Interesting! I will try the same next time I do a trip. I assume you used a CAN bus logger to capture it.
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accelerated degradation concern
- Thread starter David99
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Interesting! I will try the same next time I do a trip. I assume you used a CAN bus logger to capture it.
Quite right. But bear in mind that I'm using the BT module that does something like 100 frames per second so there were around 3 million lines of data. I had to use 64-bit Excel manipulate and even then, had to split the CSV file into 3 parts.
I believe the same effect can be observed while charging. I've been casually observing very strange charging behavior recently, i.e. calculated charge efficiency using charge energy added around 100%, or sometimes wildly exceeding that for short charges. I've also observed the time for each percent charge added seems quite variable.
I will have to get harder data on this, but it appears like what's happening now is I have 6-8% real degradation on-top of the ~3% degradation comparing 100% SoC miles from new, or the ~4% degradation from CAN usable energy at 80.8kWh.
skitch23
Member
I just had my car in for service this week for a bunch of stuff including the battery. I was told when I picked it up today that I was seeing a typical “correction” for summer and that my range should return when it cools off. I live in AZ, so yes it’s hot, but my degradation seems a bit out of the norm to me. It was in service for 42 months before I got it with about 8 miles loss. My max charge Feb 2017 was 201, now it is 184. It was pretty steady for the first three months I had the car but it has started to drop and I’ve lost 4 miles in just the last 4 weeks. (It’s been hot since May so I’m not really buying into the summer correction stuff).
Looking at the original graph from that crowd sourced battery info, I’d be one of the outliers at 72k miles. The tech told me to bring it back in to them in Oct/Nov if the battery is still dropping after the car has a chance to adjust to the cooler weather. I ran the battery all the way down to 7mi left when I brought it in to help rebalance the pack, but it still lost 1/2mi from my last completed charge.
I’ve also had several instances where the car gains 4-6 miles while idling only to lose it a day or two later. Or I get 150% or 60% efficiency on my drives because the battery depletes too slow or too fast. Something is going on with my pack.
Looking at the original graph from that crowd sourced battery info, I’d be one of the outliers at 72k miles. The tech told me to bring it back in to them in Oct/Nov if the battery is still dropping after the car has a chance to adjust to the cooler weather. I ran the battery all the way down to 7mi left when I brought it in to help rebalance the pack, but it still lost 1/2mi from my last completed charge.
I’ve also had several instances where the car gains 4-6 miles while idling only to lose it a day or two later. Or I get 150% or 60% efficiency on my drives because the battery depletes too slow or too fast. Something is going on with my pack.
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Still seems like it. Detailed Test Information points to https://www.fueleconomy.gov/feg/pdfs/EPA test procedure for EVs-PHEVs-11-14-2017.pdf which basically says that: "the vehicle is driven over successive city cycles until the battery becomes discharged (and the vehicle can no longer follow the city driving cycle)." For the other two procedures, it's the same but it's a different cycle or set of cycles.
@skitch23
I can’t see a change of rated range on my car based on ambient temperature. I’ve kept detailed records long enough that seasonal changes would show up. If anything, a warmer battery has more range because it is more efficient. That’s what the ‘range mode’ option does. It warms up the battery to a higher temperature than normal. So I’m not sure the technician talking about summer vs winter range estimates makes any sense.
I used to see range jumps (mostly up) in the first 2 years I owned my car. In the last 2 years I haven’t seen it any more. My theory is that they optimized the BMS and range estimates. My battery is very well balanced even now after 173k miles so I doubt cell imbalance was the cause back then. But it could be an explanation in your case. If the difference between cells becomes too big you have to subtract some capacity because the weakest cells limit the entire pack. That could explain the jumps in range. There could be other reasons, though.
I can’t see a change of rated range on my car based on ambient temperature. I’ve kept detailed records long enough that seasonal changes would show up. If anything, a warmer battery has more range because it is more efficient. That’s what the ‘range mode’ option does. It warms up the battery to a higher temperature than normal. So I’m not sure the technician talking about summer vs winter range estimates makes any sense.
I used to see range jumps (mostly up) in the first 2 years I owned my car. In the last 2 years I haven’t seen it any more. My theory is that they optimized the BMS and range estimates. My battery is very well balanced even now after 173k miles so I doubt cell imbalance was the cause back then. But it could be an explanation in your case. If the difference between cells becomes too big you have to subtract some capacity because the weakest cells limit the entire pack. That could explain the jumps in range. There could be other reasons, though.
skitch23
Member
@David99
Yeah when I dropped the car off a diff tech told me that the pack would have been reset when I got it as a CPO so it is correcting itself to what it should be. Since these are polar opposite responses, I'm not sure I can believe either one. And I have yet to see anyone post about gaining ~3% of range while the car is parked so that is a bit confusing to me as well (this has happened multiple times... winter and summer). I really like my car, but if I am going to continue to lose 12-15mi (or more) of range every year it just won't be wise to keep it.
Yeah when I dropped the car off a diff tech told me that the pack would have been reset when I got it as a CPO so it is correcting itself to what it should be. Since these are polar opposite responses, I'm not sure I can believe either one. And I have yet to see anyone post about gaining ~3% of range while the car is parked so that is a bit confusing to me as well (this has happened multiple times... winter and summer). I really like my car, but if I am going to continue to lose 12-15mi (or more) of range every year it just won't be wise to keep it.
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