A question that has been asked since the birth of EVs (at least those of 21st Century vintage) and still remains unsatisfactorily answered... The Leaf capacity meter and aftermarket tools came the closest (possibly because the Leaf suffered horrendous capacity loss)...

 

I guess what I'd like to see is a gauge that tells me that my battery is 95% or 97% or 100% balanced. Is this even possible? Could it be achieved via a software update?

You can certainly display your battery balanced percentage on a display, but that has nothing to do with degradation or health of your pack, it's just a temporary difference between multiple batteries. (But still of interest, and, well, I'm working on it)

The true capacity of a pack can only be determined by fully charging and discharging it while measuring energy in and out, often repeated for days or weeks, with a couple hundred thousand dollars of equipment. Then repeat that a few times I year ago to know your true battery health over time?

That's what the BMS attempts to do to watch battery consumption and make a somewhat educated guess of it's capacity and state of health. Easy if you have a nice constant charge and discharge rate. Next to impossible when your discharge load is widely varying and spiking as is normal when driving.

The Teslafi graphs are still the easiest/best way to track battery capacity over time, as long as you have the understanding that it is not a hard number and the result of a lot of guessing. But it's now summer and I've gone on some long trips, and my pack hasn't come back up, so maybe I can put a bit more faith in my lower range number. But there's always hope

 

But it appears to me that the Teslafi info shows the TOTAL range lost to battery imbalance(temporary loss) AND degradation(permanent loss). These two issues are completely separate and unrelated and combining the two results in useless information(it seems to me). Is there not a reasonable way to separate and communicate these numbers?

 

Best way to solve the problem?

Just don't worry about it. Assume a couple percent per year and be happy if it is less.

The only time it matters is when it starts to get down around 70%. And that becomes evident when you charge to 100% and you travel 50% of your distance and you have only a few percent left.

 

The only time it matters is when it starts to get down around 70%.

This is where it becomes REALLY important, and is part of the reason for the thread. Let's imagine that as the battery warranty period nears expiration(120K miles in my case), my displayed range begins to dip below the warranted 70%(310x.7=217, for me). How can I determine whether I should be covered by the warranty or not, and further, how can Tesla prove that my issue is balancing and not degradation. Unless you believe that Tesla will encounter 0 battery range warranty issues(I don't), then someone will be put in a position of proving that their battery has not performed as warranted. Exactly how can that be done? I'm not stressed about it at all, I would just like to know how this issue might be handled.

 

Just learned about:
https://www.recurrentauto.com

Monthly Battery Reports​

​

Get a free personalized monthly battery analysis of your EV while helping accelerate the adoption of EVs everywhere.​

I'm skeptical of "free" anything. Just wondering if anyone has tried this group?

Perhaps someone might do a compare and contrast with existing tools.

Bob Wilson

 

Just learned about:
https://www.recurrentauto.com

Monthly Battery Reports​

​

Get a free personalized monthly battery analysis of your EV while helping accelerate the adoption of EVs everywhere.​

I'm skeptical of "free" anything. Just wondering if anyone has tried this group?

Perhaps someone might do a compare and contrast with existing tools.

Bob Wilson

I signed up Middie and Middy on this.

We'll see what's what but I'm not holding my breath that they'll get anything more than just "Estimated Range" from the Tesla API, which is what TeslaFI uses.

 

For some reason I can't recall I signed up for Recurrent. As above, it's the same data teslafi uses, just presented a little differently. Here's what one of their reports looks like. Not a typical month for me, very little driving as I was furloughed and back in quarantine mode, no road trips or anything.

 

Another data point on battery degradation.

Here is a graph of actual battery capacity in kWh over the past year, obtained from CAN bus logging, from my 2019 SR+:

In October I've though "that's it, battery degradation kicked in" with 48kWh of capacity remaining.
However, now it is slowly crawling back, 49.7 currently - so it is hard to determine if battery degraded even if you have access to actual capacity data the car provides.

