Why does my charging time change like this?

Jason Bourne

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#1
My Model3 is plugged in to a Blink L2 charger that is on my employer's campus. There are currently 4 chargers available to employees, but I'm not sure if they are connected to each other or dedicated runs, from a wiring standpoint. I have been using these chargers (any of the 4 randomly) since I got my car, but today is the first day I notice something weird.

It's very hot outside, so every few hours I use the iOS app to put the AC on for a minute to prevent the interior from getting too hot (I don't have the OS version yet that has the cabin overheat protection). When the AC is not on, it shows me that I have 5+ hours remaining to charge. Totally on point with what I'd expect. But when I turn the AC on via iOS app from my office, the charging time immediately skyrockets to 24+ hours. The change is immediate, approx within 15 seconds. I performed this test 3 times today at different times of day, all with the same result.

But the charging power doesn't change (volts, amps, or MPH). So I don't know why this is happening. There have also been other days in the past month when I've put the AC on via iOS app (same exact method and purpose) that has not affected projected charging time.

Anyone have any ideas?
 

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KarenRei

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#2
My Model3 is plugged in to a Blink L2 charger that is on my employer's campus. There are currently 4 chargers available to employees, but I'm not sure if they are connected to each other or dedicated runs, from a wiring standpoint. I have been using these chargers (any of the 4 randomly) since I got my car, but today is the first day I notice something weird.

It's very hot outside, so every few hours I use the iOS app to put the AC on for a minute to prevent the interior from getting too hot (I don't have the OS version yet that has the cabin overheat protection). When the AC is not on, it shows me that I have 5+ hours remaining to charge. Totally on point with what I'd expect. But when I turn the AC on via iOS app from my office, the charging time immediately skyrockets to 24+ hours. The change is immediate, approx within 15 seconds. I performed this test 3 times today at different times of day, all with the same result.

But the charging power doesn't change (volts, amps, or MPH). So I don't know why this is happening. There have also been other days in the past month when I've put the AC on via iOS app (same exact method and purpose) that has not affected projected charging time.

Anyone have any ideas?
You're on a very low power charger. Using the AC is taking up practically all of the power available.

Depending on how it estimates AC power, the charge time estimate should hopefully adjust back down once the car cools down and AC power demand can be reduced.
 

Jason Bourne

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#3
You're on a very low power charger. Using the AC is taking up practically all of the power available.

Depending on how it estimates AC power, the charge time estimate should hopefully adjust back down once the car cools down and AC power demand can be reduced.
Thanks for your feedback, but this does not make sense to me for a few reasons. First, I've done exactly the same thing on other days and did not get the same result. Meaning, the charge time did not change at all on those days. Second, I'm surprised to hear that you think 240v/24a is very low power. Sure, it's not ideal but getting 18MPH of charge is not small. I could see your point better if I was plugged in to a 110v/15a circuit.
 

KarenRei

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#4
Thanks for your feedback, but this does not make sense to me for a few reasons. First, I've done exactly the same thing on other days and did not get the same result. Meaning, the charge time did not change at all on those days. Second, I'm surprised to hear that you think 240v/24a is very low power. Sure, it's not ideal but getting 18MPH of charge is not small. I could see your point better if I was plugged in to a 110v/15a circuit.
240V@24A is 5,76kW - if there were no losses (there always will be). I don't know about the AC on the Model 3, but at peak output the HVAC system on the Model S can draw over 6kW.

I'd guess that the previous times you did this the car didn't run the AC compressor on as high of a power draw. Peak draw on an AC can be high, but average draw is usually not nearly so high. Cooling down a car takes a lot more energy than maintaining a temperature, and how fast the car tries to cool it down will be relative to how much it needs to lower the temperature.

Just try leaving the AC on. It should hopefully settle back down shortly.
 

Jason Bourne

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#5
Thanks. I'll let it run for a while for the temp to stabilize at the target temp and see what happens.
 

Jason Bourne

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#6
@KarenRei you were definitely right, thank you. I left the AC on for 30 minutes and once the temp stabilized, the charging speed went back up. It's just strange that it never did that before.
 

