Battery Replacement Under Warranty

[alohart]

The other odd thing you'll see is that after we got the car back (they did a software update and battery test), the max kappa value mysteriously increased from 13.7 to 14.9 and we are seeing a slight increase in range. Did they just 'give' us a sliver of the reserved battery capacity to delay a warranty claim?

None of us knows for certain. It could be that the Batt. Kapa. max value, which is calculated, could have been calibrated to more accurately display the usable capacity.

Or BMW mechanics might be able to increase the usable capacity of the battery pack by reducing the unusable capacity which is ~13% for a 60 Ah battery pack when new (total capacity - usable capacity / total capacity, or 21.6 kWh - 18.8 kWh / 21.6 kWh = 13%). If this is happening, very few battery packs will be replaced under warranty because the BMW dealer capacity test could be rigged to keep the usable capacity above the 70% warranty level unless the actual capacity drops by more than 30% + 13% = 43%.

We know that the usable capacity can be increased using an older version of BMW's proprietary maintenance software. This capability was removed in recent versions, but is it available in some other maintenance software that BMW mechanics currently use? Or is the battery management system (BMS) running in every i3 capable of automatically decreasing the usable capacity to decelerate the battery cell degradation rate? I don't think we know.

It seems that significant loss of actual range as opposed to predicted range is limited to 60 Ah battery packs, at least for now. If true, is this due to improved battery cell chemistry in 94 Ah and 120 Ah battery cells? Or is it due to the 60 Ah BMS being the only BMS that can reduce the usable capacity because 60 Ah battery packs are most likely to suffer capacity degradation greater than the 30% warranty limit?

 

[jadnashuanh]

One article I read today (Not BMW specific) said it seems the average battery degradation on those in their survey was about 2.6% per year and worse on those that used lots of DC fast charging. But, that also included some that did not have active liquid cooling like the i3 has (notably the Leaf). So, assuming that's the average, over 8-years, the average owner would not hit the threshold to get them replaced. On one Tesla rental with something like 300K miles, the battery was still giving about 200-miles over the original 260-miles.

 

[i3Houston]

One article I read today (Not BMW specific) said it seems the average battery degradation on those in their survey was about 2.6% per year and worse on those that used lots of DC fast charging. But, that also included some that did not have active liquid cooling like the i3 has (notably the Leaf). So, assuming that's the average, over 8-years, the average owner would not hit the threshold to get them replaced. On one Tesla rental with something like 300K miles, the battery was still giving about 200-miles over the original 260-miles.

48 months and 30K miles later, the range has slightly dropped, for example full charge shows 68 miles vs 72 miles range. If rate of degradation is constant then i would fall into the average owner category and happy to be there!!

 

[JLB2]

Opposum,
Our stats are pretty close. My 2014 i3 has about 56k miles on it and kappa max is 13.9kw. Pretty good that your dealer did the check and confirmed 72%. Max range I get under any scenario now is about 57 miles. When this drops to about 53/54 miles, I'll have the local dealer check the capacity. They quoted me about $400 to do this if it turns out the capacity is still above 70%. If below 70%, the warranty kicks in and there is no cost. Based on recent degradation, I expect this to happen sometime in Spring or Summer.

Does anyone know if they do a straight replacement for 60ah battery back or if they will offer the upgraded 94ah battery? Given that battery technology improves over time, Tesla installs the latest technology battery when an older battery fails under warranty. I'm hoping BMW will do the same even if they charge an upgrade fee. We know this is possible since they've always offered the upgrade option in Europe.

Does anyone have any experience with this?

 

[opossum]

JBL2, I'm a little surprised they're talking about charging you for a battery capacity check, given that you're reasonably close to the warranty threshold. My service ticket (BMW North Scottsdale) was written up as a customer complaint of diminished range on the order of about 70% of original and they did not charge me for the capacity check. However, I had a warranty repair of the driver's seat heater on the same service ticket, so maybe they were okay with just billing corporate for the one warrantied item? Not sure. You'll get confirmation of your diminished capacity soon enough, I guess. This spring, I expect my capacity to fall below 70%. Oddly enough, it has been about a month since my capacity check and my kappa is still between 14.9 and 15.2. No worries. I've been through this once before with the 2011 Leaf, so I'm sure the capacity will drop below the threshold in no time once we get our desert heat back.

