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Should I charge to 90% every night, or somewhere between 50-70%

Hi, guys,

Fianlly, just bought my Tesla. And in order to keep its battery healthy, I checked some videos on youtube. But some of them said, they've done many research, and lower % (but above 50%), would be lower the degradation. (if this one is true, then I will keep the battery charged between 60-70% since I don't need to drive everyday)

On the other hand, someone said, some experts told him we should always keep the battery charged to 90%.

So, wonder which one is true?

Thank you
 

patrick40363

Active Member
Mar 25, 2014
1,267
676
Cali
Hi, guys,

Fianlly, just bought my Tesla. And in order to keep its battery healthy, I checked some videos on youtube. But some of them said, they've done many research, and lower % (but above 50%), would be lower the degradation. (if this one is true, then I will keep the battery charged between 60-70% since I don't need to drive everyday)

On the other hand, someone said, some experts told him we should always keep the battery charged to 90%.

So, wonder which one is true?

Thank you
I have been charging to 90% for almost 5 years. No problems.
 
What I have heard is that it is best to leave your car in the 20-90% range over the long term. Charging up to 95+% or letting the car get down to 5% does no harm at all as long as the battery does not stay in that state for an extended period. I personally charge to 85%, but I also don’t drive very much so 85% goes a long way. If I drove more, I would consider charging up to 90%. But you definitely don’t need to leave it at 90%.
 
I believe it’s well excepted that a lower SoC and narrow range of operation will help minimize the rate of battery degradation. The reference chart provides a great summary of the charging strategy and degradation.

upload_2019-9-13_22-3-52.jpeg


Having said that my daily commute is 70 miles total which I burn through approximately 42% of total battery capacity. As such I leave a little extra for unexpected errands and charge nightly to 75% and return home to about 38% give or take. Since I keep my cars on average for 10 years that puts my total degradation at an estimated 90% capacity. Not bad if it actually makes it that long.

Seems that puts puts me nearly at the top (between cyan and magenta) of the ideal operating range for battery longevity.

If you don’t drive much I’d shoot for the 75% to 45% range.
 
Much of the discussion about how to charge the battery is based on experience with gas cars. Most drivers are used to driving to the gas station, filling it up and driving until the gauge drops somewhere below a 1/4 tank. If you have a home charger then the EV charging model can be quite different because you can charge the car daily. Letting the battery drop below 5% and leaving it for an extended period seems to present risks. I have seen 20% suggested as the lower end of a charge range while traveling. If anything, keeping the battery SOC lower is linked to longer life. Higher charging percentage tracks with higher battery voltage and that correlates with shorter battery life. BlueOvalFan provides a chart that clearly shows how battery charge level relates to battery life. Charging daily minimizes the difference between the high and low SOC which also improves battery life.

So instead of looking for a magic number, I suggest a simple use-based calculation. Begin by determining how much of the battery charge is used on a typical day. For many people this will be commuting to and from work plus errands. When you are comfortable that you have a reliable percentage, double it to cover the possibility that power problems or something else prevents you from charging the car overnight. Add the doubled percentage to 20% and the total is your routine charge level. The routine charge percentage will depend on your daily driving habits and size of the EV battery. The use-based approach will minimize the battery SOC for daily driving.

I don't have a daily commute so the use-based calculation doesn't apply to me. I currently charge to 70% but I am thinking of going down to 60%. My charger delivers 11.5 kW so I can add 10% battery capacity in a little less than an hour when needed. If I am pushing the battery capacity with a round trip to a location without a supercharger then I charge to 90% overnight and add the final 10% in the hour and a half before I leave. When traveling long distances I try to keep above 20% at the bottom of the range mainly as a buffer to cover unforeseen events. I try to avoid charging over 80% because the charging rate drops significantly and unnecessarily extends the duration of a charging stop.

Just my 2 cents...
 
  • Informative
Reactions: KerryOH
Much of the discussion about how to charge the battery is based on experience with gas cars. Most drivers are used to driving to the gas station, filling it up and driving until the gauge drops somewhere below a 1/4 tank. If you have a home charger then the EV charging model can be quite different because you can charge the car daily. Letting the battery drop below 5% and leaving it for an extended period seems to present risks. I have seen 20% suggested as the lower end of a charge range while traveling. If anything, keeping the battery SOC lower is linked to longer life. Higher charging percentage tracks with higher battery voltage and that correlates with shorter battery life. BlueOvalFan provides a chart that clearly shows how battery charge level relates to battery life. Charging daily minimizes the difference between the high and low SOC which also improves battery life.