Ed Woodrick

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#7
@KarenRei you were definitely right, thank you. I left the AC on for 30 minutes and once the temp stabilized, the charging speed went back up. It's just strange that it never did that before.
My question is why you feel the need to turn on the AC throughout the day. All it will do is waste energy and wear the parts of the car down quicker. Cars are built to stand in the heat for long periods of time. At 100 degrees in PA, you are well below the temps that are seen in AZ.

My recommendation, don't turn A/C on during the day, only enable as you are walking out the door. Also, you ought to get used to unplugging the car during the day. The chargers may not be full now, but as more EVs get on the road, you should make them available for others to use.
 

Jason Bourne

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#8
My question is why you feel the need to turn on the AC throughout the day. All it will do is waste energy and wear the parts of the car down quicker. Cars are built to stand in the heat for long periods of time. At 100 degrees in PA, you are well below the temps that are seen in AZ.
Just for the same reason that some people prefer to leave their home's AC running at a moderate temperature during the day - so it's not heat soaked at the time you want to be in that environment and it doesn't take an uncomfortably long time to cool off. I don't want the interior to be quite hot when I get in, even if I turn the air on a few minutes earlier.
 

PNWmisty

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#9
I don't want the interior to be quite hot when I get in, even if I turn the air on a few minutes earlier.
I have the driver vent adjusted so it blows at the back of the steering wheel. This creates turbulence that makes a bubble of cool air around the driver's seat. I've found that 5 minutes or less of A/C usage before I get in is plenty to ensure all surfaces I'll be touching or sitting on are nice and cool when I arrive. EV's just don't get as heat soaked as ICE vehicles with their super hot engine bay. All those hot surfaces around the footwell/firewall in an ICE vehicle can make you feel hotter than an EV.
 

PNWmisty

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#10
I don't know about the AC on the Model 3, but at peak output the HVAC system on the Model S can draw over 6kW.
I saw the Model 3 specced at 6kW max heater draw and 2kW max A/C draw. And the heater can only draw 6 kW for a short period of time because as the element heats up, it naturally offers more resistance/less draw.
 

Ed Woodrick

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#11
Just for the same reason that some people prefer to leave their home's AC running at a moderate temperature during the day - so it's not heat soaked at the time you want to be in that environment and it doesn't take an uncomfortably long time to cool off. I don't want the interior to be quite hot when I get in, even if I turn the air on a few minutes earlier.
Take a look at all of the "it only takes 5 minute" threads about cooling the car down. While yall have indeed been a little warm on PA recently, it isn't anything that folks in the south don't see on a regular basis. Plus, what did you do for all your previous vehicles?

Turn on the A/c 5 minutes before you leave and you will never know it hasn't been on all day.

And that isn't the reason why people leave their homes A/C own during the day.
  • The mass of the house is significantly larger than a car
  • There are often living things inside the house during the day (people or plants)
  • Lots of people do set their home temperature back during the day
  • Reducing the A/C on a house does mean that you don't have to replace it as often. And it does have to be replaced, where a car often dies before its A/C does
These are the reasons why people keep and turn back the temps at home, different set than a car.
 

Umar Sear

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#13
Actually contrary to all the explanations, it does not make sense. A close inspection of the two screen shot shows that the charge rates (miles/hour) and Amps has not changed, meaning the expected time to completion should remain the same. The only thing I have noticed is that the calculation does jump momentarily and then settle back, perhaps that's what you are seeing.

The only other thing that would impact you is if the car is using power for something else, the HVAC for instance will draw a lot of power initially when turned on during charge.
 

Twiglett

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#14
Just for the same reason that some people prefer to leave their home's AC running at a moderate temperature during the day - so it's not heat soaked at the time you want to be in that environment and it doesn't take an uncomfortably long time to cool off. I don't want the interior to be quite hot when I get in, even if I turn the air on a few minutes earlier.
It’s up to you to keep doing that of course. But don’t expect to charge quickly where you are charging/wasting energy :D