Charge at 100% once per week? [LFP RWD model 3]

[zumoney515]

The message very confused me as "We recommend keeping your charge limit at 100% and charging fully once per week".

From my understanding "We recommend keeping your charge limit at 100%" meaning the every charge should at 100%.
But why they added "and charging fully once per week". Now it meaning that only charge to 100% once per week.

So which would be better for the battery. I normally charge 3 times per week. First, charge at 90% 2 times per week and at 100% 1 time per week. Or Second, charge at 100% 3 times per week.

Thank you,

so it's been 2 years and what have you been doing w your charging habit and how's the battery life since? Thank you

 

[PianoAl]

The message very confused me as "We recommend keeping your charge limit at 100% and charging fully once per week".

From my understanding "We recommend keeping your charge limit at 100%" meaning the every charge should at 100%.
But why they added "and charging fully once per week". Now it meaning that only charge to 100% once per week.

So which would be better for the battery. I normally charge 3 times per week. First, charge at 90% 2 times per week and at 100% 1 time per week. Or Second, charge at 100% 3 times per week.

Thank you,

Funny, I just complained about this poor wording in another thread. I said:

This wording has always bothered me:

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 says: Charge to 100% every day and also once per week. Logically, that doesn't make sense.

I think they mean:

If your vehicle is equipped with an LFP Battery, Tesla recommends that you keep your charge limit set to 100%, even for daily use, BUT IF YOU DON'T DO THAT, THEN YOU SHOULD fully charge to 100% at least once per week.

 

[BlouieM3]

If you have the car parked and stored with the new LFP battery. Is it best to keep it at 100% plugged in at all the time? It’s current raining like crazy so my parents new 2023 is plugged in and scheduled to top off to 100% off peak hours (12am to 6am) in the garage. Any thoughts? Thanks in advance!

 

[STS-134]

If you have the car parked and stored with the new LFP battery. Is it best to keep it at 100% plugged in at all the time?

If you want to accelerate the calendar degradation of your battery, sure.

 

[BlouieM3]

If you want to accelerate the calendar degradation of your battery, sure.

I’m sure others have questions in this too since Tesla recommends that you keep the car plugged in when it’s not in use. The the new LFP battery I’m most going to have my parents set the charge to like 90% and top off maybe once a week.

 

[STS-134]

I’m sure others have questions in this too since Tesla recommends that you keep the car plugged in when it’s not in use. The the new LFP battery I’m most going to have my parents set the charge to like 90% and top off maybe once a week.View attachment 892796

Hadn't seen that screenshot before but charging to 100% has absolutely nothing to do with maintaining battery health. It's all about maintaining accuracy of the BMS. LFP batteries have a very small voltage difference at SoC levels in the mid range and therefore the BMS estimates can drift if you don't let the BMS see the top end. However, unless you're planning on running the battery down below 20%, there's no need to know what the SoC is with that level of accuracy. You definitely want to charge to 100% just before doing a long drive on which you might want to use most of the battery's capacity though. Tesla understandably wants to avoid a situation where the BMS drifts and a customer goes on a drive and at some point, it is reading 15% and suddenly realizes that it's actually at 0%, which would be a PR nightmare. But in practice, you're probably fine setting the limit at 50% and driving it down to 35% for daily use and this habit would cause much less calendar degradation. Just be aware that the BMS can drift and the charge level might not be reliable if you haven't charged to 100% in a while.

 

[AAKEE]

A measure of charging rate is C, which is the rate divided by battery size. Not sure of your battery size, but let’s assume it is 65 kWh. Charging at 17a is 17/65 = .26 while 32/65 =.49

Generally speaking, anything below C=1 has zero impact on the battery. Note that charging at 48a is just .74

Also, the higher the charge rate the more efficient, so slower is also a bit more expensive.

This calculation is very wrong.
Old post but wrong and I did’nt find any correction.

Amps divided by kWh is not correct.

1C will make a charging session from 0 to 100% take one hour. The Model 3 LFP batteries is 55 or 60 kWh.

Per definition 1C is the same current as the capacity.

1 Amphere on a 1 Amphere hour battery is 1C.

I dont know the exact spec on the batteries, but a 55/60kWh Model 3 LFP has 106 cells in series. Each ”cell” of these 106 in series is actually several cells in parallel. The nominal Voltage is 3.2V so of 60kWh we get
60.000/(106x3.2) = about 177 Ampere hours.

If we would like to use Amps like in the post I answer to, we need to relate it to the Amphere hour from the calculation above.

As the Wall charger sends one Voltage but this is converted in the on board charger we can not use the “17 Amps” to direct calculate the C-rate.

If it is single phase 110V it is 17x 110 = 1.9kW. That is about 0.03C.
Whe need to know the Voltage and the number of phases to use the Amps for this.
The car reports the charging power in kW so it is easier to calculate via charging power / capacity.

Also, 1C is not the limit for ”safe” charging that do not cause increased degradation.

Most lithium batteries have a standard charge of 0.2 to 0.5C. Without have checked the specification on a battery we can be sure that 0.25C is a slow charging where a further reduction of the charging lower do not reduce the wear.

0.25C —> 0.25 x 55 to 60 kWh is 13.75 to 15kW charging power.

Maximum AC charge for a model 3 (at least non LFPs) is 11 kW.
This means any AC charging is “safe” for degradation from the charging power.
No need to reduce the Amps for that reason.

 

[ATPMSD]

@AAKEE

Yeah, brain was not fully engaged! Thanks.

 

[AAKEE]

@AAKEE

Yeah, brain was not fully engaged! Thanks.

Yes, I guessed it was more like a typo.