Bestest Idealest Battery charging percentage band

[Manbutter]

I know this has been discussed as nauseum but the general consensus is to keep the charge between 20-80% for lithium-ion.

My question is: can someone narrow that down to an even narrower band? In a perfectly ideal scenario, where should I keep the charge state?

My Y has 400 miles on it and I’ve been babying the battery. Charging at a super slow 5amps and keeping the battery between 45-60%. My daily usage is only 10-15% so I wanted to know what the perfect band would be. I want the car to spend the most time around the optimal percent. (e.g. if optimal pct is 50%, I should charge to 58% and run it between 58-42%, and charge daily.)


(Yeah, prob being way too anal about this.)

 

[jjrandorin]

Charging at a super slow 5amps

= doing absolutely, positively, nothing, except wasting energy. ALL home charging is "slow" to the car, even up to as fast as it will go on level 2 charging (your car = 48amps or 11.5W). Regen is like 85W. All you are doing is keeping your car awake longer, thus wasting energy with it being awake.

Yeah, prob being way too anal about this.)

Probably.

You could search this giant thread for posts from @AAKEE , and get a ton of information on this topic:

Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

If you leave it overnight sleeping with sentry off with single digit, does not need to be sub sero, and then charge to 90% and leave it sleeping for at least 2-3hrs? And following days tjexsame but different SOC’s? Yes, always sentry OFF during night. Yes sleeping sub zero and sleeping over...

teslamotorsclub.com

or, perhaps this thread in this subforum:

Battery myths

There is a lot of myths* about lithium batteries floating around. Perhaps we can use this thread to kill or bust some of these, one by one? There also might be statements that we ca not directly sort as facts or myth’s, lets find out. For staters, which myth’s did you fall for? Try this quiz...

teslamotorsclub.com

 

[ucmndd]

Charging at a super slow 5amps

This is going to cause your battery to go out of balance, potentially causing catastrophic damage or early failure. Because you have 240v split phase electric service you need to always charge in even amps otherwise one phase has to carry more power. Definitely consider switching to 6 amps.

58% max is perfect. Don't go past 59%, it causes a buildup of nickel plaque and that's when electron collisions start happening.

 

[Manbutter]

This is going to cause your battery to go out of balance, potentially causing catastrophic damage or early failure. Because you have 240v split phase electric service you need to always charge in even amps otherwise one phase has to carry more power. Definitely consider switching to 6 amps.

58% max is perfect. Don't go past 59%, it causes a buildup of nickel plaque and that's when electron collisions start happening.

I had no idea about the even amps. Why would Tesla even allow for odd amps then?

I'm going to assume 59% is sarcasm.

 

[ucmndd]

I had no idea about the even amps. Why would Tesla even allow for odd amps then?

It gets messy because some countries have 3-phase power. So in the UK 9 amps would be fine but here it’s a no-no.

 

[nwdiver]

Because you have 240v split phase electric service you need to always charge in even amps otherwise one phase has to carry more power. Definitely consider switching to 6 amps.

That's not how 240v split phase works. If you put a current meter on each line they're going to be identical. The only way for them to not be identical is if some current flows back on the neutral, a HPWC connected to 240v doesn't even have a neutral.

 

[ucmndd]

That's not how 240v split phase works. If you put a current meter on each line they're going to be identical. The only way for them to not be identical is if some current flows back on the neutral, a HPWC connected to 240v doesn't even have a neutral.

 

[dbldwn02]

That's not how 240v split phase works. If you put a current meter on each line they're going to be identical. The only way for them to not be identical is if some current flows back on the neutral, a HPWC connected to 240v doesn't even have a neutral.

Yea I wasn't sure if he was being sarcastic either. He got me!!!

 

[rjpjnk]

Unfortunately, some people are going to think the odd/even amps statement is not a joke. It is pretty funny though. Wonder what happens if we charge at an irrational number like pi amps?

 

[Supcom]

Unfortunately, some people are going to think the odd/even amps statement is not a joke. It is pretty funny though. Wonder what happens if we charge at an irrational number like pi amps?

The odd, or fractional, amp goes, of course, toward keeping the 12 V battery charged.

