Bolt EV Battery Degradation after 70,000 Miles - Chevy Bolt EV Forum
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post #1 of 195 (permalink) Old 11-04-2018, 11:10 AM Thread Starter
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Bolt EV Battery Degradation after 70,000 Miles

Hello, everybody.

So I just finished compiling my historical data and calculating my battery degradation after 70,000 miles of driving. It's a bit higher than I thought it would be, but I did notice an immediate and significant drop off immediately following the software update. That could be due to either more accurate algorithms or GM actually "reserving" about 2 kWh of battery capacity. The result is, at this point, I'm seeing about 8% less capacity now than new (it was about 5% less capacity than new at the time of the update).

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post #2 of 195 (permalink) Old 11-04-2018, 11:36 AM
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As an EE, I see no reason to worry about that degradation after so many miles. The Bolt EV can run another 70,000 miles before the loss affects your true driving range. Many ICEVs have major engine overhaul, costing thousands of dollars before reaching 70,000 miles. You will spend more replacing tires than any other item in the Bolt. So keep your Bolt EV, and pass it on to a relative when you want to upgrade to a better GM EV, maybe an autonomous version of the Bolt EV.
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post #3 of 195 (permalink) Old 11-04-2018, 02:30 PM
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When my Bolt has 70,000 miles I will be degraded much more than the battery
no worries

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post #4 of 195 (permalink) Old 11-04-2018, 05:36 PM
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@NewsCoulomb - would you be willing to publish your raw data, measurement methodology, and analysis?
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post #5 of 195 (permalink) Old 11-04-2018, 05:52 PM
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Originally Posted by NewsCoulomb View Post

So I just finished compiling my historical data and calculating my battery degradation after 70,000 miles of driving.
You definitely won the lottery. Our 12/16 build Bolt, purchased 07/17, never showed more than 58 kWh usable. Since installing Torque Pro on 06/17/18, after both battery updates were done, we have seen 58.6-56.2 kWh total capacity. It sits at 56.9 kWh, today, at 16,819 miles. The last full range check I did back on 05/28/18 showed ~55.9 kWh usable.

The first two months we charged with the factory charge cord, first on 120 volt, then on 240 volts. We have always used hilltop reserve, except just prior to leaving on a long drive. We have done 9 DC fast charges from 1-3 bars up to 80-85%. The car has always been garaged, and plugged in when temperatures fell below 40F or rose above 90F. Most of the miles have been done by my wife, driving at or below the speed limit, in D. I have done about 20% of the miles, always in L, never using the brakes, at or 2-3 mph over, the limit.
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post #6 of 195 (permalink) Old 11-04-2018, 09:47 PM
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I'm not sure what my battery capacity PID number was when new, but after 31k miles, my Nov '16 build 2017 reads 58.3 kWh. Was at a low of 56.8 a couple of months ago, but then crept up to 58.3 after some heavy fast charging usage. Go figure

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post #7 of 195 (permalink) Old 11-04-2018, 10:11 PM
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It's been proven that supercharging will balance cells to maximum capacity.

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post #8 of 195 (permalink) Old 11-05-2018, 12:28 AM
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If we are talking battery capacity as measured in torque pro, my 2017 reads 60 kWh as of my last few log sessions and I have put 18,000 miles on the car in the 6 months I have owned it with one 1100 mile round trip to Chicago, and one 2100 mile round trip to Coco Beach Florida. No idea what it read when new, I installed torque pro when I planned my first long trip where I was going to be using CCS charging.

I commute 55 miles round trip per day at 55 mph most of the way with a couple short sections at 45 mph or 35 mph, and for commuting I use hill top reserve and gentle acceleration. On weekends I am likely to drive 150 to 200 miles in a day, never less than 100 if I leave the house, so I charge up to full. I use L all the time, but when transitioning to a lower speed limit zone I coast in Neutral. On weekends I drive the car much more aggressively including a couple trips to the local 1/4 mile drag strip.

Later,

Keith

PS: I did have the battery monitoring recall done.
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post #9 of 195 (permalink) Old 11-05-2018, 07:21 AM
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@drdiesel1 - Got a reference handy? I'm wondering if L1 or L2 charging to full (or only hilltop reserve?) has the same effect. If not, it might indicate periodic (quarterly?) grooming by DCFC as a modestly-practical alternative to fuel additive worship.
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post #10 of 195 (permalink) Old 11-05-2018, 10:26 AM Thread Starter
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@NewsCoulomb - would you be willing to publish your raw data, measurement methodology, and analysis?
I'll probably have to do a follow up video on that (also explaining what was most likely the result of the software update).

The measurement methodology was very simple. I did NOT us TorquePro for this, as I've found it to have wild variances in its estimates. Plus, it's just not that easy to estimate capacity from a snapshot.

Essentially, on a first discharge (from full), I compared the kWh used to the battery percentage remaining (as displayed on the charger). I have several dozen instances over the life of the car where I was able to capture this data, and it does present a very regular downward trend in total capacity. The most consistent and accurate results appear to come from when my initial discharging of the battery from 100% was down to 1% to 5% remaining capacity (typically 52 to 58 kWh used). From there, I extrapolated the remaining capacity and determined the total available capacity at that time.

I used 60 kWh as a baseline capacity. That is what is quoted in GM's EPA filing documents, and I have no reason (based on my experiences) to doubt that accuracy.
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