Stanford: Study states that current tests for EV battery range & degradation are all wrong

RahulNagaraj · 18th December 2024, 14:09

According to the results of a new study conducted by scientists at the Stanford Battery Centre, the current tests conducted to determine EV battery range & degradation are all wrong.

Simona Onori, an associate professor and one of three lead authors of the study, mentioned, "We’ve not been testing EV batteries the right way."

Stanford: Study states that current tests for EV battery range & degradation are all wrong-models.jpg

As per reports, currently, batteries are tested similarly to engines. In the lab, the life cycle of EV batteries is determined based on a constant rate of discharge and recharge. This cycle is repeated until the battery succumbs. The EPA's (Environmental Protection Agency) methodology of projecting EV range also doesn't vary much from how the agency determines fuel economy in gas vehicles.

The EPA test is reportedly as simple as driving a fully charged vehicle until its range is exhausted. However, they don't take into account other efficiency variations like ambient temperatures, HVAC use & driving style - which leads to producing misleading results.

The report states that if the dynamic variations are taken into account, the results show that the EV batteries could last up to 38% longer. This according to the study equates to "an underestimation of lifetime mileage of up to 195,000 miles" more than currently calculated.

Onori, stated, "Real driving with frequent acceleration, braking that charges the batteries a bit, stopping to pop into a store, and letting the batteries rest for hours at a time, helps batteries last longer than we had thought based on industry-standard lab tests."

Alexis Geslin, a lead author & Stanford PhD student, stated, "For consumers using their EVs to get to work, pick up their kids, go to the grocery store, but mostly not using them or even charging them, time becomes the predominant cause of ageing over cycling."

The study, however, does mention that the exact lifespan of an EV battery can't be determined, no matter how "dynamic" the tests are. Having said that, the results from the Stanford study provide a more realistic view to their lifespan.

Source: TheDrive

Link to Team-BHP news

nidhikapoor · 18th December 2024, 15:15

Hope this will allay the doubts of the naysayers, but I doubt it.

coldice4u · 18th December 2024, 15:51

I just got my 30k service done on my 22 months old Tiago LR EV. I have DC charged this car less than 10 times during this time and slow charged using the portable charger to 100% every single time.

My SoH currently stands at 97% which I'm honestly disappointed with. My expectation was 98% if not higher. No perceptible drop in range though.

nidhikapoor · 18th December 2024, 16:14

Quote:

Originally Posted by coldice4u

I just got my 30k service done on my 22 months old Tiago LR EV. I have DC charged this car less than 10 times during this time and slow charged using the portable charger to 100% every single time.

My SoH currently stands at 97% which I'm honestly disappointed with. My expectation was 98% if not higher. No perceptible drop in range though.

Even if you extrapolate that linearly, which is not how battery SoH will actually decline, that will mean you will have 80% after 200,000kms. That's not bad at all.

ALTIMAed · 21st December 2024, 09:45

Quote:

Originally Posted by coldice4u

I just got my 30k service done on my 22 months old Tiago LR EV. I have DC charged this car less than 10 times during this time and slow charged using the portable charger to 100% every single time.

My SoH currently stands at 97% which I'm honestly disappointed with. My expectation was 98% if not higher. No perceptible drop in range though.

What I understand, acceptable degradation of an EV HV battery is 2% per year. This needs to be considered as the 'average of test readings'. If you are at 97% and your range is unaffected, I do not feel there could be any reason for you to get worried. Experts, please comment.

aadiaksh · 21st December 2024, 12:14

This study will just give manufacturers a reason and a chance to cut back on quality of batteries.

Chrome6Boy · 23rd December 2024, 11:14

Quote:

Originally Posted by ALTIMAed

What I understand, acceptable degradation of an EV HV battery is 2% per year. This needs to be considered as the 'average of test readings'. If you are at 97% and your range is unaffected, I do not feel there could be any reason for you to get worried. Experts, please comment.

Our MG ZS 2022 has had a range reduction of 3% after 2 years and 50,000 kms. It looks like this is the norm.

18th December 2024, 14:09	#1
RahulNagaraj Senior - BHPian Join Date: Mar 2021 Location: Bangalore Posts: 2,675 Thanked: 25,323 Times View My Garage	Stanford: Study states that current tests for EV battery range & degradation are all wrong According to the results of a new study conducted by scientists at the Stanford Battery Centre, the current tests conducted to determine EV battery range & degradation are all wrong. Simona Onori, an associate professor and one of three lead authors of the study, mentioned, "We’ve not been testing EV batteries the right way." As per reports, currently, batteries are tested similarly to engines. In the lab, the life cycle of EV batteries is determined based on a constant rate of discharge and recharge. This cycle is repeated until the battery succumbs. The EPA's (Environmental Protection Agency) methodology of projecting EV range also doesn't vary much from how the agency determines fuel economy in gas vehicles. The EPA test is reportedly as simple as driving a fully charged vehicle until its range is exhausted. However, they don't take into account other efficiency variations like ambient temperatures, HVAC use & driving style - which leads to producing misleading results. The report states that if the dynamic variations are taken into account, the results show that the EV batteries could last up to 38% longer. This according to the study equates to "an underestimation of lifetime mileage of up to 195,000 miles" more than currently calculated. Onori, stated, "Real driving with frequent acceleration, braking that charges the batteries a bit, stopping to pop into a store, and letting the batteries rest for hours at a time, helps batteries last longer than we had thought based on industry-standard lab tests." Alexis Geslin, a lead author & Stanford PhD student, stated, "For consumers using their EVs to get to work, pick up their kids, go to the grocery store, but mostly not using them or even charging them, time becomes the predominant cause of ageing over cycling." The study, however, does mention that the exact lifespan of an EV battery can't be determined, no matter how "dynamic" the tests are. Having said that, the results from the Stanford study provide a more realistic view to their lifespan. Source: TheDrive Link to Team-BHP news
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18th December 2024, 15:15	#2
nidhikapoor BHPian Join Date: Mar 2021 Location: Bangalore Posts: 333 Thanked: 509 Times	Re: Stanford: Study states that current tests for EV battery range & degradation are all wrong Hope this will allay the doubts of the naysayers, but I doubt it.
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18th December 2024, 15:51	#3
coldice4u BHPian Join Date: Aug 2008 Location: Delhi Posts: 451 Thanked: 1,146 Times	Re: Stanford: Study states that current tests for EV battery range & degradation are all wrong I just got my 30k service done on my 22 months old Tiago LR EV. I have DC charged this car less than 10 times during this time and slow charged using the portable charger to 100% every single time. My SoH currently stands at 97% which I'm honestly disappointed with. My expectation was 98% if not higher. No perceptible drop in range though.
	(1) Thanks

21st December 2024, 12:14	#6
aadiaksh BHPian Join Date: Sep 2022 Location: Vapi Posts: 62 Thanked: 82 Times	Re: Stanford: Study states that current tests for EV battery range & degradation are all wrong This study will just give manufacturers a reason and a chance to cut back on quality of batteries.
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