-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
HV replacement mileage ?
- Thread starter Allx
- Start date
I’m with you on that. It seems like replacement at 150k miles is a little premature if we reverse the calc (that would 500 cycles) . I’m wondering what others are seeing, maybe it’s just a one-off lemon of a battery - otherwise I’d be a little squirrelly about what’s in store in a few years…
Sure, it may be premature. But batteries aren't exact science. A 300k mile average tends to mean that for everyone that fails at 150K, there's another that makes it to 450k.
There are ICE engines that fail before 100k also.
All batteries degrade due to time, temperature, and cycle life.
The cycle life will vary widely with the level of discharge and charge. The level of discharge is the bigger of the two. You don't want to bring the battery down to zero, or a very low state, as this has a big impact on cycle life. If you charge to 100%, you don't want to leave it sitting in that state for long. Bump it up just before leaving on a road trip.
Calendar aging you can't do anything about. From what I've seen over time, 10 years is what I'd expect in calendar life. Have a replacement budgeted if you keep your cars a long time, or if you buy used.
Other undetected flaws can happen during manufacturing shorting the lifespan of a cell, but the above is what you can control.
The cycle life will vary widely with the level of discharge and charge. The level of discharge is the bigger of the two. You don't want to bring the battery down to zero, or a very low state, as this has a big impact on cycle life. If you charge to 100%, you don't want to leave it sitting in that state for long. Bump it up just before leaving on a road trip.
Calendar aging you can't do anything about. From what I've seen over time, 10 years is what I'd expect in calendar life. Have a replacement budgeted if you keep your cars a long time, or if you buy used.
Other undetected flaws can happen during manufacturing shorting the lifespan of a cell, but the above is what you can control.
Last edited:
For cycles vs lifetime we should use Full Equivalent Cycles (FCE) as the term to relate to.
One 100-0% charge-discharge cycle is one FCE. We need three 0-33% charge-discharge cycles for 1 FCE.
Or ten charge-discharge cycles of 10% DoD, for example 60-70%.
FCE will directly relate to how much energy the battery deliver (or miles that can be driven) compated to the degradation.
A Panasonic NCA, like Tesla model S/X or model 3 and Y in US would stand about 750FCE if we charge to 100% and discharge to 0% each time.
This would equal about 260K km (160K km).
But we do not use it like that, mostly.
Smaller discharge cycles reduce the degradation. All these are still discharged to 0%, but the charge level is varied.
4.2V = 100%
3.7V = about 50%
(About 10% per 10%)
(source: Research report )
We can see that the battery only lost 10% during the first 1000 cycles from the 3.7V / 50% - 0%. The inclination and bent form of the line show us that we would get perhaps 2500-3000 FCE in that case.
Most cars are cycled with relatively small cycles that wear even less.
But: Cyclic aging is only a small part of the degradation, calendar aging takes a bigger bite of the battery in the early battety life.
When batteries start getting old and work bad, it is the total degradation that matters so cyclic + calendar aging.
This persion needing a replacement after 150K, is it because the cells is worn out or is it another fault in the battery?
Its much more common to have other issues than that the cells is worn out.
Thanks for the detailed response. It sounds like you’re saying that 1500 cycles we hear refers to partial cycles and those cells really only withstand 750 FCE ? Or do you mean that discharging from a lower SOC is less hard on a pack even when the total kWh used is the same (2x 50-0 vs 1x 100-0) ?
The post I saw only mentions the model awd is 3 yrs old and has 150k miles (so beyond the warranty). It got me wondering what others are seeing mileage-wise before replacement is needed. Seems like they might have a faulty battery given the mileage and age of the car yet somehow it’s considered out of warranty.
Original post Here
1500cycles was from your friend.
I stick my head out and say that there is no such spec like ”1500 cycles”.
The specifications from Panasonic say about 500 100-0% cycles (this is the 18650 format, from what I know there are no specifications from Panasonic themself for the 2170/2170L used in model 3 and Y).
The specifications most often means charging at a higher rate (0.7C in this case) than we mostly do( about 0.25C). Also, the discharge rate is much slower in the car (0.25C ish) than the specification states (1C inbthis case)
This makes us see about 750 full 100-0% cycles, even if the datasheet is lower.
As you saw in the picture in the earlier post, 50% DoD (depth of discharge) from 50-0% reduced the degrataion substantially. 1000 FCE did degrade 10% and the curve was flattening so they would do 2500-3000 FCE in that case.
Using even smaller cycles than 50% cause the degradation to be even lower in almost any test. (Not in allthough as test setup abd checkup might differ slightly).
Yes, thats the basic thing
-Smaller DoD wear less
-Charge discharge cycles lower down in SOC wear less.
NCA cells (like teslas panasonic NCA) will sometimes show slightly different results and in some cases of DoD in combination with discharge rates they sometimes hold up better when doing large cycles. But the common thing is that the discharge rate is higher, probably heating the cell to a more convinient cycling tempersture.
For our day to day driving, smaller cycles most probably is better.
This is a picture of a cycle test of actual model 3 LR cells taken out of a not to old model 3:
You can see the dept of discharge inbthe table: 0-50, 50-100 and 0-100%
R means cycled in room temp (22C )
H mesns high temp( 45C)
These test where made with 0.33C charging (equals about 25kW AC charging) and discharge rate of 1C (equals about 75kW power or driving a full pack empty in one hour.
The high power compared to real life driving offset the results, this can be shown in other research reports.
This research report
0-100% gave us 2500 cycles at room temp.
All the other tests gave about the 750-800 FCE I was talking about. The reason for not seeing > 1000 for the 0-50% is most certainly that the 1C discharge is too high fir this cell.
If ypu look att the second picture from up, the lines hit at the same to 1A which is ~ 0.33C for that cell.
The 1C is the 3A line which kills the battery quite fast.
So, now you habe seen that they can do both 2500FCE, 1000FCE, 750FCE and even much less, depending on how they are cycled.
-Keep low SOC
-Small cycles
-charge often (to help the two above to be small and low).
-charge late, specially the times ypu need to go above 55%.
Also remember that calendar aging might cause 3 times the cyclic fegradation during the first five-eight years, and that when the battery breaks, it is the sum of the degradation that matters.
= Concentrate more on calendar aging than cyclic aging (but both benifit from the same habits).
For a car that has 150K miles, you are probably at about 650-700 FCE and that should not be where the battery breaks normally.
I inow of a model 3 P that had to change the battery because it was broken, at about 150K miles bit it was almost only supercharged 55.000 kWh SuC) and the car was used with much power very often and run on track etc.
Im quite sure it was the lithium plating thing tjähat shorted those cells.
The battery consists of cells, BMS-computer and contactors (relays).
It do not need to be the cells that are broken. Broken contactors or a faulty BMS, you know computer used for many years might start to fail)
E90alex
Active Member
It’s a myth. Low SOC is fine for the battery. You just don’t want to run it completely dead (to where it shuts off) and then leave it there.
Just as @E90alex says.
It has been tested over and over again.
In some tests running down really low (like the lowest 5% cause slightly more degradation than the lowest option to stop discharge at 5% or so, but this increase is so low that being higher up still is a worse option).
Remember, 0% displayed is about 4.5% true SOC so we wont be at the lowest fove anyway, if not driving below 0% or 0miles.
For supercharging, lithium plating (that is the bad thing from supercharging) is mostly not an issue at lower SOC, its higher up it mostly happens.
The research shows that a soft start, ramping up the charge power is beneficial, but Tesla already use that type of charging start so it is handled already.
Similar threads
