If you have a Gen 3 charger it communicates with the car. I had both Gen 2 and 3. The Gen 2 it would charge to 80% and stay. The Gen 3 allows the car to run down a bit before bringing it back up to 80% possibly to allow the BMC's to balance the batteries. What you describe is common with gen 3 charger.
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Wall Connector overcharging my MY
- Thread starter cjxmtn
- Start date
It's the car that takes the charging decisions, not the wall charger. A gen2 also has communication, to tell the car what it supports, and for the car to enable it etc...
sleepydoc
Well-Known Member
JohnnyLounge21
Member
I have seen/witnessed this wonky behavior on my Model S, However, the car is now ~5 years old and has ~125K miles, so maybe it's the age?
The repeatable behavior is created by doing the following:
In all cases, it involves Supercharging and in all cases the car is NEVER set above 90% at the home charge event. Yet it overcharges. I really HATE it that this happens. Maybe I'll try bringing down the overnight charge event to 80% for the next charge and see if that helps.
Either way, it's buggy and beneath a great car/company like Tesla to have these shenanigans.
The repeatable behavior is created by doing the following:
- Keep your car set to 90% SOC
- Supercharge at a a busy Supercharger (which defaults/overrides the SOC down to 70-80%)
- Override this moments later at either the display or on the app (done both) and put it back up 90% where you always have it
- Charge to 90% at the Supercharger
- Drive 100+ miles that day after the Supercharge event
- Get home that night and leave the settings alone (they are still set 90%)
- Charge overnight (Tesla brand charger, no more than 3 years old)
- The following morning, the car will charge to 93-95%
- SMH and and wonder why you have unnecessarily degraded your already very aging battery
In all cases, it involves Supercharging and in all cases the car is NEVER set above 90% at the home charge event. Yet it overcharges. I really HATE it that this happens. Maybe I'll try bringing down the overnight charge event to 80% for the next charge and see if that helps.
Either way, it's buggy and beneath a great car/company like Tesla to have these shenanigans.
I think your reasoning hinges on a few assumptions that are not quite right. You are expecting to be able to set a precise state of charge percentage, and you are expecting that the car can figure out exactly the current state of charge of the battery. Those are not possible, not at the precision you're asking for. If you are interested, you can read all the literature around battery voltages and how that voltage fluctuates, depending on battery chemistry. You would see that temperature plays a role, and that good measures can only be achieved in an open circuit, that sort of thing.
To make things simple, and because I am not an actual expert, I will say this: the car estimates the current total capacity of the battery and the current SOC, and it's pretty good at it, but it might be off by a few percent. That estimate will be constantly adjusted. In your specific case, by supercharging and driving etc you're raising the battery temperature. At home, eventually the battery temperature goes back down and the car starts thinking that the battery cannot hold quite as much energy. Since the charge is done, with the current voltage and less potential capacity, the overall SOC looks higher.
Said another way: it's not a bug where the car decides to charge more than you asked for. Would I prefer that it be perfectly precise? Yes. Is it technically possible? No.
To make things simple, and because I am not an actual expert, I will say this: the car estimates the current total capacity of the battery and the current SOC, and it's pretty good at it, but it might be off by a few percent. That estimate will be constantly adjusted. In your specific case, by supercharging and driving etc you're raising the battery temperature. At home, eventually the battery temperature goes back down and the car starts thinking that the battery cannot hold quite as much energy. Since the charge is done, with the current voltage and less potential capacity, the overall SOC looks higher.
Said another way: it's not a bug where the car decides to charge more than you asked for. Would I prefer that it be perfectly precise? Yes. Is it technically possible? No.
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