60% Daily Charge

[ratsbew]

We're picking up a new Y for my wife soon. Our plan is to daily charge to 60% always since her commute is very short. I'm hoping to collect data on a VERY gently cycled battery pack...no supercharging and very gentle cycling. Hopefully it doesn't throw the calibration too far out of whack.

 

[jcanoe]

You can charge to only 60% daily if you want; any charge level up to 80% daily is probably no worse for the long term health of th battery. A few times per year you should charge to above 94% so that the Tesla battery management system can properly calibrate the upper range of the battery. Also, set Sentry Mode (also Summon/Smart Summon if you have purchased FSD) to not be active when parked at your home location. Sentry mode will use more power, drain the 12V battery faster. This in turn will use more power from the battery pack and require more frequent charging.

Just as important, when Sentry mode is left always active this will prevent the Tesla vehicle from shutting down, entering sleep mode where the high voltage battery pack is disconnected from the vehicle. The Tesla battery management system needs the Tesla vehicle to periodically enter sleep mode to be able to measure the open cell voltage (OCV) within the battery pack. The OCV can only be measured when the battery pack is disconnected from the rest of the Tesla vehicle as in sleep mode.

The down side of not having a properly calibrated battery management system is that the Tesla vehicle could shut down prematurely while driving if the battery management system determines that the remaining charge in the battery pack is too low (when it isn't actually too low) to continue driving.

 

[NCC81701]

We're picking up a new Y for my wife soon. Our plan is to daily charge to 60% always since her commute is very short. I'm hoping to collect data on a VERY gently cycled battery pack...no supercharging and very gentle cycling. Hopefully it doesn't throw the calibration too far out of whack.

You should look into using Teslamate or Teslafi to help you collect data. The amount of data you can get from a Tesla is head exploding.

 

[ratsbew]

I have an inactive TeslaFi account....I'm on the FSD Beta EAP so I can't have external apps...at least not on my current car.

 

[jerm5006]

You should look into using Teslamate or Teslafi to help you collect data. The amount of data you can get from a Tesla is head exploding.

+1 for Teslamate. You can set it up on a free Google cloud instance as well. Works great! Here's one of the visuals from one of the many dashboards.

I followed these steps and it worked perfectly: How to setup and run TeslaMate for free on Google Cloud - TeslaEV.co.uk

 

[zecar]

We're picking up a new Y for my wife soon. Our plan is to daily charge to 60% always since her commute is very short. I'm hoping to collect data on a VERY gently cycled battery pack...no supercharging and very gentle cycling. Hopefully it doesn't throw the calibration too far out of whack.

The only reason to not charge to 60% is if that low starting SOC caused you to regularly go below 20%.

I've been usually charging to 60% too during covid. But I doubt its of much benefit

 

[reynolds1029]

The only reason to not charge to 60% is if that low starting SOC caused you to regularly go below 20%.

I've been usually charging to 60% too during covid. But I doubt its of much benefit

It can double the life of the pack compared to charging at 80% everyday. 3.92V is considered the perfect voltage to charge a Li-ion to. Which in a Tesla is around 60-65% SOC. If you can keep it above 20% during your daily commute, your battery will thank you and give 3-400K miles of life. Charge to 80 and you're looking at about half that.

How to Prolong Lithium-based Batteries - Battery University

Discover what causes Li-ion to age and what the battery user can do to prolong its life

batteryuniversity.com

 

[another813]

It can double the life of the pack compared to charging at 80% everyday. 3.92V is considered the perfect voltage to charge a Li-ion to. Which in a Tesla is around 60-65% SOC. If you can keep it above 20% during your daily commute, your battery will thank you and give 3-400K miles of life. Charge to 80 and you're looking at about half that.

How to Prolong Lithium-based Batteries - Battery University

Discover what causes Li-ion to age and what the battery user can do to prolong its life

batteryuniversity.com

So I have had a Model Y Long Range since September 2020 and have been charging to 50% and very rarely does it go below 20% at the end of the day. I decided to take a trip and charged up to 100% (said 100% but needed to leave so I didnt let the cells balance out). I flipped from % to range and it said 253. So I think I may need to do another charge up to 100% and this time let the cells balance out or my battery degraded heavily.

 

[silverstoned83]

So I have had a Model Y Long Range since September 2020 and have been charging to 50% and very rarely does it go below 20% at the end of the day. I decided to take a trip and charged up to 100% (said 100% but needed to leave so I didnt let the cells balance out). I flipped from % to range and it said 253. So I think I may need to do another charge up to 100% and this time let the cells balance out or my battery degraded heavily.

