Traction Battery temperatures

Faults and Technical chat for the Jaguar I-Pace
dernotte
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Joined: Tue Dec 24, 2019 2:34 pm
Location: Montreal, QC, Canada

Re: Traction Battery temperatures

Post by dernotte » Mon May 03, 2021 9:20 pm

Who told you that Canada is a cold place ? :-)

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Last edited by dernotte on Tue May 04, 2021 2:20 am, edited 2 times in total.

dernotte
Posts: 398
Joined: Tue Dec 24, 2019 2:34 pm
Location: Montreal, QC, Canada

Re: Traction Battery temperatures

Post by dernotte » Mon May 03, 2021 9:30 pm

According to this graph, can we say that the "optimal" speed should be at 4-5000 rpm ?
With a gear ratio at 9,06, this means 551rpm for the tyres, or (5000/9,06*60*3,14*0,00073) km/h => 75 km/h

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ianipace
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Location: Cardiff, UK

Re: Traction Battery temperatures

Post by ianipace » Tue May 04, 2021 10:10 am

This is very interesting for a number reasons. Here in the UK mean temperatures are approx 18ºC, over a year, though is is rare to have a wind free day. There is plenty of opportunity of finding a suitable location for a wind turbine!

So could the answer be to 'draft' behind a heavy goods vehicle at 90kph (56mph) to try to increase range? This isn't the safest method but it is reliable.

The best miles per Kwh I have ever achieved is 4.4miles per Kwh. That was on a particularly sunny day and on country roads in France!
If I could achieve that on a regular basis I would get 374 miles to a charge!!

But mostly it is 3.2 and 3.4miles per Kwh sometimes less, often down to 2.3miles per Kwh on very short local trips.
But even 3.2 miles per Kwh gives 272 miles to a charge. The GoM has never indicated that figure!
I am basing the capacity on 85 Kw by the way.
Why then with an average of 2.8miles per Kwh, which 'should' give 238 miles do I only see 220 miles on the GoM at 100% charge?
I have played with the air con and watched the GoM range going up and down as I turn the air con up and down. 17ºC and a fan speed 2 seems to not have much if any effect on the GoM.

OK the Jag is a thirsty cat, and I do understand you can't have performance and economy in one package, but I do think JLR could endeavour to increase the efficiency. Obviously Tesla lead the way followed by KIa and Hyundai who have a remarkably efficient drive chains. It is very disheartening to see a Kia e-Nero with a WLTP of 282 miles AND achieving it in real life!

Stay safe

Ian
MY2019 SE in Caesium Blue. Panoramic roof and Gloss Black 18" wheels. Ohme Smart charger.

Grunt
Posts: 94
Joined: Fri Aug 07, 2020 12:39 pm
Location: Belgium

Re: Traction Battery temperatures

Post by Grunt » Tue May 04, 2021 11:52 am

I'll add some numbers to this, based on what I understand for the moment.
I seem to have the habit of throwing in a lot of info, sorry if that bothers.

1. That the battery temperature does not increase in rather light use, is a result of the nicely low internal resistance of the I-Pace traction battery. I came across some measurements, pointing to 30 milliOhm at 20°C, raising to 40 at 10°, 70 at 0°, 130 at -10° and 210 at -20°. That is battery temperature, not environment temperature.
Looking at the data from Dernotte, driving around at 100kmh with -7°C will likely mean a consumption of about 25kW. 25kW at 400V means a power draw of 63Amps. With an internal resistance around 70mOhm, the battery internal heat loss is around 63^2x0.07 = 278Watt. That 278W is available to "heat the battery", but of course not going to achieve much...
If Dernotte could have driven at a continuous 150kmh, he would need around 63kW, drawing 158A and creating 1700W in battery heat from internal resistance. Still, nothing much.
It is quite rare to be able to maintain 150kmh, usually there will be some slowing down & accelerating again. Bad for average consumption, good for heating the battery.
During the yo-yo, accelerating and regenerating, Dernotte likely drew 300kW during acceleration, thus 750Ampere. Internal loss then is (750^2*.07) 39000 Watt. A very different story! Regen during deceleration maxes out at 150kW, with an efficiency of 70%. Meaning that 30%, or almost 50kW, gets lost = is transformed into heat.

