Why you should not scrutinize rang/SoC numbers too hard

[whitex]

I unplugged my car to go pickup something at the store. It was at 85% SoC, as per general profile I keep. I drove 3 miles according to the trip report, managed 1.7miles/KWh, so should have used 1.76KWh, but after coming back home, the car's SoC is now showing 86% (and charging does not kick in, since it's above the profile min)! So either my battery shrunk, or the car battery gained 1% SoC instead of losing 2%.

Posting it here for new EV drivers as an example of why you cannot scrutinize reported energy, SoC, etc. They are guestimations - not just the range, the SoC percentage too.

PS> I was a little surprised to see this in a Taycan, as I usually have only see SoC go up on Teslas when parked in a sunny (but not too hot) location and this happened at night with 47F outside. I guess Taycan guesstimator works differently, and obviously not super accurate.

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[nischalr]

I unplugged my car to go pickup something at the store. It was at 85% SoC, as per general profile I keep. I drove 3 miles according to the trip report, managed 1.7miles/KWh, so should have used 1.76KWh, but after coming back home, the car's SoC is now showing 86% (and charging does not kick in, since it's above the profile min)! So either my battery shrunk, or the car battery gained 1% SoC instead of losing 2%.

Posting it here for new EV drivers as an example of why you cannot scrutinize reported energy, SoC, etc. They are guestimations - not just the range, the SoC percentage too.

PS> I was a little surprised to see this in a Taycan, as I usually have only see SoC go up on Teslas when parked in a sunny (but not too hot) location and this happened at night with 47F outside. I guess Taycan guesstimator works differently, and obviously not super accurate.

Did you coast up the hills with momentum and brake strategically? would be interesting to know if your topography and route and regen actually charged your car net on your trip. I realize that this is not really possible, but a fun thought.

 

[McgR]

Did you coast up the hills with momentum and brake strategically? would be interesting to know if your topography and route and regen actually charged your car net on your trip. I realize that this is not really possible, but a fun thought.

It would have been easier to suppose he parked uphill and drive down with regen braking. But your suggestion is more adventurous

PCM was indicating he was using energy. I did have a situation when I arrived with more SoC than I left driving down hill 30 km in the mountain. But then PCM also indicated a negative kWh/Km .

 

[whitex]

Did you coast up the hills with momentum and brake strategically? would be interesting to know if your topography and route and regen actually charged your car net on your trip. I realize that this is not really possible, but a fun thought.

Impossible even in a perfect world, since this was a round-trip (end point and start point were the exact same spot in the garage). If this was a perfect world with no losses due to friction, heat, regen charging, etc, the end result of a round-trip would the same SoC, not greater.

 

[nischalr]

Impossible even in a perfect world, since this was a round-trip (end point and start point were the exact same spot in the garage). If this was a perfect world with no losses due to friction, heat, regen charging, etc, the end result of a round-trip would the same SoC, not greater.

Of course, I was just being facetious.
I certainly agree with the Range/SOC numbers being somewhat misleading and most certainly an algorithmic mystery.

 

[f1eng]

I unplugged my car to go pickup something at the store. It was at 85% SoC, as per general profile I keep. I drove 3 miles according to the trip report, managed 1.7miles/KWh, so should have used 1.76KWh, but after coming back home, the car's SoC is now showing 86% (and charging does not kick in, since it's above the profile min)! So either my battery shrunk, or the car battery gained 1% SoC instead of losing 2%.

Posting it here for new EV drivers as an example of why you cannot scrutinize reported energy, SoC, etc. They are guestimations - not just the range, the SoC percentage too.

PS> I was a little surprised to see this in a Taycan, as I usually have only see SoC go up on Teslas when parked in a sunny (but not too hot) location and this happened at night with 47F outside. I guess Taycan guesstimator works differently, and obviously not super accurate.

I have seen this sort of inconsistency and assumed it is related to battery temperature.

It may well be that after a short drive the "apparent" capacity of the battery has increased more due to it warming up than it has consumed in the short drive.

That is my guess anyway and I don't think the battery percentage number can ever be precicely calculated when there is a non-linear relationship between temperature and current capability.
I feel my car is markedly slower when accelerating out into traffic if I leave home with a cold battery in winter.

 

[Raphie]

Yup, it’s the guesstimate taking temp into account.

 

[whitex]

I have seen this sort of inconsistency and assumed it is related to battery temperature.

It may well be that after a short drive the "apparent" capacity of the battery has increased more due to it warming up than it has consumed in the short drive.

That is my guess anyway and I don't think the battery percentage number can ever be precicely calculated when there is a non-linear relationship between temperature and current capability.
I feel my car is markedly slower when accelerating out into traffic if I leave home with a cold battery in winter.

I find that accelerating fast is the quickest way to warm up the battery. I live near a main artery road (less than half mile from my house) which is 45mph speed limit, I accelerate there fast (had to learn to time it, as the Taycan speedo is not updating fast enough to properly accelerate up to speed limit or any offset above it, but that's a gripe for another thread). Full open throttle does seem to be a decent battery heater. My driving style is also accelerating quick, but never braking hard if I can help it (learned that at 17 when I bought a 2 seater and used to carry school books on my passenger seat - acceleration was ok, but braking hard would send the books to the floor or the windshield).

Then again, I drove my Teslas the same way, never came home with more range than I left with (even doing the exact same trip), wo I still find this particular situation an interesting occurrence.

 

[McgR]

Yup, it’s the guesstimate taking temp into account.

And maybe is was just between 85,499999 and and 85,5 SoC. And a bit of higher temps.

 

[WuffvonTrips]

You'll drive yourself mad analysing data from 3 mile trips.
Have you checked your phone's SoC - maybe you placed it the wrong way round on the wireless charger and charged the car from it?

 

[Raphie]

My consumption is like 54kWh /100km on short trips

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