Does anyone know if they do a straight replacement for 60ah battery back or if they will offer the upgraded 94ah battery?

Great question! I'll be interested to know this, too. Worst case, I'll probably find out at my next capacity check in maybe just a few months...

 

[joni3s]

Opposum,
Our stats are pretty close. My 2014 i3 has about 56k miles on it and kappa max is 13.9kw. Pretty good that your dealer did the check and confirmed 72%. Max range I get under any scenario now is about 57 miles. When this drops to about 53/54 miles, I'll have the local dealer check the capacity. They quoted me about $400 to do this if it turns out the capacity is still above 70%. If below 70%, the warranty kicks in and there is no cost. Based on recent degradation, I expect this to happen sometime in Spring or Summer.

Does anyone know if they do a straight replacement for 60ah battery back or if they will offer the upgraded 94ah battery? Given that battery technology improves over time, Tesla installs the latest technology battery when an older battery fails under warranty. I'm hoping BMW will do the same even if they charge an upgrade fee. We know this is possible since they've always offered the upgrade option in Europe.

Does anyone have any experience with this?

No personal experience, but i think I've read that may just change out some of the weak 8 modules under warranty.

It also appears there was some successful post warranty installs from donor i3's. I think BMW is not currently offering any upgrades due to the low uptake on the program they used to have.

 

[jpascale]

We have a 2014 BEV I3 that is showing around 50 miles range after charging overnight. We had it checked at Chandler AZ BMW awhile back and they said BMW Corp said it was still within specs. That was when we were getting around 60 miles on a charge. Been debating getting it back in there for a check. 50 miles is cutting it too close for daily commute use which is what it was purchased for.
This past week I ran across a for sale ad on Craigslist for a 2014 I3 BEV where the private seller said battery had been replaced by dealer. I emailed them a couple of times asking for details before they finally replied "I went to BMW North Scottsdale - Scott was my service provider. No magic just told them I had range issues. They tested it and said they would replace it." I asked what range they were getting and they replied "Around 50-55" . Unfortunately the replies were short so not sure they would answer anymore questions... :roll:
Going to give dealer a call and see if we can make something happen...50 mile range is so disappointing with less than 50,000 miles on ours.

 

[JLB2]

Someone on this thread was able to get his battery replaced. Not just a few modules but the whole battery pack. I'm showing 13.9 on kappa max and getting 57 miles maximum. On most occasions, overnight charging only gives me 50-55 miles. I'm waiting for maximum to drop to 54 miles or 13.2 kappa max before taking it to the dealer to have battery capacity checked.

Hopefully, the warranty can be triggered soon.

 

[joni3s]

Someone on this thread was able to get his battery replaced. Not just a few modules but the whole battery pack. I'm showing 13.9 on kappa max and getting 57 miles maximum. On most occasions, overnight charging only gives me 50-55 miles. I'm waiting for maximum to drop to 54 miles or 13.2 kappa max before taking it to the dealer to have battery capacity checked.

Hopefully, the warranty can be triggered soon.

I'm curious if an easy way to check battery capacity more accurately is to just fast charge to known values a couple times and see how much kwh are able to be used. Or is this that wildly inaccurate? Isn't that what BMW is doing more or less when they discharge and then recharge (from what i think I remember reading).

 

[jpascale]

I just checked my I3 and it is showing 12.3 on kappa max. Does outside temperature affect this reading?

 

[Oleksiy]

I just checked my I3 and it is showing 12.3 on kappa max. Does outside temperature affect this reading?

In my case low temperature seems to accelerate the rate of Batt.Kapa decrease. But the latter never picks up in summer. Check my stats here, I have a chart with Batt.Kapa over months later in the thread https://www.mybmwi3.com/forum/viewtopic.php?t=16253

 

[Oleksiy]

I'm curious if an easy way to check battery capacity more accurately is to just fast charge to known values a couple times and see how much kwh are able to be used. Or is this that wildly inaccurate? Isn't that what BMW is doing more or less when they discharge and then recharge (from what i think I remember reading).

