Used EV Battery Testing

[JerryBob]

Battery life on EV's can be variable due to how they are treated. I was offered a good deal on a pre owned Volt but I would like to check the condition of the battery pack. Does anyone know if there is a way to test a used EV's battery capacity? Looking for a more accurate reading than the bars on the battery condition meter.

 

[marshallinwa]

You might want to check out this Volt forum for help with that question.

http://gm-volt.com/forum/showthread.php?45097-OBD2-and-Vold-PIDs-for-Android-Torque-in-GoogleDoc/page8

 

[GetOffYourGas]

The best way is to put it through a full discharge cycle. That's easy on a Volt - charge it to full and run it until the gas engine kicks on. Should only be about 40-55 miles, depending on the generation of the car. The car will report distance, efficiency, and kWh from your test drive.

It's harder with a Bolt, but none of us are there yet.

 

[michael]

The best way is to put it through a full discharge cycle. That's easy on a Volt - charge it to full and run it until the gas engine kicks on. Should only be about 40-55 miles, depending on the generation of the car. The car will report distance, efficiency, and kWh from your test drive.

It's harder with a Bolt, but none of us are there yet.

That will tell one if the battery is horrible, but I wouldn't trust it to reveal moderate fade. The OP didn't specify what year Volt, but Gen 1 (2105 and earlier) have very large reserves in the battery, and it is entirely possible (nobody seems to know for sure) that software masks battery fade by widening the discharge window.

Also...the 50-ish mile range applies to Gen 2. Gen 1 provides 40-ish mile range

 

[GetOffYourGas]

The best way is to put it through a full discharge cycle. That's easy on a Volt - charge it to full and run it until the gas engine kicks on. Should only be about 40-55 miles, depending on the generation of the car. The car will report distance, efficiency, and kWh from your test drive.

It's harder with a Bolt, but none of us are there yet.

That will tell one if the battery is horrible, but I wouldn't trust it to reveal moderate fade. The OP didn't specify what year Volt, but Gen 1 (2105 and earlier) have very large reserves in the battery, and it is entirely possible (nobody seems to know for sure) that software masks battery fade by widening the discharge window.

Also...the 50-ish mile range applies to Gen 2. Gen 1 provides 40-ish mile range

Thank you for clarifying Michael. Yes, Gen 1 will give you a ~40 mile range and Gen 2 will give you a ~55 mile range. My point is that it will not take a lot of time to drive those miles (compared to doing the same full-to-empy test on a Bolt, for example).

So a question - if the Volt's battery has faded a little bit, but the available energy is the same, does it really matter to the driver?

Well no, and yes. No, it doesn't matter today. A 100% battery and an 80% battery which both provide 10.8kWh to the driver are effectively the same. Yes, it does matter for the long run because any battery will fade below 10.8kWh eventually, and an 80% battery will do so sooner than a 100% battery. Again, as you point out, noone (outside of GM) knows for sure if this is how the Volt is programmed.

So I still maintain that today, short of taking the battery out of the car for independent lab testing, the best test is as described above. It will tell you how much usable capacity you have today. It will not tell you how much you will have 5 years from now.

 

[michael]

Yes, I concur

 

[gpsman]

It (the test drive) will tell you how much usable capacity you have today. It will not tell you how much you will have 5 years from now.

Nothing will. Not even “lab testing”.
:mrgreen: