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Discussion Starter · #1 ·
I am asking this question because I thought the usable (roughly 10KWH) electric range from the Volt's battery would slowly shrink in lockstep with the shrinking overall 16/16.5 KWH total battery capacity.

Andrew Farrah, the main engineer behind the Volt, has said the Volt's battery capacity will drop 10-30% after 9 years. Was he implying that while the total 16kwh battery capacity may be reduced to say 13 kWh, the roughly 10 kWh usable window will remain the same?

If so, does that mean Volt drivers shouldn't actually have a year over year range loss until the total battery capacity is less than the 10 kWh usable window? At that point the volt would be charging to 100% and you'd be using 100% of the battery. Then, once the total capacity dropped below 10KWH, you'd start, for the first time, to see range loss.

Or at some point does the usable 10KWH window shrink in proportion to the total battery capacity loss? In this case you'd notice a range drop over the first 9 years etc...

So which is it? What actually happens?

Thank you,
MrEnergyCzar
 

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Great question. Now is it just age or number of charge/discharge cycles? Some Volt owners drive 8K-10K EV miles / year, others like me are near 20K EV miles / year. Will this have an implication on the lifespan of the pack?
 

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The usable range remains the same, up to a point as it can't do 100% DOD , the software just digs deeper into the reserve.
I thought that GM denied this. If I recall correctly, in a chat session an engineer stated that the Volt will not expand its useable SOC setpoint range. Or maybe WOT wrote it in a post here on GM-Volt.com.
 

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In 3 months of regularly reading posts on this forum, I have yet to see anyone say they have any solid evidence of a range reduction other than to say they "think" they are seeing a small one, less than 5%. Many forum member have 30,000 plus EV miles, so I would think that if there is a serious EV capacity or range reduction coming, the tip of it would be visible already.
 

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Great questions from the OP and Ari_C. I would think that the GM engineers would want to extend the life of the battery to as great an extent as possible. After all, there is an 8 year, 100,000 mile warranty on the battery for the non-California style models and an even greater mileage warranty for the California style models. Knowing that keeping a buffer at both ends, so-to-speak, allows the greatest life for the battery, I would think that the buffers would be kept throughout the life of the car and the usable range, alone, will decrease. Warranty replacement is minimized in this fashion.

What will happen when there is no more usable range? I suspect that the buffers will NOT be available for use at that point and it will then be time to replace the battery. The old battery can be re-purposed at that point as it will still be serviceable, albeit, not for use in the Volt.

I don't know enough about the effects of frequent cycling of the battery on battery life, with buffers at each end ala Volt, to form an opinion. I suspect that there would be a slight increased degradation. I'm too lazy to do the research on-line.

It's my belief, based on immense ignorance of the engineering, that the battery will propel the car well beyond the 8 years, 100,000 or 150,000 miles. 8^)

I guess we will have to wait and see.
 

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Discussion Starter · #8 ·
The usable range remains the same, up to a point as it can't do 100% DOD , the software just digs deeper into the reserve.
How do you know that? Probably 99% of Volt owners, including myself, believed the usable range would drop year after year, albeit not by much....

MrEnergyCzar
 

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Discussion Starter · #9 ·
Great question. Now is it just age or number of charge/discharge cycles? Some Volt owners drive 8K-10K EV miles / year, others like me are near 20K EV miles / year. Will this have an implication on the lifespan of the pack?
Its probably a combo of age and discharge cycles. Are you under the impression you won't see your usable range window change for many years? or do you expect the usable window to close slowly year after year?

MrEnergyCzar
 

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Discussion Starter · #10 ·
Great questions from the OP and Ari_C. I would think that the GM engineers would want to extend the life of the battery to as great an extent as possible. After all, there is an 8 year, 100,000 mile warranty on the battery for the non-California style models and an even greater mileage warranty for the California style models. Knowing that keeping a buffer at both ends, so-to-speak, allows the greatest life for the battery, I would think that the buffers would be kept throughout the life of the car and the usable range, alone, will decrease. Warranty replacement is minimized in this fashion.

