99% calibrating LFP taking well over 10 minutes

[jsugarsd]

Hello,

So, my 21 M3 SR+ NCA battery failed at ~24K. I only drove it about 9K miles myself as I got it earlier this year with only 15K. Anyhow, I was lucky to be near a Tesla service center when this happened a couple of weeks ago. I signed the waiver and have the newer LFP battery with new suspension to compensate for the increase in weight. I have had my car back for about a week now and a couple of days ago I was supercharging and at 99% it says "calibrating" for over 10 minutes but I had to leave by that point and I am wondering how much longer I would have had to wait there if I just let it run? Also, what are the repercussions if any? I'm guessing that the BMS will not be as accurate in calculating potential range but besides that if I am correct on that, what else may there be to worry about here? I am guessing some of you have already dealt with this and this may be helpful to others who may be starting to go through this and would like to share what you think best practice(s) are or may be with this. In advance I thank you for your help on this and I'm new here with this being my first post. Please coach me if I am doing anything out of the standard etiquette expected here.

Thank you,

Justin

 

[jsugarsd]

 

[FatFalcon]

Nothing to worry about. It's probably just balancing the pack, which for a brand new pack probably needs it since it's never been cycled.


Also I'm sure you know this, but supercharging to 100% is super slow and a waste of time. I know the LFP battery says to charge to 100% once a week, but that's just for range calculation accuracy, it will not hurt the battery at all to just charge to a normal level (like 80%).

 

[jsugarsd]

Nothing to worry about. It's probably just balancing the pack, which for a brand new pack probably needs it since it's never been cycled.


Also I'm sure you know this, but supercharging to 100% is super slow and a waste of time. I know the LFP battery says to charge to 100% once a week, but that's just for range calculation accuracy, it will not hurt the battery at all to just charge to a normal level (like 80%).

I appreciate that. I am thinking maybe I should go 95 max and slow charge elsewhere to 100% on a level 2 after supercharging but I want to make sure that's ok. I don't think it will "hurt" much but better to ask and be sure and have others share their thoughts so others may benefit. Thanks!

 

[hgmichna]

Yes, you can do that. It will work just as well.

Since the battery is new, I would do it to get the full capacity.

 

[gsmith123]

Regarding time to top balance, it can be extremely slow. My car has taken over two hours to charge from 98% indicates to actually done charging.

As others have pointed out there’s no reason you need to worry about doing this, but it is interesting.

 

[jsugarsd]

Regarding time to top balance, it can be extremely slow. My car has taken over two hours to charge from 98% indicates to actually done charging.

As others have pointed out there’s no reason you need to worry about doing this, but it is interesting.

Wow, 2+ hours? That's ridiculous. I appreciate you sharing that and it will probably help others figure to just move on as well. Thank you!

 

[hgmichna]

If it really needs 2 hours to balance, then you should let it do that on occasion. Could also be a software bug though. Mine has never taken longer than 15 min.

 

[gsmith123]

Err I think I might have misremembered the time (sorry), but here are the Tessie logs showing it takes over an hour at least for 98% to done. Less than two hours though.

Regardless, top balancing is slooow

 

[Max Spaghetti]

Regardless, top balancing is slooow

Yes, and I read somewhere that it’s only a passive balancing implementation, which means the only way it balances is by bleeding the highest charged cell bricks at a slow rate. It doesn’t take that energy and feed it into the lower charged bricks which is what an “active balancer” would do.

Edit: my only comparison is my DIY camper LFP battery which is 7.8 kWh at 26V. It is 8S1P with an active balancer that operates at 2A via a super-capacitor. Translating that into Tesla battery capacity, my 300Ah prismatic cells are similar to the bricks in an LFP Tesla. The Tesla just has more in series, so 2A active balancing would work similarly, but just a lot more wires to individual cell bricks.