Battery issue

[i3Houston]

City mileage is definitely higher for me too, lack of wind resistance play a huge role in that as well.

But IMO if your battery is pumping enough electrons to deliver range above 50 miles at 75mph speed then its likely healthy!

It also looks like battery is doing well given the mileage and that its in AZ!

 

[jlangham]

City mileage is definitely higher for me too, lack of wind resistance play a huge role in that as well.

But IMO if your battery is pumping enough electrons to deliver range above 50 miles at 75mph speed then its likely healthy!

It also looks like battery is doing well given the mileage and that its in AZ!

I agree Houston (was born there by the way!). I'm not really stressing over it, but just might let it play out a bit and see what happens. The dealer is aware that the number is below where it should be, and they believe their test is better than the car's indicator and that (like you said) my range is pretty decent for the age of the vehicle. So, if my battery really is going bad, I'll hit the below 70% mark pretty soon and they'll have to replace it.

In the meantime, I'm just going to drive it like I stole it!

 

[jadnashuanh]

Drag is the biggest factor of driving at higher speeds and its effect is not linear. While regen is somewhat inefficient, it's lots better than in an ICE which essentially has none. My GT does use deceleration as an opportunity to engage the clutch on the alternator to charge the battery, though. Prior to that car, I'd not seen one with a clutch on the alternator.

One factor to keep in mind, though, is that BMW says on the i3, driving with the a/c on verses opening the windows is more efficient above 25mph than shutting it off and opening the windows. Ideal would be not needing it while still having the windows closed to keep the drag and load down.

 

[i3Houston]

City mileage is definitely higher for me too, lack of wind resistance play a huge role in that as well.

But IMO if your battery is pumping enough electrons to deliver range above 50 miles at 75mph speed then its likely healthy!

It also looks like battery is doing well given the mileage and that its in AZ!

I agree Houston (was born there by the way!). I'm not really stressing over it, but just might let it play out a bit and see what happens. The dealer is aware that the number is below where it should be, and they believe their test is better than the car's indicator and that (like you said) my range is pretty decent for the age of the vehicle. So, if my battery really is going bad, I'll hit the below 70% mark pretty soon and they'll have to replace it.

In the meantime, I'm just going to drive it like I stole it!

That is great. This only becomes a deal-breaker for those who need full 72 miles range everyday and dont realize that before buying.

Pretty sure in AZs' summer and few quick charges would land you a replacement. Who knows, there might be an option to pay $ to get an larger one. I will certainly envy that, my fellow Houstonian!

 

[alohart]

Because of regenerative braking, I get much better range than on the highway even at constant speed.

As others have stated, an i3 is more efficient at city speeds than at highway speeds because of much less aerodynamic drag. Regenerative braking has nothing to do with it because it merely recaptures energy that was already consumed accelerating and maintaining speed against drag. If you were to drive a constant city speed and decelerate only by coasting, your energy consumption would be less than if you decelerated by regenerative braking because you would need to start coasting and thus consuming no energy earlier than if you waited to decelerate by regenerative braking. Regenerative braking is far less than 100% efficient but far better than friction braking which is 0% efficient.

 

[jlangham]

It seems your numbers match well. 18.9 miles on 32% of battery capacity utilized means that your pack's 100% provides for 59 miles. And if we divide this number by 12.8 kWh of Batt.Kapa reading, we arrive at 4.61 miles/kWh efficiency, which is very close to the number you provide (from the trip computer, I assume) - 4.5 miles/kWh.

Given this (albeit limited) set of data, I'd say the current capacity of your pack is about 12.5-13 kWh, or 66-69%. In case it's the real thing, and not due to the unbalanced cells (you could easily correct this by charging the car up to 100% and leaving it for some time in this state for several days in a row), or alternatively due to the accumulated BMS errors (could be corrected via battery re-initialization), you pack should be eligible for the replacement under warranty.

These are all my guesses, your dealer will have a say on this.

Ok, well I left my car on the charger (Level 1) for two days. Just checked the Battery Kapa and my range. Here are the pictures...

 

[alohart]

Ok, well I left my car on the charger (Level 1) for two days. Just checked the Battery Kapa and my range.

Because I typically charge to an indicated 90% rather than to full which would reduce the cell-balancing speed, twice recently I charged to full and left the battery pack full for several days with the OUC connected. On both occasions, Batt. Kapa. max dropped 0.2 kWh which is the opposite of what should occur if the charge levels of the battery cells had been unbalanced. Either the cells in our battery pack had been well-balanced or individual Batt. Kapa. max readings aren't very precise.

Range estimates of different i3's are difficult to compare with any precision because the estimates are so dependent on recent driving conditions. However, if I adjust your estimated range by the ratio of my to your Batt. Kapa. max readings, your estimated range would be typical of my estimated EcoPro + range: (17.4 / 12.3) * 69 = 97 miles. That is somewhat weak evidence that the capacity of your battery pack is low enough to be checked by your dealer.

 

[jlangham]

Ok, well I left my car on the charger (Level 1) for two days. Just checked the Battery Kapa and my range.

