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During charging a couple of weeks ago I walked into my garage and the temperature in the garage had to be 90 plus and the fan on the car was spinning loudly. The entire left front quarter panel (where you plug in) from the headlight to the mirror and extended some to the hood, was extremely hot. Hot enough that you could not leave your hand on it (I will need to do a thermal scan on it if it happens again to see actual temp). As I walked in it stopped, I think it was the end of the charging cycle. I thought this was a fluke, but then it happened again yesterday afternoon. I normally do not charge during the day, but I was concerned about the overheating during charging. Nothing odd happened until the last 10 minutes. The car was showing 100% complete, but 10 minutes remaining, so I went back into the house and when 10 minutes were up I was hit with the 90 plus when i went back in the garage again and the car extremely hot to the touch. A few weeks ago my car was updated to H280 and TCU to 18.2 and before the update I have never seen this behavior with my car. The only other thing which is slightly different for me is that the car was down below 10% when I started charging.

Has anyone else seen this or have any ideas? Do I have a clogged vent or a mechanical one that is not opening? It may just be another trip to dealership. I hate bringing the car in for something that may not happen every time, but i also do not want the car burning in my garage.
 
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I dug around and found a thread in May 2019 on this here: High heat after charging overnight - does this sound right?. Pasting some data from my post #13 in that thread here just for convenience, you can see just how hot things can get:

Here's the readings I got with an IR thermometer.
Columns are:
Time, Garage wall, Hood, Fender, Connector, Hottest spot on Charger Cable, Inside Bottom of Frunk

1:14pm 78 88 87 79 78 ? 37%
3:15pm 82 90 89 95 102 101 (Forgot)
5:15pm 83 93 93 98 102 107 74%
7:15pm 86 96 95 100 103 110 89%
9:20 pm 86 96 95 100 102 110 99%
10:26pm 88 97 113 105 93 143! 100%

You can see that during the final balancing act things can get really toasty.
 

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You can see that during the final balancing act things can get really toasty.
That is certainly what I am seeing in the last 10-15 minutes of charge. I feel like the fender could actually burn a young child. It is just odd that I have not seen it in the past, pre H280 and TCU 18.2. I need to run the IR thermometer on mine next time. So should I stop the charge before going to 100% to avoid this final balancing?
 

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Discussion Starter #4
I am also seeing a power spike at the end of my charge cycle now.
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Yeah, I've seen those same end-of-charge spikes every now and then; ever since I got the car in early 2019. It seems that rebalancing only occurs occasionally, most charges to "full" do not seem to have it and I often have the charge stop before full anyway. I think that unless you happen to walk in on the car in the garage during that time, typically late evening or even in the middle of the night if you use scheduled charging, that you never even realize the heat thing is occurring.

The attached image shows one back in May of 2019. (The second spike at 6:52am is the programmed preconditioning for when I was about to leave for the office that morning).
4239
 

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I suspect that the spike is other consumers, not energy that goes into the battery. I've caused that exact spike by turning on preconditioning while charging.

Regarding the extreme heat, I can't imagine that it's the battery. I suspect it's the charger and/or the AC unit. The battery pack cannot heat up that much so quickly, given its large mass and what I've observed by measuring actual battery temperature during both driving and charging. Also, the frunk is too far from the battery for the battery to cause 143F.

Ps.: I just re-read the May 2019 thread on this. Yeah if during rebalancing at the end of charging the battery dumps excess heat as CyberSlug suggests then that has to go somewhere, so the AC unit has to kick in. The battery itself should not be heating up to such extreme temperatures. Also, side note, according to JLR engineers, balancing happens regardless of SoC, but maybe it only generates excess heat at the end of charging? None of this is particularly clear to me.
 

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Regardless of the cause, it is perfectly normal, Zofran. Air being pushed/drawn by the fan through the front of a car sitting still hasn't got many escape routes. Charging equipment is biased to that side of the car so it will be the hottest.

I was thinking of trying to bake a small cake in the frunk during charging. I'll probably forget about it and land up attracting dogs chasing my cat the next time I drive it.
 

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Not quite sure that I understand the balancing process. Intuitively, I had assumed it to be a more passive equilibration event via a gentle nudging of the cells with a low potential applied. This description would seem to be incompatible with excessive heat generation.
As sciencegeek suggests, the localized heating could be due to the battery heating/cooling system venting in this area. A quick look through the battery literature seems to suggest that the heat generation associated with charging peaks at 80-90% SoC, so maybe the balancing process runs at a higher temp and requires battery heating.
 

