LFP to 100% Each Week—Assumptions?

[DuncanM]

As for me keeping a high SOC for emergency situations, it's an probability thing. The chances that I'll unexpectedly need a lot of range are very low. The benefit of a lower SOC is higher.

We just drove my 2022 TM3 RWD, 2032 miles and just arrived at our SE Arizona home. We've been here for 4 hours and the grid power to the whole valley just failed. $h*T happens. Luckily we have about a 50% SOC, but our car may be our refuge depending on how long this lasts.

We're in Portal AZ (Cochise County) Here's the outage map:

Map Viewer

ebill.col-coop.com

 

[DuncanM]

We just drove my 2022 TM3 RWD, 2032 miles and just arrived at our SE Arizona home. We've been here for 4 hours and the grid power to the whole valley just failed. $h*T happens. Luckily we have about a 50% SOC, but our car may be our refuge depending on how long this lasts.

We're in Portal AZ (Cochise County) Here's the outage map:

Map Viewer

ebill.col-coop.com

The power came back on after about 4 hours. I neglected to mention, in my quoted post, that an apparent lightning strike over the summer, when we were gone, fried all the GFI plugs in the garage and the garage door opener. Fortunately, the exterior GFI plug by the garage survived and I was able to get charging going through that. We also lost all the electronics in our family room/theatre room, despite them being unplugged.

 

[PianoAl]

Here's a cautionary tale: I have a Macbook that I rarely use. Thinking to keep the batter healthy, I got it to around 50% SOC, and set up a timer to charge it one minute per week (determined empirically). That kept it close to 50%, and it's been like that for maybe a year.

Today I needed the laptop, and started using it. After 15 minutes, BAM, it crashed. For a while I thought it was bricked. I plugged it in and saw that the SOC was 1%.

I'm guessing the Macbook's BMS was misestimating.

 

[stopcrazypp]

Here's a cautionary tale: I have a Macbook that I rarely use. Thinking to keep the batter healthy, I got it to around 50% SOC, and set up a timer to charge it one minute per week (determined empirically). That kept it close to 50%, and it's been like that for maybe a year.

Today I needed the laptop, and started using it. After 15 minutes, BAM, it crashed. For a while I thought it was bricked. I plugged it in and saw that the SOC was 1%.

I'm guessing the Macbook's BMS was misestimating.

I think it is because you used a manual method of maintaining the charge and if power consumption varied, your method can accumulate errors. My Lenovo Thinkpad instead has a way to set a upper and lower limit and keep it between that. I wish more devices allowed that (including Android; it's possible with rooting, but not on stock).

 

[PianoAl]

Well if you are using 190kWh you are driving a fair bit going by what I'm showing for my car.

That was mostly from driving the car home when we purchased it (from five hours away).

 

[PianoAl]

Here's a hypothetical to help me make decisions:

Let's say I charge to 100%, then drive until it's 70% and leave the car for two weeks (no sentry mode).

Will the BMS be as accurate at the end of those two weeks as it was right after the drive? IOW, does accuracy change over time if the car isn't driven?

 

[lowercase]

Don't even bother. I keep mine at 60% and charge to 100% just every few weeks.

 

[Whoze]

I saw the old 2013 thread, but am looking for an updated consensus on a 2023 SR.
Tesla manual says to charge it to 100% at least once a month, and when I set it to 80-90% bc I heard Musk say so the app warns me to charge it to 100% for battery longevity.

 

[DrChaos]

I saw the old 2013 thread, but am looking for an updated consensus on a 2023 SR.
Tesla manual says to charge it to 100% at least once a month, and when I set it to 80-90% bc I heard Musk say so the app warns me to charge it to 100% for battery longevity.

For battery longevity keep max at 65% or less most days. For BMS calibration, charge up to 100% at least once a month.

Pay attention to research literature, not a tweet.

 

[EfficientWatts]

This thread feels like an exercise in futility. Feels stressful to worry about what % to exactly charge it at, trying all these charging patterns, etc. I understand its one thing to try to understand the intricacies of battery life and to maximize stuff as if you're eco driving, but if this is just going to end up worry people and making them worry that their battery pack is suddenly going to die if they don't follow this exact routine, all you're doing is introducing more stress into your life, potentially costing you more in time and worry than anything you would potentially save by babying the battery pack.

Take reasonable steps (more so for non-LFP cars). But life is too short. Plug in, charge to a reasonable number for your battery pack type, and drive your car. There are bigger things to worry about in life.