My understanding is that Batt.Kapa shows the kWh that the battery is either able or allowed to accept during charging. At least that's been happening in my case (I checked this assumption many times, including after almost complete battery depletion and charging up to 100%).

As to the BMW battery capacity test procedure, I think it starts from the battery reset, then battery depletion and charging or vice versa. It's available in ISTA+, and there are people who tried it at home. I'm reluctant to since it's said to kill the 12v battery in the process.

 

[alohart]

I'm curious if an easy way to check battery capacity more accurately is to just fast charge to known values a couple times and see how much kwh are able to be used. Or is this that wildly inaccurate? Isn't that what BMW is doing more or less when they discharge and then recharge (from what i think I remember reading).

I've read that the i3's nominal battery capacity is determined by charging/discharging at a C/3 rate. That means for a 21.6 kWh battery pack (60 Ah), the charge/discharge power would be 21.6 kWh / 3 h = 7.2 kW. That's the maximum single-phase AC charging power, so measuring the kWh vended when AC charging at 7.2 kW would be a good start. However, the Idaho National Lab measured the AC charging efficiency as 93.8%, so the energy vended would need to be multiplied by 0.983 to calculate the energy added to the battery pack.

 

[CanisLupus]

I think that the one thing that's clear is if the battery is at or near the optimum temperature (~25C) during charging then it will show it's greatest capacity . Keeping it at that temperature for the duration of charging would require at least LEVEL 2 .

 

[Oleksiy]

Regardless of the ambient temperature and charging power the number of kWh the battery receives is equal to its current Batt.Kapa, taking into account 5-10% losses. That's according to my logs (daily for 20 months), but I don't think i3 battery packs are as unique as everything else these days, so I believe this should be true for all of them.

Given Batt.Kapa usually fluctuates 0.1-0.4 kWh from day to day, I assume this indicator simply shows the real amount of charge received during the previous session, extrapolated to 100% capacity.

Why Batt.Kapa and the available capacity decrease precipitously on some 60Ah cars is a totally different question. I'd be very interested to find out.

 

[panamamike]

An odd factoid. On another board several i3 owners experiencing noticeable range degradation said that after replacing their (aging) 12v battery and registering the new one, their range went back to near normal. One of the owners this happened to mentioned that when their Dealer was apprised, was told was some sort of GOM/ECU software glitch.

MKH, what do you mean by registering the new one? I have a 2015 i3 with a lower than expected Kappa that had the 12v replaced not too long ago. Wondering if I can try the registering to get the capacity to normal. The help would be appreciated.

 

[alohart]

MKH, what do you mean by registering the new one? I have a 2015 i3 with a lower than expected Kappa that had the 12v replaced not too long ago. Wondering if I can try the registering to get the capacity to normal.

Registering a new 12 V battery is telling the module responsible for charging the 12 V battery about the replacement battery including its type (e.g., AGM, flooded cell), capacity (e.g. 20 Ah), and replacement date. If the battery is the type and capacity of the original battery, only the replacement date need be registered. According to a BMW i mechanic, the replacement date tells a mechanic in the future when the battery was last replaced but doesn't do anything else. So registering a 12 V battery won't affect the usable capacity of the high-voltage battery pack.

 

[Bertone]

My 2017 i3 94Ah hidden menu shows Batt.Kapa max = 29,2 kWh. The car has 18.000 kms on the clock.

If true, I believe this is a good value since I've read that net battery capacity for a 94Ah is around 28,8 kWh...right?

 

[Kristis]

My 2017 i3 94Ah hidden menu shows Batt.Kapa max = 29,2 kWh. The car has 18.000 kms on the clock.

If true, I believe this is a good value since I've read that nominal battery capacity for a 94Ah is around 28,8 kWh...right?

Hard to tell, mine was reading 29.9 kw/h during summer and now it only shows 28.4 kw/h. Im currently at a bit lower than 39 000km But yeah, your numbers seem right

 

[JLB2]

Wow. 28kwh kappa max. I'm envious