Any way to check battery health?

[hawkeye3point1]

Re: Battery SOH.
EVs have robust built-in HVB monitoring. As far as I can tell the MME HVB is segregated into groups of cells called modules. The BECM has a direct line to each module that can measure voltage and temperature.
For a small investment you can access the OBD data bus and read BECM metrics. There is an overall SOH metric, a worst module metric (which I think is the most revealing), and a module variation % metric. Leakage is also measured, someone with more knowledge than I would have to explain that. The car also keeps track of battery age. Some screen caps from Carscanner below. Other mobile apps have comparable info. When choosing an OBD device, I recommend one that connects within the app with BLE. Always disconnect the device after a drive to avoid LVB drain. This has been working for me so far.

 

[macgyver60]

small changes in test conditions can make 'significant' changes in range estimate calculations...

There are objective ways to test battery capacity of course... but it would require:
- charging to 100% in a controlled temp environment (probably 70 degrees F)
- applying a load, probably on a dyno, until battery voltage drops to the voltage considered 'empty', which is the setpoint programed to read 0% (useful capacity)
- review the 'trip' data to find out what the actual Energy (kWhr) consumed was compared to the 'new' useful capacity.

maybe its a bad comparison andI don’t know how accurate the battery health assessments are on an iPhone or MacBook but why couldn’t they use the same method on an EV?

 

[Timelessblur]

I have found cold weather really messes with mine and has the GOM really far off. Now what I have found is pretty dead on is on a longer trip (30-40miles) and getting the mi/kwh to back calculated the number of Kwh used for the trip then use that for the 88 kWh range. My percetange drop will line up pretty close to what I did the math on. GOM on the other hand was more or less really far off.

Also compare your GOM drop in range from when you start to when you end. You will find in warmer weather it is not dropping at a 1 for 1 ratio.

 

[Timelessblur]

I am curious about everyone's' thoughts on recurrent........ I tried that out for 3 months. They came back saying my car had already lost 10% of pack capacity after that short period, and that I should really never have the battery above 80%. If I understand their business model correctly, they want to be able to give used EV buyers confidence in the battery performance specific to that VIN. I was immediately concerned that any assumptions they make, (especially if they are wrong) would ultimately devalue my car just they way Carfax issues would if their database becomes something buyers will lean on in the future.

At first glance it is trying to play on an owners fears. Mix that with their data will be heavily Tesla based which has a very different way of supply the data and showing lose.

 

[dtbaker61]

maybe its a bad comparison andI don’t know how accurate the battery health assessments are on an iPhone or MacBook but why couldn’t they use the same method on an EV?

a. phones are likely to be at about the same temp all the time... certainly close to 'room temp'
b. yes, phone are make a guess on remaining time, but the loads and operating conditions dont change very much, they can make better guesses.
c. phones are estimating battery capacity based on some nominal ah-hr capacity, but not warrantying that capacity degradation rate over years... so 'battery health' on a phone I don't think means the same thing as you want to know w.r.t the car.

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