Charging fully and not getting 100%

[minibiti]

Hello,
I noticed that on my Zoe, even though I let it charge till full, it is not always that I get 100%.
I understand that after the charging is completed, the battery stabilizes itself with time and the final results can be 98 or 99%. Maybe a bit less during winter.

But I have 2 questions:
1. Would it make sense for the car to try charging again after a while in order to reach 100%, say after 12h or 24h? This way, it would also ensure that the car is fully charged even if left unused for several days.
2. Do other cars do that? Or all the cars charge till 100% and leave it at that till the cable is manually removed and plugged back in?

Thanks!

[zbk]

Zoe seem to employ some rules that stops charging early if the battery is cold. My 2014 Q210 showed 93% this morning with a battery temp of ~1°C, but normally it is 97-100% even during winter. Charging immediately after a trip (while the battery still has some leftover heat) is one way to "improve" this.

[minibiti]

No one has any more comments on my 2 questions, especially from people with cars with battery packs which don't have temperature management?

[Burger]

My i3 and Leaf charges to 100%

But my leaf can have less than 100% if I pre heat the car. Ie the drain to heat the car is more than my charger so it uses the battery. When the car gets warm, the drain is less than the charger and the battery tops up again. Never seen it below 98% though.

[minibiti]

Thanks!

The Zoe also usually charges up to 100% if it is not too cold, and also I get less than 100% if I pre-conditioned it in the morning, which is fair enough since it uses 5 kW to do that while my charger provides only 3.6 kW.

But my question is really about if other cars charge the battery to 100% on their own if you leave them plugged in for a longer period of time without using them, aka do they detect after say 1 week that they are down to 95% and then start charging on their own to 100% again, without the need for a manual intervention.
The Zoe does not do that. Once it reached full charge, it does not charge anymore even if the cable is plugged in unless you open the door or do something manually.

[sylwester]

It's bad for the battery to get continuously charged from 98%-100% so my best guess is that none of the cars do this.

Also 100% is a moving target. What constitutes 100% SOC is whatever level of energy that matches a certain current when charging with constant voltage. It stops the charge and updates SOH. SOH changes like the stock market but on average the value decreases. My car stops at max 94% when I want 100% and that is of 89,5%SOH so compared to a new car it's 84% of 100% SOH.

[minibiti]

I see I see.. It is all making sense now
But I could imagine that the car could start charging on its own if still connected to the charger and if the SoC decreases to e.g 80%.
This way it would improve the chances that the car is always (mostly) fully charge when you take it.
On the other hand, I guess it is rare to loose 20% SoC just by leaving your car standing idle, even for several weeks at a time.

[sylwester]

I think it's very depending on the car. I know the VW's cars have a mnimum SOC which is default set to 35%. When you have charging timer on and plug it in it will charge up to 35%, then wait with starting the charge so that it can finish in time for the timer setting. I'm not sure if this happens more than once.

Tesla has very active management so I guess its car will probably keep the charge to whatever % it is set on, but I also bet it will behave differently above 90%.

On my Leaf i have timer 00-00 such that it will start charging right away and stop at 80%. If I need more I do it from the app. Should the car be connected at midnight it will start charging again and stop at 80%. It usually sends med a message at midnight saying it's finished. Since I have the 80% setting I donæt hesitate to charge my car ever. Thus I can drive 8km to 75% SOC and plug it in to get it to 80% again several times a day. I'm not sure I will do that when I have the new car that does not stop at 80%.

[Burger]

Sylwester: I've set up charging timer on the Leaf so it resets charging every day. Sunday to Friday I charge to 80% and Saturday to 100%. The change is at 00:00 every day and then it turns on charger for a bit. Never let it sit for a week without a charging timer so I can't help you there. If we're away I will set all days to charge to 80%. The i3 is so new that I have no relevant experience, sorry.