I’ve tracked battery degradation in the EVs we’ve driven during the past decade. The short answer is that our Nissan Leaf lost a lot, our Chevy Bolts not so much.
I keep detailed logs of our EVs. Beginning with a Nissan Leaf through two Chevy Bolts, I’ve recorded more than a dozen different parameters each time the car is charged. I do this so I can authoritatively answer questions from newbies to EVs and those considering an EV what kind of battery degradation they can expect.
Our 2015 Leaf suffered serious battery degradation in the heat of Bakersfield, California summers where temperatures above 110 F (44 C) are not uncommon. Consequently, the car’s limited range was reduced even further after three years. The Leaf lost 17% of its capacity in only 17,000 miles of travel, leaving us with a piddly 19 kWh when we returned the car to Nissan.
Since switching to the Bolts, we’ve traveled nearly 70,000 miles on three different batteries. Each battery has lost about 5% of its capacity over 20,000 to 30,000 miles. Importantly, this modest capacity loss hasn’t affected how we use the cars or how far we can drive them.
Disclosure: I worked for GM’s Delco-Remy Division 1968-1970 as a cooperative engineering student. I was a member of UAW Local 1981 until the National Writers Union left the UAW in May 2020. The Chevy Bolt is assembled by UAW Local 5960.
Nevertheless, I continue to track the Bolt’s performance. I enter the data on a paper record and then later enter the data into a spreadsheet.
90% of my charging is done at home, and I always charge to 100% when I am not on the road. My reasoning is that most EV drivers will do likewise. Most people will not make any effort to extend the battery’s life. Instead, they will treat the EV much the same as the gasser they replaced it with. They’ll simply “fill it up” and that’s what I am trying to replicate.
Here’s a list of the previous articles I’ve written on this topic.
In this version of the chart, I’ve dropped the Bat Cap Est as it’s determined directly by the Raw Ah capacity. This has eliminated some of clutter in the chart making the trends easier to see.
What’s noteworthy is that the calculated capacity has only declined 5%. The calculated capacity is what we use to actually drive the car. That’s the number of kWh the car believes it has to work with.
Percent Used Method to Calculate Battery Capacity
We can infer battery capacity by knowing how much of the battery was used for so many kWh consumed between full charges. For example, if on a full charge, we consumed 31.2 kWh and arrived home with 45.9% State-of-Charge. The battery’s calculated capacity is 57.7 kWh.
31.2 kWh/(1-0.459) = 57.7 kWh
This is the battery’s calculated capacity remaining. It’s a good measure of how much battery capacity you have to work with. As noted above, the calculated battery capacity has declined about 5% over 20,000 miles.
After 20,000 miles, the new battery has approximately 60 kWh of usable capacity. The average efficiency of the Bolt during this period is 4.3 kWh/mile. The remaining usable capacity at the average efficiency I’ve measured provides an approximate range of 258 miles after 20,000 miles of use. This is roughly comparable to the EPA estimated range of 259 miles when the battery was new.
I keep detailed logs of our EVs. Beginning with a Nissan Leaf through two Chevy Bolts, I’ve recorded more than a dozen different parameters each time the car is charged. I do this so I can authoritatively answer questions from newbies to EVs and those considering an EV what kind of battery degradation they can expect.
Our 2015 Leaf suffered serious battery degradation in the heat of Bakersfield, California summers where temperatures above 110 F (44 C) are not uncommon. Consequently, the car’s limited range was reduced even further after three years. The Leaf lost 17% of its capacity in only 17,000 miles of travel, leaving us with a piddly 19 kWh when we returned the car to Nissan.
Since switching to the Bolts, we’ve traveled nearly 70,000 miles on three different batteries. Each battery has lost about 5% of its capacity over 20,000 to 30,000 miles. Importantly, this modest capacity loss hasn’t affected how we use the cars or how far we can drive them.
Disclosure: I worked for GM’s Delco-Remy Division 1968-1970 as a cooperative engineering student. I was a member of UAW Local 1981 until the National Writers Union left the UAW in May 2020. The Chevy Bolt is assembled by UAW Local 5960.
Nevertheless, I continue to track the Bolt’s performance. I enter the data on a paper record and then later enter the data into a spreadsheet.
90% of my charging is done at home, and I always charge to 100% when I am not on the road. My reasoning is that most EV drivers will do likewise. Most people will not make any effort to extend the battery’s life. Instead, they will treat the EV much the same as the gasser they replaced it with. They’ll simply “fill it up” and that’s what I am trying to replicate.
Here’s a list of the previous articles I’ve written on this topic.
- Slight Chevy Bolt Traction Battery Degradation after Nearly 30,000 Miles
- Battery Degradation 2020 Bolt Relative to 2017 Bolt EV
- Our Bolt is back with a New Pack—In Limbo No More
- Capacity of 2020 Chevy Bolt with New 2022 Battery after 6500 Miles
- Capacity of 2020 Chevy Bolt with New Battery after 11,500 Miles
In this version of the chart, I’ve dropped the Bat Cap Est as it’s determined directly by the Raw Ah capacity. This has eliminated some of clutter in the chart making the trends easier to see.
What’s noteworthy is that the calculated capacity has only declined 5%. The calculated capacity is what we use to actually drive the car. That’s the number of kWh the car believes it has to work with.
Percent Used Method to Calculate Battery Capacity
We can infer battery capacity by knowing how much of the battery was used for so many kWh consumed between full charges. For example, if on a full charge, we consumed 31.2 kWh and arrived home with 45.9% State-of-Charge. The battery’s calculated capacity is 57.7 kWh.
31.2 kWh/(1-0.459) = 57.7 kWh
This is the battery’s calculated capacity remaining. It’s a good measure of how much battery capacity you have to work with. As noted above, the calculated battery capacity has declined about 5% over 20,000 miles.
After 20,000 miles, the new battery has approximately 60 kWh of usable capacity. The average efficiency of the Bolt during this period is 4.3 kWh/mile. The remaining usable capacity at the average efficiency I’ve measured provides an approximate range of 258 miles after 20,000 miles of use. This is roughly comparable to the EPA estimated range of 259 miles when the battery was new.
