Clarification on battery "Imbalance" versus "Degradation"

[Allistah]

Hey all --

I've been learning quite a bit about degradation and imbalance in regard to our model 3 batteries. I wanted to open a discussion around the words so that we (I) would really know the difference because it wasn't very clear to me when I started looking for information.

BATTERY IMBALANCE
From what I understand, the banks of cells within the main battery pack can get into a state where there are various levels of charge. This (from what I understand) is what can lead to "range loss". It is also not to be confused with actual battery degradation which I'll attempt to describe below. With range loss, it's possible to recover that by exercising the battery in a fashon that allows the BMS (Battery Management System) to re-learn where the "top" and the "bottom" of the battery are so that it can report the range accurately. This is what I've learned about correcting this so far:

• It won't fix itself it one charge - appears to take a number of cycles to 100% and days of charging to 90% in between
• Not everyone is successful in getting it fixed, not sure why
• Unclear if slower charging helps the banks of batteries naturally balance
• I keep hearing about rebalancing happening from 93% SOC upward (I would think that charging to 95% a few days could help invoke this if its true, without going to 100%. Just an idea at this point, if the 93% thing is true.
• I'm not sure if when charging to 100% if that should be at a SuperCharger or at home - does it make any difference? I read that some people get to 100% and then the car reads "Calculating" for some time and people suspect this is when the rebalancing is happening. If that is true, can this happen at home as well or maybe this only happens at SuperChargers (different code path maybe?)

BATTERY DEGRADATION
I am completely uneducated around this or now to tell if you actually have this. From the little information that I've read, I think this can be shown when you charge to 100% and your car stops at 97%, always and is impossible to actually get to 100%. Is that true? Is that what true degradation looks like? It would be good to understand this so that people would understand what they're seeing.

I'm doing some experimentation with our car to see if I can fix our range loss now. Will report my findings when I get something to report - it takes a week or so to get any data - if I make any progress at all that is.

Thanks for contributing to this discussion, not looking for more "Just drive it" or saying this or that is bad, I've seen it all. I'd like this to be just an open discussion around the two terms above, how we can tell the difference, and what we can or cannot do about them once accurately identified. Right now I think our car is in the rebalancing arena. We have a LR AWD. I charged it to 100% using 5A and when it reached "Complete" that was about an hour and a half after reaching the 100% mark. It sat there forever taking in 5A but not giving any additional range. I could only think this is where the rebalancing was happening but I'm not sure. I'm not sure if this rebalancing only happens at SuperChargers or if we can do it with the Tesla Wall Connectors just the same. Maybe going through the internal inverters power and code path don't allow for rebalancing - who knows? Man, I'd love to sit with someone that knows the internals very well to get definite answers to some of these questions. Thanks for listening and contributing to the discussion if you decide to reply.

 

[toolman335]

You did an excellent job recapping what everyone has reported.
You asked questions appropriately. You were so nice about it that the trolls who will tell you this is all covered in a 500 page/10,000 post Master Thread might play ball with you too

 

[Allistah]

You did an excellent job recapping what everyone has reported.
You asked questions appropriately. You were so nice about it that the trolls who will tell you this is all covered in a 500 page/10,000 post Master Thread might play ball with you too

Hah, thanks. Hence the boiling down of the 500 page/10k posts begins. Would be cool to boil all that information down into a top/sticky post with our discovered facts in it that people could go directly to and read without having to sift through all that text and conversation in order to get the info. I've seen some people that take the stance where if you weren't willing to run the marathon of reading the 10k posts, you weren't worthy of having the info. I feel like we could all gain from boiling down the information so that we could continue to build on it with our learning and actually figure this stuff out. I'll admit, it's a lot of info and I feel like boiling it down could further help support our cars in the community. I'll also admit, I'm being selfish in that I actually want the information myself and want to answer some of those questions but that has been a tough gig, the opinions of people are so distributed that it could be a bit tough to come to any one set of conclusions from all of the information in all these threads. Figured I'd start off with some basic definitions and go from there.

 

[dave4444]

Good questions, but unfornantely no answers yet. I saw something similar on my S last week for the first time. Was going on a long trip so wanted to start out at a full 100% (instead of normal daily 80%), set it to charge to 100% and it only reached 97% then "charging complete". Also over the next 8-12 hours before I started the trip it was burning through power just parked there like crazy, the HV was on constantly (high pitched hum) and burned off about 2-4% over a few hours.