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Keeping an Infrequently Driven LFP Happy

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I'm an LFP virgin, and our second Tesla will have an LFP battery. My wife and I are retired, and this car will only be used on the rare times that we both need a car. The two cars will share one charger.

I've read:

If your vehicle is equipped with an LFP Battery, Tesla recommends that you keep your charge limit set to 100%, even for daily use, and that you also fully charge to 100% at least once per week.

That suggests to me that it's best to keep the SOC around 100% (?) So, let's say this LFP car is driven on average thirty miles per week. What would you recommend for a charging protocol?

Thanks!
 
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I think the BMS needs to see 100% regularly, but the battery doesn’t need to stay at 100%.
OK, good. Perhaps I'll charge it to 100% and let it drop down as it's used, charging it back up after it's down to 40% or so. I don't care if the BMS occasionally gives wonky range estimates, since this car will rarely drive more than 50 miles in one go.

Anyone know how the BMS is affected if the car doesn't see 100% often? Overestimate range? Underestimate?
 
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Anyone know how the BMS is affected if the car doesn't see 100% often? Overestimate range? Underestimate?
Here is an example LFP voltage / SoC graph for a 12V battery:
12V-graph-2-1024x669.jpg

Note the flatness in the middle part of the curve. If the BMS does not see 100% (or very low) SoC for a while, it would lose track of the actual SoC. If it overestimates, it may result in the driver seeing 20% and then a sudden drop to 10% or so when the SoC finally enters a range with a significant voltage drop.

It is probably better to park the car mostly at 70% or lower, although LFP batteries tend to degrade less and slower than NCA batteries, so charging habits may make much less difference with LFP batteries than NCA batteries.
 
I'm an LFP virgin, and our second Tesla will have an LFP battery. My wife and I are retired, and this car will only be used on the rare times that we both need a car. The two cars will share one charger.

I've read:



That suggests to me that it's best to keep the SOC around 100% (?) So, let's say this LFP car is driven on average thirty miles per week. What would you recommend for a charging protocol?

Thanks!
very curious to hear if the lfp chemistry has the same very aggressive taper at the top of the battery charge state that the nickel Cobalt lithium ion shows?
 
Hi, I am in a similar position. Due to collect my M3 RWD in December. We use the car mainly twice per week to and from work (40mi per day). We will have a home charger and there is charging at work. Should we always look to charge to 100%?
 
Hi, I am in a similar position. Due to collect my M3 RWD in December. We use the car mainly twice per week to and from work (40mi per day). We will have a home charger and there is charging at work. Should we always look to charge to 100%?
Either set charge level at 50% plugged in, or charge up to 100% and run it down as low as you're comfortable with before charging to 100% again (like a gas car).

Lots of people on here will say: "just charge to 100% everyday - who cares if there's 5% extra battery degradation after 5 years because it's gonna be the next owner's problem." Even if you don't plan on keeping the car long term, I think it's environmentally wasteful to degrade the useful life of a car/battery if you don't need the 100% range on a daily basis.
 
The problem happens, as 3sr explained, when you go a long time without charging to 100%, resulting in an SOC estimate that's way off. Tesla says to not go longer than a week ...
From other threads and looking at various research it seems best thing to do for low usage is to sit at ~50% and then once a week top up to 100% to ensure the BMS allows for accurate est range.

There is conflicting opinions wherever you go. some say charge to 100% all the time and not to worry, others say keep it at 50%.. I am probbaly going to hit somewhere in the middle. I think I'll set mine to ~70% and then do a 100% once a week ahead of the weekend (unless I have any particularly long journeys coming up mid week).

I plan on keeping the car a long time so want to protect the battery as much as possible but realistically would like a bit of extra range in case something pops up and it's required.
 
I was looking forward to 100% all the time, but I'm also overprotective. Have to think about it some more.

BTW, driving the 5.5 hours home from picking up Tessie (see sig), we charged her to 100% and Nick to 90% at a hotel, and she had a higher listed range (273 miles). I'm hoping some of Nick's range loss is due to BMS calibration, but in any case, it demonstrates the advantage of LFP batteries.
 
