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Battery degradation is nothing new, it’s actually expected with all electric vehicles on the market including the Tesla Model S. We were originally expecting to see the Bolt only lose around a 10% of its capacity over a span of 8 years, but now we find out that it could lose as much as 40% of its capacity.

Taken from the Bolt EV owner’s manual, a snippet form page 322 says:

Like all batteries, the amount of energy that the high voltage “propulsion” battery can store will decrease with time and miles driven. Depending on use, the battery may degrade as little as 10% to as much as 40% of capacity over the warranty period. If there are questions pertaining to battery capacity, a dealer service technician could determine if the vehicle is within parameters.
With an 8-year/100,000 mile warranty, a 10% reduction wouldn’t be too bad as it’ll only drop the Bolt’s 238 mile range to 214. But if the battery does degrade 40%, the Bolt’s range will drop down to 143 miles.

Chevy could be taking pre-emptive action to protect themselves so they won’t be hit with a class action lawsuit like Nissan if the batteries were to degrade more than expected, especially in hotter climates. The lawsuit resulted in Nissan completely replacing the batteries for plaintiffs named in the suit.

We really won’t know if the Bolt’s battery capacity will be reduced by 40% until the vehicle is delivered into the hands of customers and driven for a certain period of time.
 

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Sounds more like CYA than anything else. I wonder how this relates to California where they require 10 years and I think 150,000 miles? It seems like California would need a separate set of numbers.
 

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There is similar language in the Volt's warranty information (Note unlike the Bolt EV GM does not list warranty information in the Volt's user manual but very similar language is in the Volt's warranty information). And Volt's have not seen significant degradation. The vast majority of other manufacturers don't even put a degradation threshold in their warranty and degradation is not covered at all.

The 40% mention is likely based on a very severe use case plus a large safety factor.
 

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Since it can switch to gas, the Volt has a distinct advantage in that it can enforce the battery operating in a narrow range (like 30-90% of charge) and avoid both deep discharge and overcharge. The Bolt EV's battery could be pushed to extremes a Volt never sees and start degrading more/sooner.
 

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Guess the key to good battery maintenance is to charge it to 90% and don't drain it too much before the next charge. Also, the 40% seems to come from owners living somewhere hot. Guess that combined with the battery generated heat reduced the battery capacity a lot faster than if someone lived in Canada.
 

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That title is misleading and can be defined as a LIE. Change it to the real fact:
Bolt EV Battery Capacity Could See as much as 40% Reduction Over 8 Years
 

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Since it can switch to gas, the Volt has a distinct advantage in that it can enforce the battery operating in a narrow range (like 30-90% of charge) and avoid both deep discharge and overcharge. The Bolt EV's battery could be pushed to extremes a Volt never sees and start degrading more/sooner.
I don't think the Volt has a distinct advantage because you're forgetting that the Bolt also has the distinct advantage of having a lot more range. So you can effectively limit your charging and discharging to around the 50% mark most of the times.

For example let's say everyday you only need about 100 mile range (which should be plenty in most situations), you can probably just program it to charge up to around 167 miles only, which is 70% of 238 miles. And if you drive 100 miles that day, you'll only go down to about 30% of the full charge and still have about 70 miles left.

So in the end, you'll end up operating between 30%-70% most of the times, which is even much better than whatever depth you need to pull out of the Volt battery to get its 38 mile range.

Only once in a while will you need the full 238 range, if ever. So overall, that Bolt battery should be much less stressed than the Volt battery in the first place.
 

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Assuming the clip below from Wikipedia is correct the Volt (and likely the Bolt too) appear to already use a "middle slice" of the battery. When we charge the the battery "fully" we aren't charging it to absolutely %100, but rather 100% of usable (allowed capacity) likewise when the battery is "fully" discharged it isn't really at true 0%, but rather at the lowest usable (allowed) charge level. If this is correct is there any benefit to reducing this usable slice of the battery further?

The 2011 Chevrolet Volt has a 16 kWh / 45 A·h (10.4 kWh usable) lithium-ion battery pack that can be charged by plugging the car into a 120-240 VAC residential electrical outlet using the provided SAE J1772-compliant charging cord. No external charging station is required.[3] The Volt is propelled by an electric motor with a peak output of 111 kW (149 hp) delivering 273 lb·ft (370 N·m) of torque. Capacity of the battery pack was increased to 16.5 kWh (10.9 kWh usable) for 2013 models, which increased the all-electric range from 35 to 38 mi (56 to 61 km). Other specifications remained the same. The battery pack capacity was increased to 17.1 kWh for 2015 models. This incremental upgrade is likely to reflect in an improvement in range over previous model years, but as of July 2014, the 2015 Volt has not been re-certified with the EPA.[5]
 

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Assuming the clip below from Wikipedia is correct the Volt (and likely the Bolt too) appear to already use a "middle slice" of the battery. When we charge the the battery "fully" we aren't charging it to absolutely %100, but rather 100% of usable (allowed capacity) likewise when the battery is "fully" discharged it isn't really at true 0%, but rather at the lowest usable (allowed) charge level. If this is correct is there any benefit to reducing this usable slice of the battery further?
In the case of the Leaf they allocated a bit too much of the "top" of the battery as "available" because they were trying for the most range possible. GM didn't have to be that daring with pack allocation, but they may have anyway, to get the maximum EPA range possible, to solidly beat Tesla. I'm one of those who think they should have tried for a solid 200 or 210 mile EPA range and left more of the top of the charge profile reserved, but only time will tell for sure.
 

