Accuracy of state of charge indicator?

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mluisbrown
Posts: 78
Joined: Wed Mar 08, 2023 4:46 pm
Location: Lisbon, Portugal

Post by mluisbrown »

The other morning I started with 80% SOC (I usually charge to 80%), did a short trip of about 7km and parked. When I came back to the car to return home, it was showing 81% SOC 😅 I did the 7km home (all city driving) and arrived back home with it indicating 80%, the same as I had started with.

This leads me to believe that the SOC shown is not super accurate.

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2023 Born 58kWh, Glacial White, 19" Typhoon Copper, Skyline, Blue Dinamica electric seats, Cargo, Privacy, Pilot M+, Tech M
2003 Audi A3 8L 1.9TDi PD 130 with 360,000kms.

daern
Posts: 154
Joined: Wed Jul 20, 2022 1:31 pm

Post by daern »

mluisbrown wrote: Fri Jun 02, 2023 1:28 pm This leads me to believe that the SOC shown is not super accurate.
It's not. But none of them are.

It's all guess work really and some very complicated algorithms to attempt to work out what's left in the battery based on what went in, what's been taking out and some relatively rudimentary readings on what you can see outside (voltage and temperature, basically). This is a problem with modern batteries and it's best to assume that the percentage reading is just a "best guess" at that point in time based on the chemistry of the battery and a load of pre-performed tests calibrated into the algorithm.

As to why it varies? Temperature is a good basic variable that can affect the overall capacity of the battery and, consequently, the amount of usable charge left in it at a given point.

My experience is that the MEB does a pretty good job of guesstimating what's left and that whatever accuracy level it has, is no more variable than my driving is - i.e. I can impact it far more by the way that I drive, or the conditions on the road, than any slight inaccuracies in the reading would have.
alanjs
Posts: 105
Joined: Mon Jun 27, 2022 3:14 pm

Post by alanjs »

I don't think there is any logic behind the figures that are shown,
On Wednesday morning, after charging to 80% "My Cupra" showed a potential range of 153 miles.
On Thursday, with no trips made, it showed 80% with a potential range of 96 miles.
On Friday, after a 34-mile round trip, it showed 63% with a potential range of 118 miles.

I place more faith in the Tronity app which gives much more consistent information.
Born V3, Aurora Blue, Tech (M) pack, Firestorm wheels, Pano roof
Ordered 21 June, 2022, delivered 17 Jan 2023
davmatjo
Posts: 66
Joined: Thu May 05, 2022 2:08 pm

Post by davmatjo »

alanjs wrote: Fri Jun 02, 2023 3:29 pm I don't think there is any logic behind the figures that are shown,
On Wednesday morning, after charging to 80% "My Cupra" showed a potential range of 153 miles.
On Thursday, with no trips made, it showed 80% with a potential range of 96 miles.
On Friday, after a 34-mile round trip, it showed 63% with a potential range of 118 miles.

I place more faith in the Tronity app which gives much more consistent information.
The Thursday reading will be due to a long standing bug that will sometimes run a kilometers to miles conversion on a number somewhere in the process that is already in miles. The bug has been present since day 0 as far as I know.
TheBornIDentity
Posts: 151
Joined: Mon Jul 18, 2022 5:55 pm

Post by TheBornIDentity »

The Cupra app range is complete nonsense; ignore it, it’s bugged.

The in car SoC is susceptible to environmental changes such as temperature. It’s not uncommon for it to go up, especially when the temperature has gone up a lot since the car was on charge.
alanjs
Posts: 105
Joined: Mon Jun 27, 2022 3:14 pm

Post by alanjs »

davmatjo wrote: Sat Jun 03, 2023 4:56 pm
The Thursday reading will be due to a long standing bug that will sometimes run a kilometers to miles conversion on a number somewhere in the process that is already in miles. The bug has been present since day 0 as far as I know.
Yep, I'm aware of that - it happens frequently.
Born V3, Aurora Blue, Tech (M) pack, Firestorm wheels, Pano roof
Ordered 21 June, 2022, delivered 17 Jan 2023
alanjs
Posts: 105
Joined: Mon Jun 27, 2022 3:14 pm

Post by alanjs »

TheBornIDentity wrote: Sat Jun 03, 2023 9:53 pm The Cupra app range is complete nonsense; ignore it, it’s bugged.

The in car SoC is susceptible to environmental changes such as temperature. It’s not uncommon for it to go up, especially when the temperature has gone up a lot since the car was on charge.
Oh yeah and then some! I just found it interesting that it changed, all by itself, sitting in the garage. But as above, it's probably due to a conversion to Kilometers, then it woke up.
It goes along with all the unplanned, unrequested changes to all sorts of stuff that the car makes up its own mind to do. Just something you get used to.
Born V3, Aurora Blue, Tech (M) pack, Firestorm wheels, Pano roof
Ordered 21 June, 2022, delivered 17 Jan 2023
Elea4
Posts: 166
Joined: Fri Jun 10, 2022 5:19 pm

Post by Elea4 »

Interestingly, reading the SoC value with an OBDII adapter gives slightly different values, usually a little bit higher than the in-car displays.
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