Gen 1 GM Volt Plug-In Hybrid (2011-2015)

[edatoakrun]

surfingslovak

Why would a 15.25 kW static-load discharge test be appropriate?...

I believe that is the kW used in the Constant Power Discharge Test, not the Static Capacity Test.

... That is why one cannot reconcile the 15.2 kWh capacity from the "Static Capacity Test" shown in Table 1 with the 15.53 kWh one-hour discharge rate capacity shown in Table 3. I do not trust Table 1 since it indicates a 5% capacity drop within the first 8478 miles but only a 2% drop over the next 14,836 miles. No explanation of that table is given. It is my estimation that Table 1 may have been fabricated to support the (foregone) conclusion provided in the report...

Isn't this the explanation for the Static Capacity Test?

Figure 1 shows battery voltage versus energy discharged. This graph illustrates voltage values during constant-current discharge versus cumulative energy discharged from the battery at a C/3 constant-current discharge rate at BOT and EOT.


... Static Capacity and Constant Power Discharge test procedures are based on the USABC Electric Vehicle Battery Test Procedures Manual Rev 2, January 1996, Procedures 2 and 3, respectively...

http://avt.inel.gov/pdf/EREV/battery2011volt0815.pdf" onclick="window.open(this.href);return false;

129 more pages of documentation here:

...CONSTANT CURRENT DISCHARGE TEST SERIES

Purpose:
The purpose of constant-current testing is to determine the effective capacity of a test unit using very
repeatable, standardized conditions. A series of current levels can be applied to simply characterize
the effect of discharge rate on capacity. A specific test at the 3-hour rate is included as a mandatory
core performance measurement to verify the capacity rating of all test units. These tests do not
necessarily establish the actual (maximum) capacity of the battery...

Excerpt above From p 8.

http://file.yizimg.com/381618/2012082208232052.pdf" onclick="window.open(this.href);return false;

 

[SanDust]

EV's don't have tailpipes. If it has a tailpipe, its a hybrid.

Whatever you want to call it, both the Volt and the i3 tailpipe hybrids will give you more zero emission (electric) miles than a Leaf. Except of course if you take the tailpipe off the i3, which will reduce the zero emission miles.

But hey, if it makes your day so you can feel better about the Leaf, call these things whatever you like! :lol:

 

[LeftieBiker]

Then by your judgment, the BMW i3 with Rex cannot be correctly termed an EV, or even correctly termed an Electric car with a gasoline-powered range extender. WHat is it, then? Are you going to call BMW a liar if they refer to the i3 Rex as an EV with extended range?

This is really simple to understand unless one has an agenda.

EV's don't have tailpipes. If it has a tailpipe, its a hybrid.

If it uses that tailpipe, sure. What if the Rex just sits there, unused? What if I stick a tailpipe on my Leaf? There is only one sure thing in life: there are no sure things...

 

[SanDust]

It is a very strange conclusion, given what I read in the report. They act as if the battery is only 2.2% below its rated capacity at the end of the test. By my reading, the battery is either 7%, 9% or 11% down at the end of the test. Take your pick! Should I believe Table 1, which contains a starting capacity well below the Volt batteries rated capacity and an ending capacity which is only slightly lower? Or should I believe Table 3, which contains a staring capacity closer to the rated capacity and a lower ending capacity, with the two numbers showing a more linear loss of capacity?

Interesting question. It may be that part of the battery is held in reserve for other overhead functions. That would be my guess.

However, if you owned a Volt, you'd be hoping that there was a 9% drop in the first year over 8000 miles and a 2% drop over the next 14000 miles since that would suggest that degradation was leveling off. In this case you'd predict another 1% over the next 14000 miles. I doubt that's the case but going from a 9% loss over fewer miles to a 2% over more miles would strongly indicate that the rate of capacity loss had greatly slowed.

 

[RegGuheert]

Isn't this the explanation for the Static Capacity Test?

Figure 1 shows battery voltage versus energy discharged. This graph illustrates voltage values during constant-current discharge versus cumulative energy discharged from the battery at a C/3 constant-current discharge rate at BOT and EOT.


... Static Capacity and Constant Power Discharge test procedures are based on the USABC Electric Vehicle Battery Test Procedures Manual Rev 2, January 1996, Procedures 2 and 3, respectively...

http://avt.inel.gov/pdf/EREV/battery2011volt0815.pdf" onclick="window.open(this.href);return false;

Thanks, Ed! I missed that.

