Does age of EV battery matters if it has low mileage?

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New member
Oct 17, 2019
Hi everyone!
A helpful member of the InsideEV forum directed me to post over here. I have a question that I can't seem to find the definitive answer to no matter how I Google it. Is the life of a liquid-cooled EV battery shortened by passage of time? I am in the market for a used EV that will last me for for a while. I found a 2014 FFE that is listed within my budget. The car is around 6 years old, but have low 5 digits mileage on it. I am talking about just breaking 10,000 miles on the odometer. My daily commute is about 50 miles round trip. Should I be concern that the battery will give out in a few years? How can I find out the remaining capacity of this FFE before I complete the purchase? Your input most be most appreciated! Thank you!

p.s. Also, how much would you think would be a fair price on an FFE like this out in California?
You can see remaining capacity in BECM module.
Use FORScan with any elm327 adapter
I see many ffe 2012-2014 years and real capacity after full charge 17...19 kilowatts
There are two things that degrade lithium batteries, age and usage. So to answer your question, yes all lithium batteries degrade with the passage of time. Lithium batteries don't like to be deeply discharged nor kept 100% fully charged. keeping a lithium battery for extended periods of time at either extreme state of charge will accelerate degradation. The FFE limits the top end state of charge to 90% so keeping a FFE fully charged all the time isn't that big of a deal as it really is only charging to 90% even though the car's system indicates 100%.
Hi scottt,
They are asking for $12,000.

Hi Dobrinia,
I just picked up a WiFi FORScan OBD2 Adapter from Amazon to see if I can get a reading on the remaining capacity. What should I be looking for? What is the FORScan "field name" that tells remaining capacity? What is the value scale, in kWh?

Hi triangles,
Thank you for your input.

Here are questions for all three of you:

A) If there are degradation caused by passage of time, would the "remaining capacity" read by FORScan reflect that in a lower remaining capacity?

B) Is the value of "remaining capacity" read by FORScan altered by the current state of charge? I recently tagged a long with a friend who went to buy a new PHEV. But the dealer there did not even have the small propulsion battery of that vehicle charged at all. Thus, I am pretty sure this FFE that I am looking at will not be in a fully charged state when I show up with my OBD2 adapter. That is why I am asking if what FORScan detected for "remaining capacity" will be influenced by amount of charge in the battery.

C) Can any of you elaborate the negative effect from passage of time -- does your battery just suddenly die, or the effect are just further degradation of remaining capacity? That vehicle is 2 years from the end 8 years battery warranty. I just don't want to be driving on the way to work/home and the battery, without any forewarning, die on the freeway on year 8.1.

D) Lastly. With my daily mileage at 50 miles, I would be aiming for 80% (60 miles) of remaining capacity or more. Thus -- much would each of you say is a fair price for this vehicle if it has 80% or better of remaining capacity?

Thanks a bunch!

A) Yes

B) Forscan just has an estimated battery capacity remaining to empty. Alternatively there is an "enhanced" trip meter that says how many kWh/ have been used from the battery. I have used this with a little math to estimate my usable capacity. For example full charge down to 10% battery remaining would be 90% of my usable capacity. If the enhanced trip meter says I used 15kWh to get down to 10% left, my estimated total capacity would be 15kWh/0.9=16.67 kWh total capacity.

Below is a screen grab showing my FFE at nearly full charge last winter. About half way down you will see "Hybrid/EV Battery Energy to Empty - Estimated" Mine was at 16.2 kWh. In summer as the battery warms up the capacity goes up. IIRC my battery capacity is a little more than 1 kWh more capacity in summer. It started out at 19 kWh when new.

These parameters are under the BECM module.

C) The short answer is it's very gradual, akin to just having a few more charge cycles on it that it actually does. I don't know that anyone has any hard data on how calendar age affects the FFE battery. I would guess it's maybe 1% to 2% per year and probably isn't linear? From battery degradation reported on Tesla's you lose up to 5% fairly quickly and then the degradation is very gradual. Not sure if this translates well to the FFE battery or not and this data is for ALL degradation not just calendar age. In my 5 years of ownership I've only lost about 5-10 miles of range, although some of that may be due to the fact I don't try to drive efficiently as much as when I first got the car.

D) If you need to go 50 miles daily, I hope it doesn't get cold where you live. Winter weather can sap up to 40% of your range.

Also you better have good LRR tires. Normal tires can sap 10+ miles of range.

Also depends on how you get there. An EV is the opposite of an ICE vehicle. You don't get as far on the expressway as you do in town. If you think you're going to drive 80 mph and get 60 miles of range you will be greatly disappointed.

I"m not trying to talk you out of it, just trying to give you realistic expectations.
$12,000 is WAY too much. You should be paying no more than $8000
Hi all,
Here is the status update. I never got to plug in the OBD adaptor and ran FORScan. The car was sold before I got there. :|
Thank you for all your insight and assistance in helping me understand better!