flynt wrote: ↑
Wed May 13, 2020 8:54 am
New user here. Love my 14 REX, aside from this battery degradation thing. Here's my story:
I got my car around this time last year. I'd get around 75 miles of range on battery-only power for the first 7-8 months of ownership. Then I never got more than 65 miles. Chalked it up to cooler temps in the fall and winter, no big deal. I always charge the car to full on my 220 charger. When the car is ta home, it's usually on the charger.
In January I started seeing 60 miles max per charge, and the weather was warmer. Read about "batt. kappa max" here on the forum and started tracking it. First entry in my spreadsheet is January 27th - 48 degrees Fahrenheit, 52 miles of range, batt kappa max at 13.8. By April by April 26th - 3 months later- I saw my range drop to around 52 miles (83 degrees, 50 miles range, 13.2 batt. kappa max). My low for a single charge was 44 miles. You can see as you red down the spreadsheet - 13.8, 13.6, 13.4, 13.3, 13.2. It's a pretty smooth decline..
According to my calculations I was at 70.2% battery capacity. Granted, batt. kappa max is an estimate, etc.. but it was trending down over a fairly short period of time. Falling off a cliff, really. To go from a consistent 75 miles to 55 miles TOPS in a year is unacceptable. Time to call the only people I know of that have the ability to look into this problem for me - the dealer.
This is where the story gets weird. The dealer is cagey about what info they'll give. I ask what they do in this situation, how they check capacity? They tell me they plug the car in and BMW looks at the car and tells them how to proceed. They then measure the capacity of the battery with their diagnostic software. Questions are answered with rambling non-answers. No real info for me. 6 days later I get the car back and magically I'm at 16.2 batt kappa max. The car says it has roughly the same range, but after a couple drives it goes up to 64 miles. Dealer says I had 77% capacity. Also says they'd be happy if I was at the threshold for a warranty claim as they'd love the work. Right.
Now, I'm happy they've returned some range to me. What I'm afraid of is owning a failing battery pack which my local dealer (or BMW corporate) has moved the "safety stops" on. I had a pack which according to the car (batt. kappa max) was at 70%. I have the same pack, which is now miraculously at 86%. Not only did the dealership not tell me that they got me more capacity, they didn't tell me how they test capacity or what parameters they check. Doesn't seem right (legal?) to engineer and sell a car with certain parameters built into how the main power source functions, and when it stops functioning in that way the manufacturer reengineers it.
I'm going to call the dealer and try to get some info. Just thought I'd share some real world experience here. There doesn't seem to be much out there.