Is Charging to 100% every night really that bad?

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RIP_OPEC

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#1
I have the long range model 3, and I'm missing out on 31 miles by charging to the recommended 90%. Let's be honest... in a couple of years from now I'm sure we can agree the battery degradation will still be less than 31 miles, so what exactly is the point of charging lower? (I rarely supercharge btw, as I believe it's much worse for the battery than slowly charging to 100% at home over 5-10 hours).
 

garsh

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#3
Basically, Lithium Ion batteries prefer to remain at 50% state of charge (SOC). When the SOC is really high or really low, they are susceptible to growing a "film" on the anode and cathode which ends up limiting their usable capacity. This is why it's generally recommended that you only charge to 90%.

The other piece of advice I've heard is that charging to 100% (or discharging close to 0%) isn't that bad, as long as you don't leave the car in that state for a long period of time (more than a few hours). So if you want the extra range, consider timing the last bit of charging to 100% to coincide with when you're about to leave.

HTH!
 
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Troy

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#5
  • You are not missing out on the 10%. It is there when you need it.
  • The point of charging to 90% is that leaving the battery at 100% or 0% is bad for battery life and if you charge to 100% you are more likely to leave it at 100% for one, two or multiple hours every day. That's not good for the battery. When you charge to 100%, you should drive off instead of leaving it sitting at 100%.
  • Based on survey data, Supercharging more or less frequently has no effect on battery life. People who Supercharge twice a week have the same usable battery capacity as people who Supercharge once or twice a year. See the stats here.
 

Twiglett

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#6
I have the long range model 3, and I'm missing out on 31 miles by charging to the recommended 90%. Let's be honest... in a couple of years from now I'm sure we can agree the battery degradation will still be less than 31 miles, so what exactly is the point of charging lower? (I rarely supercharge btw, as I believe it's much worse for the battery than slowly charging to 100% at home over 5-10 hours).
A good source of information is the manual which has some recommendations on how to treat the battery.
Not sure what you think you’re missing unless you regularly drive 310 miles in one trip or between charges.
Again reference to manual for charging guidance.
 

Dr. J

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#8
This is a good source: https://electrek.co/2018/04/14/tesla-battery-degradation-data/. About the only way to screw it up is, as @garsh says, to leave it near full or empty for more than a couple of hours. However, I'll be following the advice to keep the charge oscillating around the 50% level, probably by charging to 65%-70% overnight, then higher as needed for trips, up to 100% (with departure properly timed). I plan to own this car forever, if the gods allow.
 

RIP_OPEC

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#10
Basically, Lithium Ion batteries prefer to remain at 50% state of charge (SOC). When the SOC is really high or really low, they are susceptible to growing a "film" on the anode and cathode which ends up limiting their usable capacity. This is why it's generally recommended that you only charge to 90%.

The other piece of advice I've heard is that charging to 100% (or discharging close to 0%) isn't that bad, as long as you don't leave the car in that state for a long period of time (more than a few hours). So if you want the extra range, consider timing the last bit of charging to 100% to coincide with when you're about to leave.

HTH!
I agree with you. Another downside is charging to 100% limits regenerative braking, more than enough reason to limit to 90% for me.
 

Vin

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#11
I remember the head of battery science at Tesla (Jeff Dahn) mentioned in regards to daily charging...“I would recommend charging to 70% normally. When you need a long trip, charge to 100%.”
However Elon stated in the past he recommended the "daily charge to be between 30-80%"

The point I think is that you can charge to 90 if you want to and there's very little loss, but if you can why not stay between 30-80%
I find it easy to charge in my situation so I do keep it between about 40-80% (charge for a few hours like every 3 days is pretty easy because it's only like 3 hours of charging and I use a HWPC at 32A even though I can go to 40A, but didn't want to push my townhome setup all the time unless nec,I figured slower charge might be better in the longterm anyway.
If I have a few errands or it's near the weekend I occasionally charge to 90. If Roadtrip to 100% but will drive immediately once it hits the full charge.
Hope that helps.
I think no matter how we charge, the battery will still last a very long time.
 

Ed Woodrick

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#12
I have the long range model 3, and I'm missing out on 31 miles by charging to the recommended 90%. Let's be honest... in a couple of years from now I'm sure we can agree the battery degradation will still be less than 31 miles, so what exactly is the point of charging lower? (I rarely supercharge btw, as I believe it's much worse for the battery than slowly charging to 100% at home over 5-10 hours).
I think that this is a really easy answer. Do you use 90% of the battery every day? Or even 80%? I don't. This allows me to keep the better in its optimal range and I don't lose anything.

Go back to your ICE vehicle. Did you fill it up every day? Did you always have 300+ miles in the tank? I doubt it. Since you charge your EV every day, I suspect that you probably just about always have more miles than your ICE vehicle did.

I know that you've got range anxiety, Go ahead and charge it to 100% every night for a month. Then look back and see how many times you rolled bac into the garage with less than 30%.
 

scaots

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#13
I wanted long range because I want it to be as useful as possible for travel. I also plan to have this car as long as possible and want it to still be useful when I do have some battery degradation. That said, I normally charge to 70% and even then only plug in about every other night as my commute at 50 miles round trip will still leave me enough the next day commute plus anything extra within reason.