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"We were originally expecting to see the Bolt only lose around a 10% of its capacity over a span of 8 years, but now we find out that it could lose as much as 40% of its capacity. "

The Chevy Bolt news writer needs to be fired. What a ridiculous conclusion!
 

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What I got from that is the fact we have just about nothing to worry about and if your like me you won't be holding onto a Bolt for too long, which i define by 4-5 years. By the looks of things we won't have to change the battery till after then. Still, i'll be on the look out for battery core price since we'll get money back on that when getting a new battery. In the end it might not be that bad at all looking at cost to replace with parts and labor.
 

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I think it's a bit of a mistake to compare the Bolt to the Volt. The Volt gets a significant amount of it's propulsion from the ICE. This guy who put 300,000 miles on his Volt did so overwhelmingly on gasoline. It would be interesting to know how religious he was about plugging it in and getting a full charge.

The high, trouble free mileage doesn't surprise me. The Volt is symbiotic in that the electric motor helps the ICE and the ICE helps the electric motor. It really is a fantastic hybrid system and why people still to this day buy Prius is beyond my comprehension.

Still it does sound like GM has really worked out the battery management and that is indeed encouraging for the Bolt.
 

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It really is a fantastic hybrid system and why people still to this day buy Prius is beyond my comprehension.
The Prius PHEV will get 50+ MPG even if left uncharged. It's the superior car for driving long distances, and for carrying people and cargo. The Volt is better for trips under 40 miles.
 

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I think it's a bit of a mistake to compare the Bolt to the Volt. The Volt gets a significant amount of it's propulsion from the ICE. This guy who put 300,000 miles on his Volt did so overwhelmingly on gasoline. It would be interesting to know how religious he was about plugging it in and getting a full charge.

The high, trouble free mileage doesn't surprise me. The Volt is symbiotic in that the electric motor helps the ICE and the ICE helps the electric motor. It really is a fantastic hybrid system and why people still to this day buy Prius is beyond my comprehension.

Still it does sound like GM has really worked out the battery management and that is indeed encouraging for the Bolt.
That Volt owner still has put well over 100k EV miles on his Volt, including 2 full charge cycles pretty much every day. I think he is at around 330k miles now, and he has recently reported he still gets the same EV range he got when it was new. While it's not an apples to apples comparison, the fact his Volt has held up so well is good news for potential Bolt owners.
 

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That Volt owner still has put well over 100k EV miles on his Volt, including 2 full charge cycles pretty much every day. I think he is at around 330k miles now, and he has recently reported he still gets the same EV range he got when it was new. While it's not an apples to apples comparison, the fact his Volt has held up so well is good news for potential Bolt owners.
Now that's impressive but i'm still going to be on the look out for more, always helps to have a good sample size to base an overall expectation off of, but so far that's amazing.
 

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The high, trouble free mileage doesn't surprise me. The Volt is symbiotic in that the electric motor helps the ICE and the ICE helps the electric motor. It really is a fantastic hybrid system and why people still to this day buy Prius is beyond my comprehension.
The Hybrid system in the Volt is very similar to the Hyrbid in the Prius. Both use a dual electric motor system with a planetary gear set tying them together with the ICE. The advantage that the Volt has is a set of clutches that can mechanically isolate the ICE from the wheels, and also has beefier electric motors. The advantage of the Prius is lower cost, a simpler setup, a body design that makes creates more interior space, seats 5, and is the standard bearer for hybrids.

They appeal to two different market segments, despite their similarities. Both are excellent cars.
 

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I'm one of those who think they should have tried for a solid 200 or 210 mile EPA range and left more of the top of the charge profile reserved, but only time will tell for sure.
If you prefer to operate the car that way then you can set its charge profile to the "90% hilltop reserve" mode to prevent it from "filling up" that last 10% of capacity. The nice thing is that you still have the option to change the settings to get a 100% charge on those rare occasions where you think you might really need it.
 

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Now that's impressive but i'm still going to be on the look out for more, always helps to have a good sample size to base an overall expectation off of, but so far that's amazing.
What that Volt sample size of one rather persuasively suggests is that there's no fundamental limitation in the technology that's going to cause premature battery degradation for all users. There may be issues in some specific cases such as consistently extreme temperature operation or driving styles, but the battery itself appears to be capable of lasting very well even over thousands of charge cycles and hundreds of thousands of miles.
 
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