Is 100% charge on MYLR once a month good for extended battery life?

[AAKEE]

Thanks for sharing. For LFP after charging to 100%, then down to what % within how long time would be a good for the battery health? For example, may be back to 90% or lower within 10 hours?

There is a steep step in LFP at ~70%. 72% technically in the upper picture. Depends on the central graphite peak).
This is just one test on a specifik cell a few years back.
The exact number might vary little between different LFP’s.

This is a more recebt test.
100 and 87.5% has the same calendar aging at 15C, ( but a slight difference at 45C)

75% has slightly less calendar aging at 15C, but you need below that to reduce calendar aging more.
The resolution is not very high in this test (but still better than many other tests).

Theslas use ~ 4.5% buffer and LFP vary the buffer with BMS uncertiness.
The buffer means that the true SOC is higher than the displayed SOC.
With the lowest buffer, true SOC is around 1.5% more than you read on the display at around 70%.

So 70% is good according to the research on the upper picture (does not show the sharp limit at 72% on the picture but the research report had the data).

It could be a good idea to aim to reduce the time above 70% displayed.

 

[crunchor]

There is a steep step in LFP at ~70%. 72% technically in the upper picture. Depends on the central graphite peak).
This is just one test on a specifik cell a few years back.
The exact number might vary little between different LFP’s.
View attachment 1047644

This is a more recebt test.
100 and 87.5% has the same calendar aging at 15C, ( but a slight difference at 45C)

75% has slightly less calendar aging at 15C, but you need below that to reduce calendar aging more.
The resolution is not very high in this test (but still better than many other tests).
View attachment 1047645

Theslas use ~ 4.5% buffer and LFP vary the buffer with BMS uncertiness.
The buffer means that the true SOC is higher than the displayed SOC.
With the lowest buffer, true SOC is around 1.5% more than you read on the display at around 70%.

So 70% is good according to the research on the upper picture (does not show the sharp limit at 72% on the picture but the research report had the data).

It could be a good idea to aim to reduce the time above 70% displayed.

I am surprised actually let battery stay at 0%, 12.5% has the smallest calendar aging. I thought the manual said having 0% would instantly seriously damage the battery.

 

[AAKEE]

I am surprised actually let battery stay at 0%, 12.5% has the smallest calendar aging. I thought the manual said having 0% would instantly seriously damage the battery.

Thats one of the most common myth.
Take 15 minutes, and read the manual. Its not much said, but read it and do not ad own thought between the lines.

One thing mentioned is that other equipment can be damaged from going so low that the car shuts down.
For example, the older type of low voltage battery (12V lead acid) do not at all like to be discharged below 50% so when the HV-battery shuts down, you will damage the 12V battery in a short time frame, as it discharges.

The HV batt will *sugar* down before it reaches bad levels (i.e at latest at 0% true SOC) and from that position it can be very long time before it is any issue. In fact it will degrade the least in that state).

There are not a single serious research report that finds 0% bad, from the > 300 I have read. The research is very very agreeing on that.
Remember, 0% is not completely dead but the voltage where the battery manufacturer says ”stop discharging”.

This probably kills a few myths:

These Panasonic NCA cells where cycled between 100% and 0%.

The cells is 2.9Ah, so the normal current rate for highway driving is compared to around 0.7A or so.
The cells held for ~ 750 cycles cycled between 100% and 0% (the true 0% where the Tesla* shut down the battery.)

This equals 750 cycles from full to the car stops, so around 250miles for a LR.
Thats 180K miles until 25% is lost.

100% doesnt kill instantly (or even ”at all”)
0% doesnt kill instantly (or even ”at all”).

I could post a high number of different calendar aging tests, but I have already done that a lot. Search for calendar aging by user AAKEE and you will find it.

I’ll post one: actual model S cells taken from a almost new model S.
Even if 0% isnt in this test, it matches virtually all other tests. By comparing we can understand that it is very probable that the cells will do 0% just as all other cells does.

I bought 35 pieces of Panasonic 2170 of two batches > 2 year ago. (”Model 3/Y cells”)
I had them at 0-2-55-80 and 100%.
The result matches the research…


*) we have around 4.5% buffer below 0% on the LR/P’s so 0% displayed is 4.5% true SOC.

 

[crunchor]

This guy using Tesla statements to argue LFP should be charged to 100% every time to maximum the range, look like reasonable with Tesla statements.

 

[AAKEE]

This guy using Tesla statements to argue LFP should be charged to 100% every time to maximum the range, look like reasonable with Tesla statements.

The manual did state that, "Maximizes available range" and it is in the line with that the BMS reserves more capacity below 0% displayed ( = buffer), if you do not charge full often enough. Charging to 100% often enough will minimize the buffer to around 4.5%, thus giving more energy above 0%.
Getting a larger buffer means less energy to drive on above 0%.

This info (I think) was removed from the manual, I think it was when they changed the manual so that people should check in the car instead of reading in the manual and still not understanding what type of battery the car has. (Was very common before, thats clearly better now).

 

[crunchor]

https://www.reddit.com/r/TeslaModel3/s/CgI63hNv2D

Is 20 years really possible?

 

[QtownTaxiGreg]

I don't reddit but yeah, calendar aging carries on regardless so you would wind up with 20 years worth on top of the wear and tear of usage. Could be 60% available range at 20 years? Just a WAG.

 

[ucmndd]

There are plenty of early Teslas still on the road a dozen years later with their original NCA battery packs. I don’t see why a modern LFP pack couldn’t make it 20.

The biggest problem is pack =\= cells. While the cells may last that long, many pack failures have nothing to do with the cells but rather the packaging, BMS electronics, etc etc.

3000 cycles on a Model 3 RWD LFP pack represents about 800,000 miles. That’s ~40k miles a year over 20 years - more than double what most people actually drive.

 

[andy.connor.e]

There is probably something to be said about doing regular deep discharge/charges, i know that NiMH/Ni-cd batteries required this regularly as that battery chemistry had a memory so to speak if you repeatedly did not full charge it. My knowledge on Lithium batteries recalls that this memory analogy does not exist with this chemistry.

In conclusion, charging to 100% once a month is not going to do anything to damage your battery health. This deep discharge/charge myth has people very confused on the matter. Battery health maintenance is very very simple.

Charging to 100% is like running your gas car very close to max RPM. It doesnt destroy your car, but it might speed up needing to get an oil change. If you do that all the time you might wear out other engine components faster.

The tips given about frequent >80% and <20% charges and discharges are correct but need to be taken from a relative perspective. Every day will noticeably degrade your battery faster. Thats about it. There is some nuance for instance, highly NOT recommended to take your car to a supercharger frequently and charge above 80%.

Once a month wont do anything.