 

[PianoAl]

This thread feels like an exercise in futility. Feels stressful to worry about what % to exactly charge it at, trying all these charging patterns, etc. I understand its one thing to try to understand the intricacies of battery life and to maximize stuff as if you're eco driving, but if this is just going to end up worry people and making them worry that their battery pack is suddenly going to die if they don't follow this exact routine, all you're doing is introducing more stress into your life, potentially costing you more in time and worry than anything you would potentially save by babying the battery pack.

Take reasonable steps (more so for non-LFP cars). But life is too short. Plug in, charge to a reasonable number for your battery pack type, and drive your car. There are bigger things to worry about in life.

It's funny that when I heard that I'd be getting an LFP car, I was, "Great, now I'll just charge to 100% all the time and not think about it." Ignorance is bliss.

I may take your advice, but it's hard to charge it to 100% and leave it.

 

[DuncanM]

I saw the old 2013 thread, but am looking for an updated consensus on a 2023 SR.
Tesla manual says to charge it to 100% at least once a month, and when I set it to 80-90% bc I heard Musk say so the app warns me to charge it to 100% for battery longevity.

This is quoted from the latest version of the M3 manual (my emphasis):

Note
For vehicles with Lithium Iron Phosphate (LFP) high voltage Batteries, Tesla recommends you keep your charge limit to 100%, even for daily use, and that you also fully charge your vehicle to 100% at least once per week. To determine if your vehicle is equipped with an LFP battery, navigate to Controls > Software > Additional Vehicle Information. If your vehicle has an LFP Battery, "High Voltage Battery type: Lithium Iron Phosphate" is listed. If your vehicle does not have an LFP Battery, the high voltage Battery type is not specified. See Lithium Iron Phosphate Batteries for more information.

 

[Whoze]

This is quoted from the latest version of the M3 manual (my emphasis):

I read that too. Thanks

 

[PianoAl]

What they forgot to include in the manual:

We recommend this even though it will cause your battery to degrade faster because we need to keep the BMS well calibrated. Otherwise people might be stranded, resulting in a front page story about how Teslas run out of charge unexpectedly.

 

[DuncanM]

What they forgot to include in the manual:

We recommend this even though it will cause your battery to degrade faster because we need to keep the BMS well calibrated. Otherwise people might be stranded, resulting in a front page story about how Teslas run out of charge unexpectedly.

I haven't seen any evidence that charging TM3 LFP batteries according to the recommendations causes the battery to degrade faster.

 

[PianoAl]

It depends on whether you trust this article and others like it.

The Puzzling Reason Why Tesla Misleadingly Recommends Charging the LFP Batteries to 100%

Tesla recommends owners of Model 3 cars with LFP batteries charge them regularly to 100%, but this is not the way to go if you want to extend the battery's life

www.autoevolution.com

I would really like to be convinced that I should leave our LFP car at or near 100% all the time. I am convinced that it will degrade faster, but perhaps not enough to make a difference.

 

[DuncanM]

It depends on whether you trust this article and others like it.

The Puzzling Reason Why Tesla Misleadingly Recommends Charging the LFP Batteries to 100%

Tesla recommends owners of Model 3 cars with LFP batteries charge them regularly to 100%, but this is not the way to go if you want to extend the battery's life

www.autoevolution.com

I would really like to be convinced that I should leave our LFP car at or near 100% all the time. I am convinced that it will degrade faster, but perhaps not enough to make a difference.

I do not trust that article because it's just speculation and presents no data to back up it's claims.

Evidence would be LFP M3s showing less range loss using a specific charging strategy. No one has presented evidence to that effect. The collected data from hundreds of LFP M3s seems to show that the only correlation for range loss is miles driven and calendar age.

If using a 50% charging limit, or some other strategy, made a difference we'd know about because it would readily apparent by now, given the fact that hundreds of thousands of these vehicles are being driven daily and have accumulated 10s of millions of miles driven.

 

[stopcrazypp]

I do not trust that article because it's just speculation and presents no data to back up it's claims.

Evidence would be LFP M3s showing less range loss using a specific charging strategy. No one has presented evidence to that effect. The collected data from hundreds of LFP M3s seems to show that the only correlation for range loss is miles driven and calendar age.

If using a 50% charging limit, or some other strategy, made a difference we'd know about because it would readily apparent by now, given the fact that hundreds of thousands of these vehicles are being driven daily and have accumulated 10s of millions of miles driven.

