Checking battery on used '14--large discrepancy between guess-o-meter and the calculation method

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New member
Feb 27, 2024
Richmond, VA
Hi everyone,

I test drove a '14 yesterday, and it was fun. The car obviously hadn't been driven in a while and the 12 V battery was dead (I also noted some rust on the rotors which came right off after the first couple of times braking). When I got into the car the battery meter behind the well was one bar above the midpoint and the car said 28 miles remaining. I drove it for a bit, parked and then read how to calculate the battery capacity from these forums using the % divided by the different types of usage after pressing the leaf button. This value was a compilation of my driving (~5 miles or so) and anyone else who drove it previously. The capacity calculated using that method (I did it twice at different times) was 21 and kWh, which seemed good.

The dealership replaced the 12V battery and charged it to 100% overnight and showed me the guess-o-meter this morning--it read 46 miles. That's a pretty large discrepancy from the calculated capacity. The car is a couple of hours away, so it is not easy for me to do another test drive starting from full to recalculate. Should I be concerned? What would you have them do to prove the battery still has high capacity?
Measuring battery capacity using the readouts on the infotainment screen is only useful when the car has been charged to 100% and then discharged (ideally to below 50% remaining). It's possible that they had charged (not to 100%) and discharged it once or twice before you drove it, so what looked like 21 kWh (which is more than the usable capacity in a brand new 2014; reports vary, but it was likely ~17.3 kWh) was probably 21 kWh over multiple shorter charge cycles. If I only charge my 2014 Spark to 80-90% over and over, my energy used can show, say, 50 kWh.

I will say that my 2014 Spark has around 80% of its original capacity or a bit less, and I see 45-50 miles at full during the really cold months here in northern Wisconsin if I've been using the heat a lot and preheating the car before leaving work. That's seeing economy of 3.2-3.4 mi/kWh for my ~13.5-13.8 kWh usable capacity.

If it's been cold where that Spark lives and they've been running the heat, 46 miles at full may mean it's in similar shape to mine and has 80% of its original capacity. If you've been having mild weather and the economy on the dash has been in the 4s, that could indicate significantly more degradation.

EDIT: I've had my Spark for almost two years now, and I haven't noticed any additional degradation from when I got it. I get 68 miles or so at full during nice weather when I'm getting 4.7-5.1 mi/kWh, and I get 45-50 miles in the coldest of winter. It's been the perfect car to get me to work 10.5 miles from home, and I drive it all year 'round. I put on over 8,000 miles last year!
I had a very similar experience buying a '14 Spark at the end of the year last year. The predicted mileage is based on recent driving, and things like heating temperature. I also see around 55mi of range in colder weather, but on warmer days, or if I preheat the cabin while it's plugged in I see pretty good range. And if I don't drive with a lead foot I can see 75 miles of range.

Actually I was really nervous driving it home because I had 65 miles to drive! I drove *very* conservatively on the highway, and hit rush hour traffic on the way, and I managed to drive the whole 65 miles and still had 10 miles of predicted range left! I think I managed to get 4.5 mi/kWh on that drive. Now that I'm home and I drive fast and turn the heat on I don't even get 4 mi/kWh all the time.

What mi/kWh does the instrument cluster show?
xaviersjs -- I applaud your boldness at trying a 65 mile trip. I wouldn't dare. Our experience is that the range-o-meter is reasonably accurate. We have a '14 with 47k miles on it. We bought it used and have owned it for 8 years. I am in the SF Bay Area so we don't get super cold in winter or hot in summer. Today it showed 62 miles. I generally get 4.0 to 4.5 m/Kwh depending on how hilly the drive. Our area is hilly. I almost never turn on the heat or AC because that kills range. I expect to see upper 60's on the range gauge this summer. Unfortunately this means our safe driving radius is down to 20 or 25 miles, which is beginning to pinch. We're ready to sell it to and have already bought a newer, longer range EV. We will miss it's compact size and sports car performance.
Here is a link to my writeup of our purchase of a used 2015 Spark EV.

I have pics of what I call "Tech Warranty Battery Capacity Report", I don't know what Chevy calls it but I kept asking until they produced the data I needed to know I wasn't getting an abused battery.

I can take pictures of the pages 2-5 of pic #2 if someone wants to see them.

Good Luck
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I have a 2014 Spark with 90,000 miles and about 12 KWH of battery capacity left. I average 5-6 miles/KWH in town and 5 on the freeway ( hyper miling @ 55 mph ) and can go about 60 miles freeway driving. The GOM looks at an average of power usage over several days driving for it's readings. If your doing 70-80 on the freeway your milage will plumet. If you keep the draw on the battery at 10 KWH consumption or under you will get the greatest range.
I don't know the exact algorithm for the guess-o-meter (does anyone here?), but I think you'd have to go through quite a number of charging cycles before it even then only approximated your range based on a rolling average of past driving. You could record the mi/kWh and/or actual kWh used for several runs from full charge to near zero. But If you really want to know your battery capacity, there are a number of detailed posts on here to help, usually needing other tools, OBD port scanner, Torque-Pro etc.

... If you're doing 70-80 on the freeway your mileage will plummet ...

So true. On the other hand, in traffic, your efficiency soars. I often drive 25 miles each way on a round trip on Long Island, New York in the summer, when everyone's going to the Hamptons. The traffic is terrible, sometimes barely 10 to 20 mph, but I'll nearly double my efficiency. the guess-o-meter will only go down 25 miles for a 50 mile trip!

Funny, when I first bought the car, I drove it home 30 miles from New Jersey, but in rush hour traffic (took nearly four hours to get home). Being new to EVs, I was terrified I'd run out of charge from sitting in traffic. It never occurred to me that My economy might double or triple when driving that slowly:)