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Model 3 SR+ LFP Battery Range, Degradation, etc Discussion
- Thread starter Baluchi
- Start date
AlanSubie4Life
Efficiency Obsessed Member
What is this? I wasn’t aware of any such buffer.
This is to make sure you don’t get stranded (very important!), not for battery health.
([EDIT: sounds like @AAKEE has clarified his meaning, but in any case not charging to 100% won’t cause any harm, other than perhaps leaving you stranded by the road…which obviously is not desirable.)
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I mean that there is no issue with charging to 100% with LFP.
They can do very many full 100-0% cycles so charging all the way to 100% is not a problem.
While I havent dug deep into Teslas LFP setup I would say that there probably is no top buffer.
LFP’s is much less sensitive than NCA and NMC for high SOC. Tesla do not use any top buffer for these.
So the need for a top buffer is non existing.
A top buffer would also reduce the usable capacity of a already limited LFP capacity.
Tesla use a variable bottom buffer for the new LFP’s. I havent gotten into it but saw some posts about this here on TMC.
As the BMS can be more or less certain about the remaining energy it seems wise to increase the buffer when uncertain and reduce the buffer when not that uncertain.
LFP’s itself do not need buffer for protection of the battery as full 100-0% cycles wear very little.
AlanSubie4Life
Efficiency Obsessed Member
Yes, that observation implies some buffer, but exactly how big it is is unclear. Someone would have to regen down a big hill from 100% and monitor SMT; not hard to figure out. (Very unlikely 5% as you indicated.) I would expect it to stop regenerating after recapturing less than 1kWh (less than 1000 feet), but that is just a wild guess.
The dynamics of how the LFP can accept charge near 100% is likely different than the NCAs. I’m not sure exactly what all the electrochemical issues are, but this could affect both how much more you can charge it (and impacts on battery heath) as well as the RATE at which you can charge/overcharge it, which affects utility of regen; two distinct issues here (@AAKEE may (will) know more). The rate at which you can add charge to an NCA gets very slow at high SOC, which makes the utility of a higher charge limit very low, completely neglecting any safety or damage issues due to overcharging (would take a long time to get to a higher limit, which makes it not very useful). This rate limiting at high (near but below 100%) SOCs seems to be less of an issue for LFPs.
The 2.5kWh you mention is bottom buffer. It is 4.5% (but can increase to 11% for the LFPs apparently if the BMS is in doubt; this is special LFP behavior, and can be observed in SMT).
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2 months old RWD - 8000km @435km. Have been consistent at that number for few weeks now.
Same around 8000 km but 100% shows 431 km. Not sweating about it. I use energy instead of km. Whats your chargimg habbit though?
Charge to 100% every alternate day. So during a week 3 days car remains unplugged.
Agreed. I have a 2021 SR+ with LFP battery. 20,000 miles. I plug it in every night and start every day with 100% charge. Supercharge on trips (at least once a month). I lost 4-5 miles of range in first 2,000 miles. Hasn’t changed since. I enjoy the simplicity compared to my old battery.
Its not the same as degradation.
You only need one 100% full charge to reset the kWh counter in the BMS. As soon as the charging stops the BMS is back on track and knows the true SOC.
There is no risk of loosing capacity by not charging full but when the BMS looses track there is a risk of getting stranded with no energy left in the battery because the BMS thought it still was energy left in the batt.
The advice from Tesla is real and the risk of getting stuck with 0% is, so its vice to folow that advice.
The BMS do not ”forget the capacity”.
You do not loose any capacity. You only get a BMS that lost track of the SOC.
A single full charge resets this.
On a selfish note, it'd be helpful if people would include the max range of their car when it was new in these posts. Between the changes Tesla has made to ranges and the conversion between miles and kilometers, I really can't get much out of these posts without the extra context. But maybe it's because I'm a boob.
25,000 mile (40,000 km) update for my Sep 2021 SR+ LFP. The car is now about 11 months old and was originally rated at 253 miles on a full charge. The Tessie app shows a battery capacity of 52.8 kWh (down 3.3% from my original 23 Oct 2021 post of 54.6 kWh), and a max range of 244 miles (down 3.6% from my original post of 253 miles). I've had Tessie since my first day or two or ownership, so this data shows the entire life of the car.
Note that my capacity loss appears to be leveling off, with the most severe decline in range coming between 4,000-5,500 miles on the odometer.
According to the car's screen, I'm now averaging 217 Wh/mi over the life of the car (down from 220 during the 20,000 mile update). Seasonal temps and driving style are HUGE when it comes to the car's efficiency. In the winter I can expect 240+ Wh/mi, and in ideal temps (75-85f) I routinely manage under 200 Wh/mi on my 100 mile roundtrip commute. Assuming I could tap into the current 52.8 kWh battery at my lifetime average 217 Wh/mi efficiency, that gives me a real-world range of 243.3 miles.
