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michael

Well-known member
Joined
Jan 29, 2015
Messages
651
We know...

Chevy has described the battery as 60 kWh
Several testers have demonstrated 60 kWh useful capacity
Chevy provides the hilltop option of 90% charging
Chevy has a worst-in-class 60% capacity guarantee

I think...

The battery is actually 60 kWh capacity, not the 20% larger or so that one typically would expect.
The way they get 238 mile range at a reasonable cost is to use the battery's full capacity
The conservative design in the Volt is NOT used
Despite the above, the battery can last a long, long time if used in an intelligent manner, not running full charge/discharge cycles.


Anyone see it the same way? Disagree? Why? Why not?

Until I have evidence to the contrary, my money's on: the battery has 60 kWh capacity, all of it usable. Use it in a careful, reasonable manner or it will degrade.

I'm still totally happy with this, I need 100 miles on a typical day. The battery is plenty large that I can run it at very low stress.

Comments???/
 
michael said:
We know...

Chevy has described the battery as 60 kWh
Several testers have demonstrated 60 kWh useful capacity
Chevy provides the hilltop option of 90% charging
Chevy has a worst-in-class 60% capacity guarantee

I think...

The battery is actually 60 kWh capacity, not the 20% larger or so that one typically would expect.
The way they get 238 mile range at a reasonable cost is to use the battery's full capacity
The conservative design in the Volt is NOT used
Despite the above, the battery can last a long, long time if used in an intelligent manner, not running full charge/discharge cycles.


Anyone see it the same way? Disagree? Why? Why not?

Until I have evidence to the contrary, my money's on: the battery has 60 kWh capacity, all of it usable. Use it in a careful, reasonable manner or it will degrade.

I'm still totally happy with this, I need 100 miles on a typical day. The battery is plenty large that I can run it at very low stress.

Comments???/
Click to expand...
Worst in class?
Tesla, Ford, Mitsubishi and Fiat specifically exclude degradation in their warranty. They flat out will not cover it no matter how severe.

And using 100% of actual capacity? Not a chance and not really worth discussing.
 
Not a chance and not worth discussing? Why do you say that? What's your basis other than sheer assumption?

As far as I'm aware, all manufacturers quote total battery capacity. Chevy included. Why not worth discussing?

And yes, it's the worst warranty. I can't compare lack of warranty with a stated warranty.

Hopefully INL will do an actual test, but for now I don't have any basis in fact to assume battery is larger than 60 kWh TOTAL capacity.
 
The "capacity" of a cell is not a hard line that cannot be crossed, thus calling it a 60KWh battery is somewhat arbitrary, depending on how close to destruction you choose to charge it - the lower the charge voltage, the longer the cells last, over a wide range.

IMHO, having a warrantee at all is a good indication that Chevy engineers have been conservative in rating the battery at 60KWh, and it seems to me that "60KWh" is just a description of their choice of charge level.

Debating whether that represents 100% of the batteries "capacity" is pointless. It doesn't.
 
The 90% hilltop charging was not done to undercharge the battery for people who don't believe engineers know what they are doing.

Its purpose is to avoid an issue created by a fully charged car at the top of a hill. The problem is that when you go down the hill, the Regen generates too much power for a fully charged car to use or waste as heat, so the car switches to hydraulic braking Only and the pedal suddenly becomes Very Hard without the motor doing most of the work. This feels just like brake failure - nasty.

In my Spark EV and my friend's Tesla as well, the sudden no-brakes feeling is very disconcerting, and could easily cause an accident if the driver was not expecting it.
 
The 40% degradation warranty does not mean Chevy expects the batteries to degrade that much; quite the opposite. The warranty means if the battery somehow degrades more than that, such as 41%, then they'll replace it. So the warranty is only for severely unusual cases. The actual degradation would certainly be much much less than that, especially if the battery is charged and discharged wisely.
 
michael said:
Not a chance and not worth discussing? Why do you say that? What's your basis other than sheer assumption?

As far as I'm aware, all manufacturers quote total battery capacity. Chevy included. Why not worth discussing?

And yes, it's the worst warranty. I can't compare lack of warranty with a stated warranty.

Hopefully INL will do an actual test, but for now I don't have any basis in fact to assume battery is larger than 60 kWh TOTAL capacity.
Click to expand...
Not a chance = unless LG/GM reached a breakthrough that they have managed to keep secret, using 100% of the battery capacity will greatly accelerate degradation, bring the warranty into play, and they will be replacing lots of packs. @$145/kWh, it makes no sense (engineering or financial) not to include some buffer.