 

[CSFTN]

Sarcasm aside, ideal is to oscillate around 50%. So for you that probably means charge to 56%. That being said, it makes very little difference unless you are commonly going > 80% or commonly < 20%, and only a little bit more in the adjacent 10% (10-90%). Anything outside those limits leads to measurable degradation. Also, there was an article several years ago noting that there's also a "charging too slowly" or more precisely "spending too much time charging" scenario. One of the EEs used to be on here did a very technical evaluation of the charging system itself and found IIRC that ~ 32 amps was ideal, but Tesla has changed its charging system since then.

If I were to bottom line it, I would think its 32 amps to 70% for routine, and then occasionally charge to 90% for the heck of it, and once per year go 10-90% twice in a row to help balance the cells. That what I do; my first Tesla lost about 3% over 4 years.

 

[Manbutter]

Sarcasm aside, ideal is to oscillate around 50%. So for you that probably means charge to 56%. That being said, it makes very little difference unless you are commonly going > 80% or commonly < 20%, and only a little bit more in the adjacent 10% (10-90%). Anything outside those limits leads to measurable degradation. Also, there was an article several years ago noting that there's also a "charging too slowly" or more precisely "spending too much time charging" scenario. One of the EEs used to be on here did a very technical evaluation of the charging system itself and found IIRC that ~ 32 amps was ideal, but Tesla has changed its charging system since then.

If I were to bottom line it, I would think its 32 amps to 70% for routine, and then occasionally charge to 90% for the heck of it, and once per year go 10-90% twice in a row to help balance the cells. That what I do; my first Tesla lost about 3% over 4 years.

Thank you! The one answer I needed and one of the few posters who actually helped instead of making a joke of it. You, sir are awesome.

I need a CSFTN response for every question in my life. Direct, to the point, filtered through 208 pages of debate from the other thread.

 

[watsongrg]

I charge to 87% routinely, plugged in all the time, 240V/30A. I’ve charged to 100% several times right before leaving on long drives. I’ve supercharged maybe 18-20 times traveling, typically to 90%.

One year and 30K miles later, I have a 1% depredation, per tests/ calculation. I got a good one.

 

[Manbutter]

I charge to 87% routinely, plugged in all the time, 240V/30A. I’ve charged to 100% several times right before leaving on long drives. I’ve supercharged maybe 18-20 times traveling, typically to 90%.

One year and 30K miles later, I have a 1% depredation, per tests/ calculation. I got a good one.

No history yet for my 3 month old 1,000 mile Tesla but my Radrunner ebike has lost about 15% of capacity in 12 months use. Charged to 100% each time from 30% maybe 26x. That kinda sucks.

 

[andy.connor.e]

I know this has been discussed as nauseum but the general consensus is to keep the charge between 20-80% for lithium-ion.

My question is: can someone narrow that down to an even narrower band? In a perfectly ideal scenario, where should I keep the charge state?

My Y has 400 miles on it and I’ve been babying the battery. Charging at a super slow 5amps and keeping the battery between 45-60%. My daily usage is only 10-15% so I wanted to know what the perfect band would be. I want the car to spend the most time around the optimal percent. (e.g. if optimal pct is 50%, I should charge to 58% and run it between 58-42%, and charge daily.)


(Yeah, prob being way too anal about this.)

40-60 is idealest.

 

[BillRadio]

can someone narrow that down to an even narrower band?

Looking at research that has been shared in these forums, the narrowest band is 50% to 55%. The lower figure is not critical, and I feel fine charging up to 55% every few days just to make sure I have enough at the ready. I agree, charging less than 12amps is counterproductive. Conversely, I never hesitate charging up to 90% before any trip. I am of the opinion that optimizing the charge cycles is actually an interesting pursuit (I even focus on my utility's ability to deliver solar and wind energy to determine my charge times), but I'll also change the charge whenever it's more useful or convenient to me. </common sense>

 

[Manbutter]

Looking at research that has been shared in these forums, the narrowest band is 50% to 55%. The lower figure is not critical, and I feel fine charging up to 55% every few days just to make sure I have enough at the ready. I agree, charging less than 12amps is counterproductive. Conversely, I never hesitate charging up to 90% before any trip. I am of the opinion that optimizing the charge cycles is actually an interesting pursuit (I even focus on my utility's ability to deliver solar and wind energy to determine my charge times), but I'll also change the charge whenever it's more useful or convenient to me. </common sense>

Thanks for the insight. I’m thinking along the same lines.

