Any definitive answer on charging to 100% or not?

[BigStu]

Picked up my Tesla Model 3 SR last week and before and after have been reading up on what you should charge you battery to and really cannot work out what it should be.

I even thought i read a tweet from Musk saying 100% is ok!

At the moment i have it set to max at 85% but does it matter if it is 100%? What is latest best info on 2021 Model 3?

 

[PC__LoadLetter]

When you look at the charging limit gauge on your MCU, does it have daily & trip at the top of the slider?

If so, limit it to where the line says daily, or something under that. It means you have conventional batteries, probably NCA batteries, and fully charging those is unwise, except for the first leg of a long trip.

If not, set it to 100%. It means you have the new LFP batteries - as in all the new Shanghai SR+ cars. LFP need to go to 100% at least once a week.

 

[BigStu]

When you look at the charging limit gauge on your MCU, does it have daily & trip at the top of the slider?

If so, limit it to where the line says daily, or something under that. It means you have conventional batteries, probably NCA batteries, and fully charging those is unwise, except for the first leg of a long trip.

If not, set it to 100%. It means you have the new LFP batteries - as in all the new Shanghai SR+ cars. LFP need to go to 100% at least once a week.

Oh right - sorry where is the 'charging limit gauge on the MCU'?

 

[BigStu]

Actually looking up the vin decoder the 7th letter of my VIN is F which means it is LFP which means charge to 100%.

 

[cafz]

Oh right - sorry where is the 'charging limit gauge on the MCU'?

It's on the Charging screen that opens up when you open the charge port. The bit where you set the % to charge to.

 

[moa999]

Any new SR+ since March 2021 has the LFP battery where it is recommended to charge to 100% on a regular basis.

Older SR+ and all LR/P have NCA/NCM batteries where an occasional charge to 100% is OK,
but they are best charged to a max of 80-90% on a regular basis.

 

[positiv]

Picked up my Tesla Model 3 SR last week and before and after have been reading up on what you should charge you battery to and really cannot work out what it should be.

I even thought i read a tweet from Musk saying 100% is ok!

At the moment i have it set to max at 85% but does it matter if it is 100%? What is latest best info on 2021 Model 3?

Depends on chemistry
LFP -> 100%
Nickel based (NCA, NMC) -> 80-90%

Your SR would be LFP.

 

[Leeroy]

What is the consensus with leaving an LFP at 100% charge? Meaning charge it fully today and leaving a high SOC until the next day? I'm off work at the minute so would like to 'fill er up' with the sunny days but only using the car locally and not every day.

 

[aegidius]

You can charge any battery to 100% but it will not regen for a little while. Keep it to 95% and you'll be fine. LFP batteries don't mind being in a high SOC more often (and being left in a high SOC) but I don't think there's anything to say they _need_ to be charged to 100% regularly.

 

[Squidward]

A slight OT--- are car batteries anything like phone batteries? Lithium ion chemistries vary in how they degrade.. the thing I notice that kills my phone battery is being overheated during charging situations. Such as getting charged in a backpack or docked in a full cradle.

Anyway this gets me thinking what temperature situations should we avoid or encourage in regard to charging our batteries?

 

[paulp]

A slight OT--- are car batteries anything like phone batteries? Lithium ion chemistries vary in how they degrade.. the thing I notice that kills my phone battery is being overheated during charging situations. Such as getting charged in a backpack or docked in a full cradle.

Anyway this gets me thinking what temperature situations should we avoid or encourage in regard to charging our batteries?

The car heats and cools the battery as required using the aircon. You’ll often hear it running whilst charging. The car charges faster and more efficiently at the optimal temperature as well.

 

[Leeroy]

You can charge any battery to 100% but it will not regen for a little while. Keep it to 95% and you'll be fine. LFP batteries don't mind being in a high SOC more often (and being left in a high SOC) but I don't think there's anything to say they _need_ to be charged to 100% regularly.

On the note of regen, this may or may not interest you.
100% charge and regen leaving my home. Whilst it does always give the regen braking, it doesn’t ALWAYS go back into battery.

 

[aegidius]

Whilst it does always give the regen braking, it doesn’t ALWAYS go back into battery.

The Model 3 may be different... my old S just rolls down the hill with no braking at all if I charge it to 100%, with a warning message on the dash display.
Consistency would certainly be desirable, but I don't know where it can dump 50kW or more of power if it can't go into the battery. Does the 3 have a huge resistor somewhere? Or maybe just apply the brakes instead? Curious..

 

[Leeroy]

Yes i agree, I don’t know where it’s going!! Waste heat? Can’t find the heat sink
I took some you tube videos for other people asking (different forum) and it definitely has a consistent braking feel. It also went from 99% back to 100% on one occasion also.

This is yet another occasion from 100% charge, same braking characteristics but nothing into the battery until 92%

 

[cafz]

The Model 3 may be different... my old S just rolls down the hill with no braking at all if I charge it to 100%, with a warning message on the dash display.
Consistency would certainly be desirable, but I don't know where it can dump 50kW or more of power if it can't go into the battery. Does the 3 have a huge resistor somewhere? Or maybe just apply the brakes instead? Curious..

It's only the 2021 SR+ (with the LFP battery chemistry) that has this regen-at-100%-indicated-SOC behaviour. The LR/P with nickel chemistry batteries warn about no regen.

As you point out, the energy has to go somewhere. Perhaps it's dumping waste heat into the motors somehow. It would be interesting to see what would happen if you started at Charlotte Pass with 100% and headed down hill - would it eventually give up and say you have no regen available?

 

[Hong Konger]

Hi all, based on what I understand from the above, my LR Model 3 should also be equiped with LFP battery? It’s a Made in China car and was delivered 6 weeks ago, also there are no day/trip words on the charging page.

If yes, I should ideally be charging the battery to 100% once a week? Thanks in advance for any contributions.

 

[cafz]

Hi all, based on what I understand from the above, my LR Model 3 should also be equiped with LFP battery? It’s a Made in China car and was delivered 6 weeks ago, also there are no day/trip words on the charging page.

No, the LR has a nickel chemistry battery. I have a recently delivered LR as well, the "Trip" and "Daily" indicators are there.

 

[Pobby]

there are no day/trip words on the charging page

I found that the day/trip words do not show initially until you adjust the limit on that page.

 

[PC__LoadLetter]

LFP batteries are heavy and bulky. They fit nicely in the SR+. They don’t fit in the LR or P - at all.

 

[ausevdriver]

Yes i agree, I don’t know where it’s going!! Waste heat? Can’t find the heat sink

Honestly, I'm only 3 weeks in, but it's really got me interested in getting scanmytesla / obd dongle to see what's actually happening in real time.

I have a fairly steep down hill, followed by a roundabout as I leave home. At 100% charge, it's very slightly less braking than when I'm at 70% or whatever.

I.e. at 70% SOC I can let off the accelerator when in view of the roundabout and stop in time, at 100%, I need to let off earlier, and even then still need to use the brake just a tiny bit occasionally.

No "low regen warning" like when it's cold though.

If I had to guess, the regen capacity would be about 80% of what I get at lower SOC/higher temperatures.