How to Deliberately Lose Battery Capacity

[WalterH]

I was inspired by this thread (https://www.mybmwi3.com/forum/posting.php?mode=reply&t=17400&sid=2c6c29ded0240deaf60cfda493e555e9) about a successful battery replacement, so I just took my 2014 BEV to a BMW dealer. The Kapa max reading when I bought it used in 2017 was 19. I did not recheck it until 2021, when it was 14.4, and now it is 13.3. It only has 27k miles but gets less than 50 miles per charge.

The dealer’s overnight test said my battery capacity is now 72%. The 8-year warranty clock started ticking on August 7, 2014, so I have just over 3 months before it goes out of warranty.

Is there anything I can do to help the battery lose another 3% capacity in the coming months, so I can get a replacement battery? Something in the way I drive and/or charge it?

 

[eNate]

The worst things for batteries are storage at high and low charge levels, particularly at temperature extremes, fast discharge and charge rates, and internal temperature extremes.

According to your numbers, you've been losing on average a little less that 0.1% per month, and you're desiring to increase that rate by 1000% to 1% per month.

I'm sure there's a way, but a 10x increase sounds like a fool's errand – are you sure you want to subject yourself to that? It would take some real commitment, and there's a good chance you'll end up with a 70% battery that just barely doesn't reach warranty thresholds (or BMW installs a software update and hand you a car that's magically back to 73%).

What about cashing out and buying a model with a larger battery and years more life expectancy? Is that a tenable alternative?

 

[3pete]

I would add that there is enough mystery around capacity and how BMW measures it that it seems tough to intentionally fail the test.

If you drain to near zero and DC Fast charge every single day for the next 3 months, you might drop below 70% but there's no guarantee. And that's a lot of wasted time and money on DCFC for no guaranteed benefit.

More importantly: BMW is NOT obligated to get you a new battery. If you went in today with a test of 69%, they could replace one module, get you to 72% to take care of you for the next 3 months and they'd be in the clear. Historically they have swapped full battery packs, but that's no guarantee they would in the future.

With that in mind, it's *probably* not worth it to try and game the system. But if you do, please let me know. Mine is at 73%.

I'm still holding out hope that it will become more common/practical to do a HV battery swap. I think we might see more about this once the first 2014s actually do pass their warranty threshold this year.

 

[agzand]

I think BMW i3 is one of the few EVs that has a slim chance of some sort of aftermarket battery option in the future. The reason is that the production number is significant, the car is pretty desirable, and the original batteries up to 2019 are small, so a replacement battery with larger capacity could provide significant benefit. But battery cost needs to drop further to make this a reality.

 

[Anonymous]

I think BMW i3 is one of the few EVs that has a slim chance of some sort of aftermarket battery option in the future. The reason is that the production number is significant, the car is pretty desirable, and the original batteries up to 2019 are small, so a replacement battery with larger capacity could provide significant benefit. But battery cost needs to drop further to make this a reality.

Has started in Europe...

http://www.i3upgrade.cz/en/cenik.html?fbclid=IwAR1QR-7X12it4ppxP2uzLPXi6skAm56fLcdQTy8hpcfi0IjGOYUJdJhdgk0

 

[alohart]

If you went in today with a test of 69%, they could replace one module, get you to 72% to take care of you for the next 3 months and they'd be in the clear.

Because the i3's battery pack contains 96 cells wired in series, the capacity of the battery pack is the capacity of the lowest-capacity cell. If all cells have roughly the same degraded capacity, replacing a module with a module containing higher-capacity cells wouldn't increase the capacity of the battery pack. Only if one module contains one or more cells with significantly lower capacity that all other cells would replacing that module increase the battery pack's capacity. This is why I think that BMW generally replaces the entire battery pack.

 

[3pete]

Only if one module contains one or more cells with significantly lower capacity that all other cells would replacing that module increase the battery pack's capacity. This is why I think that BMW generally replaces the entire battery pack.

Yeah, that's a good point and I agree they'll generally keep replacing the entire pack when a car is below the warranty threshold. Just wanted to point out that it's not guaranteed even if you fail their test.

Sabotaging your car from 72-69 is one thing if you know you'll go to 100% but I think it's worth knowing that there is a possibility you'd go 72 ---> 69 ---> 71 even if it's unlikely.

 

[WalterH]

Thanks everyone for these super helpful replies. It doesn’t sound like there is much I can do other than hope that the hot Georgia weather will take a few more percentage points out of those batteries this summer. I will keep monitoring the Kapa max for now. The dealer test only cost me $200, so it might be worth doing again the week before my warranty is up. A brand new battery on BMW’s dime would definitely extend the value and lifespan of this vehicle for me, even if it is just another 60 Ah pack.

 

[alohart]

The dealer test only cost me $200, so it might be worth doing again the week before my warranty is up.

