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LFP to 100% Each Week—Assumptions?

I've lived long enough to know that life constantly gets in the way of such assumptions. Given the small distribution of proven battery degradation from owner reports, it just isn't worth it to put oneself in a situation where the available range is an unknown quantity to the car's own BMS and nav system.
So just assume that the bottom 10-20% isn't there and either:
1) Charge to the amount you think you need +20%
2) Take another car in the rare event that something comes up
3) Charge to 100% if you get ample notice

It's way better than causing unnecessary degradation just because you're constantly afraid something might come up. Especially if you drive only 25 miles a week.
 
So just assume that the bottom 10-20% isn't there and either:
1) Charge to the amount you think you need +20%
2) Take another car in the rare event that something comes up
3) Charge to 100% if you get ample notice

It's way better than causing unnecessary degradation just because you're constantly afraid something might come up. Especially if you drive only 25 miles a week.
There isn't any clear owner data that 'unnecessary degradation' is occurring regardless of the charging strategy.

You live in the SF Bay area. Has anything unexpected ever happened there (or is likely to happen there), that might put you in a situation where you unexpectedly need the full capabilities of your car?
 
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There isn't any clear owner data that 'unnecessary degradation' is occurring regardless of the charging strategy.
@AAKEE has posted plenty of data showing degradation at high SoC levels. This applies to LFP batteries as well as NCA.
You live in the SF Bay area. Has anything unexpected ever happened there (or is likely to happen there), that might put you in a situation where you need the full capabilities of your car?
You mean all ~260-355 miles range (depending on speed, weather, etc.)? Nope. What am I going to do? Drive over to Nevada because there was an earthquake? Why would I do that? Most I have ever needed on short notice was around 50-60% of the range. And that was to get to where I needed to go and back. I could have charged somewhere at my destination if I really had to.
 
@AAKEE has posted plenty of data showing degradation at high SoC levels. This applies to LFP batteries as well as NCA.

You mean all ~260-355 miles range (depending on speed, weather, etc.)? Nope. What am I going to do? Drive over to Nevada because there was an earthquake? Why would I do that? Most I have ever needed on short notice was around 50-60% of the range. And that was to get to where I needed to go and back. I could have charged somewhere at my destination if I really had to.

M3 LFP owner reports do not support that data.

Unexpected things happen all the time.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
13,565
10,166
I've lived long enough to know that life constantly gets in the way of such assumptions. Given the small distribution of proven battery degradation from owner reports, it just isn't worth it to put oneself in a situation where the available range is an unknown quantity to the car's own BMS and nav system.
As another pointed out, the uncertainty that affected LFPs is only 10%. OP can add 20% for even more margin. I don't see the point of needing the car always close to 100%, especially for a LR.

I've never come up to a situation (nor can I even make one up) where I see the need to drive 200+ miles on short notice without even stopping at a supercharger (which is a very simple way to address longer trips). I doubt most people can too. For me personally, leaving an extra 50 mile margin is enough for me (I have an NCA car). If I had LFP, I would add another 10-20% (or around 27-55 miles rated range), and call it a day.
 
As another pointed out, the uncertainty that affected LFPs is only 10%. OP can add 20% for even more margin. I don't see the point of needing the car always close to 100%, especially for a LR.

I've never come up to a situation (nor can I even make one up) where I see the need to drive 200+ miles on short notice without even stopping at a supercharger (which is a very simple way to address longer trips). I doubt most people can too. For me personally, leaving an extra 50 mile margin is enough for me (I have an NCA car). If I had LFP, I would add another 10-20% (or around 27-55 miles rated range), and call it a day.
I'm making a 20 mile trip to my dentist and hop on the freeway. The traffic suddenly grinds to a halt and after a few minutes I call and cancel the appt. An hour or so later the traffic starts to move, and then the RCMP routes everyone over to the opposite side of the freeway and I get home about 5 hours later.... A chemical spill closed the freeway.

I'm driving home to our SE Arizona home at 65mph on a bare road, after a short trip for dinner, and within minutes I'm crawling along at less than 20mph in a whiteout blizzard...

Last year, parts of the Fraser Valley were without power for several weeks due to massive floods. Homeowners, in some cases had only minutes to flee.

It's a chaotic world and I keep my car at a high SOC for a reason. There's a multitude of owner reports that indicate, very clearly, that M3 LFP battery degradation happens at basically the same rate regardless of the charging strategy. The very last thing I want is to be stuck somewhere in a car with both a low SOC and an unreliable BMS and nav range indicator.
 
Here's an idea to brainstorm: When you get in the car, it displays a message:

"Based on your recent charging activity, the stated range may be off by up to 20%. Thus, your maximum dependable range is 72 miles. "

Charged Tessie to 100% for the first time since delivery a few days ago, and now she's sitting at 83%.

Screenshot_20221125-090542_Tesla.jpg
 
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Here's an idea to brainstorm: When you get in the car, it displays a message:

"Based on your recent charging activity, the stated range may be off by up to 20%. Thus, your maximum dependable range is 72 miles. "

Charged Tessie to 100% for the first time since delivery a few days ago, and now she's sitting at 83%.
So the car is saying that "83%" could really be as low as 63%, and that 63% will only give you 72 miles?
 
Here's an idea to brainstorm: When you get in the car, it displays a message:

"Based on your recent charging activity, the stated range may be off by up to 20%. Thus, your maximum dependable range is 72 miles. "

Charged Tessie to 100% for the first time since delivery a few days ago, and now she's sitting at 83%.
Well if you are using 190kWh you are driving a fair bit going by what I'm showing for my car.

