Universal EV Battery Health measurement

monkey_boy

monkey_boy

monkey_boy

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Hi All,

Is there an established way of measuring the health of EV batteries from all brands? When shopping for cars, it would be useful to be able to see if the battery has been looked after and what sort of percentage it can charge to compared to new.

Thanks,
 
The short answer is no. The long answer is that you'll need to take your own OBD2 reader and the relevant app on your phone or a proper diagnostic reader to have a look at what the car reports.

In reality, outside of a Nissan Leaf, you'd be really unlucky to find a car that isn't a shed on high miles that has a material amount of degradation over and above what you'd expect for a used electric car at that point in its lift cycle..
 
well not yet - company in the eu using AI learning where they monitor battery during some charging & discharging to provide a 3rd party warrantied certificate of its health,

but yes it's a problem for any test drives, you can't drive the car until it's empty to see whether it will deliver the range and discharge performance the manufacturer promises,
rather something to evaluate during your 14 day return period of 2nd hand ev (it's on my list anyway).

that's a plus in my book - as a varifocal user if I look out top of glasses I wouldn't be able to focus on a close surface.

e: dekra who you'll be familiar with in France
jpaul said:
[
Independant companies seem to be offering ev battery test capability (cant but believe AA will soon)
that's the kind of thing that will make 2nd hand purchase / near warranty end purchase more palettable
these folks commonly do mot's in france https://www.dekra.com/en/battery-test-for-electric-cars/
In 15 minutes and four steps, our battery test determines the capacity of a used electric car battery:​
  1. Preparation: Access the battery test URL on your smartphone. Connect the Vehicle Communication Interface (VCI) to the cable then the cable to the OBD port.
  2. Static test: After entering general vehicle data, required diagnostic data is read out and general readiness is verified.
  3. Dynamic test: Data is gathered during a brief acceleration.
  4. DEKRA report: TThe evaluation is ready in minutes and shows the residual battery capacity in a clear, comprehensible format. The entire report with additional information can be sent to the user by email.
The battery test with its patented algorithm has been validated by the prestigious RWTH Aachen University. The test is sophisticated, fast and precise, with the added benefit of providing an independent and objective assessment of the residual battery capacity of these electric cars. This helps promote transparency and trust surrounding used EV sales.​
seems to be models they construct showing expected voltage drop when you remove a known amount of charge https://publications.rwth-aachen.de/record/804631/files/804631.pdf
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And you have to be careful what each app reports as battery health as well.

The app for the Hyundai's report a battery state of health SoH and people assumed that was degradation but it's actually just the voltage balance between the cells so a car with really high milage could still show 100% SoH

It seems some BMS systems will show you their metrics for cell degradation but others seem to keep it more hidden, there's really no easy way at the moment.

Saying all that as long as you're not buying a Nissan leaf it's not really that big of an issue nowadays from what i can see anyway.
 
I think both have an effect, the biggest thing which damages modern cells is them being outside of their voltage range for any great period of time.

They like to be between 20% and 80%, any time spent above or below that will degrade the cell much more quickly.

Also lots of rapid charging can take their toll on the cells, if they've been charged at a high C rate for a lot of their life that'll cause quicker degradation than if they were slow charged, so try and see if there's any data for number of rapid charges it's had and work that out with the milage of the car.
 
CaptainRAVE said:
What is more detrimental, mileage or age? I don’t do much mileage, but tend to keep my cars these days.
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For a battery. Recharges and age.

There is no reliable way to test how long a battery will last really. The car might say it's fine and then the next day it's dead. The high voltage components can also go bad and don't last forever. The problem is there hasn't been enough time to gather accurate data.

It's one of the reasons it's really hard to sell old EVs. Once the battery warranty ends you are on borrowed time before an enviable financial hit.
 
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b0rn2sk8 said:
A bit like an engine then….or basically anything…
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But a lot less likely with an engine and it won't cost as much to fix. Also that's based on mileage, not age. For batteries death is guaranteed eventually, probably before 15-20 years old. Lots of Teslas from around the 2010 era have had to have new batteries, or the infotainment has died and basically bricked the car etc.
 
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A lot of the roadsters have needed doing (the ones which didnt catch fire). So have Model Ss, so even newer ones.

So it's looking like 15ish years is the mark right now.
 
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"There hasn't been enough time to gather accurate data"

Then spews a load of unsubstantiated guff about battery life, likelihood of failure etc. as if it's based on some sort of knowledge or data.

Classic Nasher posting.
 
Jonnycoupe said:
Like I said, put the keyboard down. You don't work in the automotive space, have a degree in engineering or run an electric car yet have the audacity to call me a hypocrite... absolute lunatic with words and abuse of the English language.

Go back to chewing crayons, the crumbs make more sense.
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I don't need to work in the automotive industry to see what's good or bad.

Also a degree in something doesn't make you good at it. I'm sure plenty of people have degrees at JLR ;)
 
Well actually you do, it was the lack of the 12V battery in the Roadster that let to bricked HV batteries and nothing to do with the infotainment.

You are just a consumer harvesting vitriol and diatribe then Mashing it up. nothing more.
 
Jonnycoupe said:
Well actually you do, it was the lack of the 12V battery in the Roadster that let to bricked HV batteries and nothing to do with the infotainment.

You are just a consumer harvesting vitriol and diatribe then Mashing it up. nothing more.
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No you don't. You just need to use it or work on it/disasemble and see what breaks and what doesnt. Then you start to see patterns and the weird design decisions and cost cutting which cause things to fail...

Most of the modern automotive industry only cares about the initial warranty period.
 
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