Using 85%+ range per day, best charge strategy?

[67King]

I usually charge to 90% every day. In the warmer months, with no rain, no problem. But sometimes if I throw a bike or two on the roof during the day, it kills range. Now with teh cold, especially when it rains, I'm using more and more of my battery. Twice this week, I have gotten down to 1-2% by the time I'm all done. So far this morning, I've gone from 90% down to 45%, and I typically make the same rounds of trips in the evenings (though I won't be waiting in the car or in line in the car in 25 degree weather, so the load from the heater will be reduced).

So what is the best charge strategy to preserve battery life? I only lost 3% range in the first 40,000 miles, but I've lost another 6% in the past 14,000. Car is a Performance, lifetime is 306 w-hr/mi, so far today I'm at 360 w-hr/mile.
1. Charge to 100% every day
2. Charge to 90% every day and run down to <5%
3. Charge to 80-90% every day, and add charge* in the middle of the day to get through the day

* Sometimes I may only be able to charge for an hour or so, so about 15% range.

I've never done 1 for daily usage. I usually charge to 90%, and when it isn't cold or rainy, I can finish the day at 20% or so (well.....I used to be able to, but unsure now with battery degradation). I've occasionally topped off a little bit, but have a couple of times tried #2.....but I've gotten REALLY close. Like 1% last night.

I'm inclined to think 3, but I don't know exactly how a "cycle" is calculated by Tesla, knowing that they are only good for so many cycles, and that number would not allow the cars to be charged daily and last for the warranty period, so I'm guessing there's more to it than just plugging it in.

 

[Big Earl]

So a few things that might help:

A "cycle" is the equivalent of a full charge - it can be two half charges, four quarter charges or one full charge. 1,500 cycles on a 75 kWh battery pack would be 112,500 kWh. If you average 3.5 miles per kWh, you could expect close to 400,000 miles out of the battery pack.

The car has a DC kWh charge counter that ticks up as you charge on Superchargers or CHAdeMO. When you reach a certain point, Supercharging speeds will be throttled in order to maximize long term battery life. Those exact details on how many kWh have to be added before the car starts throttling haven't been nailed down for the Model 3 yet, but my car has begun throttling after >15,000 kWh added (probably closer to 23,000 kWh). It still charges plenty quick on road trips, but not as quickly as it did when it was new.

I would personally charge to 95% and run it down to 5-10%, giving it a small boost on a Supercharger during the day if needed.

 

[Chisale]

If all you cared about was battery longevity and didn't mind the slight extra time to top off on rainy/cold days then I would do #3 above. Charge to 90% and complete charging right about the time you are going to leave. Then if it's dry and warm you don't have to stop. If it's cold and wet it then you can top off. If it's really a nasty day then charge to 95% and drive right away. Getting down to 1-2% on a regular basis should be avoided at all cost if maintaining battery health is primary. My guess is that 90-95% for short duration is better than 1-2% for short duration.

 

[67King]

If all you cared about was battery longevity and didn't mind the slight extra time to top off on rainy/cold days then I would do #3 above. Charge to 90% and complete charging right about the time you are going to leave. Then if it's dry and warm you don't have to stop. If it's cold and wet it then you can top off. If it's really a nasty day then charge to 95% and drive right away. Getting down to 1-2% on a regular basis should be avoided at all cost if maintaining battery health is primary. My guess is that 90-95% for short duration is better than 1-2% for short duration.

Usually not an issue. I'm gone from 4:30-9:00, then home from 9:00-3:00 (on most days), then gone again from 3:00 until about 8:30. I can top off in the day with the wall charger and add about 15% per hour. Some days it will be less "top off" and more like just adding an extra 15-30%.

When you reach a certain point, Supercharging speeds will be throttled in order to maximize long term battery life. Those exact details on how many kWh have to be added before the car starts throttling haven't been nailed down for the Model 3 yet, but my car has begun throttling after >15,000 kWh added (probably closer to 23,000 kWh).

Don't supercharge unless I'm on a trip (which unfortunately is happening a lot more lately). Do not recall it throttling me in early December, but I do think it did in mid January. I attributed it to a slower supercharger, but that may be it. I currently have 17kWh on the clock. I'll be going to Nashville, yet again next week. Will see how that does. So that 15-ish kWh may be that point.