And no, all manufacturers do not quote total capacity. Some give actual/usable, some give usable, some give pack capacity, others are silent on what their capacity figure represents.
One example: Kia quotes 27 kWh in their specs. That is the usable portion of a 31.5 kWh pack.

Are you really saying that covering a set amount of degradation is a worse warranty than specifically excluding it? It's not that it isn't mentioned, it states it is not covered. Ever. No matter the amount. It could degrade to 20% and not be covered.

From the Tesla warranty book:
The Battery, like all lithium-ion batteries, will experience gradual energy or power loss with time
and use. Loss of Battery energy or power over time or due to or resulting from Battery usage, is
NOT covered under this Battery and Drive Unit Limited Warranty.

Ford, Mitsubishi and Fiat have substantially the same language.
 
OK, I was going to drop this, but here's the deal...

2015 Spark battery is rated at 18.5 kWh

Idaho National Lab tested four of them, using standardized procedure. From their report:

Battery test results include those from the Static Capacity Test and the Electric Vehicle Pulse Power
Characterization (EVPC) Test, based on test procedures from the United States Advanced Battery
Consortium Electric Vehicle Battery Test Procedure Manual, and pre-released USABC recommended
testing practices at the time of testing. These tests were performed for the US Department of Energy
Vehicle Technology Office's Advanced Vehicle Testing Activity, which is conducted by the Idaho
National Laboratory and Intertek Testing Services, North America

In other words, you can't just make up the result...their is a standard way to measure it and that's what they did.

In their testing of four cars, when almost brand new (less than 1000 miles), the results were:

18.3 kWh
18.2 kWh
18.2 kWh
18.3 kWh

In other words, it appears to be Chevy's practice, similar to most other manufacturers, to specify the TOTAL BATTERY CAPACITY WHEN MEASURED BY STANDARDIZED PROCEDURES.

Chevy rates the Bolt battery at 60 kWh, so it is likely that this is the full capacity.

Now, since several road tests have shown the available energy to be very close to this same value, that is the reason I am asking the question whether Chevy is making the entire charge window of the battery available. This is a method they might have used to generate the 238 mile range rating while keeping the cost reasonable.

It's not a stupid question to be asking. It's something every owner of a Bolt should want to know.

With regard to the hilltop reserve...yes, I know that to make the car more usable is the CLAIMED reason for doing this, but the second effect is to allow easy charging to a less degrading 90% value while not running afoul of the stupid EPA requlations that caused Nissan to remove the option to charge to a lower value.

Think about it guys...don't overlook the possibility that they are doing what I'm suggesting they might.

When someone does a standardized test of the Bolt battery full capacity, we will know. But historically Chevy has claimed full capacity, not usable capacity.

And no, I'm not saying that a 60% warranty is a worse warranty than none...I'm saying it's the lowest threshold for failure of anyone who is setting a warranty.

If you look at other message boards (other cars), you will see people complaining about the fact that their car doesn't let them use the full charge window, even in emergency cases. If Chevy has done as I suggest they might possibly have done, it's not a bad thing...but you need to know this so you don't run it from full to empty routinely ASSUMING that there is protective margin at top and bottom. That's what I'm asking...How much buffer, if any is in place?

It's not a stupid thing to ask.


And one other thing....

Over 100,000 miles, it's only about 500 charge/discharge cycles. Look at the data sheets for typical Lithium batteries....Even when run over 100% DOD they will retain over 60% of their initial capacity for 500 cycles. In fact that the the EXACT specification of the LG Chem LG-ICR18650HE2 battery...60% of initial capacity after 500 FULL (4.2 v to 2.5V) charge/discharge cycles. The Bolt battery doesn't have to work as hard to go 100K miles as does the battery in a 80 mile car.

Think about it...
 
michael said:
OK, I was going to drop this, but here's the deal...

2015 Spark battery is rated at 18.5 kWh

Idaho National Lab tested four of them, using standardized procedure. From their report:

Battery test results include those from the Static Capacity Test and the Electric Vehicle Pulse Power
Characterization (EVPC) Test, based on test procedures from the United States Advanced Battery
Consortium Electric Vehicle Battery Test Procedure Manual, and pre-released USABC recommended
testing practices at the time of testing. These tests were performed for the US Department of Energy
Vehicle Technology Office's Advanced Vehicle Testing Activity, which is conducted by the Idaho
National Laboratory and Intertek Testing Services, North America

In other words, you can't just make up the result...their is a standard way to measure it and that's what they did.

In their testing of four cars, when almost brand new (less than 1000 miles), the results were:

18.3 kWh
18.2 kWh
18.2 kWh
18.3 kWh

In other words, it appears to be Chevy's practice, similar to most other manufacturers, to specify the TOTAL BATTERY CAPACITY WHEN MEASURED BY STANDARDIZED PROCEDURES.