I was out of town for 2 weeks and I used less than I normally do by a fair amount. I only did 725 kms (around 450 miles)
and this is on winter tires with temps between -5 °C and 8°C (23° to 46° F) and used less energy than you.

[cost is not the same so don't look at that!! .06 / kWh 😇 ]

IMG_4448.PNG
 
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When there's a flood, you flee to higher ground. Which is a hell of a lot closer than 200 miles away.
When the entire town is a valley, and you have only minutes to flee, just how far are you going to make it before the flood drowns you? While you are on foot and haven't even reached the hills yet...I think that's why @DuncanM laughed :)

Duncan, you're from Canada and the other forum members (and Musk) are from California, no wonder they don't understand snow and the danger of hypothermia if stranded. I share your views and always charge to 90%, and I think about the Lucid with 521 miles of range compared to my Tesla (Musk says more range is a waste). Then I could keep the heater going for many hours if I get stuck or buried in snow.
 
Let's say you don't charge the car all the way to 100% weekly and the BMS miscalculates. Would this then be a permanent issue? Can you just charge it to 100% weekly and the BMS will fix itself eventually? Or is the BMS permanently "damaged".
The BMS will correct itself when the car is charged to 100%. There's no permanent damage done.
 
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stopcrazypp

Well-Known Member
Dec 8, 2007
13,565
10,166
When the entire town is a valley, and you have only minutes to flee, just how far are you going to make it before the flood drowns you? While you are on foot and haven't even reached the hills yet...I think that's why @DuncanM laughed :)
Your nearest evacuation zone is 200+ miles away? I think that was the point. Very rarely do people need to flee 200 miles, it's simply not a reasonable margin to leave for most people (keep in mind OP only travels 25 miles per week and also in California).
Duncan, you're from Canada and the other forum members (and Musk) are from California, no wonder they don't understand snow and the danger of hypothermia if stranded. I share your views and always charge to 90%, and I think about the Lucid with 521 miles of range compared to my Tesla (Musk says more range is a waste). Then I could keep the heater going for many hours if I get stuck or buried in snow.
Not everyone is in snow country, and even for most areas that see snow, they don't see it every day of the year. For most people charging that high is only unnecessarily putting extra wear on their battery.
 
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Your nearest evacuation zone is 200+ miles away? I think that was the point. Very rarely do people need to flee 200 miles, it's simply not a reasonable margin to leave for most people (keep in mind OP only travels 25 miles per week and also in California).

Not everyone is in snow country, and even for most areas that see snow, they don't see it every day of the year. For most people charging that high is only unnecessarily putting extra wear on their battery.
The key point is not the range remaining in the battery, but having a reliable estimate of the remaining range, which is only possible in an LFP battery that is regularly charged to 100% to allow the BMS to accurately estimate SOC. However, if keeping the battery at a high SOC doesn't harm it, then why not do it. Events that present a threat to life and limb tend to be rare, but those events are when you're most likely to need your vehicle and when the charging infrastructure might not be available:


There's no evidence, based upon multiple user reports, that charging a M3 LFP battery to a daily or weekly 100% SOC, causes increased 'wear and tear' on the battery. Degradation seems to correlate to battery age and miles driven.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
13,565
10,166
The key point is not the range remaining in the battery, but having a reliable estimate of the remaining range, which is only possible in an LFP battery that is regularly charged to 100% to allow the BMS to accurately estimate SOC.
This was addressed in another post, but the inaccuracy is at the bottom 10%. Just add that to whatever margin you have set. There is no need to charge to 100%. It's not like without charging to 100%, it will suddenly drop to zero while you are at 50%. Just assume the bottom 10% is unreliable (or as others mentioned can raise to 20%).
However, if keeping the battery at a high SOC doesn't harm it, then why not do it. Events that present a threat to life and limb tend to be rare, but those events are when you're most likely to need your vehicle and when the charging infrastructure might not be available:


There's no evidence, based upon multiple user reports, that charging a M3 LFP battery to a daily or weekly 100% SOC, causes increased 'wear and tear' on the battery. Degradation seems to correlate to battery age and miles driven.
There is not enough data either way for M3 LFP batteries specifically given how young they are (it's only been about a year since they shipped to the US), but it's been linked up thread LFP batteries in general still have worse degradation at higher SOCs (as others pointed out even in reports done on the same CATL LFP cells). They do better than NCA (and have better cycle life in general), but the impact is not zero.
 
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This was addressed in another post, but the inaccuracy is at the bottom 10%. Just add that to whatever margin you have set. There is no need to charge to 100%. It's not like without charging to 100%, it will suddenly drop to zero while you are at 50%. Just assume the bottom 10% is unreliable (or as others mentioned can raise to 20%).

There is not enough data either way for M3 LFP batteries specifically given how young they are (it's only been about a year since they shipped to the US), but it's been linked up thread LFP batteries in general still have worse degradation at higher SOCs (as others pointed out even in reports done on the same CATL LFP cells). They do better than NCA (and have better cycle life in general), but the impact is not zero.
There have been 100s of thousands of LFP M3s sold and there's just no owner data indicating that keeping the actual M3 battery at a high SOC increases degradation. If there was consistent data showing increased degradation due to keeping the car at a high SOC, we'd know about it by now.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
13,565
10,166
There have been 100s of thousands of LFP M3s sold and there's just no owner data indicating that keeping the actual M3 battery at a high SOC increases degradation. If there was consistent data showing increased degradation due to keeping the car at a high SOC, we'd know about it by now.
No you won't, because the calendar degradation doesn't show up yet. One year is not enough data to determine that. Cycle life also is not tested enough yet. Having 100s of thousands of samples is irrelevant if few of them have lots of miles on it or have the calendar wear on it yet.
 

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