Picked up my new model 3 RWD with LFP about 7 weeks ago. When new, it showed 272 miles of range on the car’s display.

My charging practice was to charge to 70-80% daily using only 5-10 amps of draw on my home wall charger. I’d also charge the car to 100% at least once per week per Tesla’s recommendation.

After 4 weeks and 2,200 miles of driving, the displayed full range after charge had dropped to 266 miles. I was concerned about so much range loss (2.2%) over only a month’s time, so I started watching the max range more closely (switched the display to miles instead of %). It remained at 266 each after charging each day.

Concerned, I decided to change my charging practice and keep the charge limit to 100% and plug in almost every day as Tesla recommends. I also increased my wall charger charging current back to max. At first nothing changed, the car’s computer continued to show 266 miles of range immediately after my daily charge. After a few days of charging this way, the full range went back up to 267. Then a couple days later it went to 268…then 269. Today, after 7 total weeks of ownership and 3,200 miles on the odometer, the displayed max range went back up to 270 of the original 272.

This is not conclusive data by any means, and may just be BMS noise, but it was enough to convince me to just follow Tesla’s recommendation on my vehicle. I’m going to keep the charge limit at 100% and plug in almost every night.

One thing to consider is that charging to 100% may not just be to help the BMS calibration. It may also help keep the cell voltages balanced, which could help prevent degradation over time.
 
I have an LFP home battery and they're set up to charge all the way to 100% as often as my solar panels can do it (basically every day unless it's cloudy all day). Even once they hit 100% SoC, they draw 100w, so my battery manufacturer is definitely not worried about overcharging them. The battery is warrantied for 80% capacity after 7 years and 70% capacity after 10 years, so it seems that LFP batteries will be happy getting charged to 100% all the time.
 
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Research shows that LFP has the highest calendar aging around 80-90% and that is is less at 100%.
It is also lower at or below 70%.
EFFBAF92-C4CC-4C3E-BCA5-B11E4365FB6B.jpeg


100% is not that bad unless its very hot.

Its not worth to aim for 80-90% if you try to minimize the degradation.
 
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Here's where we stand now. We've had the car for two weeks. We charged it on the way home from buying it (5.5 hour drive. Supecharger and hotel charger) and charged it to 100%. A few minutes of charging on Oct 30 and none since. It's been on a few 30-60-mile drives, and it's currently at 42% SOC.

Just to get a better understanding, here's a question: At this point, is the BMS likely to have a bad estimate of the remaining range?

(In this graph, the "Other" charging on Oct 29 was at home. The car didn't yet know where home was.)

Screenshot_20221109-085916_Tesla.jpg
 
I am also an infrequent driver with a LFP M3.

I drive around 100-150 miles a week. I charge to 100% once a week and 70% the rest of the days.

Some days I come back home with 55-65% battery and I'm set to charge it to 70% that day. Should I not charge and wait until I run it down to 30-40%, or just charge from 55-65% to 70%? What's the best practice in this case? Is there any benefit to running it down, then charging. Or should I just always be charging, even if I just need to go from 60%-70%?
 
It's been driven very infrequently recently, and I can report that despite the knowledge that LFP batteries will last a long time, it's no fun to charge to 100% and then watch it go down by only a percent or so per day.

A new development is that I've discovered that Tessie is more efficient than Nick. Part of that is due to Nick's roof rack and part due to many trips with a surfboard on there. I'm going to do some experiments and calculations to see if we should drive Tessie more.

Screenshot_20221223-143401_Tesla.jpg
 
I just bought a ‘23 RWD and work from home, so will probably drive it only 50-100 miles per week. My plan is to charge to 100% only once A) charge has dropped below 40% and B) it’s the night before I plan to go somewhere the next day (I always go somewhere on Sundays, for example). At other times, I will probably keep it plugged in, but not charging. This will mean a variable SOC and probably only charging to 100% once or twice a month.