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Charge at 100% once per week? [LFP RWD model 3]
- Thread starter TonyUsa
- Start date
Yeah, and these EV batteries are so big, that any AC charging is "slow". There's basically no impact on battery life no matter whether you charge at 16A, 32A, or 48A (for the long range/performance models). But there IS an impact on efficiency, because the computers run and consume a constant amount of power (in the hundreds of watts) whenever the car is charging, so it's better to AC charge as quickly as possible.
As for charging to 100%, it's actually better for the battery to not do it all the time, but the BMS needs to see 100% frequently because there's not too much of a voltage difference across SoC levels. As long as you charge it to 100% every 1-3 weeks it's probably fine. You just don't want the thing to get way off target.
LBM4
Tesla Fealty
You CAN charge to 100% every time, but it isn't recommended by Tesla, UNLESS you have an LFP battery, which you do not.
I tend to follow those that have had their Model 3 for years and only show minor degradation of their battery. They are doing something right, so I follow what they are doing.
ATPMSD
Active Member
With the LFP battery there is no harm in charging to 100% everyday. The Tesla recommendation is to charge to 100% at least once a week.
Charging a LFP battery to 100% all the time still increases degradation although not as much as it does on a NCA battery. But not charging to 100% regularly can cause the BMS to lose track of where the top and bottom are because of the very narrow voltage vs SoC curve in the center. If I had a LFP battery though, I still wouldn't really worry unless I planned to go below 20-30%, in which case I'd charge to 100% immediately before doing that. I'd probably also charge to 100% every 2-4 weeks instead of every 3-4 months.
ATPMSD
Active Member
While this is true you really do not see any significance degradation for many, many years. My advice is if you plan to replace the car within say 5-years to not worry about this. Charge the car when it is convenient, or all the time, and enjoy the car.
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Charging to 100% all the time versus charging to 70% most of the time and 100% approximately once per week probably does make a small difference in degradation of LFP batteries, but many drivers may not consider the difference to be worth the bother, since LFP batteries appear to degrade to a much lesser extent than NCA batteries.
For any type of battery, setting home charging to finish shortly before you leave may be a no-effort way to limit degradation by minimizing the amount of time parked at high states of charge.
To clarify: Earlier single motor (RWD) cars, such as mine, have NCA battery chemistry. No matter if they are LR, MR, or SR. In the last year or so Tesla switched the single motor cars, which are now all SR cars, to LFP chemistry. It is these latter SR cars that Tesla recommends regular 100% charging.
jackmott
Member
The same amount of "harm" is done to an LFP pack charged to 100% as any other pack. It just has to be done or the computer can't know how much range you have left. I repeat there only reason Tesla wants you to charge to 100% weekly is so that battery capacity estimation is accurate. It isn't good for the cells, its just "ok".
But there is nothing magic about 100%, the rate of age based degradation just steadily goes up as state of charge goes up. The good news is that *overall* degradation is not so bad on LFP, so accepting the harm of once a week 100% charges is fine.
ATPMSD
Active Member
Source? This seems to contradict your statement:
“Battery Charging Behavior: Tesla Recommends Charging LFP Models To 100%; The Key Is Voltage. Thanks to the low voltage at which they work as compared to other ternary chemistries, LFP batteries offer better behavior during recharging, significantly increasing the life cycle.”
Unfortunately, there is likely no authoritative source.
jackmott
Member
Yeah, part of what I said was overall degradation of LFP is not as bad. Batteries degrade from using them, and from just time. State of charge has about the same impact on LFP age based degradation as NCA, but since *overall* the LFP holds up better, you get similar overall lifetime even if you charge to 100% regularly
source ( and there are many such studies, that all agree)
If you wanted to maximize your LFP pack life, you can still follow the 100% once a week advice, just try to schedule that charge such that you drive shortly after getting to 100%, and then let drop all week and don't charge it back up again beyond ~70% or whatever you need for your daily routine. LFP does really well once you are below 70%
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There’s no contradiction here. There’s two separate statements separated by a semicolon.
1. Tesla recommends charging LFP to 100% (to prevent BMS from SOC overestimation).
2. LFP has lower degradation than ternary chemistry in part due to lower voltage.
Note carefully that Tesla does not say that charging to 100% increases lifespan or reduces degradation.
LFP batteries were put in US Model 3 for some late 2021 model year SR+ (most 2021 SR+ had NCA batteries) and all 2022 RWD.