The BMS has most likely lost calibration with the pack's true capacity due to rarely spending enough time at different high/low States of Charge. There's no way the cells could be out of balance enough to lose that much capacity, nor could it have already degraded that much with the way you're maintaining the charge. The BMS simply doesn't know how much capacity it has to work with because it is rarely, if ever, fully utilized.

 

[another813]

The BMS has most likely lost calibration with the pack's true capacity due to rarely spending enough time at different high/low States of Charge. There's no way the cells could be out of balance enough to lose that much capacity, nor could it have already degraded that much with the way you're maintaining the charge. The BMS simply doesn't know how much capacity it has to work with because it is rarely, if ever, fully utilized.

Suggestions? Options?

 

[jcanoe]

Turn off Sentry Mode, also Summon Standby (if your Tesla has FSD) when parked at your home location. This will enable the Tesla to enter sleep mode. The battery management system periodically needs to be able to measure the open cell voltage (OCV) within the battery pack, can only measure the OCV if the battery pack is disconnected from the vehicle as when the Tesla is in sleep mode.

Charge above 94% just before driving. Drive without charging, even if over several days, until the battery state of charge is less than 30%. Repeat a few times. For daily driving consider charging to 80% to 90% (I charge daily, up to 85%) No matter what you do, as far as charging, the battery pack will lose some capacity as it ages.

 

[drtimhill]

We're picking up a new Y for my wife soon. Our plan is to daily charge to 60% always since her commute is very short. I'm hoping to collect data on a VERY gently cycled battery pack...no supercharging and very gentle cycling. Hopefully it doesn't throw the calibration too far out of whack.

Remember that all the calibration being "out of whack" means is that the car has lost track of where the battery is from overall charge capacity. Recalibrating doesnt change or improve the battery health, it just lets the car report whatever state the battery IS in more accurately. So dont fret over it, stick to your "gentle" wash-cycle, and enjoy your car worry-free

 

[ratsbew]

So what happens if the BMS loses calibration and you want to drive a long distance? Say you charge to 100% but it only shows 260 miles (EPA), will you be able to travel farther (extract more kWh) than that as the car discovers that it has more capacity than it thought?

I need to do a calibration routine on my Model 3 since it's down to 290 from 316 (quite suddenly).

 

[jcanoe]

So what happens if the BMS loses calibration and you want to drive a long distance? Say you charge to 100% but it only shows 260 miles (EPA), will you be able to travel farther (extract more kWh) than that as the car discovers that it has more capacity than it thought?

I need to do a calibration routine on my Model 3 since it's down to 290 from 316 (quite suddenly).

The Tesla could shut down prematurely if the battery management system incorrectly determines that the battery pack is at the minimum state of charge when there is still adequate charge available to continue powering the drive motors.

 

[ratsbew]

So it won't see that there is still plenty of Voltage in the pack and know that there is a lot more left?

 

[jcanoe]

So it won't see that there is still plenty of Voltage in the pack and know that there is a lot more left?

Not without calibration. When the Tesla battery management system decides your done ... you're done. This would probably only happen when your battery drops into bottom 20% of the battery range. Under a standard Supercharger routine of stopping to charge at a Supercharger for ~20 minutes every 2 hours or 120 to 140 miles you would probably never experience this as an issue.

 

[ratsbew]

Fascinating. I still think that I will go with a 60% daily charge in order to preserve the actual capacity of the pack. This will mostly be a city driver and we will use our older Model 3 for longer road trips. If I anticipate a long trip with the Y I will go through a calibration routine to help out the BMS.

My guess is that the BMS will say the pack is empty and if you park it for long enough it will realize that the open cell voltage of the pack is actually like 15%.

 

[hgmichna]

Here is another example of somebody charging a Model 3 SR+ (US) to 60% for the same reasons.

I charge more when I need more. For long-distance trips I charge to 90% or to 100% if that helps me get to my destination faster. I don't drive long-distance often though.

I would recommend that you do a near-zero to 100% charge when the car is new and measure the time, so you have a baseline for the battery capacity and don't need to give anybody your Tesla password. Just assume that the battery has the nominal capacity. Repeat this perhaps once a year to compare and measure degradation.

The mathematics are pretty simple, so I don't explain them here. Note that you can set the Tesla app to report charging start and finish through notifications, so you don't have to watch the car charge to 100%.