Battery percentage living its own life

Faults and Technical chat for the Honda E
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Haaploos
Posts: 33
Joined: Tue Oct 27, 2020 7:10 pm
Location: Oslo - Norway

Post by Haaploos »

I haven't thought of this before but the last couple of months, I have noticed that when I plug in a charger the battery percentage drops significantly usually around ~10%.
Once I plugged into a wall-box charger, and the battery indicator inside the car said 7% when parking before plugging in and when checking the car through the app a few minutes later it said 0%.

Last monday, the temperature was around 5 degrees C. Drove 10km(~6.2miles), first halv in city then rest in 80-90kmph(49-55mph) to a fast charger, charged 7,97kWh. Then drove another 6km(3.7miles) 80-90kmph and parked the car outside with 30%.
Came out 1h25m later and the battery status said 36%. :shock:

These are the times I have actually noticed the battery drop, or increase. Other times I can vaguely remember that I also plugged into fast charger at ~21% and it dropped to 13%.

I was thinking that if the car/battery is cold, you have less usable energy and then the car thinks that the % is larger. So when you plug into a charger the car readjusts the usable battery capacity to 100%(net capacity)?
Anyone else noticed anything like this or have any clue of why this is happening?
Modern steel advance 17"

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keithr
Posts: 448
Joined: Fri Feb 07, 2020 1:30 pm
Location: Dorset, UK

Post by keithr »

Yes, my car has been doing a similar thing for about a year (see Battery loosing charge? dicsussion). It mostly loses about 4% over a day, once or twice it lost 9% over about 5 days of being parked (thanks to covid lockdowns). Then after about 6 months it started sometimes gaining 4% aswell. For example, on Sunday this week it lost 4%. On Monday I charged the car for about 40 minutes which increased the SOC by 14% - about what I would expect. Then I drove about 2 miles and parked for about 2.5 hours. When I got in the car again it had gained 4%. The dealer and Honda haven't come up with any explanations, but I'm guessing it is battery temperature related, and perhaps one of the battery pack temperature sensors is faulty or giving inconsistent readings.
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