That said, in six weeks I have already full charged 4 times for distance travels. I set the amperage to a level that, based on time remaining shown, will hit full charge just a little before my planned departure. That way it doesn't sit fully charged. If you give it a moment, the estimated time is reasonably accurate within .5-1 hour and it usually finishes a little before the predicted time.

My normal charge rate is only 16 amps despite having 32 amps available with UMC. I do this because it is normally plenty fast, and I have read that slower charge rates are easier on the battery mostly due to reduced heating at lower current. No idea if that is true or not. I doubt that it really makes all that much difference in the end, but I will take whatever extra life I can get. I also read that once you get below 12 amps the efficiency of the charging may be reduced so you might use extra electricity at lower rates.
 

garsh

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#14
I have read that slower charge rates are easier on the battery mostly due to reduced heating at lower current.
True, but at AC charging levels of 16 - 48 amps, it's not going to make much of a difference. Supercharging at 200-250 amps is where you have to worry about all the heat. But even though people have long expected Teslas that supercharge a lot to show more battery degradation, studies have shown very little (if any) difference. So, I wouldn't let that be a concern.

EDIT: @Brokedoc actually found an article about a Model S Taxi that was run to low SOC and supercharged almost continuously. That car showed some 20% battery degradation after 160k miles. So yeah - supercharging is hard on the battery.
 
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Triangles

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#15
Scaots, in other words even L2 charging at 48 amps is still "trickle" charging the TM3 pack.

I normally charge mine at 32A to 70% or if I am charging to full for a long distance I will set it slower if necessary so that it is 100% about the time I am ready to roll out the door. I plug in when my capacity drops below 40%. I have a 15mi roundtrip commute so I only charge about once a week. I will say I am greatly disappointed in the 1-3% daily vampire drain. I was blindsided by this as I expected better from Tesla. My first gen short range EV has 0 vampire drain. After being parked for 30 days my old EV has 0-1% capacity loss from the traction pack where my TM3 would probably be at least 30-50% depleted! Elon please fix this embarrassment.
 

Bernard

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#16
A good source of information is the manual which has some recommendations on how to treat the battery.
Not sure what you think you’re missing unless you regularly drive 310 miles in one trip or between charges.
Again reference to manual for charging guidance.
Besides, the actual EPA range is 338 ;-) Tesla had asked EPA to quote 310 instead of the 338 EPA had measured, and used 310 as top of the range in its software. Nobody quite knew why (speculation was it was an attempt to keep the S100D as king of the hill in all respects, including range), but now it seems that the reason was to be able to quote the same 310mi range for all versions of the model 3 with the long-range battery, in spite of the fact that the AWD versions are less efficient than the RWD versions delivered so far (again as measured by EPA: average of 290W/mi for AWD instead of 260W/mi for RWD in the EPA test cycle).
So the 10% you don't get by leaving your charge setup to 90% just means that you still have 310mi EPA range, just not the full 338mi ;-)
 

Scuffers

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#17
Assides all of that, we don't actually know what the capacity of the battery is on the 3, all we do know is that tesla only charges it to some ~78Kwh (based on EPA submissions)

I expect considering the risks of having batteries degrade on a mass market car like the 3 would murder Tesla, they will have deliberately down-rated the cells somewhat. From independent tests on the 2170 cells, people have shown between 5.75 and 6 AH, this would make the LR pack some 91-98 kWh, so that's some significant difference, ie. tesla have 'limited' the pack to a ~75kWh capacity in a 90+kwh battery thus ensuring they never get charged to 100% (and quite possibly, never discharged to zero).

Long term, with people ignoring the 80% advice etc, if they had not done this, can you imaging the problems in 2-4 years time? I can see the sharks circling now with some class-action.
 

littlD

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#18
Assides all of that, we don't actually know what the capacity of the battery is on the 3, all we do know is that tesla only charges it to some ~78Kwh (based on EPA submissions)

I expect considering the risks of having batteries degrade on a mass market car like the 3 would murder Tesla, they will have deliberately down-rated the cells somewhat. From independent tests on the 2170 cells, people have shown between 5.75 and 6 AH, this would make the LR pack some 91-98 kWh, so that's some significant difference, ie. tesla have 'limited' the pack to a ~75kWh capacity in a 90+kwh battery thus ensuring they never get charged to 100% (and quite possibly, never discharged to zero).

Long term, with people ignoring the 80% advice etc, if they had not done this, can you imaging the problems in 2-4 years time? I can see the sharks circling now with some class-action.
Maybe these details provide us with more information on pack size:

https://www.teslarati.com/tesla-model-3-battery-details-partial-teardown-analysis/
 

Scuffers

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#19
Nothing in there that helps with the capacity question, we already know the LR pack has 4416 cells in 96 'bricks'

What would be useful to know is the final cell charge voltage and the voltage at zero charge (or what Tesla deam zero charge).