2. Yes, battery capacity decreases with colder temperatures. That goes for all batteries. Lithium Ion batteries fare much better than lead batteries, but the effect remains.
What I took from a variety of sources (studies, papers etc) is all rather consistent and looks like
Battery temp / Net capacity
25° / 100%
20° / 100%
15° / 98.1%
10° / 96.2%
5° / 92.3%
0° / 88.5%
-5° / 81.7%
-10°/ 75.0%
Some users on this forum have provided different numbers (Maxwell400?); higher numbers, at cold temperatures. Something like 75kWh (almost 90%) at -10°; if memory serves. I am not sure what to make of those. Were the temperatures battery temperatures (from OBD2 readings) or environment temperatures? Was the capacity estimated by Wattcatt (via API) and/or via OBD2 (Power Cruisecontrol, Torque Pro...)? Were those estimations confirmed (as in: car was driven, battery remained at that -10°, 75kWh was actually consumed)?

3. I suspect that the I-Pace does heat the battery during driving, but only a little bit; with the 278W available in the case of Dernotte, I seriously doubt that the battery temperature would have stayed so high (10 above ambient). The fact that the I-Pace does not heat up the battery more is likely a choice: for range it won't help (of any significant amount) to spend 7kWh to bring the battery temp up and increase your available capacity with about the same amount; because you also need to maintain that temperature at a higher level or you precious kWh disappear again, costing more energy again.
When preconditioning the battery, I observe that the battery temp goes up to 17°C, no higher. Likely that beyond this, there is nothing relevant to be gained anymore. I wonder if somebody has experience what happens to the battery tempterature when driving at very low temperatures but starting with a preconditioned battery. I would suspect that the I-Pace roughly maintains that temperature, or would it decrease.

The key benefit of heating the battery, as Tesla does when heading to a rapid charger, is that it increases the charge rate. I have seen Youtube movies showing that the battery temp is increased to 45° (with ambient temperatures of -10) and gives the luxury of fast charging on arrival. This comes at a considerable cost, in terms of kWh spent (10kWh on one such cycle) and in terms of battery longevity.
Given how Jaguar overprotects the batteries, it is not surprising that we do not have such a feature.
Silver lining: because of that overprotection, the battery loss of I-Paces over time looks to be a fraction of what Tesla batteries loose. Teslabjorn has done multiple tests showing 8-10% battery degradation after 2.5 years, compared to 3-4% for a comparable I-Paces.

Grunt
Posts: 94
Joined: Fri Aug 07, 2020 12:39 pm
Location: Belgium

Re: Traction Battery temperatures

Post by Grunt » Tue May 04, 2021 12:04 pm

dernotte wrote:
Mon May 03, 2021 9:30 pm
According to this graph, can we say that the "optimal" speed should be at 4-5000 rpm ?
With a gear ratio at 9,06, this means 551rpm for the tyres, or (5000/9,06*60*3,14*0,00073) km/h => 75 km/h
Why would that be optimum?
The optimum speed (as in "lowest consumption per distance travelled") for all EVs is much slower, actually. KIA ran one of their eNiro's for 1000km at a single charge. They did so at 30kmh. Be sure that this was not a random guess...
For the I-Pace it is no different; under perfect conditions (18" etc) and at a steady 32kmh the range should exceed 850km.
At 75kmh, steady speed throughout, 25° etc, you should be able to go over 600km.

dernotte
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Location: Montreal, QC, Canada

Re: Traction Battery temperatures

Post by dernotte » Tue May 04, 2021 4:23 pm

Grunt wrote:
Tue May 04, 2021 11:52 am
I wonder if somebody has experience what happens to the battery tempterature when driving at very low temperatures but starting with a preconditioned battery. I would suspect that the I-Pace roughly maintains that temperature, or would it decrease.
Yes I do. When I did my trip in late January, the amb temp was -20c when I left home, and I did a preconditioning of the battery. I turned the heater off in the car (Yes, I know I had to be crazy...) and I had to open the window otherwise I had fog on the windshield... I had to do this because I was going to a ice track for a full day in the mountain, no charger over there, and no idea how much energy I needed so I wanted to keep as much energy as I can in the battery. When I arrived at the ice track, 90 min later, the ambient temp was -33c, but I was equipped for that temperature: warm boots, warm coat, warm gloves, warm hat, ... I did not record the battery temp but I monitored it and it was constantly declining from the 19c at the beginning of the journey, and remember the heater was off in the car. If I remember correctly, the battery temp was at 13c when I arrived at the ice track.
BTW, it was a really fun day. Unfortunately, I was not able to disengaged all driving assistance, but still, very pleasant day.