 

Another data point on battery degradation.

Here is a graph of actual battery capacity in kWh over the past year, obtained from CAN bus logging, from my 2019 SR+:

In October I've though "that's it, battery degradation kicked in" with 48kWh of capacity remaining.
However, now it is slowly crawling back, 49.7 currently - so it is hard to determine if battery degraded even if you have access to actual capacity data the car provides.

So it seems obvious that you aren't looking at battery degradation. Degradation should only be a descending line.

 

Interesting discussion. My car is now 3 years old (give or take a week) and has just about 80k miles displayed on the odometer. As far as I can tell, my displayed maximum range is around 300 miles. Tesla sold it to me with a range of 310 so just 10 miles of degradation over 80k miles. Of course, over the lifetime of the car, Tesla has gotten LOTS better at managing the motor and I'm sure the car is way more efficient at using its battery juice than it was when I bought it. So who knows what the real degradation is... and I don't think I care.

Another obvservation. Early in Max's lifetime, I used the Navigation to charge and I would always charge a bit longer than it suggested to give myself a "range cushion." Why? A few times I ended up arriving at a SC with less than 10% charge displayed (!) and once I ran into a powerful headwind and didn't have enough charge to make it and had to turn around and juice up again. So I always charged longer just in case. This last trip (4200 miles) was different, I never felt the need to charge longer. I used Tesla's Navigation exclusively, stopped charging when it said we were ready to go, and arrived at the next SC with around 50 miles to spare every time.

My new mantra when doing long trips comes as the voice of Obi-wan: "Trust the Navigation Luke, er Jim"

 

highly technical discussion that I don't understand much.

here is what I know:

1. Car is now 2 years old (this week)
2. just got to 10000M
3. always been charged at 80%.
4. When was new - it charged with 237mies left.
5. Now its on 222miles for same so roughly 6% loss.
6. I know at the time when Tesla was able to add 5 miles range it was a big deal... somehow the 15miles seems to be "why even worry about it? just enjoy your car"
7. I know when a new buyer will come to buy it ... he is going to look at this range. He/she might be comparing it to other cars. or might be looking at it as battery degradation. I know I wont be able to explain any of this "don't worry about it, just enjoy the car will probably not work"
8. Am reading here on rebalancing/resetting battery but not clear is this is real thing or urban legend as some other claims.
9. My drives, when I drive, are fairly short (16 miles a day)
10. Car is in garage and temp are around 45f
11. Regular home charge 120V (5Miles an hour)

So I am with the original OP. At a leading EV company, one that does "battery days" event, celebrate how they squeeze another 5 miles into a range ... I wish they can provide a specific guide and if possible (assuming they know what to do) a utility in the car that guide the user what to do. Can be something like smart "maintenance schedule" that says ... times to discharge to X level, time to charge up to Y level....

The fact there is nothing official is frustrating.

That being said - anyone can point to the "battery balancing" procedure dont mind trying it out ....

 

3. always been charged at 80%.
...
9. My drives, when I drive, are fairly short (16 miles a day)

The BMS (Battery Management System) can sometimes find it difficult to correctly estimate how much energy the battery can hold. Constant supercharging can really throw it out of whack. But also, keeping the state of charge in a very narrow range will cause it to lose accuracy over time. So if your state of charge has been bouncing between 75%-80% for a long time, it could very well be confused.

That being said - anyone can point to the "battery balancing" procedure dont mind trying it out ....

JWardell outlines the procedure here:

So many things affect the range value that your car and Teslafi uses for that plot. It is not a real gauge of your battery's physical condition and degradation. It's a software algorithm that averages tons of parameters over a long period of time, and it doesn't recalibrate all that often. The best thing you can do I switch your gauge over to percent and stop stressing over range.

