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Discussion Starter · #1 ·
For the first time in the 2 months I've owned my M3 AWD LR, I needed to charge it away from home tonight. With 58% SOC, I asked the car to navigate to the nearest 250kw supercharging station at the Hilton Heathrow which was 20 miles away. It displayed a red message "preconditioning battery for supercharging" but to my surprise it used 20% charge to travel just 20 miles at approx 45 mph (instead of the expected normal 5%) meaning that the preconditioning had actually used 4 times the usual power so I arrived at the charger with only 38%. The supposed 250kw charger was only showing 145kw on the charging screen despite 30 minutes of preconditioning on the way to the charger, and then it actually took 18 minutes to add a mere 22kw (which is only about about 75kw/h).

Is this all usual?

If the car is going to gobble up 20% of the charge to travel 20 miles, then maybe it should warn you otherwise you spend the first period of your charge just putting back the energy it took to precondition the battery!

How much faster does a preconditioned battery charge than a non-preconditioned one?
 

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Ioniq 5
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You travelled a short distance to a Supercharger, in cold weather. Yes it will use a lot of energy to heat the pack.

You then started the charge at 38%, which is above the point tapering starts. Also, the battery may not have been properly warm. Hence the slower charge.

If you use Superchargers for what they're intended for, which is en-route travel, they work well.
 

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Discussion Starter · #3 ·
You travelled a short distance to a Supercharger, in cold weather. Yes it will use a lot of energy to heat the pack.

You then started the charge at 38%, which is above the point tapering starts. Also, the battery may not have been properly warm. Hence the slower charge.

If you use Superchargers for what they're intended for, which is en-route travel, they work well.
What is tapering? How low should it be when you start charging. I was using the charger en route just gave up when I had enough to get home rather than wait any longer. It was 6 degrees outside so quite cold.
 

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Between 10-20% SOC.

If you're not driving the car hard in cold weather then the pack won't heat up enough.

See this chart:
137949


Remember that most Model S and X will charge at a maximum of 145 kW. Which is well above what most EVs charge at today.
 

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Discussion Starter · #8 ·
Thank you. Interesting chart which bears put what happened tonight with 38% SOC at arrival. The problem is that to get to the charger with 20% of charge I would be nervous about how much power the car would use just preconditioning the battery and if the charger is out of order then you will not have much charge to left to find another charger.

How long should it take to precondition? I thought 30 minutes / 20 miles would be enough.
You might find Bjorn's video helpful:
Just watched the video. Brilliant. Thank you.
 

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Thank you. Interesting chart which bears put what happened tonight with 38% SOC at arrival. The problem is that to get to the charger with 20% of charge I would be nervous about how much power the car would use just preconditioning the battery and if the charger is out of order then you will not have much charge to left to find another charger.

How long should it take to precondition? I thought 30 minutes / 20 miles would be enough.

Just watched the video. Brilliant. Thank you.
I think battery preconditioning doesn't draw too much power and what happened on your journey was mostly due to cabin warming.

If I know I'm going to a DC charger (even a "slow" 50kW one) I preheat the car before leaving, which also warms the battery up, I usually do it for 30min.
 

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I still think there's a bit too much of an error here.
Going from 38% to 66% (which is 38%+22kWh) you should be looking at a charge rate starting at 170kW and falling to 85kW.
Sounds like the battery temperature effectively capped you to 145kW (at least to start). However, even, so with 20 mins you should be adding a bit more than 22kWh.
Would be interesting to see the curve for different temperatures, but clearly you'd have been better off charging at home in this instance.
 

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Discussion Starter · #11 ·
I think battery preconditioning doesn't draw too much power and what happened on your journey was mostly due to cabin warming.

If I know I'm going to a DC charger (even a "slow" 50kW one) I preheat the car before leaving, which also warms the battery up, I usually do it for 30min.
Normally, cabin a/c whilst driving only draws 1% per 3 miles so I would have expected a 6% loss for a 20 mile journey. It lost 20% with the preconditioning so the additional drain must have been due to the heating of the system as it was cold outside and I could not drive faster than 40-45mph.
I still think there's a bit too much of an error here.
Going from 38% to 66% (which is 38%+22kWh) you should be looking at a charge rate starting at 170kW and falling to 85kW.
Sounds like the battery temperature effectively capped you to 145kW (at least to start). However, even, so with 20 mins you should be adding a bit more than 22kWh.
Would be interesting to see the curve for different temperatures, but clearly you'd have been better off charging at home in this instance.
I wasn't at home so charging en route was the only option. Next time I will try it without preconditioning and see what difference it makes.
 
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