Battery Heating Software Level 3

[Daveion]

I thought I would raise a new thread on this topic as I had a different take on what it means after watching Chris from Battery Life on Youtube.
If I understood correctly he was saying in the last year heating his batteries whilst driving had cost around 50 euros in electrical costs.
That is the additional charge cost required to put back what battery heating took out over and above his drive. Although cost was a repeated theme in the video what I found more interesting is the impact on range, in particular several short jouneys where you get the batteries to temperature and after stopping for 2 or 3 hours have to repeat the heating process again because they have cooled down.
Although we know heating the batteries decreases range there was a side to this that's not much discussed. That is, what impact there is to performance overall if you just allow the normal drive to bring the battery temperature up without supplementary heating?
Until the batteries are at the correct temperature you dont have full expendable output or regen. So heating the batteries brings this level up much quicker than just the process of driving and battery use.
But do you really need that?
Does it damage the batteries if you use the car for short runs without being at the correct temperature?
Is it in itself a big impact on range if your batteries were not heated?
The battery heating will be amended in level 3.0 as we are to understand which will improve Winter (cold weather) range and although I'm guessing, it maybe you can choose to not have battery heating switched on knowing you will not be so quick off the mark or be able to regen to the same degree initially.
When we have seen posts about pre heating the battery pack I have assummed that this is the way to go for highest efficiency and range.
If pre heating in level 3.0 is not selected maybe there will not be any supplementary heating to the battery pack which will also possibly improve cold weather range.
It will be interesting to see what affect this all has on shorter journeys in cold weather.

[G43FAN]

There are two things certain in life, Death Taxes and Battery Degradation.
Respectfully, I doubt VW will leave decisions on battery management to the driver, or move that far from it's pretty cautious management already. They will have collected a lot of data over the first 12 months of cars in the real world and this update will be just another tweak I imagine. The warranty underwriters have 2028(?is it) in their sights and won't want to be paying out to refresh a couple of hundred thousand battery packs. At most maybe a 'Maximum Range' option but the BMS will still be in control of heating etc.

Driving without heating the battery - As I said above, I can't see that ever being in the drivers control, I thought I had read that the change would mean the heater not kicking in until below 5 degrees C rather than 12 or 15 whatever it is now. Ultimately that will reduce power consumption and therefore increase range assuming there isn't a head wind or denser air due to the cold, or rain and sleet. These all need to be added to the picture of efficiency.

Damage to the Battery is more likely to occur due to excessive heat and or high rates of Charge or discharge. Batteries have a C rating (Well 2 C ratings) one for Maximum charging rate and one for Discharge. The latter usually being a lot higher then the first. Charging rates of 5C are not uncommon in smaller multi cell batteries(for an 62kWh ID.3 this would mean charging the battery from 0 -100% in 12 minutes and would need 310kW+ charger) VWs recent talk about increase to allow 125kW charging is edging towards a conservative 2C rate. (Discharge rates can be 10 times those figures)

Short journeys will still be inefficient, but as they are short and you can top up charge as much as you want, it shouldn't matter?

[Daveion]

That is three things not two
We shall see how it pans out. I think you are right that it wont necessarily be the drivers choice but if the result is no heating to the battery under lower ambients than today essentially the outcome is much the same.
Is there data on what percentage of battery heating is achieved as a result of driving versus the 5kW or so specific battery heating.

[rwh202]

Although we know heating the batteries decreases range there was a side to this that's not much discussed. That is, what impact there is to performance overall if you just allow the normal drive to bring the battery temperature up without supplementary heating?

This is the big question I've been wanting to understand. OK, a cold battery has greater internal resistance, so higher I2R losses, but all that does is heat the cells, so why not let that do the job instead of pumping energy into resistive heaters?

As you've mentioned, you have reduced maximum power output (and regen) until things get up to temperature, but that's true of most modern IC engines too. We don't see too many of them using heaters to bring engines up to temperature quicker.

Maybe there's something fundamental I don't understand about the chemistry where operating at lower temperatures reduces the total amount of energy released.

[Daveion]

Although we know heating the batteries decreases range there was a side to this that's not much discussed. That is, what impact there is to performance overall if you just allow the normal drive to bring the battery temperature up without supplementary heating?

This is the big question I've been wanting to understand. OK, a cold battery has greater internal resistance, so higher I2R losses, but all that does is heat the cells, so why not let that do the job instead of pumping energy into resistive heaters?

As you've mentioned, you have reduced maximum power output (and regen) until things get up to temperature, but that's true of most modern IC engines too. We don't see too many of them using heaters to bring engines up to temperature quicker.

Maybe there's something fundamental I don't understand about the chemistry where operating at lower temperatures reduces the total amount of energy released.

I'm also trying to understand this. It would seem a waste of energy to get the batteries to temperature more quickly so we can enjoy the full power and regen ability which then translates into a better range. In my decades of ICE motoring I always allow the engine to warm before driving it normally. Although the two are not technically comparable the principle is much the same in that the efficiency is best when things are at the correct operating temperature.
5kW or 6kW of battery heating for maybe 15-20 minutes on a 20 minute journey seems a waste on the face of things but without more data on affect to batteries or oveall performance we will not know.
Pre heating the battery plugged in is something I would do if it does come with level 3.0 SW.

[MotMot]

So theres a curve for battery performance / efficiency and how it changes with temperature

A curve for how quickly the battery warms itself up - according to the current drawn/added - probably how this changes with temperature too

A curve for how much energy the battery uses to warm itself up over a range of different temperatures

And some curves as to how all of above affect battery degradation.

Combine these and you get the answer

[Daveion]

Do you have any links to tge graphs?

[G43FAN]

I think the graphs referred to are Generic..

If you really want to spend some time in and around this complex area, then Battery University has a lot of information and many graphs, the EV data is mostly Tesla based but the principals of Lithium Battery management are similar.

https://batteryuniversity.com/article/b ... vehicle-ev

[mediaguy]

That's a pretty great page. Most importantly you point anyone to https://batteryuniversity.com/img/conte ... endar2.jpg anytime the question "Why shouldn't I leave my car at 100% in my drive" arises.

[MotMot]

That’s a great article