I’ve learned so much about battery optimization since getting my EV. I find myself unplugging my Ebike at 70%

 

[AAKEE]

As usual, there is more "non truths" and myths in these threads than we find truths.

First thing first, there is not any true story behind the 20-80% myth.
-Below 20% is very safe, if we only think of the battery itself. Range anxiety might be a valid point but should not be mixed into this as it probably is a good base for further myths. Read this post from me: A lot of cycles down to 0%

- Deep cycles is often discussed and by definition the term is missleading. The bad part of a deep cycle is in the top, not in the bottom.

If we only look at what is best for the battery itself it will be like this:
-Small cycles is better than large cycles = charge often
-The lower the cycle is placed in terms of SOC, the better. 30% down to 10% is better than 50% to 30% is better than 60% to 40% is better than 70 to 50% is better than 80% to 60% is better than 90% to 70%. Going below 20% is very safe for the battery. In fact, below 20% is best.
This means: Do not charge more than you need until the next charge, and activate the next charge as soon as possible.

Above was for keeping the cyclic degradation low.

For calendar aging, which will be the dominant part for the absolute most people for at least the five firste years, this is valid:
- The lower the SOC is when the car is not used, the lower the calendar aging. Do not charge more than you need until the next charge, and charge late/just before the drive: this keeps the average SOC low which is good in terms of calendar aging.

For panasonic NCA there is a clearly marked step at 58% SOC where the calendar aging will be halv if below, and double if above. As Tesla hides about two percent of the true SOC (due to the buffer) on should aim to be below about 56% displayed SOC.
If using LG NMC cells like some 3/Y in Europe, the step is a little higher, like 62% so aim for 60% displayed or lower.

 

[AAKEE]

Looking at research that has been shared in these forums, the narrowest band is 50% to 55%. The lower figure is not critical, and I feel fine charging up to 55% every few days just to make sure I have enough at the ready. I agree, charging less than 12amps is counterproductive. Conversely, I never hesitate charging up to 90% before any trip. I am of the opinion that optimizing the charge cycles is actually an interesting pursuit (I even focus on my utility's ability to deliver solar and wind energy to determine my charge times), but I'll also change the charge whenever it's more useful or convenient to me. </common sense>

55% (or 56%) displayed, is the highest SOC that will cause low calendar aging. i.e is below the "step" in the graph.

The chart below is not the only graph showing this. More or less all research support this. There is some research reports that hide part of it, due to a muggy research test setup.
So, for all science know today, this is valid.
The NCA chart is for Panasonic NCA (18650 in this chart). 2170 NCA looks about the same.(the form factor do not change this).

The lower SOC you leave the battery with, the less calendar aging you get, down to 0%.

0% is not completely empty, 0% is the defined minimum discharge voltage set by the battery manufacturer.

For Teslas ( NCA, NMC) with 50% as the lowest charging setting, this will be the best charging setting possible when it comes to calendar and cyclic aging.
Theoretically: using a even lower charging setting by interrupting /stopping the charging at a lower SOC would be even better but 50% will be good enough.

A NCA/NMC will stand at least 500 to 1000 full 100-0% cycles. This means in plain text that the cyclic degradation per year will be some 1% or less for the most owners.
Calendar aging on the other hand can degrade the battery 5-10% the first year.
Its not the cycles you should be afraid of.

 

[AAKEE]

I have lived by the facts shown by science, and my car is doing very well.
56.000km after two years, the nominal full pack is about 79 kWh and last full charge showed 497km (507km "new range").

I have 46 supercharging sessions and 3 charges at another brand(200kW charger). I have charged to full (or 98% or more about 30 times.
If driving down to below 20% was bad, I would need a new battery today.

Still, its not just "he got lucky in the battery lottery". The degradation shown today is more or less on spot with the calcuation.
There was a range dip in this summer but a 100% to 0% drive showed that the capacity was about 79 kWh, this was at the time the degradation report showed the lowest range. It was only a BMS calibration issue.

I charge to 55%. I know 50% would be marginally better but 55% is good enough for me. As I charge just before the drive it would actually be possible to charge higher than 55% and still get low calendar aging. For longer drive I do that.