dernotte
Posts: 398
Joined: Tue Dec 24, 2019 2:34 pm
Location: Montreal, QC, Canada

Re: Traction Battery temperatures

Post by dernotte » Tue May 04, 2021 4:47 pm

Grunt wrote:
Tue May 04, 2021 11:52 am

When preconditioning the battery, I observe that the battery temp goes up to 17°C, no higher. Likely that beyond this, there is nothing relevant to be gained anymore. I wonder if somebody has experience what happens to the battery tempterature when driving at very low temperatures but starting with a preconditioned battery.
Here is an old graph that I took this winter during a preconditioning phase. The battery reports 3 temperatures on the OBD2 : Avg, min, and max (green, yellow and red lines). At the end of the battery preconditioning, the avg was at 19c, max at 22c, and min at 17c.

Capture d%u2019écran, le 2021-04-16 à 09.25.23.png


Maxwell_400
Posts: 441
Joined: Mon Oct 14, 2019 10:09 am
Location: Norway

Re: Traction Battery temperatures

Post by Maxwell_400 » Tue May 04, 2021 5:20 pm

dernotte wrote:
Mon May 03, 2021 9:30 pm
According to this graph, can we say that the "optimal" speed should be at 4-5000 rpm ?
With a gear ratio at 9,06, this means 551rpm for the tyres, or (5000/9,06*60*3,14*0,00073) km/h => 75 km/h
I get the lowest consumption when I average 65km/h-75km/h.
I-Pace SE++, MY20, 18" summer & winter, no panoroof, towbar, spare wheel, 20C, TCU 19.2, BECS: BP-AAE-BC-AC-BE

Maxwell_400
Posts: 441
Joined: Mon Oct 14, 2019 10:09 am
Location: Norway

Re: Traction Battery temperatures

Post by Maxwell_400 » Tue May 04, 2021 5:37 pm

Grunt wrote:
Tue May 04, 2021 11:52 am
2. Yes, battery capacity decreases with colder temperatures. That goes for all batteries. Lithium Ion batteries fare much better than lead batteries, but the effect remains.
What I took from a variety of sources (studies, papers etc) is all rather consistent and looks like
Battery temp / Net capacity
25° / 100%
20° / 100%
15° / 98.1%
10° / 96.2%
5° / 92.3%
0° / 88.5%
-5° / 81.7%
-10°/ 75.0%
Some users on this forum have provided different numbers (Maxwell400?); higher numbers, at cold temperatures. Something like 75kWh (almost 90%) at -10°; if memory serves. I am not sure what to make of those. Were the temperatures battery temperatures (from OBD2 readings) or environment temperatures? Was the capacity estimated by Wattcatt (via API) and/or via OBD2 (Power Cruisecontrol, Torque Pro...)? Were those estimations confirmed (as in: car was driven, battery remained at that -10°, 75kWh was actually consumed)?
I use OBD2 and divide energy spent (kWh) on SOC change. As an example, 25kWh spent, SOC change of 30% give 83.3kWh without internal resistance loss. Then I calculate internal resistance and calculate the loss due to internal resistance, this is added to the battery capacity. The internal resistance is about 7 times higher at -10 than at +25.

This may be why our numbers are a bit off, your table is what you get out of the battery and probably at a too high discharge current, while I calculate the capacity of the battery but loose accuracy as I do not change SOC 100% (Actually 96%). Next winter I will be a bit more scientific.

But nice table, I wish state of health would be more consistent and follow that table but SOH seems to be all over the place.
I-Pace SE++, MY20, 18" summer & winter, no panoroof, towbar, spare wheel, 20C, TCU 19.2, BECS: BP-AAE-BC-AC-BE

dernotte
Posts: 398
Joined: Tue Dec 24, 2019 2:34 pm
Location: Montreal, QC, Canada

Re: Traction Battery temperatures

Post by dernotte » Tue May 04, 2021 6:31 pm

Maxwell_400 wrote:
Tue May 04, 2021 5:20 pm
dernotte wrote:
Mon May 03, 2021 9:30 pm
According to this graph, can we say that the "optimal" speed should be at 4-5000 rpm ?
With a gear ratio at 9,06, this means 551rpm for the tyres, or (5000/9,06*60*3,14*0,00073) km/h => 75 km/h
I get the lowest consumption when I average 65km/h-75km/h.
At 4000 rpm on the motor, this gives (4000/9,06*60*3,14*0,00073) km/h => 60 km/h
So the range 4000-5000 rpm , on 20", is 60-75 km/h

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