Bad battery. Finding out required detective work - Jaguar I-Pace EV400 Forum
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post #1 of 27 (permalink) Old 09-15-2019, 12:34 PM Thread Starter
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Bad battery. Finding out required detective work

Yesterday I figured out that my battery is bad. I don’t know when it happened but it was sometime between March and August. In March we did a trip to the desert and the battery behaved as expected in both discharge (range) and charging at fast chargers.

Then over the summer I noticed that the range went to shits. 140 miles on a full charge; not the GoM though .. the GoM still thinks I have 230 miles even though I have been proving it wrong every day.

I started keeping track of all trips in August.

I thought that it was my driving. I kept track of kWh SoC as provided by WattCat. Indeed, I was churning through tremendous kWh, and the SoC *percentage* as reported by the car matched the kWh. [I calculated the correlation, WattCat’s kWh SoC correlates with car-reported SoC %age at R-squared of >0.99. There's a plot in another post.]

My consumption, even on totally benign, not-pushing-it, trips has been insanely high, by both reported SoC %age and kWh.

Yesterday I used a fast charger for the first time since March because I went up to the mountains and had to charge. I used it twice, once on the way up and once on the way down.

Here are the kWh added as reported by the charger (first number); the difference in kWh pre- and post-charging as reported by WattCat (second number); and the difference in percentage SoC pre- and post-charging as reported by the car (third number).

31.9 58.1 69%
38.7 63.7 74%

So: assuming no loss from the fast charger, my total battery capacity is:
31.9 kWh / 0.69 = 46.2 kWh
or
38.7 kWh / 0.74 = 52.3 kWh

(If you consider ~3% or so loss it's even worse)

And last night I did the same with my L2 charging cable, same story.

So: in contrast to @ThinAir (see the WattCat thread, page 4), in my case both the reported SoC %age *and* the reported kWh SoC is erroneous. (Not WattCat's fault, obviously, but the car's because it reports an incorrect value).

How is it possible that the car doesn’t report an error when the issue is this extreme?!?
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post #2 of 27 (permalink) Old 09-15-2019, 12:54 PM
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Geeze. This sucks. I need to get an extended warranty.

Photon FE, 2013 FR-S, 2017 RAM 1500, 2014 Forester
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post #3 of 27 (permalink) Old 09-15-2019, 05:15 PM
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Geeze. This sucks. I need to get an extended warranty.

For the first time, I bought the extended warranty....10 years and up to 125,000 miles. I have a feeling that this is going to pay out in a big way.
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post #4 of 27 (permalink) Old 09-15-2019, 10:42 PM
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****. How many total miles do you have on the battery? I hope you can talk some sense into someone at your JLR dealership service department and get a new battery. It might be complicated if the car reports everything is fine which seems to be the case.



If you're able to see past the crappiness of the situation, it's very interesting data. This probably explains the wild consumption numbers you were calculating. I wonder how the car was coming up with the consumption numbers it was presenting. It may have somehow been compensating for the battery problem or it may measure the power it actually pulls from the battery instead of trusting the battery reported SoC. Not much seems straightforward about the I-Pace's software.



There seems to be a recent spate of reports of bad I-Pace high voltage batteries on forums. We're all warrantied for a long while yet, but I'm going to keep a closer eye on mine than I have been.


May your mitigation be swift, painless, and effective.
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post #5 of 27 (permalink) Old 09-16-2019, 12:30 AM Thread Starter
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****. How many total miles do you have on the battery?
Just under 6000

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This probably explains the wild consumption numbers you were calculating.
Yup, exactly.

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I wonder how the car was coming up with the consumption numbers it was presenting.
Yup, exactly. Whatever the reason, the measurements it takes (or considers) are somehow incomplete, so under a certain failure regime that my battery has, it is blind to it. I'm hoping that a real battery diagnostic will reveal the issue, as it is quite pronounced.

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May your mitigation be swift, painless, and effective.
Thank you!
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post #6 of 27 (permalink) Old 09-19-2019, 08:00 PM
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I took my car into Jaguar and asked them to test the battery. Long story short I am getting a new battery. Great experience at the service desk at my dealership.

My experience underscores the need for EV owners to track battery performance so that they can detect problems early.
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post #7 of 27 (permalink) Old 09-19-2019, 11:25 PM Thread Starter
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I took my car into Jaguar and asked them to test the battery. Long story short I am getting a new battery. Great experience at the service desk at my dealership.

My experience underscores the need for EV owners to track battery performance so that they can detect problems early.
Excellent. Thank you for sharing the precedent. How long did they say will it take?
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post #8 of 27 (permalink) Old 09-20-2019, 12:58 PM
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Difference calculation method

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Originally Posted by sciencegeek View Post
Yesterday I figured out that my battery is bad. I don’t know when it happened but it was sometime between March and August. In March we did a trip to the desert and the battery behaved as expected in both discharge (range) and charging at fast chargers.

Then over the summer I noticed that the range went to shits. 140 miles on a full charge; not the GoM though .. the GoM still thinks I have 230 miles even though I have been proving it wrong every day.

I started keeping track of all trips in August.

I thought that it was my driving. I kept track of kWh SoC as provided by WattCat. Indeed, I was churning through tremendous kWh, and the SoC *percentage* as reported by the car matched the kWh. [I calculated the correlation, WattCat’s kWh SoC correlates with car-reported SoC %age at R-squared of >0.99. There's a plot in another post.]

My consumption, even on totally benign, not-pushing-it, trips has been insanely high, by both reported SoC %age and kWh.

Yesterday I used a fast charger for the first time since March because I went up to the mountains and had to charge. I used it twice, once on the way up and once on the way down.

Here are the kWh added as reported by the charger (first number); the difference in kWh pre- and post-charging as reported by WattCat (second number); and the difference in percentage SoC pre- and post-charging as reported by the car (third number).

31.9 58.1 69%
38.7 63.7 74%

So: assuming no loss from the fast charger, my total battery capacity is:
31.9 kWh / 0.69 = 46.2 kWh
or
38.7 kWh / 0.74 = 52.3 kWh

(If you consider ~3% or so loss it's even worse)

And last night I did the same with my L2 charging cable, same story.

So: in contrast to @ThinAir (see the WattCat thread, page 4), in my case both the reported SoC %age *and* the reported kWh SoC is erroneous. (Not WattCat's fault, obviously, but the car's because it reports an incorrect value).

How is it possible that the car doesn’t report an error when the issue is this extreme?!?
I used a different method to calculate my battery capacity which you may want to try.
I take the reported charge after charging and divide that by SoC after charging and get a good estimate of battery capacity.

Last edited by ThinAir; 09-20-2019 at 01:06 PM. Reason: Post was wrong
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post #9 of 27 (permalink) Old 09-20-2019, 05:41 PM Thread Starter
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Originally Posted by ThinAir View Post
I used a different method to calculate my battery capacity which you may want to try.
I take the reported charge after charging and divide that by SoC after charging and get a good estimate of battery capacity.
That works for you because in your case the reported charge is correct. In my case the reported charge is incorrect (the second column), which is why it took me a while to figure out what's wrong.
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post #10 of 27 (permalink) Old 09-23-2019, 10:11 PM Thread Starter
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Update:

Dropped off the iPace at JLR Livermore today. Got a Velar for a loaner (I'll post another thread for entertainment). Service guys think it may have to be escalated to JLRNA. Glad I did so much documentation, it's a bit of a hill climb to get people to not be skeptical. Overall good experience, everyone was professional and personable and spent quality time for discussion. I'm attaching the summary documentation I provided them with.
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