At $200, it seems likely that no system software update was included. Is that correct? My dealer requires a system software update prior to the capacity test and wants ~$450 for both.

After your capacity test, did Batt. Kapa. max or your actual range increase as it has for some?

 

[WalterH]

They did not mention anything about a software update, but I noticed that some of my settings were returned to factory default, and the 12 V battery icon is different on my main drive screen. The Kapa Max reading also went up, to 15.4, and my GOM says I’ve now got over 60 miles of range — though I doubt it is actually much better in practice.

Is there anywhere I can check to verify whether the software or firmware has been updated?

 

[alohart]

They did not mention anything about a software update, but I noticed that some of my settings were returned to factory default, and the 12 V battery icon is different on my main drive screen. The Kapa Max reading also went up, to 15.4, and my GOM says I’ve now got over 60 miles of range — though I doubt it is actually much better in practice.

Is there anywhere I can check to verify whether the software or firmware has been updated?

One clue is the change in your battery pack icon. I noticed that change when the system software on our 2014 i3 was updated, probably in November, 2018, although possibly as early as July, 2016. Another clue is parameters being reverted to their factory defaults. So your i3's system software was almost certainly updated.

It's unfortunate that the system software version, a.k.a. the integration level, can't be displayed in iDrive (or maybe it's there but I haven't found it). It can be found by backing up your driver profiles to a USB flash drive using the iDrive driver profiles back up command, inserting the USB drive in a computer, opening the MPD file in a text editor, and reading the value of the <i-step> tag. For our i3, this value is I001-18-11-520 which indicates that this version was released in November, 2018. It would be interesting to learn the system software version on your i3 which could be a March, 2022, version, I001-22-03-5xx.

I suspect that you will find that your actual range has increased. This is common after these battery pack capacity tests which says to me that the BMS is artificially reducing the usable capacity. The system software update resets the BMS increasing the usable capacity, at least for several months during which the BMS might gradually reduce the usable capacity. An EV's BMS can hide the actual battery cell degradation which I think occurs with the i3's BMS. Several 60 Ah i3 owners have used BMW's ISTA+ maintenance software to reset the BMS which almost alway increases the usable capacity.

I wish that BMW would perform the capacity test without first updating the system software. The resulting increase in capacity makes failing the capacity test very unlikely.

 

[WalterH]

It's unfortunate that the system software version, a.k.a. the integration level, can't be displayed in iDrive (or maybe it's there but I haven't found it). It can be found by backing up your driver profiles to a USB flash drive using the iDrive driver profiles back up command, inserting the USB drive in a computer, opening the MPD file in a text editor, and reading the value of the <i-step> tag. For our i3, this value is I001-18-11-520 which indicates that this version was released in November, 2018. It would be interesting to learn the system software version on your i3 which could be a March, 2022, version, I001-22-03-5xx.

Art, you are a wealth of knowledge and helpfulness. Thank you. I might try to determine that software update version, if I can scrounge up an old flash drive somewhere.

 

[SuperPoly]

The opposite of what would be good for the battery:

Fast charge only

Store at low state of charge when not using

Drive it as hard as you can

Maybe tow something heavy and repeatedly fast charge

This reminds me of the Simpsons episode “King-size Homer”

It’s unfortunate that they don’t offer a granular look at the module health and a way to replace or repair them at the module level. A new pack would cost as much as a new EV (after incentives).

 

[alohart]

It’s unfortunate that they don’t offer a granular look at the module health and a way to replace or repair them at the module level. A new pack would cost as much as a new EV (after incentives).

As I posted earlier in this thread, if all cells have degraded similarly (common), replacing a module with a module containing stronger cells, or even replacing one or more cells in a module if that were possible, wouldn't increase the battery pack capacity.

 

[WalterH]

This reminds me of the Simpsons episode “King-size Homer”

I remember that episode!

It reminds me more of sweating off weight for high school wrestling, wearing a rubber sweatsuit and jumping rope in a steaming shower room.

Hopefully this Atlanta heat will knock my i3 down into a lighter weight class where they give out free high-voltage batteries.

 

[3pete]

I think BMW i3 is one of the few EVs that has a slim chance of some sort of aftermarket battery option in the future. The reason is that the production number is significant, the car is pretty desirable, and the original batteries up to 2019 are small, so a replacement battery with larger capacity could provide significant benefit. But battery cost needs to drop further to make this a reality.

Has started in Europe...

http://www.i3upgrade.cz/en/cenik.html

Wow, with the used car market where it is right now I would absolutely pay $4,900 for a 60ah to 94ah upgrade!

Now we just need someone to offer it in the US for similar price. I feel like this shop might be willing to do it as a custom request but none of their locations are close enough to me to even reach out and ask. https://electrifiedgarage.com/