So, Table 1 contains capacity data from a constant-current discharge at C/3 and Table 3 contains capacity data from a constant-power discharge at 15.25 kW, which is close to a C rate. Given that, my objections to Table 1 remain. Given the voltage characteristics of this chemistry, the load on the battery would be significantly lower for the entire test for Table 1.

Interesting question. It may be that part of the battery is held in reserve for other overhead functions. That would be my guess.

I don't think so since my interpretation is that the battery is tested outside the confines of the BMS in the car. I assume NRELs battery testers are separately powered so there should be no "overhead functions".

This is why I'm interested in this test result. It is the first one I've seen for the Volt battery that does NOT have the car wrapped around it.

However, if you owned a Volt, you'd be hoping that there was a 9% drop in the first year over 8000 miles and a 2% drop over the next 14000 miles since that would suggest that degradation was leveling off. In this case you'd predict another 1% over the next 14000 miles. I doubt that's the case but going from a 9% loss over fewer miles to a 2% over more miles would strongly indicate that the rate of capacity loss had greatly slowed.

Agreed that is another interpretation. As you say, that is not overly credible.

 

[SanDust]

I assume NRELs battery testers are separately powered so there should be no "overhead functions".

This is why I'm interested in this test result. It is the first one I've seen for the Volt battery that does NOT have the car wrapped around it.

Perhaps the question is whether there is a "charged" battery that does not have a car wrapped around it. If they charged the battery in situ then the battery wouldn't charge to 100% SOC. I'm thinking that they're still using the car charger since not using it raises many issues.

 

[scottf200]

It may be that part of the battery is held in reserve for other overhead functions. That would be my guess.

I was at a local EV club meeting on a while ago and there was a very interesting presentation by a Chicago company's CEO related to "Advancements in Li-ion Battery Safety and Thermal Management". He claimed to have some early design discussions with GM/LGChem as I recall. It mentioned the Volt in a few places. Some of the knowledge/estimates were pretty interesting. In particular some of that 16kWh-10.4kWh left over is used for the overhead/TMS.

Title: Advancements in Li-ion Battery Safety and Thermal Management
Presentation: https://docs.google.com/open?id=0B5lA7Kfp45ULUUFHank2QjNzQXM
Said Al-Hallaj - AllCell Technologies LLC 2321 W. 41st Street Chicago, IL 60609
http://www.allcelltech.com/

Chevy Volt BTMS – **best estimates**
Capacity: 16 kWh (10.5-12.0 kWh usable)
Cells: 288 – 15Ah LG Chem Li-Mn polymer cells
Range: 25-50 mi AER before CS mode
Thermal load: 824 kJ in EV mode (1C-rate equivalent heat gen); 300 W continuous in CS mode
Cooling components
• 144 aluminum plates, 6.5 kg, 1 mm thick
• 12L liquid in system, 12 kg
• 10 lpm pump, 150W consumption,1.5 kg
• Compressor, 350W consumption, 2 kg
• Tubes
• Radiator
• Debris filter
Mass: 197 kg [435 lbs]
Power consumption: 500 W

Gen 1 Chevy Volt uses 16 kWh battery to achieve 25-50 mi AER
~11 kWh go to vehicle propulsion
+3.5 kWh oversize to limit SOC window and heat generation
+1.5 kWh oversize for thermal management power requirements
=16 kWh

Pack Level
-- Active Cooling
---- Liquid Cooling (refrigerant)
---- Air Cooling
-- Passive Cooling
---- Phase Change Material (PCM)

Presenters info/bio:

Said Al-Hallaj, Co-Founder, Chairman/CEO

Said Al-Hallaj is the co-inventor of AllCell’s PCM technology and a world-renowned expert in thermal management of lithium-ion batteries. He possesses 20 years of experience in renewable energy research and development (with a focus on thermal management and electrochemical engineering of lithium-ion batteries) and is an adjunct professor at the Department of Chemical Engineering at the University of Illinois at Chicago (UIC).

Said’s research ranges from the design and optimization of renewable energy systems to the use of advanced battery and fuel cell systems in electric vehicles and has been published 32 times in peer reviewed journals. Additionally, he has been a featured speaker at over 25 alternative energy and battery conferences and has three registered patents.

Said holds a Ph.D. in chemical engineering from the Illinois Institute of Technology and an M.Sc. and B.Sc. in chemical engineering from the Jordan University of Science and Technology.