 

[Big Earl]

Usually not an issue. I'm gone from 4:30-9:00, then home from 9:00-3:00 (on most days), then gone again from 3:00 until about 8:30. I can top off in the day with the wall charger and add about 15% per hour. Some days it will be less "top off" and more like just adding an extra 15-30%.



Don't supercharge unless I'm on a trip (which unfortunately is happening a lot more lately). Do not recall it throttling me in early December, but I do think it did in mid January. I attributed it to a slower supercharger, but that may be it. I currently have 17kWh on the clock. I'll be going to Nashville, yet again next week. Will see how that does. So that 15-ish kWh may be that point.

Multiply by 1,000. 15,000 kWh or 15 MWh. Our lifetime power added through both AC and DC charging is somewhere around 27,000 kWh in just shy of 100,000 miles, at least according to the trip odometer, with at least half of that (probably closer to two thirds) being Superchargers or CHAdeMO. The actual total is higher since the trip odometer doesn't account for any energy used while not driving.

 

[Rocky_H]

I'm inclined to think 3, but I don't know exactly how a "cycle" is calculated by Tesla, knowing that they are only good for so many cycles, and that number would not allow the cars to be charged daily and last for the warranty period, so I'm guessing there's more to it than just plugging it in.

Cycles aren't "calculated" by Tesla. As @Big Earl was saying, that is an actual definition from the battery industry. You are mixing up charging events with charging cycles.
So I thought this question was because where you were driving was entirely away from resources so there was some reason why you couldn't get to any charging points. But if you actually have the car at home for some periods of time, and you have the wall connector there, there would never be any reason why you should avoid using it to prevent your battery from running down really low later in the day from more driving. So yes, #3 if you have access to some charging sometime in the day.

 

[Big Earl]

Usually not an issue. I'm gone from 4:30-9:00, then home from 9:00-3:00 (on most days), then gone again from 3:00 until about 8:30. I can top off in the day with the wall charger and add about 15% per hour. Some days it will be less "top off" and more like just adding an extra 15-30%.



Don't supercharge unless I'm on a trip (which unfortunately is happening a lot more lately). Do not recall it throttling me in early December, but I do think it did in mid January. I attributed it to a slower supercharger, but that may be it. I currently have 17kWh on the clock. I'll be going to Nashville, yet again next week. Will see how that does. So that 15-ish kWh may be that point.

I didn't realize you had home charging in the middle of the day. By all means, do that.

 

[Apprunner]

Honestly, you should just plug it in whenever you get home. Thats probably the best for battery longevity.

There are studies that say, depth of discharge plays a role in battery health

 

[camalaio]

#3 is the obvious recommendation from the outside, especially if convenient.

This problem is only going to get worse as the battery approaches 10-15% capacity loss, so better to build the preventative habits now so you don't get stranded. You may need to start charging to 95% in the colder months.

I'd seriously consider a PHEV in your case, but if you are OK toughing it for the EV then good on you. You're riding the edge of its capability.

 

[Rocky_H]

I'd seriously consider a PHEV in your case, but if you are OK toughing it for the EV then good on you. You're riding the edge of its capability.

Well, it shouldn't have to be pushing the edge of its capability. It's just that there was a huge detail that was a glaring omission from the original question that was not mentioned until comment #4.

then home from 9:00-3:00 (on most days),

Being home for a few hours in the middle of the day to charge makes this a non-issue.

 

[davewill]

I would add that the OP should not just add enough to get them to the end of the day at a low battery charge. They should add at least enough to keep that final charge level above 30% or so, if possible. The easiest (and probably best) is to plug it in all the time that it is home, and set the charge level to 80-90%.

 

[Big Earl]

Just charge it to 80-90% overnight, run around in the morning, come home for lunch, charge back to 80-90 or however close you can get, run around in the evening, come home and charge it back to 80-90 for the next day. Easy.