What will happen when there is no more usable range? I suspect that the buffers will NOT be available for use at that point and it will then be time to replace the battery. The old battery can be re-purposed at that point as it will still be serviceable, albeit, not for use in the Volt.

I don't know enough about the effects of frequent cycling of the battery on battery life, with buffers at each end ala Volt, to form an opinion. I suspect that there would be a slight increased degradation. I'm too lazy to do the research on-line.

It's my belief, based on immense ignorance of the engineering, that the battery will propel the car well beyond the 8 years, 100,000 or 150,000 miles. 8^)

I guess we will have to wait and see.
So are you saying the usable range won't remain the same in order to keep the buffer in place?

MrEnergyCzar
 

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Discussion Starter · #11 ·
In 3 months of regularly reading posts on this forum, I have yet to see anyone say they have any solid evidence of a range reduction other than to say they "think" they are seeing a small one, less than 5%. Many forum member have 30,000 plus EV miles, so I would think that if there is a serious EV capacity or range reduction coming, the tip of it would be visible already.
It wouldn't be visible for many years if the same usable 10KWH buffer is kept in place as the total capacity shrinks..... it would slowly be noticeable if the same buffer is not maintained from the get go as the total battery loses capacity.

I don't know where else to get the answer to the question. Its either one or the other or some unforeseen scenario...

MrEnergyCzar
 

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Li-ion batteries in general degrade with the number of charge cycles, and depth of discharge has nothing to do with it. Two half discharges and recharges is equal to one full discharge and recharge. However, the greatest damage is done near full charge or full depletion, hence the limited charge window the Volt uses. Given that, I expect that the degradation is directly related to EV miles traveled, not so much to time.

I also remember GM saying that the charge window never expands. If it did, that would be a great way for GM to hide degradation until past the warranty period, at which point, using 100% of the DOD, the battery would degrade rapidly. I hope GM is true to its word about not expanding the charge window.
 

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Discussion Starter · #13 ·
Li-ion batteries in general degrade with the number of charge cycles, and depth of discharge has nothing to do with it. Two half discharges and recharges is equal to one full discharge and recharge. However, the greatest damage is done near full charge or full depletion, hence the limited charge window the Volt uses. Given that, I expect that the degradation is directly related to EV miles traveled, not so much to time.

I also remember GM saying that the charge window never expands. If it did, that would be a great way for GM to hide degradation until past the warranty period, at which point, using 100% of the DOD, the battery would degrade rapidly. I hope GM is true to its word about not expanding the charge window.
Do you mean GM won't be "maintaining" the same 10KWH charge window? WOT clearly pointed out the the SOC window will not be expanded but I don't see why it every would need to be anyway. It would just need to be either maintained at 10KWH or slowly shrink as the total battery capacity shrinks etc...

MrEnergyCzar
 

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Here's my "sediment-laden" water cooler analogy:

Say you've got a 16 gallon water cooler. But the drain spigôt is several inches from the bottom, so the most you can drain out is 10 gallons, leaving 6 gallons in the bottom below the level of the spigot. Then you refill it again with 10 more fresh gallons.

But now this was done on purpose, because the only water you can get is laden with sediment, and this design alows the sediment to sink to the bottom and not come out the tap (if it did, we could call that sediment anxiety, or throat damage:))

But each time we add water, more sediment gradually fills in the bottom space that once held water.

But still the same 10 clear gallons come out, thanks to the design,

Eventually though, all 6 gallons at the bottom fill up and sediment comes out, and eventually the spigot clogs. Our cooler (battery) has failed as a drink provider (for automotive purpose)

Due to this analogy being apt, I believe the Volt battery will usually last 15 or 20 years or more, but when it does reach the end, you'll quickly see the signs of it and need a replacement or junk the car.

But the brilliance of the overdesign of charge window (not to mention battery triplets) is I believe you will usually see ABSOLUTELY no change in range or performance until that point.

My 2 cents.
 