Chevy rates the Bolt battery at 60 kWh, so it is likely that this is the full capacity.

Now, since several road tests have shown the available energy to be very close to this same value, that is the reason I am asking the question whether Chevy is making the entire charge window of the battery available. This is a method they might have used to generate the 238 mile range rating while keeping the cost reasonable.

It's not a stupid question to be asking. It's something every owner of a Bolt should want to know.

With regard to the hilltop reserve...yes, I know that to make the car more usable is the CLAIMED reason for doing this, but the second effect is to allow easy charging to a less degrading 90% value while not running afoul of the stupid EPA requlations that caused Nissan to remove the option to charge to a lower value.

Think about it guys...don't overlook the possibility that they are doing what I'm suggesting they might.

When someone does a standardized test of the Bolt battery full capacity, we will know. But historically Chevy has claimed full capacity, not usable capacity.

And no, I'm not saying that a 60% warranty is a worse warranty than none...I'm saying it's the lowest threshold for failure of anyone who is setting a warranty.

If you look at other message boards (other cars), you will see people complaining about the fact that their car doesn't let them use the full charge window, even in emergency cases. If Chevy has done as I suggest they might possibly have done, it's not a bad thing...but you need to know this so you don't run it from full to empty routinely ASSUMING that there is protective margin at top and bottom. That's what I'm asking...How much buffer, if any is in place?

It's not a stupid thing to ask.


And one other thing....

Over 100,000 miles, it's only about 500 charge/discharge cycles. Look at the data sheets for typical Lithium batteries....Even when run over 100% DOD they will retain over 60% of their initial capacity for 500 cycles. In fact that the the EXACT specification of the LG Chem LG-ICR18650HE2 battery...60% of initial capacity after 500 FULL (4.2 v to 2.5V) charge/discharge cycles. The Bolt battery doesn't have to work as hard to go 100K miles as does the battery in a 80 mile car.

Think about it...
Click to expand...
The Chevrolet Spark EV battery is made with 192 (2p96s) LG Chem cells, each cell is rated at 27 Ah and 3.75 V. This represents a total of 19.44 kWh (192 x 27 Ah x 3.75 V). The battery volume is 135 L and the mass is 215 kg, this means an energy density of 144 Wh/L and 90 Wh/kg at the battery level, not cell.
http://pushevs.com/2016/08/30/battery-chevrolet-bolt-ev-vs-chevrolet-spark-ev/

So yes, Chevy does advertise usable capacity. And that is what INL tested, not actual pack capacity.

If you look a the press release specs, they round to 19 kWh on the battery, but also state 54 Ah and 400 V. That equates to something north of 20 kWh (21.6 to be precise, but with rounding errors ??)
http://media.chevrolet.com/media/us/en/chevrolet/vehicles/spark-ev/2016.tab1.html
 
GM lists the 2015 Spark EV (the model year at issue here) as 18.4 kWh (same as a 2016-2017 Volt):

http://media.gm.com/media/us/en/chevrolet/vehicles/spark-ev/2015.tab1.html

Also, repeated here in textual form:

http://media.gm.com/media/us/en/chevrolet/vehicles/spark-ev/2015.html
 
DucRider said:
The Chevrolet Spark EV battery is made with 192 (2p96s) LG Chem cells, each cell is rated at 27 Ah and 3.75 V. This represents a total of 19.44 kWh (192 x 27 Ah x 3.75 V). The battery volume is 135 L and the mass is 215 kg, this means an energy density of 144 Wh/L and 90 Wh/kg at the battery level, not cell.
http://pushevs.com/2016/08/30/battery-chevrolet-bolt-ev-vs-chevrolet-spark-ev/

So yes, Chevy does advertise usable capacity. And that is what INL tested, not actual pack capacity.

If you look a the press release specs, they round to 19 kWh on the battery, but also state 54 Ah and 400 V. That equates to something north of 20 kWh (21.6 to be precise, but with rounding errors ??)
http://media.chevrolet.com/media/us/en/chevrolet/vehicles/spark-ev/2016.tab1.html
Click to expand...

I am sorry, but you are factually incorrect on three points:

1. As noted above, Chevy DOES rate the car as 18.4 kWh

2. You CANNOT multiply battery pack Voltage by its Ampere-hour rating to determine pack energy. The reason is that the Voltage drops as it discharges and depending on load. When discharged at constant power, more and more current is drawn as the Voltage gets lower and lower. Multiplying 54 AH by the peak voltage (400) gives a grossly inaccurate estimate of pack energy. You simply cannot calculate it that way...it doesn't give the correct number. 400 V is the approximate Voltage when fully charged (4.16 V/cell) Your estimate of 21.6 kWh is not correct.

