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Discussion Starter #1 (Edited)
Idaho National Laboratory publishes Gen1 Battery Pack Capacity End-of-Test Results

Vehicle #1078
Vehicle #3491
Vehicle #3929
Vehicle #4313

Idaho National Laboratory's long-term battery pack testing of four 2013 Chevy Volts has reached end-of-test with the results linked in .pdf format above.

At quick glance, seems the worst performer was VIN #3491 which experienced @10% loss of Measured
Average Energy Capacity (kWh) dropping from a baseline of 16.7 kWh down to 15.0 kWh after 137,741 miles while the best performing, VIN #1078, only lost @8% (16.6 kWh baseline down to 15.2 kWh after logging 121,434 miles)


Going by this last measured data point for the worst Volt performer VIN #3491,

At 137,741 miles 16.7 kWh - 15.0 kWh = 1.7 kWh loss / 16.7 kWh = @10% total capacity loss

@10% / 137,741 miles = .0000726 capacity loss per mile

Following this established metric, we could roughly calculate our Volts should experience 25% capacity loss occuring at 25 / .0000726 = @350k miles and would this mean it is possible the battery pack in our Gen1 Volts will only be able to get 50% or half their original range clear out at an amazing @650k miles 50 / .0000726 = 688,705 miles baring no major battery pack failure!?:confused:



https://avt.inl.gov/vehicle-button/2013-chevrolet-volt

Other useful vehicle stats are posted over at this .gov site for the 2013 Volts such as the average Operating cost of the Gen1 Volt is only @14 cents per mile as shown above compared to the 2013 Leaf which is shown below to be as high as 26 cents per mile!:eek:

 

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Excellent info. 8-10% loss at about 125,000 miles. We plan to keep ours to about 180,000 miles, so maybe 12% loss. Our gas engine will have about 50,000 miles on it at that point. This couldn't be more perfect.
 

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Did the loss of battery capacity result in loss of range? In other words did the loss reduce the size of unused buffer or the 65% of the battery that is used, or did it reduce both proportionately?
 

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Check last two columns in the PDF's tables. They lost only about 100Wh of usable energy.
 

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Check last two columns in the PDF's tables. They lost only about 100Wh of usable energy.
That is about 0.4 miles or just 2,112 feet of range.
 

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I don't understand how they are measuring total capacity loss if the Volt only uses ~65% of the battery.
 

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They are claiming some awfully low resale values, wow.
 

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What would be nice to see is a capacity vs years (or miles) chart so if we could see if the change is linear, accelerating or decelerating.
 

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Discussion Starter #10
I don't understand how they are measuring total capacity loss if the Volt only uses ~65% of the battery.
I believe that Intertek who conducts these periodic battery capacity tests for the Idaho National Lab actually drops the pack out of the vehicle in order to measure the true capacity on a test bench independent of any of the Volt's charge limiting hardware/software.

Too bad the testing of these four specific Volts now seems to have been completed. Would have been interesting seeing Gen1 battery capacity results at +250000 or more miles!;)
 

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Let me start by stating I think Volt Battery very solid long term.

That said, I don't think this research really tells us anything. The reason being it doesn't define what % miles were in CD (charge depleting) electric only mode, verses miles with CS (charge sustaining with the gas engine running.

For instance the pic #3491 state 134K miles, but MPG is 40 over that time frame. That would likely indicate 90% plus of all miles driven were in charge sustaining mode. Likely battery at low state of charge in it's most protective state. The battery is also very protected without having multiple discharge - recharge cycles.

Only the government could spend so much money for such a long research project, and design it so poorly. It really tells you nothing. Things that need to be defined to quantify all the variables as it relates to PEV battery durability.
% miles in all electric
% miles with range extender running.
Define number of full discharge - recharge cycles
define partial discharge - recharge cycles
If running with range extender define % miles with SOC of battery for instance if in hold mode at 90% vs totally depleted battery. If this car was running with range extender on most of the time, what was the state of charge????

If you do the study, but then run a car constantly with range extender you are only determining the shelf life of the battery because the amount of electricity cycled in and out of battery is negligible relative to the batteries capacity. Essentially zero stress on the battery.

Other things to consider. Lets say you own a volt and have a 5 mile commute, you essentially routinely drive 10 miles then plug in. I suspect this battery would last extremely long time and many miles with little degradation. Verses someone with a 20 mile commute to work who drives 40 miles between plug ins. These deep cycles likely are more implacable. If both these cars 150K miles I'd suspect car A would be better off. Does this study add any clarity to this scenario??? NO

The whole thing seems extremely poorly thought out to me. Did anyone prior to this study, or in the last 5 years think a volt battery wouldn't last if you barely used it??? I think everyone already agreed that lithium batteries last a long time without use as long as they aren't left at 100% state of charge.