Battery balancing will trigger only when over 90% -let's say charge to 92% to be sure, but no need for 95 or higher- and only if the BMS thinks things are out of whack enough to do so. No need to start from 20% or whatever.
But the calculations and range will not update until after a balance the car then goes for a good drive and gets the battery below 50%.
After driving below 50% and sitting, parked, not charging, it will start updating the range calibrations. You might even notice it in TeslaFi if you see the range going UP while sitting there parked.

I triggered that a week and a half ago, and had some more 90% charges due to lots of travel last weekend too, where normally I only ever charge to 80%. You can see the bump at the tail end of my TeslaFi battery graph. Otherwise, there is a big overarching effect of average temperature over the previous several WEEKS. Tesla corrects for seasonal temperature and it's very apparent in my graph.

 

Thank you @garsh and @Ed Woodrick for the useful tip.

I am happy its not a real battery degradation and its "only a calculation issue" - as long as I can bump it up - am happy. As long as I cant - I not happy and consider it degradation regardless if its due to calculation or a true battery issue.
I am not planning on getting anywhere close to 10% so I will never see (I hope) if those lost 15 miles are true loss or just calculation. But am fairly sure a buyer will care and will look at it as lost mile.

I will give it a try and see how goes....

thanks again!

 

This is long but I’ll try to summarize my degradation problems that has my 2015 85D currently at the Tesla service center waiting for remanufactured battery at 112,856 miles.

My full charge range when new in 2015 was about 268 but after a few months and 8,000 that was down to about 261. After that it was a very gradual loss to about 242 at 90k miles in the spring of 2019. A year ago at 103,000 miles the range had dropped to 226 miles and that was when the first signs of a problem with the HV battery showed up. I was driving it each Wednesday or Thursday 140 miles north to our cabin(all highway at mostly 75mph) and I would set it to charge to 90% with the departure timer so it wouldn’t sit at that 90% level for more than 20 minutes. I’ve never achieved better than about 82% of rated miles when driving 75mph on the highway so charging to 200 miles should allow me to go 160ish miles but less than that in freezing temperatures.
On a return trip from the cabin last spring I started out with about 205 miles on the meter and 135 miles later started getting warning messages to charge at about 40 miles on the meter. 3.5 miles later I was stranded on the side of the highway with 32 miles left on the meter. I had the vehicle towed to the Tesla service center and they diagnosed and told me everything was normal with the battery. A couple weeks later I got the same message as I was rolling into are driveway at the cabin after the same 140 mile trip in slightly warmer, 50* temperatures. The battery meter was at 38 miles when the warning started. I took it back to the service center the following week(stopped at a supercharger on the way home as I didn’t want to risk another tow). They gave me the same story and recommended that I not drive the vehicle below a 15% charge level, lol. At this point I was super frustrated as I wrongly thought I had a range guarantee which they didn’t have on the Model S until 2020. The service center was not sympathetic to the fact that i couldn’t drive the vehicle below about 50 miles without fear of getting stranded.
The problem of making the 140 mile weekly trip back and forth to our cabin went away once the weather warmed up as I could start with a full charge of about 220 miles and arrive with about 50 miles remaining on the battery meter. Once fall arrived we no longer went to the lake and I normally only drive about 50 miles a day so I no longer had any reason for range anxiety. By December of 2020 the max range had dropped under 200 miles but I guessed part of that could be the cold MN winters.

That reasoning was obviously faulty which I discovered last week when making a 85 mile round trip to visit my son at college. 80 miles into the trip with about 55 miles left on the battery meter, I lost all ability to accelerate or hold a high speed over 62 mph and by the time I reached home max speed was 55 mph. Luckily i made it home and was able to drive it normally after charging back up to 175 miles. Tuesday the day before i got it in for my appointment the service advisor called and said they would be replacing the battery. I’m not sure exactly why they changed their viewpoint but I was told swapping out batteries under warranty was much easier this year due to a change in policy. It will be interesting to see how the new one performs.