Battery degradation???

[tomas]

My wife's SR+ is a little over six months old and we followed a similar charging regime and she's gone from 250 miles new to 228 now.

I've also read a handful of posts from people here to claim to charge to 90% every time / day and see no reduction in "max range".

It does seem to be a battery lottery or some other factor that we aren't aware of. Really I think there'd be a lot less of these posts from concerned owners if Tesla would just show a "usable Kwh" number. I'm assuming teh car has to know that number if it is using it vs rated miles to get range. Then there would be no speculation about range given outside temperature, use of climate control, hwy vs city, rated vs GOM, etc. Straight up if you showed, say, 51.5kwh when you bought it and now it says 49.3kwh, then you've lost capacity. Simple but I think they don't do that because they want it to be nebulous for marketing purposes.

Actually, the reality is well known and broadly published in this forum. Unfortunately, the Noise to signal ratio drowns it out. Rated range is the BMS’s estimate of available kWh multiplied by a constant that varies by model and wheel size. So there is no advantage to having available kWh as a gauge vs rated range. Both could be off for the following 4 reasons:

temperature. Extreme hot or cold will influence the BMS’s estimate

balancing between cells. Not going to explain this here, but if you charge regularly, To 90% your battery will stay balanced. It may balance at lower levels, there’s debate.

calibration off. BMS needs to occasionally experience high/low charge levels in order to accurately estimate. Occasionally run down below 20% and charge to 90.

Degradation.

Sure there are instances of batteries with bad cells. Few. Very few. Much of the variability reported is down to the first 3 factors. Most of the people worrying have no cause to.

 

[SageBrush]

What I was trying to convey is that there are situations where your max miles on the screen can go down, but not due to degradation. Over time and relatively similar driving style it can be used as a rough measure of battery degradation, but there are other factors which influence that number (driving style).

NO

Not clear ? NO

 

[ftmaybe]

Actually, the reality is well known and broadly published in this forum. Unfortunately, the Noise to signal ratio drowns it out. Rated range is the BMS’s estimate of available kWh multiplied by a constant that varies by model and wheel size. So there is no advantage to having available kWh as a gauge vs rated range.

I think there is an advantage. a straight battery capacity is readable by anyone, without needing to visit a forum to get a rated constant by car and wheel size. Anyone who owns a tesla immediately knows how the battery is based on the battery capacity number .. no extra information or knowledge necessary. This also leaves out the confusion as evidenced here with people perpetuating the estimated miles is based on driving style. No reason to speculate about GOM or not for battery capacity when you know the battery capacity for real because its right there on the screen.

Most of the people worrying have no cause to.

If it seemed that everyone's battery performed the same, I'd agree. But when some report little to no range loss while others (myself) are seeing a noticeable loss of range in a short period of time, IMO this inconsistency justifies the concerns of owners. My wife's car appears to be running a 9% loss after six months. IIRC I think several people here have reported almost 20% loss on their SR+ (200ish miles). If it seemed that everyone also saw this capacity loss, I wouldn't worry about it either.


Though I'm not really "worried" about it. Even a degraded battery is more than enough range for my purposes, and I'm willing to throw money into the EV goal as a consumer in order to advance the tech. It'll work out somehow .. maybe batteries become so cheap we don't care, or they become so large that even a 50% degraded battery is "400 miles", or they don't degrade as much, etc.

 

[SageBrush]

This is patently wrong. On a Tesla, driving style does NOT impact rated range. This myth has been propagated by people who do not know the facts, including purportedly some Tesla customer service people - though that could also be how it was heard rather than said. Promoting this is a disservice to owners as it causes unnecessary confusion.

No doubt.

People have tried for years to clear up the confusion the poster you replied to has when it comes to kW and kWh. His inability to grasp the idea of energy makes it very unlikely that he will ever grasp that the rated miles meter is an energy remaining meter in disguise.

 

[DougWantsALeaf]

Sagebrush,

How many lines of code have you contributed to Teslas source code base upon which to believe that so confidently? What is your basis of evidence behind that statement if it isn't direct code contribution?

 

[SageBrush]

Sagebrush,

How many lines of code have you contributed to Teslas source code base upon which to believe that so confidently? What is your basis of evidence behind that statement if it isn't direct code contribution?

You might as well ask me why I am confident that Tesla has a factory in Fremont

 

[Phlier]

I started a thread, what seems like a year ago, where I asked people who had zero or minimal deg to provide their charging regimen data, etc. So many of these threads are by people with large amounts of deg, and very few are about people with little deg, so I was trying to see if there were any winning battery strategies.

What did I find? Basically, there was little to no pattern in what people did to achieve zero or minimal deg, according to what the BMS reports. My recommendation to people unhappy with what their BMS is reporting for range, is to change up their charging strategy. That's the only thing that seemed to help some people.

I've been charging to only 61% since last Fall, and while I haven't driven much, ~12k, my battery still shows 310 miles of rated range. One would think being parked outside in a cold clime I would have lots of BMS drift, but that doesn't seem to be the case. My rated range variation has been almost all temperature-related.
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Great post.

Anyone that would like all the information they could possibly ever use about their car's battery health should pony up the couple of bucks for the Stats app. It does a great job of tracking battery degradation, and presents it in an easily understood manner.

A five second glance at one screen on the Stats app will tell you more than hours and hours spent reading internet forums about Tesla batteries. And even better? It'll tell you about YOUR Tesla battery... the only one that matters.