How hot should the batteries get while charging?

[chamshaw]

In theory but from what I've read, and i'm just a layman, the benefit of doing so doesn't outweigh the complexity, increased cost, and relatively small amount of energy a capacitor can store.

Right; but multiply by thousands? When I was a kid had a pal who would charge a capacitor then leave pockmarks on brass door-handles by shorting them on the metal. There's a kick available, if tiny.

 

[Gasaraki]

Recent research into capacitive rapid recycling has led to hybrid arrays which seem to combine modified Li-ion cells and capacitors. Could cells charge capacitors which can then be flash-discharged to obtain power? Just asking...

Why does this have to be asked in a zombified thread...

 

[Candleflame]

The target temperature for On Route Battery Warmup is 40°C, based on a comment by a Tesla engineer at the V3 Supercharger test station when it first opened in Fremont. I think the battery will charge at max rate when that temp has been reached, which is not trivial in cooler weather and with only a 7 kW of heating from both motors. Based on Tesla Bjorn videos, the charge rate will throttle down below the optimum taper when the batteries heat to 60°C.

Like you experienced, I've also seen in his videos where the car is heating the battery very late in the charge cycle but I don't understand the rationale, unless it's as simple as it always tries to heat the battery to just under 60°C. You may have noticed, but after the charge session stops, the car then tries to vigorously cool the batteries. Based on this, it's clear the Supecharger protocol is optimized for charging speed rather than charging efficiency.

It is as simple as that! The car doesnt care about chargerate either. If you dc charge at 30kw it will still try to actively heat the battery to 60c.

 

[rrolsbe]

It is as simple as that! The car doesnt care about chargerate either. If you dc charge at 30kw it will still try to actively heat the battery to 60c.

According to SMT that 40C/104F target was true for DC fast charging a few years back; however, the target is now closer to 60C/140. When the target was 40C, I charged at 144KW at a 150KW SC when first plugging in. I do not believe the charge time has reduced much if any with the 60C arrival temp. The question is are we wasting energy to heat the battery 20C higher or does the battery last longer when charging at the higher charge temps? Normally excessive heat is BAD for batteries, electronics and mechanical devices ie.. pumps, electric motors, etc. BTW, if you push on screen message indicating preheating is active the message goes away but the heating, via the stator windings, does NOT stop!

 

[Candleflame]

According to SMT that 40C/104F target was true for DC fast charging a few years back; however, the target is now closer to 60C/140. When the target was 40C, I charged at 144KW at a 150KW SC when first plugging in. I do not believe the charge time has reduced much if any with the 60C arrival temp. The question is are we wasting energy to heat the battery 20C higher or does the battery last longer when charging at the higher charge temps? Normally excessive heat is BAD for batteries, electronics and mechanical devices ie.. pumps, electric motors, etc. BTW, if you push on screen message indicating preheating is active the message goes away but the heating, via the stator windings, does NOT stop!

I dont think 60c matters for the 30min you spend charging... Ambient temperature while the car is resting is way more important.

 

[rrolsbe]

Candleflame you are probably right; however, since you are heating approximately 800lbs? of battery mass (the pack weighs around 1000lbs) for the long range M3 an additional 36F, that has to require several KWH of energy. With SC rates currently averaging around 40 cents/KWH in California, that could add up to some non-trivial additional out of pocket cost. .

 

[Candleflame]

Candleflame you are probably right; however, since you are heating approximately 800lbs? of battery mass (the pack weighs around 1000lbs) for the long range M3 an additional 36F, that has to require several KWH of energy. With SC rates currently averaging around 40 cents/KWH in California, that could add up to some non-trivial additional out of pocket cost. .

the car actively heats the battery during dc charging which uses 7.5kw. (or prior to charging with preconditioning).
whether it needs to or not is completely irrelevant.
Even if you plug into a shitty 30kw charger it still heats with 7.5kw so you only get 22.5kw.

 

[antonpirulero]

the car actively heats the battery during dc charging which uses 7.5kw. (or prior to charging with preconditioning).
whether it needs to or not is completely irrelevant.
Even if you plug into a shitty 30kw charger it still heats with 7.5kw so you only get 22.5kw.

But you can enter service mode and disable this heating.

 

[Candleflame]

But you can enter service mode and disable this heating.

service mode only works in close proximity to service centre i thought? apart from the one software update we had last year where you could enter the developer menu.

 

[antonpirulero]

service mode only works in close proximity to service centre i thought? apart from the one software update we had last year where you could enter the developer menu.

You can enter service mode anytime, just press for a few seconds "model 3" under the software menu and use the password "service" (without quotes). Then, under the service settings, you can deactivate battery heating.
I don't know to what extent this could void your warranty, use at your own risk.

 

[TunaBug]

service mode only works in close proximity to service centre i thought? apart from the one software update we had last year where you could enter the developer menu.

Here in Washington state it is most definitely geofenced, yet I have no reason to doubt @antonpirulero 's experience that it is not geofenced. I think it is different depending on what country you're in. I read somewhere that in the EU it is not geo-fenced, with speculation that it had to do with EU right-to-repair laws.

 

[jankratochvil]

I read somewhere that in the EU it is not geo-fenced, with speculation that it had to do with EU right-to-repair laws.

I have tried it and I cannot get into any service mode/menu/anything.

 

[antonpirulero]

I have tried it and I cannot get into any service mode/menu/anything.

I am in Europe, so probably that's the reason.

 

[TunaBug]

Here in Washington state it is most definitely geofenced, yet I have no reason to doubt @antonpirulero 's experience that it is not geofenced. I think it is different depending on what country you're in. I read somewhere that in the EU it is not geo-fenced, with speculation that it had to do with EU right-to-repair laws.

Somebody just gave this a downvote. At the time I wrote it service mode was geofenced in Seattle. That is no longer the case. I'm not sure how long that has been.