Because I typically charge to an indicated 90% rather than to full which would reduce the cell-balancing speed, twice recently I charged to full and left the battery pack full for several days with the OUC connected. On both occasions, Batt. Kapa. max dropped 0.2 kWh which is the opposite of what should occur if the charge levels of the battery cells had been unbalanced. Either the cells in our battery pack had been well-balanced or individual Batt. Kapa. max readings aren't very precise.

Range estimates of different i3's are difficult to compare with any precision because the estimates are so dependent on recent driving conditions. However, if I adjust your estimated range by the ratio of my to your Batt. Kapa. max readings, your estimated range would be typical of my estimated EcoPro + range: (17.4 / 12.3) * 69 = 97 miles. That is somewhat weak evidence that the capacity of your battery pack is low enough to be checked by your dealer.

Thanks Art. I was just going by the suggestion of Oleksiy to do this. Just thought it was interesting that it went down, but appreciate your explaination.

As I said before, if it's not something that is important why would it even be on the hidden menu? I know they have a better test to indicate true battery health, but they have this value here in the menu and it would be nice if there was a true way to know what signifigance it has in determining that.

And, on top of that, mine appears to be the lowest anyone on this forum has ever seen. I'm just curious about it because it's so low.

I'm not worried about being stranded or that I'm not going to get from A to B as indicated by my Guess-O-Meter. It's been pretty accurate so far, so until it starts showing some super low values, I'm not sweating it. I am going to drive it for a while and see how it goes. Either way, I think it will need a battery replacement within warranty.

Everyone on this forum is very helpful and responsive to questions. I wish all forums were this good!

 

[gasEX]

I am new to this forum and am submitting via "post a reply" since I can't find another way to post; this is not a "reply".
Here is my problem: I bought my i3 in July 2014, now with 46k miles. I live in Jacksonville, Florida; we get a few days of freezing temps in the evening annually. The full charge on my car in the summer is 72-74 miles (82 originally), and has been commonly 68 in the winter. This winter in cold weather my car has charged to 46 miles (I am not talking about freezing temps: nightime temps during cold spells are in the 40's!). Charging at higher temps, in the 60's, the full charge is maxing at 57 miles. This occurs charging at home or work. Took it to the dealer. After 3 days I got got a call, the service desk person first suggesting that the battery was learning my driving habits! I told him that this was ridiculous. He responded that this was suggested by regional experts they called. However, for the price of $750 they would perform a 24 hour diagnostic suggested by the regional experts. The cost would be absorbed by BMW in the event that the battery needs replacement. Otherwise I would be billed. Of course I asked what other possibility exists to explain this problem ,as I am not interested in spending $750 on a test that does not allow a solution to this problem, and I got what amounted to a blank stare over the phone. Does any of this sound legitimate?

 

[i3Houston]

Range on i3 was also in the same ballpark when temperature dropped. Battery kappa was showing 14.3 but as weather warmed up range bounced back.

 

[Oleksiy]

However, for the price of $750 they would perform a 24 hour diagnostic suggested by the regional experts.

I wonder why the cost of the test is so high... AFAIK, it's performed simply by connecting ISTA+ software to the car via ODB2 port and running a diagnostic in the app. The car is gradually discharged using climate settings with windows open, and then charged again. Or visa versa. Haven't tried it myself but may do someday.

 

[alohart]

I am new to this forum and am submitting via "post a reply" since I can't find another way to post; this is not a "reply".

First, choose the appropriate subforum for your new topic (e.g., "Problems/Troubleshooting"). Then along the left edge of the page, click the "New Topic" button.

After 3 days I got got a call, the service desk person first suggesting that the battery was learning my driving habits!

The numbers that you are reporting are likely the range estimates that are displayed on the instrument panel. The range estimate is likely adjusting based on the conditions encountered during your last 18 miles of driving which includes ambient temperature, vehicle speed, wind, vehicle weight, terrain, precipitation, usable battery pack capacity, etc. This estimate uses your recent driving efficiency in miles driven per kWh of energy consumed (mi/kWh). If your driving efficiency hasn't changed much but your actual driving range has decreased, the capacity of your battery pack is likely to have decreased.

So you should pay attention to your driving efficiency to determine whether your battery pack has lost usable capacity before spending $750 for a dealer to measure the usable capacity.

 

[Anonymous]

What AlohaArt said

Plus try charging it fully, with pre-conditioning/departure time set, and see what range is displayed once pre-conditioning has finished, right when you unplug and first get in the car, and it hasn't time to re-adjust to outside temp, etc.

If I set pre-conditioning/departure time, I get 74+/- miles range, (with an EPA rating for 2015 Rex of 72 miles per charge), and that's on the default "comfort" drive setting. Without pre-conditioning, on cold days, can easily drop 10+ miles off the range (and it doesn't get that cold in Dallas).

 

[Mcjim]

Ok i got ista 4.10 been tring to fig out how you reset the bms help please.

 

[alohart]

Ok i got ista 4.10 been tring to fig out how you reset the bms help please.

Included in my mega.nz download of ISTA+ is an "Instructions" folder. Download just that folder to get instructions that I copied and Google-translated from a couple of Internet sources. I've never used ISTA+ to initialize the BMS, so I can't provide advise regarding these instructions. Let us know what you learn.