Even multiplying the nominal (as opposed to peak) Voltage by the AH rating gives a wrong estimate of energy unless the cell is discharged slowly. As an example, if you look at the data sheet for the LG Chem 18650 H2 here

https://www.nkon.nl/sk/k/hg2.pdf

You will see that it is rated at 3.6 V, 3 AH. By your method, it would seem to indicate 10.8 Wh. But this rating is obtained at 0.2 C rate (five hour discharge).

However, if you look at the table, at 3 A, it delivers only 10.2 Wh. It turns out the 3.6 V and 3 AH numbers (for this particular battery) apply only if discharged at the 5 hour rate. Pushevs.com estimate of 19.44 is also not correct.

You have to go by the manufacturer's rating. They follow specific procedures to get the number, and they are not as simple as multiplying Ah by V.

3. The INL testing most certainly does measure the full rated capacity. They specifically cite the test that they do. This is the way manufacturers rate the full capacity of their batteries. They use equipment such as this:

http://www.avtestsystems.com/av-900

make the measurement. The "usable" energy is determined once the battery is installed in the car, and the car's battery management system controls the maximum charge and discharge levels.
 
Based on someone knowledge who has extensive hands on with the Chevy Volt battery and charging here is how I see this. The battery is likely 60 kWh and the normal charging procedure will charge only to 80 percent so in effect a 48 kWh battery. The question is how efficiently is it being driven and how efficient is the Bolt ? The best I ever did with my original Nissan Leaf was about 200 Watt Hours / Mile. Using that number with a 48 kWh battery you arrive at (drum roll) 240 miles. But that would only be achieved with low speed urban driving (max 50 mph) and slower acceleration and max regeneration. The hill top mode allows for charging past 80 percent which as we all know is harder on the battery.

As to warranty - most warranties are structured so there is minimal expectation that it will go into effect. That is, Chevy does not want to be replacing batteries. That is not a measure of battery life expectation which is going to vary all over the map based on how the car is used both in terms of total miles and acceleration.

The display in the Bolt (on the left of the instrument cluster) is a range display based on the last 30 miles (Tesla will show this also) and is a fair predictor of range absent of inputting the expected terrain (Tesla can add that factor in another display). Switch in and out of regeneration and the number changes quite a bit. Big bonus for one pedal driving. So in sum I think what Chevy is advertising is close enough to truth.
 
mtcohn said:
... The hill top mode allows for charging past 80 percent which as we all know is harder on the battery....
Click to expand...

Nope. Hilltop mode stops charging at 90% of the car's programmed shutoff of charging. So, if you say normal charging is 80%, Hilltop mode will stop charging at 72%..

I tend to believe the battery will charge to and make available a full 60 kWh at the point it cuts off charging. My gut check is that good, efficient driving should yield about 4mi/kWh. 240 miles divided by 4 is about 60 kWh.

My money is that the battery has a higher capacity than 60 kWh, somewhere in the 66-72 range, and that GM has cut full charge off at 60 kWh or in the 80-90% range.
 
michael said:
We know...

Chevy has described the battery as 60 kWh
Several testers have demonstrated 60 kWh useful capacity
Chevy provides the hilltop option of 90% charging
Chevy has a worst-in-class 60% capacity guarantee

I think...

The battery is actually 60 kWh capacity, not the 20% larger or so that one typically would expect.
The way they get 238 mile range at a reasonable cost is to use the battery's full capacity
The conservative design in the Volt is NOT used
Despite the above, the battery can last a long, long time if used in an intelligent manner, not running full charge/discharge cycles.


Anyone see it the same way? Disagree? Why? Why not?

Until I have evidence to the contrary, my money's on: the battery has 60 kWh capacity, all of it usable. Use it in a careful, reasonable manner or it will degrade.

I'm still totally happy with this, I need 100 miles on a typical day. The battery is plenty large that I can run it at very low stress.

Comments???/
Click to expand...

Until I have actual facts, I'm not going to waste my time on an internet forum by guessing what might be true, since I see such activity as a total waste of my time.
 
when i was in process of picking up my Bolt yesterday, i was told that a GM engineer was in the dealership last week. The engineer told the staff that there is indeed a buffer on both the top end of charge and the bottom end of discharge. The staff were not clear on exactly how large the buffers are (one said "about 10%). I came away with the impression that setting "hilltop" mode will stop the charge somewhere in the 80% range :) sorry if this redundant information.
 
Look at the high voltage cut off voltage divided by he number of series cells and compare to any similar chemistry cell spec sheet to see about how high they are taking the charge.
 

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