Same comment made a few months ago, but hundreds of thousands of vehicles and millions of miles is quite irrelevant if each individual pack have not accumulated enough cycles and calendar wear. To put it more clearly, here's two scenarios, say you have 100 million miles of data:
1) 1000 cars traveling 100k miles
2) 100k cars traveling 1000 miles

#1 will tell you a lot about long term wear. #2 will tell you almost nothing. Currently the LFP fleet is a lot closer to #2 than #1. There's probably a while before there are many 100k mile LFPs on the road.

@AAKEE already posted the data on the basic chemistry of LFP that shows 50% will do better than 100% for storage. Tesla's statements don't contradict that and the only reasoning that Tesla have presented to recommend the 100% is because the LFP BMS has inaccurate capacity estimates at low SOCs below ~10% (increasing the risk of stranding). Besides from that article, I previously linked a tweet thread by Elon that makes it much more clear:

https://twitter.com/x/status/1498859400525750272

I Picked up my Model 3 today. How can I tell if has LFP battery pack?

Basically it's a double whammy. The LFP packs + the 16V lithium LV battery means that if the HV shuts off unexpectedly (instead of a gradual shutoff), the LV battery can die very quickly (given it has much lower capacity of 6.9 Ah vs 45 Ah for the lead acids). This is one reason why I actually may prefer the lead acid (other than also easier to find a generic replacement if it dies).

 

[DuncanM]

Same comment made a few months ago, but hundreds of thousands of vehicles and millions of miles is quite irrelevant if each individual pack have not accumulated enough cycles and calendar wear. To put it more clearly, here's two scenarios, say you have 100 million miles of data:
1) 1000 cars traveling 100k miles
2) 100k cars traveling 1000 miles

#1 will tell you a lot about long term wear. #2 will tell you almost nothing. Currently the LFP fleet is a lot closer to #2 than #1. There's probably a while before there are many 100k mile LFPs on the road.

@AAKEE already posted the data on the basic chemistry of LFP that shows 50% will do better than 100% for storage. Tesla's statements don't contradict that and the only reasoning that Tesla have presented to recommend the 100% is because the LFP BMS has inaccurate capacity estimates at low SOCs below ~10% (increasing the risk of stranding). Besides from that article, I previously linked a tweet thread by Elon that makes it much more clear:

https://twitter.com/x/status/1498859400525750272

I Picked up my Model 3 today. How can I tell if has LFP battery pack?

Basically it's a double whammy. The LFP packs + the 16V lithium LV battery means that if the HV shuts off unexpectedly (instead of a gradual shutoff), the LV battery can die very quickly (given it has much lower capacity of 6.9 Ah vs 45 Ah for the lead acids). This is one reason why I actually may prefer the lead acid (other than also easier to find a generic replacement if it dies).

Again, just speculation. LFP RWDs have been on sale and in production for ~ 2 years now. Where's the data showing less range loss due to a specific charging strategy?

 

[Niroc]

Same comment made a few months ago, but hundreds of thousands of vehicles and millions of miles is quite irrelevant if each individual pack have not accumulated enough cycles and calendar wear. To put it more clearly, here's two scenarios, say you have 100 million miles of data:
1) 1000 cars traveling 100k miles
2) 100k cars traveling 1000 miles

#1 will tell you a lot about long term wear. #2 will tell you almost nothing. Currently the LFP fleet is a lot closer to #2 than #1. There's probably a while before there are many 100k mile LFPs on the road.

@AAKEE already posted the data on the basic chemistry of LFP that shows 50% will do better than 100% for storage. Tesla's statements don't contradict that and the only reasoning that Tesla have presented to recommend the 100% is because the LFP BMS has inaccurate capacity estimates at low SOCs below ~10% (increasing the risk of stranding). Besides from that article, I previously linked a tweet thread by Elon that makes it much more clear:

https://twitter.com/x/status/1498859400525750272

I Picked up my Model 3 today. How can I tell if has LFP battery pack?

Basically it's a double whammy. The LFP packs + the 16V lithium LV battery means that if the HV shuts off unexpectedly (instead of a gradual shutoff), the LV battery can die very quickly (given it has much lower capacity of 6.9 Ah vs 45 Ah for the lead acids). This is one reason why I actually may prefer the lead acid (other than also easier to find a generic replacement if it dies).

China have been using the LFP battery pack for awhile. The data so far, does suggest the LFP degrades slower than the NCA.

I had a 2019 M3 and I babied that battery. My SOC went from 240 to 218 after just 20,000 miles. Not good. I am expecting my new M3 LFP to have much less degradation.