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Charging % Question
- Thread starter Captain78
- Start date
The displayed % state of charge (SOC) and the estimated range are only an estimate. When the Tesla Model Y is new, with a brand battery pack, the Tesla battery management system (BMS) has to rely on the battery pack's manufacturing data when estimating the state of the battery.
Over a period of weeks, if you let the Tesla Model Y enter Sleep Mode, the BMS can measure the open cell voltage (OCV) of the battery at different levels of state of charge (SOC). You do this (enable Sleep Mode) by setting Sentry Mode to be turned off when parked at your Home location. Sentry Mode and also Summon Standby (a full self driving (FSD) feature) will cause the Tesla Model Y to remain in Standby Mode, never enter Sleep Mode (where the high voltage battery contactors open and the battery disconnects from the Tesla Model Y vehicle.)
Cell balancing can also improve the accuracy of the BMS in determining the state of charge of the battery. Cell balancing will periodically take place automatically when the Tesla Model Y is charged to a high state of charge (i.e. at or above ~95%.) The battery pack does not need to be charged to 100% although you can periodically charge to 100% (this takes much longer than charging to ~95%.) Cell balancing will slightly prolong the charging session until completed.
Once you charge the Tesla Model Y to a high state of charge then you should drive the vehicle shortly after charging completes (it is good practice not to leave the battery at a high state of charge for long periods of time.) Once fully charged to at or close to 100% drive the Tesla Model Y to lower the state of charge of the battery to between 50% and no more than 80% as recommended for daily use. You can absolutely charge to 90% or even 100% if needed for road trips without damaging the battery. Just don't leave the battery at the higher state of charge for long periods (especially in high summertime temperatures.) In practice it is rare that you would need to charge to 100%.
After OCV data has been collected at various SOC levels while the Tesla Model Y is parked, in Sleep Mode and after cell balancing the BMS may estimate slightly higher state of charge (the range value is derived from the battery capacity, battery SOC, temperature and the EPA combined City/Highway estimate for energy consumption.) After a time, if you charge daily as Tesla recommends to between 50% and no more than 80% the BMS may again need to perform OCV measurements over a wider range of charge and perform cell balancing for best accuracy.
Many Tesla owners, recognizing that the estimated range value displayed next to the battery icon does not reflect their driving style, vehicle driving history prefer to switch the display to % SOC. You can switch the displayed value between Estimated Range and % SOC by tapping on the displayed value (next to the battery icon) on the Tesla main screen or within the Tesla app.
The Tesla Navigation System Trip Planner does take into account the vehicle's recent driving history when you set a destination in the Trip Planner. The estimated arrival SOC for the next waypoint/charging stop or destination will be updated as you drive along the planned route. The estimated arrival % SOC and range are usually very accurate. I.e., if the Tesla Trip Planner estimates that you will arrive at your destination with XX % battery SOC it will be very close to the actual value upon arrival. Changes in weather and road conditions, detours and traffic will impact consumption and the arrival SOC of the battery.
If you are uncomfortable with the Tesla Trip Planner's estimated arrival % SOC and range , i.e. less than 10% SOC, upon arrival at your destination, then be sure to charge for a bit longer (extend the charging time to add an additional ~10%) at the last charging stop so you can be confident you will arrive at your destination with the battery % SOC at a level that meets your comfort level and local driving needs, at least until you can plug in and charge.
Over a period of weeks, if you let the Tesla Model Y enter Sleep Mode, the BMS can measure the open cell voltage (OCV) of the battery at different levels of state of charge (SOC). You do this (enable Sleep Mode) by setting Sentry Mode to be turned off when parked at your Home location. Sentry Mode and also Summon Standby (a full self driving (FSD) feature) will cause the Tesla Model Y to remain in Standby Mode, never enter Sleep Mode (where the high voltage battery contactors open and the battery disconnects from the Tesla Model Y vehicle.)
Cell balancing can also improve the accuracy of the BMS in determining the state of charge of the battery. Cell balancing will periodically take place automatically when the Tesla Model Y is charged to a high state of charge (i.e. at or above ~95%.) The battery pack does not need to be charged to 100% although you can periodically charge to 100% (this takes much longer than charging to ~95%.) Cell balancing will slightly prolong the charging session until completed.
Once you charge the Tesla Model Y to a high state of charge then you should drive the vehicle shortly after charging completes (it is good practice not to leave the battery at a high state of charge for long periods of time.) Once fully charged to at or close to 100% drive the Tesla Model Y to lower the state of charge of the battery to between 50% and no more than 80% as recommended for daily use. You can absolutely charge to 90% or even 100% if needed for road trips without damaging the battery. Just don't leave the battery at the higher state of charge for long periods (especially in high summertime temperatures.) In practice it is rare that you would need to charge to 100%.
After OCV data has been collected at various SOC levels while the Tesla Model Y is parked, in Sleep Mode and after cell balancing the BMS may estimate slightly higher state of charge (the range value is derived from the battery capacity, battery SOC, temperature and the EPA combined City/Highway estimate for energy consumption.) After a time, if you charge daily as Tesla recommends to between 50% and no more than 80% the BMS may again need to perform OCV measurements over a wider range of charge and perform cell balancing for best accuracy.
Many Tesla owners, recognizing that the estimated range value displayed next to the battery icon does not reflect their driving style, vehicle driving history prefer to switch the display to % SOC. You can switch the displayed value between Estimated Range and % SOC by tapping on the displayed value (next to the battery icon) on the Tesla main screen or within the Tesla app.
The Tesla Navigation System Trip Planner does take into account the vehicle's recent driving history when you set a destination in the Trip Planner. The estimated arrival SOC for the next waypoint/charging stop or destination will be updated as you drive along the planned route. The estimated arrival % SOC and range are usually very accurate. I.e., if the Tesla Trip Planner estimates that you will arrive at your destination with XX % battery SOC it will be very close to the actual value upon arrival. Changes in weather and road conditions, detours and traffic will impact consumption and the arrival SOC of the battery.
If you are uncomfortable with the Tesla Trip Planner's estimated arrival % SOC and range , i.e. less than 10% SOC, upon arrival at your destination, then be sure to charge for a bit longer (extend the charging time to add an additional ~10%) at the last charging stop so you can be confident you will arrive at your destination with the battery % SOC at a level that meets your comfort level and local driving needs, at least until you can plug in and charge.
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