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Li-ion batteries in general degrade with the number of charge cycles, and depth of discharge has nothing to do with it. Two half discharges and recharges is equal to one full discharge and recharge.
So would you say it is better to NOT keep the volt plug all time? Simply wait until we are near the deplete state. OR pushing this to the limit, fully deplete the battery and consume one or two litter of gas before we plugin back to the wall?

This way instead of doing small recharge of 2-3-4 kwh we will always do full recharge.
 

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So would you say it is better to NOT keep the volt plug all time? Simply wait until we are near the deplete state. OR pushing this to the limit, fully deplete the battery and consume one or two litter of gas before we plugin back to the wall?

This way instead of doing small recharge of 2-3-4 kwh we will always do full recharge.
I'm no expert, but I don't think you need to overthink this as GM protected the battery extremely well. Leave it plugged in all the time to condition the battery as needed for temperature control. The battery is never fully charged or fully discharged so traditional thinking about charge cycles won't really apply very well to the Volt. Batteries are generally most damaged with heat and full charges and full discharges, the Volt never allows either of these two things to happen if you leave it plugged in. Keep it plugged in, and enjoy your car.
 

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So would you say it is better to NOT keep the volt plug all time? Simply wait until we are near the deplete state. OR pushing this to the limit, fully deplete the battery and consume one or two litter of gas before we plugin back to the wall?

This way instead of doing small recharge of 2-3-4 kwh we will always do full recharge.
I thought I said that two half discharges and recharges were equal to one full discharge and recharge, so, no, waiting until the battery is depleted doesn't make any difference. Do ten cycles of only 1/10th charge, and you have the same result as fully cycling it once. Besides, GM recommends leaving it plugged in all the time to run the TMS when necessary.
 

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Do you mean GM won't be "maintaining" the same 10KWH charge window? WOT clearly pointed out the the SOC window will not be expanded but I don't see why it every would need to be anyway. It would just need to be either maintained at 10KWH or slowly shrink as the total battery capacity shrinks etc...

MrEnergyCzar
The charge window I was talking about was 65%, and my understanding is that it remains 65% as the battery degrades. However, I just came across this video where Frank Weber, who helped design the Volt, says the electric range at beginning of life would be similar to that at end of life (at 0:40). He didn't define end of life, although car companies usually consider about ten years to be the life of a car, and when asked for specifics on what he meant, he waffled, saying, "we do many things." Note, however, that he left GM before the Volt went into production, so this presentation was about a car that didn't exist yet in its final form.


The time I thought they denied ever expanding the window, though, was (I thought) an Internet chat session where many joined and asked questions. Does anyone else remember the specifics? I am having a hard time finding it right now.

The problem with expanding the SOC window as the battery ages is that the ultimate life of the battery is shorter. You may enjoy a slightly longer range for a few more years, but resale value of the car could be severely impacted.
 

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Discussion Starter · #20 ·
The charge window I was talking about was 65%, and my understanding is that it remains 65% as the battery degrades. However, I just came across this video where Frank Weber, who helped design the Volt, says the electric range at beginning of life would be similar to that at end of life (at 0:40). He didn't define end of life, although car companies usually consider about ten years to be the life of a car, and when asked for specifics on what he meant, he waffled, saying, "we do many things." Note, however, that he left GM before the Volt went into production, so this presentation was about a car that didn't exist yet in its final form.


The time I thought they denied ever expanding the window, though, was (I thought) an Internet chat session where many joined and asked questions. Does anyone else remember the specifics? I am having a hard time finding it right now.

The problem with expanding the SOC window as the battery ages is that the ultimate life of the battery is shorter. You may enjoy a slightly longer range for a few more years, but resale value of the car could be severely impacted.
Great 2009 video clip. When the guy asks, "so you're changing the band", and he got brushed off by the speaker, what did he mean by that question? Did he want to know if they are maintaining the same usable 10KWH as the total battery capacity shrinks? The speaker sounds like they do "lots of things" to keep the usable range the first 10 years. Why is this such a secret?
 
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