 

[67King]

I'd seriously consider a PHEV in your case

No, I'm way too much of a gearhead - mine's a Performance. I'd rather try to kick an opioid habit than to deal with any hybrids. I'd start driving my BMW again, first. Only recently an issue exacerbated by a few things:
A) Weather. Not a problem when it isn't cold and/or raining. I mentioned my morning routine was 360 w-hr/mi. This afternoon it was mid 50's, rather tahn 20's, so 280.
B) COVID. I'm sitting in the car waiting on kids longer than I used to because we don't let them ride the bus, and for their swim practice, the lobby is closed to parents (pool is a ways away, my workouts don't take the full 2 hours, so I have some downtime). SO the heat can be on for 20 minutes while parked, and another 30 minutes while going through car lines.
C) I'm recovering from a surgery, so at times, I am dropping off, going home, and coming back instead of dropping off, hitting a different pool in town where I swim, then taking them back home to get ready for school. Similar issue in PM
D) Like I said, my battery seems to have taken a hit recently, with the loss going from 3% in the first 40K miles to 9% after 54K miles. Can't get around that, unfortunately.
E) I have some "range" tires for trips. 18" all season on aftermarket aero wheels. Put the performance tires back on.....makes a big difference.

Thanks, everyone. I guess I'm still stuck thinking like phone maintenance, where reducing charging events is important for battery life. Seems that isn't teh case here.

 

[67King]

Just charge it to 80-90% overnight, run around in the morning, come home for lunch, charge back to 80-90 or however close you can get, run around in the evening, come home and charge it back to 80-90 for the next day. Easy.

Yeah, exactly. Now that I know taht isn't hurting by battery life!

 

[Zoomit]

They should add at least enough to keep that final charge level above 30% or so, if possible.

Do you recommend this to have a buffer for unexpected trips or poor weather? If the final charge level is lower than 30%, it's certainly not an issue for battery health.

 

[davewill]

Do you recommend this to have a buffer for unexpected trips or poor weather? If the final charge level is lower than 30%, it's certainly not an issue for battery health.

I figure that if someone is aiming at getting home with 15%, then they are likely to sometimes find themselves at, say, 5%, which IS detrimental, so I suggested to aim at at least 30% instead.

 

[Candleflame]

I usually charge to 90% every day. In the warmer months, with no rain, no problem. But sometimes if I throw a bike or two on the roof during the day, it kills range. Now with teh cold, especially when it rains, I'm using more and more of my battery. Twice this week, I have gotten down to 1-2% by the time I'm all done. So far this morning, I've gone from 90% down to 45%, and I typically make the same rounds of trips in the evenings (though I won't be waiting in the car or in line in the car in 25 degree weather, so the load from the heater will be reduced).

So what is the best charge strategy to preserve battery life? I only lost 3% range in the first 40,000 miles, but I've lost another 6% in the past 14,000. Car is a Performance, lifetime is 306 w-hr/mi, so far today I'm at 360 w-hr/mile.
1. Charge to 100% every day
2. Charge to 90% every day and run down to <5%
3. Charge to 80-90% every day, and add charge* in the middle of the day to get through the day

* Sometimes I may only be able to charge for an hour or so, so about 15% range.

I've never done 1 for daily usage. I usually charge to 90%, and when it isn't cold or rainy, I can finish the day at 20% or so (well.....I used to be able to, but unsure now with battery degradation). I've occasionally topped off a little bit, but have a couple of times tried #2.....but I've gotten REALLY close. Like 1% last night.

I'm inclined to think 3, but I don't know exactly how a "cycle" is calculated by Tesla, knowing that they are only good for so many cycles, and that number would not allow the cars to be charged daily and last for the warranty period, so I'm guessing there's more to it than just plugging it in.

tesla is annoyingly silent about the factors and how they affect degradation, in particular Tesla is very secretive about the damage to the battery from discharging the battery to i.e. 5% or 0%. A lot of users, including me have a suspicion that as long as you drive very gently below 10% (no flooring) you dont harm the battery at all.
From conventional lithium ion research 90 - <5% is FAR healthier than 100% to <15%. Also keep in mind that on the model 3 you have a 4.5% buffer plus maybe 1% brick protectio so you are really discharging to 10% not 5%.

 

[Candleflame]

Extending Battery Lifetime by Avoiding High SOC got an itneresting paper here which shows that even flogging the battery (4C discharge) at low SOC seems to be healthier for the battery than gently driving it at 60-70% SOC (1C discharge)