My charging is mostly Level 2 from a Grizzl-E on a 40 amp circuit in my garage. Until recently, I charged at 32 amps, but I started getting unexpected errors that would stop my charging sessions in the middle of the night, so I dropped my charge rate to 24 amps and that seems to have fixed the problem. I charge most nights due to a long commute, typically to about 70-80% a few times per week and a 100% once or twice a week.
Tessie says I've spent $711.33 on electricity for the life of the car, while the same driving in my old Ford Focus would've cost $2,723.42 in gasoline. So my fuel costs have been 26% compared to keeping my old car. Assuming the average US emissions of 0.85 pounds CO2 per kWh, the 5,928 kWh used while driving equates to 5,038 pounds of CO2 spent driving my Tesla. If I'd kept my 2012 Ford Focus (37mpg), I would've used 685 gallons of gas to travel these 25,358 miles. At about 19 pounds of CO2 per gallon, that would've been 13,015 pounds of CO2. So I'm spewing 39% of the carbon emissions than I would've released in my efficient little Focus. As the grid moves toward more renewables, that should only get better over the life of the car.
ScanMyTesla says I've used 143 charge cycles. LFP batteries are supposedly good for 5,000 cycles before degrading to 80%, so I've used 2.8% of those cycles since I bought the car on 23 Sep 2021. I don't know how accurate any of these numbers are, but at this rate, the car *should* last longer than I do.
I'll try to post another update at 30,000 miles. That should be when we're getting nice fall weather, so I'm betting my average Wh/mi will be even lower.
Note that my capacity loss appears to be leveling off, with the most severe decline in range coming between 4,000-5,500 miles on the odometer.
According to the car's screen, I'm now averaging 217 Wh/mi over the life of the car (down from 220 during the 20,000 mile update). Seasonal temps and driving style are HUGE when it comes to the car's efficiency. In the winter I can expect 240+ Wh/mi, and in ideal temps (75-85f) I routinely manage under 200 Wh/mi on my 100 mile roundtrip commute. Assuming I could tap into the current 52.8 kWh battery at my lifetime average 217 Wh/mi efficiency, that gives me a real-world range of 243.3 miles.
My charging is mostly Level 2 from a Grizzl-E on a 40 amp circuit in my garage. Until recently, I charged at 32 amps, but I started getting unexpected errors that would stop my charging sessions in the middle of the night, so I dropped my charge rate to 24 amps and that seems to have fixed the problem. I charge most nights due to a long commute, typically to about 70-80% a few times per week and a 100% once or twice a week.
Tessie says I've spent $711.33 on electricity for the life of the car, while the same driving in my old Ford Focus would've cost $2,723.42 in gasoline. So my fuel costs have been 26% compared to keeping my old car. Assuming the average US emissions of 0.85 pounds CO2 per kWh, the 5,928 kWh used while driving equates to 5,038 pounds of CO2 spent driving my Tesla. If I'd kept my 2012 Ford Focus (37mpg), I would've used 685 gallons of gas to travel these 25,358 miles. At about 19 pounds of CO2 per gallon, that would've been 13,015 pounds of CO2. So I'm spewing 39% of the carbon emissions than I would've released in my efficient little Focus. As the grid moves toward more renewables, that should only get better over the life of the car.
ScanMyTesla says I've used 143 charge cycles. LFP batteries are supposedly good for 5,000 cycles before degrading to 80%, so I've used 2.8% of those cycles since I bought the car on 23 Sep 2021. I don't know how accurate any of these numbers are, but at this rate, the car *should* last longer than I do.
I'll try to post another update at 30,000 miles. That should be when we're getting nice fall weather, so I'm betting my average Wh/mi will be even lower.
Good to hear from you Baluchi, though I’m a bit let down because I expected you would have 100k miles by now. My first anniversary is coming up in a little more than a month as well. I’m thinking of celebrating by going big, and removing the little sheet of plastic that has been covering my MCU since I bought the car…
RayK
Active Member
Probably. I'm not sure about LFP battery degradation curve but with NCA it seems to be higher at first, then tapers off. My 4 year old LR RWD (NCA) has lost about 5% (315 -> 298) but I didn't monitor the loss on a weekly basis. My suggestion is don't worry about it for now but check on it once every couple of months. I believe with the LFP battery is that you don't want to discharge it too far. In other words, keep it more full than more empty.
rpiotro
Active Member
Calibration of the range computer perhaps? Just spitballing here. What was the temperature difference? You driving habits during that time? Etc.
Good info. I've always wondered how does SMT determine what mileage is a discharge cycle? When you do the math, it's 186miles/cycle. Presumably they have to include transmission inefficiency and non-driving usage. And why are there 7 more charge cycles than discharge cycles? Shouldn't it be 1 more charge than discharge, or is that also due to non-driving usage?
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