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This is unfortunate that the API does not report any battery temperature. It is probably available on the CANbus but difficult to query with the API.. :). That would be great if we can compare what the charger "sees" and that the car "sees". You seem to charge at a steady 7kw. Can you post the graph from the charger of your next charging session, and a screenshot of this page at the end of the charging session (https://ipace.herokuapp.com/static/charge.html). It will collect detailed metrics from the car and display them on a graph. Just connect the page at the beginning of the charging session.
 

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Some definitions..... Do we know for sure that Jaguar is using the passive cell balancing technique ?

Cell Balancing Techniques
The fundamental solution of cell balancing equalizes the voltage and state of charge among the cells when they are at a fully charged state. Cell balancing is typically categorized in two types:

  1. Passive
  2. Active
Passive Cell Balancing
The passive cell balancing method is somewhat simple and straight forward. Discharge the cells through a dissipative bypass route. This bypass can be either integrated or external to the integrated circuit (IC). Such an approach is favorable in low-cost system application. The fact that 100% of the excess energy from a higher energy cell is dissipated as heat makes the passive method less preferable to use during discharge because of the obvious impact on battery run time.

Active Cell Balancing
Active cell balancing, which utilizes capacitive or inductive charge shuttling to transfer charge between battery cells, is significantly more efficient because energy is transferred to where it is needed instead of being bled off. Of course the trade-off for this improved efficiency is the need for additional components at higher cost.
 

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I suspect that the spike is other consumers, not energy that goes into the battery. I've caused that exact spike by turning on preconditioning while charging...
I'm certain that the spike at the end of the charge it isn't coming from preconditioning since it see it reasonably frequently on the chart but I rarely use preconditioning and that's set for a completely different time.

The spike may simply be the energy draw from the car's cooling fans since at that stage is where I've occasionally found them roaring at full blast in the final charge stages of the charge in the garage. Maybe the fan cooling draw during rebalancing is more pronounced for me because I'm in Texas and the garage is not insulated on the sunward side of the house. I've even opening the garage doors and turned on a floor fan to help move the final charge heat away from the car during those final stages (even though outside here is exceeding 100 degrees recently so I'm not sure it helps a lot)

It would certainly be interesting to know why some circuitry near the frunk gets so hot during that last part of rebalancing. 141 degrees at the bottom of the frunk is hot!
 

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I'm certain that the spike at the end of the charge it isn't coming from preconditioning since it see it reasonably frequently on the chart but I rarely use preconditioning and that's set for a completely different time.
Yes I totally agree, I just meant that turning on the AC deliberately (via precon) causes a spike like that, so it stands to reason that the car turning it on automatically also causes a spike like that.
 

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Discussion Starter #15
Charged my car a couple of days ago with about 8% remaining and this time it did not do the extreme heating and did not do the blip on the charge graph as it did last time. Hopefully the re-balancing of the batteries is not a common thing. I was getting concerned when it happen the last two times I charged, but had never happened before in the previous year I have owned the car.

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AC cell balancing, at the top of a charge, is done with 120vac, this could be why it is getting so warm. When a 240vac charging supply is plugged in, only 1/2 of a phase (1 wire) and the ground wire are being used on the charging cord(and the car's wiring to the charger) for balancing. The car can tell this is a 240vac charger supply and bump the 120vac up to 16amps(SAE J1772 standard) during this balancing. I suspect Jaguar is pushing the limit at the end knowing it will only be in service a short while. I don't know that this is the heating issue for a fact, but from what I do know, it agrees with the result. Normally, the US 120vac charger breakers are limited to below 12amps.
 

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A post on the UK site had this about cell balancing.

"You might have a problem with self balancing of the cells as well. A dealer said that to do thorough self balancing you need to;

  • Drive the car to SOC 10% or lower
  • Connect the car to a granny charger, charge power should be about 2kW
  • Let the car be unlocked with the hazard lights on, this is to prevent the car from shutting down.
(If the car shuts down the self balancing works in a different mode)
  • Charge the car to 100%, should take more than 40 hours
  • Reset GOM and read out range and estimated energy. "
That just doesn't seem right.
 

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FWIW that's what JLR told my dealer to do when they tried to resurrect the battery of my first I-Pace. (The noodling down to low and then L1 charging back up)
 

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Someone should try it and capture the data using dernotte's https://ipace.herokuapp.com/static/charge.html

I'm a bit far from < 10% charge and don't think I could tolerate a 40 hour outage at the moment. A couple of my ICE vehicles are sidelined with broken springs. (How do specially imported, heavy duty springs break on cars sitting in driveways? Old age? 16 years on one and 12 years on the other. It's just my luck.)
 
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