery heating would extend the charging time. I can't see a practical, reliable way to have the car at 100% battery and pre-heated at the time I'm ready to go. I can't see that pre-heating the battery at the expense of range (using the energy in the battery to pre-heat) is going to be a winning strategy.

If you have to have over 20-30% charge in hand to pre-heat when approaching a rapid charger, that isn't going to happen either, most of the time. And again, is there really a point? If you don't use up charge to pre-heat then you're starting from a higher SoC - you don't have to charge so much. A warm battery is going to have to speed up the charging to a miraculous extent to make up for that loss, and I don't think it does.

I appreciate that much of the trouble in Chicago was caused by people taking stone-cold batteries to superchargers. But I'm not going to be doing that anyway. If I'm rocking up at a rapid charger, I will have been driving for over 100 miles by the time I get there.

Intelligent battery heating. This was what I was going to try tomorrow, although maybe it's not cold enough? 7ºC in the morning dropping to 3ºC by the time I get home. I've got 150 miles of range showing, though that is pessimistic as it's based on a series of short evening journeys, and I plan on driving 120 miles in the day altogether. I have an opportunity to charge on a type 2 while I'm in the theatre if it's looking tight, or there are ultra-rapids I can stop at on the way home otherwise, but I anticipate not needing to charge.

But really, if intelligent battery heating eats range rather than conserving it, I don't see the point of any of it.

 

[fnegroni]

Pre-heating. I can't pre-heat using mains electricity

You need the car to be upgraded to allow pre-heating when connected to a charger but not charging (whether at 100% or less). It will then use the HV battery.
You will still need to top up the charge, I'd say account for 3-4 % extra use (1.5 to 2kW).

I can't see that pre-heating the battery at the expense of range (using the energy in the battery to pre-heat) is going to be a winning strategy.

Depends on whether it is several degrees sub zero or it's above 5C.
At -10C you warming up the battery makes sense because otherwise you will have reduced power.
At 5C or above, it's a winning strategy if you plan to super rapid charge within 10/15 minutes, otherwise the intelligent battery heater will take care of it if you plan to rapid charge at some point on your journey.

If you have to have over 20-30% charge in hand to pre-heat when approaching a rapid charger

No you don't. 3 to 4% to pre heat. Intelligent battery heater might get the battery to temperature while driving with less (2%), which is what I use on long journeys instead of battery pre-heating if the temperatures are mild. I only pre-heat (plus intelligent battery heater) if the starting temperature is 0 or below.
But not if I planned one or two short journeys for the entire day: then I don't see the point, unless it's like -10C or something.

If I'm rocking up at a rapid charger, I will have been driving for over 100 miles by the time I get there.

And your battery might still be stone cold if it's LFP and the outside temperature is really low.
The disadvantage of efficient (and less powerful) motor combined with the LFP chemistry will not help generate waste heat.

Intelligent battery heating. This was what I was going to try tomorrow, although maybe it's not cold enough? 7ºC in the morning dropping to 3ºC by the time I get home. I've got 150 miles of range showing, though that is pessimistic as it's based on a series of short evening journeys, and I plan on driving 120 miles in the day altogether. I have an opportunity to charge on a type 2 while I'm in the theatre if it's looking tight, or there are ultra-rapids I can stop at on the way home otherwise, but I anticipate not needing to charge.

But really, if intelligent battery heating eats range rather than conserving it, I don't see the point of any of it.

It will eat a little bit of range at first, but by the time you've done the 150 miles, it will be recovered by Regen mostly and you will gain a more efficient power delivery from the battery which will benefit mileage (a tiny bit).
Admittedly 7 to 3C is borderline: I'd say leaving it on would be better IMHO.