Don't Baby Your EV, Hard Acceleration Extends Battery Life

[AKrietzer]

But the tires don't last as long.

https://www.autoblog.com/news/stop-...n-actually-extends-battery-life-by-195k-miles

 

[KevinRS]

It doesn't really say hard acceleration extends the life, it says real world driving does. Lab test slow charge and discharge is worse than the real world pulses that occur with real driving, stop and go traffic, etc. So many drivers are getting more lifetime miles out of batteries than expected.

 

[AZFox]

@KevinRS makes a good point. The article's title is misleading. They just charged and discharged batteries in a manner that more realistically represents the way EV batteries are actually charged and discharged.

Here are some snippets from the article in Nature Energy that the AutoBlog article is reporting about:

Dynamic discharge profiles
We designed four different types of discharge duty cycle to simulate different operating conditions (Fig. 1). These consisted of (1) baseline constant current cycling profiles (with or without rest periods), (2) periodic duty cycles (including regenerative braking portions), (3) synthetic discharge profiles generated from field data and (4) real discharge profiles from field data. To create the synthetic profiles, we used field driving data that encompassed both highway and urban driving41. [...]

Synthetic protocols
Synthetic discharge protocols were designed to emulate trips between a start and end location. We tested several different synthetic profiles that captured highway driving, urban driving and a combination of the two, based on driving data from two cities. Synthetic profile 1a contained a single highway trip from City 1 followed by a rest. Synthetic profile 1b contained four consecutive highway trips from City 1 followed by a longer rest. Profiles 2a and 2b contained characteristic urban driving trips from City 1 and City 2, respectively. Synthetic profile 2c contained a characteristic urban driving trip from the driving profiles of City 1 and City 2 combined. Finally, synthetic profile 3 captured mixed urban and highway driving obtained by concatenating profiles 2a, 2b, 2c and 1a. These synthetic profiles were generated from the real city driving data from City 1 and City 2 using an algorithm previously developed by Moy et al.67 (for details, see ref. 41).

 

[ScooterAsheville]

There are dozens if not hundreds of individual chemistries out there. Changing monthly. Same number of variations in pack design, cooling design, and pack control systems.

Just follow the OEMs guidance and stop trying to be a battery engineer. True fact. A family friend WAS a battery engineer (for 50 years). His batteries were in space, under the ocean, in cars, and in the air. He used to roll his eyes anytime I started to talk batteries. Then he'd spend three hours patiently explaining to me how really battery design really works. Hint: It's all about tradeoffs.

I learned a lot from him, once I learned to zip my lips and just listen.

 

[AKrietzer]

By the time the Slate goes into production in 13 months or so, they may have a completely different battery than they have now. Hopefully it is cheaper, to reduce the total cost.

 

[E90400K]

There are dozens if not hundreds of individual chemistries out there. Changing monthly. Same number of variations in pack design, cooling design, and pack control systems.

Just follow the OEMs guidance and stop trying to be a battery engineer. True fact. A family friend WAS a battery engineer (for 50 years). His batteries were in space, under the ocean, in cars, and in the air. He used to roll his eyes anytime I started to talk batteries. Then he'd spend three hours patiently explaining to me how really battery design really works. Hint: It's all about tradeoffs.

I learned a lot from him, once I learned to zip my lips and just listen.

The things I found about this study that was a bit short of consideration is pack design and temperature. If I read the data correctly and the test regime, the batteries were all tested at a stable temperature of 35 deg. C. (95 deg. F) and compensation for pack design/configuration is not in any of the test data results. I think pack design and the resulting limitations of individual cell cooling and effect of operating real EV battery pacts in cold climates need to be synthesized in the test design as well, realizing there are limitations to the test design dictated by testing apparatus/facilities and battery cells.

The study results state the test design also recharges the battery cells at constant voltage and current (and assuming constant temperature), which is not real-world charging scenarios.

The headline claim of 195,000 additional miles can be expected from former lab test results of constant current vs. dynamic current testing really wasn't elaborated on in the text. The referenced tables in the supplementary data did not make clear from where the 195,000 mile under estimation is derived. It would be a service to the reader if the test summary expanded on that point given the impetus of the magazine articles discussing the test are to assure EV owners their vehicle's batteries are going to last a very long time beyond their expectations.

 

[AKrietzer]

I was wondering about battery operating temperature.
https://www.laserax.com/blog/ev-bat...hich is between 68°F and 77°F (20°C and 25°C).

 

[E90400K]

It doesn't really say hard acceleration extends the life, it says real world driving does. Lab test slow charge and discharge is worse than the real world pulses that occur with real driving, stop and go traffic, etc. So many drivers are getting more lifetime miles out of batteries than expected.

And if EV batteries are already getting 250,000 - 300,000 miles before they degrade to 70% SOH, what more does an owner want to ask for. As one who has taken several cars past 200,000 miles, it takes a huge amount seat time to get to such mileages. My experience and observation has been that any tolerable one-way commute of just an hour or a bit more one way, the average speed is around 45 MPH. When I was driving 35,000 miles a year for the commute to my office 80 miles away, I was in the car around 3 hours 45 minutes to 4 hours, my average speed recorded by the trip computer was between 45 to 50 MPH miles per tank. Outside of a livery job where one drives all day, it is time consuming to rack up 200,000 - 300,000 miles on a car.