Charging

[Decibelle]

I am away on a four week trip and the battery was at 70% when I left. Before leaving I plugged the car in and also lowered the charge level to 50% so I could determine the daily draw of the car when not in use until it reached 50%. I figured it would then keep the battery at 50% until I got back home, but It seems the battery keeps charging to the level it was when I plugged in before leaving (70%). Is this normal behavior? It has now been a week and every time I see the % go down on the Tesla App, it then goes up again to 70%.

 

[whitex]

The battery % can go up and down with temperature (I've seen our 75D gain range when parked in the sun once - unplugged). With the car plugged in, the car is using shore power for everything it needs, so the battery doesn't get drained. A plugged in Tesla battery will not experience vampire drain. Maybe you're just watching a battery estimated SoC change - just a theory.

 

[TexasEV]

No it's not normal behavior. The car should not be charging above 50% if you have it set st 50%. What should happen is vampire drain will occur until the charge gets below 50% and then the car would charge back up to 50% every few days. My guess is you thought you set it to 50% but that setting didn't take.

 

[animorph]

Can you check the charge limit setting via the Tesla app?

 

[tga]

The battery % can go up and down with temperature (I've seen our 75D gain range when parked in the sun once - unplugged). With the car plugged in, the car is using shore power for everything it needs, so the battery doesn't get drained. A plugged in Tesla battery will not experience vampire drain. Maybe you're just watching a battery estimated SoC change - just a theory.

That's not correct. The car will vampire drain the main battery for a bit (I don't know how much) before turning on the contractor in the UMC/HPWC/EVSE to turn on the AC supply to the car. The AC power does not stay connected to the car when it's done charging. I believe (but I'm not home to check) that it will turn on the AC for preconditioning as well.

 

[murphyS90D]

I am away on a four week trip and the battery was at 70% when I left. Before leaving I plugged the car in and also lowered the charge level to 50% so I could determine the daily draw of the car when not in use until it reached 50%. I figured it would then keep the battery at 50% until I got back home, but It seems the battery keeps charging to the level it was when I plugged in before leaving (70%). Is this normal behavior? It has now been a week and every time I see the % go down on the Tesla App, it then goes up again to 70%.

You can set the maximum percentage anywhere between 50 and 100% from the app. You may have accidentally raised it while using the app.

 

[EVCarGUy]

With the car plugged in, the car is using shore power for everything it needs

Not true.

 

[animorph]

I have my car scheduled to charge a little after midnight. It remains plugged in all the time. It charged to 90% yesterday morning, 270 rated miles for me. Per TeslaFi logging, the charge dropped to 268 miles during the day (no driving). That was not low enough to trigger a charge this morning. I'm currently sitting at 267 rated miles. It will continue dropping until it reaches maybe 10 miles down before it triggers another charge.

There were a few posters a year or so ago complaining that their scheduled charging was happening up to 6 hours after their scheduled time. It was due to this effect. The battery was not below the trigger point at the scheduled time, but did end up below the trigger point a few hours after and Tesla was allowing a 6 hour window for scheduled charging (IIRC).

That said, if you turn on climate control while plugged in, or otherwise use the car, it will draw power from the plug rather than the battery. Regardless of scheduling. You can see that on the charge screen. However, it is not charging the battery, the amperage is usually pretty low.

 

[mblakele]

With the car plugged in, the car is using shore power for everything it needs

Not true.

Owners Manual, p133:

Note: Whenever Model S is plugged in but not actively charging, it draws energy from the wall instead of using energy stored in the Battery. For example, if you are sitting in Model S and using the touchscreen while parked and plugged in, Model S draws energy from the wall outlet instead of the Battery.​

To demonstrate this, plug in your vehicle but do not start charging. Turn on climate control. Observe the charge port light blinking green.

 

[Decibelle]

Thanks for the replies. I looked at the Tesla App and the charge limit is still set at 50%. I just looked at the App and it shows 275 Kms and it says "Charging Complete". I will check again tomorrow and see if it goes back to 280 Kms (starting point when I left 4 days ago).

 

[EVCarGUy]

Owners Manual, p133:

Note: Whenever Model S is plugged in but not actively charging, it draws energy from the wall instead of using energy stored in the Battery. For example, if you are sitting in Model S and using the touchscreen while parked and plugged in, Model S draws energy from the wall outlet instead of the Battery.​

To demonstrate this, plug in your vehicle but do not start charging. Turn on climate control. Observe the charge port light blinking green.

They key phrase there is "Turn on climate control"

Plus, I responded to this "the car is using shore power for everything it needs"

This statement simply isn't true. If the car isn't charging, and it's just sitting there in the garage, the car's electronics are still powered on and discharging the 12v battery. The car hasn't turned on the charger, so there is zero power being supplied from the plug. The car is not "using shore power for everything it needs" 100% of the time it's plugged in.

Anyone with a Tesla can clearly see this is true. Even when plugged in, after charging is complete the range will drop several miles per day as the car has to frequently use the traction battery to recharge the 12v battery. "Vampire" drain occurs even when plugged in. So, clearly, "the car is using shore power for everything it needs" is not a true statement

 

[EVie'sDad]

perhaps after you selected the setting in the app, when you plugged in the charging interface referenced the last setting inside the car? Or perhaps a software update somehow reset the default value after updating the system (I have seen once or twice other values reset or get altered from my current selection after a system software update).

 

[Decibelle]

I did set the limit in the car and not in the app if that is what you are asking. When I get back to the car in a few weeks I will see what the limit is on the "big screen" in case it has changed while the app still shows 50%.

 

[Decibelle]

Update:
It seems to work the way it was intended to. I just logged on and it shows 253kms. So it seems the battery is losing around 4kms/day, a little less than 3 miles per day while plugged in. I don't know what happened the first four days as it was going down and then up again to the max level several times. Maybe the car doesn't read the exact state of charge and I was receiving an approximation of Kms remaining.
Thanks to all!!

 

[Decibelle]

Last update:
The car is now down to 50% and is keeping the state of charge at this level. After 15 days of not charging, it seems the draw has been about 3.5 miles per day. I checked in on the car via the Tesla App around 8 times. The temperature has been around 70F throughout this period.

 

[TexasEV]

Last update:
The car is now down to 50% and is keeping the state of charge at this level. After 15 days of not charging, it seems the draw has been about 3.5 miles per day. I checked in on the car via the Tesla App around 8 times. The temperature has been around 70F throughout this period.

You do know that checking on your car has increased the draw, right? It prevents it from staying in a deeper sleep.

 

[Decibelle]

I do realize the car needs to wake up every time I log on, but the weird thing is that the draw was less during the first half of the trip when I checked about every 2nd day. The last 8 days I only checked once towards the end and the average draw was still about the same as when I checked earlier on. (After the initial period when the charge seemed to go up and down for the first three or so days).