So instead of looking for a magic number, I suggest a simple use-based calculation. Begin by determining how much of the battery charge is used on a typical day. For many people this will be commuting to and from work plus errands. When you are comfortable that you have a reliable percentage, double it to cover the possibility that power problems or something else prevents you from charging the car overnight. Add the doubled percentage to 20% and the total is your routine charge level. The routine charge percentage will depend on your daily driving habits and size of the EV battery. The use-based approach will minimize the battery SOC for daily driving.

I don't have a daily commute so the use-based calculation doesn't apply to me. I currently charge to 70% but I am thinking of going down to 60%. My charger delivers 11.5 kW so I can add 10% battery capacity in a little less than an hour when needed. If I am pushing the battery capacity with a round trip to a location without a supercharger then I charge to 90% overnight and add the final 10% in the hour and a half before I leave. When traveling long distances I try to keep above 20% at the bottom of the range mainly as a buffer to cover unforeseen events. I try to avoid charging over 80% because the charging rate drops significantly and unnecessarily extends the duration of a charging stop.

Just my 2 cents...
so if one drives 75 miles a day round trip for work+ any possible extra needed for an errand or 2 -how would you figure to what % one should charge to daily?? 75%?
 
so if one drives 75 miles a day round trip for work+ any possible extra needed for an errand or 2 -how would you figure to what % one should charge to daily?? 75%?

I suggest that you get the percentage directly from the car. In the car menu, select Display>Energy Display>Energy to convert the small dashboard display from miles to percentage. The numbers beside the green horizontal bar at the bottom left will read directly in battery State of Charge percentage. Just check the percentage before the first drive in the day and again when you are finished for the day. The difference is percentage of battery use for that day. I would do this for a few days to a week but not include any days when you don't follow your normal routine (ie. days off). Work out the average then double it and add 20 to get the routine charge percentage. Set the charge percentage on the charging display with the slider. You don't have to be precise.

I see you live in Colorado so you should probably check the average again when the weather gets to winter cold as consumption will go up as the car uses energy to heat the battery and warm the cabin. If you can, take advantage of the phone app to turn on the car heater about 20 to 30 minutes before you leave. If the car is connected to your charger it will use house power for heating and leave your battery capacity untouched. If you are a creature of habit and always leave around the same time then you might want to activate the feature that lets the car learn when you normally leave and automatically switch the heat on at the right time to have it ready for you.

I hope you will find something useful in all this.
 

dark cloud

Active Member
Apr 14, 2018
2,278
2,693
BC
I believe it’s well excepted that a lower SoC and narrow range of operation will help minimize the rate of battery degradation. The reference chart provides a great summary of the charging strategy and degradation.

View attachment 454512

Having said that my daily commute is 70 miles total which I burn through approximately 42% of total battery capacity. As such I leave a little extra for unexpected errands and charge nightly to 75% and return home to about 38% give or take. Since I keep my cars on average for 10 years that puts my total degradation at an estimated 90% capacity. Not bad if it actually makes it that long.

Seems that puts puts me nearly at the top (between cyan and magenta) of the ideal operating range for battery longevity.

If you don’t drive much I’d shoot for the 75% to 45% range.

What that graph shows is that it doesn't matter. If you use 50% of the battery 1000 times, or you use 10% of the battery 5000 times it ends up at the same capacity, as long as you stay away from 100%.
 
What that graph shows is that it doesn't matter. If you use 50% of the battery 1000 times, or you use 10% of the battery 5000 times it ends up at the same capacity, as long as you stay away from 100%.

Exactly what I was thinking when I read the graph, with the exception of it highlighting that charging to 100% will degrade your battery's capacity more quickly. the 100%-40% and the 85%-25% both use 50% of the battery's capacity, but charging to 100% definitely degrades it more quickly.

I set mine to 90% all the time with the exception of charging to 100% right before I leave on a long trip. I have experienced less than 0.1% degradation in my 10k km of ownership.
 

dark cloud

Active Member
Apr 14, 2018
2,278
2,693
BC
so 70% daily charge vs 90% doesnt really matter to battery longevity?

Well the answer is 1 or 2 below,

1) Yes, but I am no expert and I have no proof.
2) No, but I am no expert and I have no proof.

Seriously, all I was saying was that graph shows no difference, but no idea where that graph came from. The best advice going is from the mouth of Jeff Dahl, and everyone else is just copying what he says.

Now if we project the battery out 15 years and 500,000 miles on the odometer if the guy who charged religiously to 70% SOC has a 90% range of 205 miles, and the guy who charged to 90% daily has a range of 199 miles, I would argue who cares. But there are some who jump all over that and say "see, I told you not to charge above 70%!!!"

But as it turns out there is some evidence that shows some with frequent supercharging to 100% have just as good, and in some cases better range as those who never supercharged and never went above 90%. So there are other unknown factors at play.

So it doesn't matter. :D
 

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