This was a tremendous waste of tax dollars in my opinion without the context of the variables outlined.
 

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At quick glance, seems the worst performer was VIN #3491 which experienced @10% loss of Measured
Average Energy Capacity (kWh) dropping from a baseline of 16.7 kWh down to 15.0 kWh after 137,741 miles while the best performing, VIN #1078, only lost @8% (16.6 kWh baseline down to 15.2 kWh after logging 121,434 miles)


Going by this last measured data point for the worst Volt performer VIN #3491,

At 137,741 miles 16.7 kWh - 15.0 kWh = 1.7 kWh loss / 16.7 kWh = @10% total capacity loss

@10% / 137,741 miles = .0000726 capacity loss per mile

Following this established metric, we could roughly calculate our Volts should experience 25% capacity loss occuring at 25 / .0000726 = @350k miles and would this mean it is possible the battery pack in our Gen1 Volts will only be able to get 50% or half their original range clear out at an amazing @650k miles 50 / .0000726 = 688,705 miles baring no major battery pack failure!?:confused:
Most of the miles driven for all 4 cars were in CS mode!

Unfortunately, they don't give a simple voltstats-like breakdown of miles powered by battery and miles in Charge Sustaining mode. They give stats for miles driven in entirely CS trips, miles done in trips entirely on battery, and miles done in what they call "mixed" (presumably where the trip starts out BEV then switches to CS).

Given that, all four traveled at most 42k BEV miles and undoubtedly really much less.

Even (conservatively) estimating #3491 did 35k battery miles, then capacity loss per mile comes to:

10% / 35,000 = .002857 %/mile, so 25% loss (assuming linearity) happens at 87,500 miles on the battery.

Granted, this is the worst of the four cars, but the picture you outlined is far too optimistic for those not running ~2/3 of the time in CS mode.

Also, note that the average air temperature was stated as ~90 deg F and the lab is at 5,000 feet both of which add efficiency the car's operation. (AC use and hills will degrade it, though).

While I love my Volt, numbers is numbers and numbers need context.
 

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Don't forget the built in buffer...
Joe,
I didn't forget the buffer. In fact that was my whole point. Volt has a big buffer so battery is protected even at full charge. We already know that.
Thus if you never send significant electrons into, and out of it, the battery lives a very stress free life. Everyone already knows that too.

If you don't cycle the battery as deeply as the manufacturer sets the buffer it really doesn't tell you anything. If fact we know nothing about the degree, or number of cycles associated with this research. Thus the research tells us nothing other than how the battery does sitting if it were sitting on a shelf. Everyone already knew that info prior to the volt's existence.

Bottom line the study was so poorly designed that is was a colossal waste of money. I doubt anyone can tell us what this research revealed that wasn't already known as fact about relatively static lithium batteries that sit at at state of charge between 15% and 80%.
 

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These "Scientist" did a plug in battery study, and rarely plugged in the battery. That pretty much sums up how well thought out this study was.
 

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Unfortunately, these tests are atypical of ordinary customer driving habits and environment. The large majority of miles driven are in charge sustaining mode using the gas engine. As I recall, the cars were driven by a delivery service in the southwestern US (Arizona?) and were probably plugged in overnight and not much during the day. Average trips were mostly city driving around 8 miles. EV driving was probably under 30%. A/C was on around 90% of the time.

Here are the operating summaries of the vehicles:
https://avt.inl.gov/pdf/phev/phevop2013Volt1078PHEV.pdf
https://avt.inl.gov/pdf/phev/phevop2013Volt3491PHEV.pdf
https://avt.inl.gov/pdf/phev/phevop2013Volt3929PHEV.pdf
https://avt.inl.gov/pdf/phev/phevop2013Volt4313PHEV.pdf
 

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I can speak for him. lifetime 40 mpg. If the car averages say 35 in charge sustaining and the car has 135K miles most are in charge sustaining. For example if the car had 70,000 all electric plug in miles the lifetime MPG would be 80ish.

This was a waste of our tax dollars. They studied a plug in hybrid to quantify how long a plug in battery lasted, and they rarely plugged it in.
 

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Good info. this validates my point that whoever designed the study wasted our tax dollars. They had people drive the cars who never plugged them in. You should have study participants who's driving / usage / plug in frequency that is representative of what your research is designed to measure.
They did a traction battery study, but had participants how rarely used the traction battery exclusively or even plugged it in.

Terrible study design. Waste of money.
 

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The testing could have been more reflective of typical consumer driving patterns, I agree. But there's still a lot of useful information here.

The battery is being charged and discharged when in charge sustaining mode, and contributes to the number of cycles that the battery is subjected to. A Prius is never plugged in but still experiences loss of battery energy capacity.
 
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