 

[edatoakrun]

It is a very strange conclusion, given what I read in the report. They act as if the battery is only 2.2% below its rated capacity at the end of the test. By my reading, the battery is either 7%, 9% or 11% down at the end of the test. Take your pick! Should I believe Table 1, which contains a starting capacity well below the Volt batteries rated capacity and an ending capacity which is only slightly lower? Or should I believe Table 3, which contains a staring capacity closer to the rated capacity and a lower ending capacity, with the two numbers showing a more linear loss of capacity?

Interesting question. It may be that part of the battery is held in reserve for other overhead functions. That would be my guess.

However, if you owned a Volt, you'd be hoping that there was a 9% drop in the first year over 8000 miles and a 2% drop over the next 14000 miles since that would suggest that degradation was leveling off. In this case you'd predict another 1% over the next 14000 miles. I doubt that's the case but going from a 9% loss over fewer miles to a 2% over more miles would strongly indicate that the rate of capacity loss had greatly slowed.

="RegGuheert"...So, Table 1 contains capacity data from a constant-current discharge at C/3 and Table 3 contains capacity data from a constant-power discharge at 15.25 kW, which is close to a C rate. Given that, my objections to Table 1 remain. Given the voltage characteristics of this chemistry, the load on the battery would be significantly lower for the entire test for Table 1...

To review:

IMO, the large loss of capacity in Table three is largely reflecting an increase in resistance resulting in a decrease in usable DC kWh out of the battery after ~18 months and ~8k miles (add 12 months to Volt age I stated in my earlier posts, my error) when tested at a ~ C/1 discharge rate.

RegGuheert, if I understand you correctly, you still see a conflict between table 3 BOT results of 15.57 kWh (at ~C3) and the 15.2 BOT from the static (~C/1) test on table one, since resistance would be expected to have been higher at the higher discharge rate, resulting in lower, not higher kWh out of the battery pack ?

Yes, that does look odd to me also.

But I haven't actually read the hundreds (?) of pages of test documentation to see if there is another explanation, beyond just lack of accuracy in one or both of the discharge capacity tests.

Table one shows The Volt was at ~5% below "new spec" in kWh 15.2/16.0 kWh, and ~9% lower 14.9/16.0 kWh after another ~8 months and ~15,000 miles, when tested at a ~C/3 discharge rate, right?

But I don't think that this necessarily means the Volt battery was either ~5%, or ~9%% "degraded" from "new" in the two tests.

Couldn't the initial ~5% shortfall in the first test be partially or entirely due to alternate explanations, such as that the Volt Battery not being to spec when "new", or that the battery was charged and tested at lower temperatures by the DOE, than GM used (do we even know if GM used a discharge test, and if so, at what kW?) to set the 16kWh capacity spec?

Of course, for the LEAF, which uses passive thermal management for the battery pack, the variations in battery capacity due to variations in battery temperatures would be expected be much larger, as all the LEAF battery capacity tests now seem in fact to be showing.

Which, IMO, is one of the principle reasons why it is erroneous to state that the 2011 LEAF always has a "new" available battery capacity of ~21 kWh.

 

[Stewy13]

EV's don't have tailpipes. If it has a tailpipe, its a hybrid.

Whatever you want to call it, both the Volt and the i3 tailpipe hybrids will give you more zero emission (electric) miles than a Leaf. Except of course if you take the tailpipe off the i3, which will reduce the zero emission miles.

Care to explain?
You can do 40-80km/charge in a Volt and you can do 100-160km/charge in a LEAF.
Your math doesn't add up as they say.

 

[SanDust]

+1.5 kWh oversize for thermal management power requirements

That's more than we're looking for though. Maybe it's as suggested just different measurements. This isn't like reading a ran gauge. Early on here one of the Nissan folks made an off-hand remark about the battery having more energy than 24 kWh. I think he just meant that the actual capacity could be a bit higher than the rated capacity, but folks here got all excited and started claiming the battery capacity was more like 28 kWh.

I'm very puzzled about the mileage and the gas and kWh used. Seems like 441 gallons of gas and 1000 kWh would get you a lot more than 14,000 miles.

 

[scottf200]

EV's don't have tailpipes. If it has a tailpipe, its a hybrid.

Whatever you want to call it, both the Volt and the i3 tailpipe hybrids will give you more zero emission (electric) miles than a Leaf. Except of course if you take the tailpipe off the i3, which will reduce the zero emission miles.

Care to explain?
You can do 40-80km/charge in a Volt and you can do 100-160km/charge in a LEAF.
Your math doesn't add up as they say.

Perhaps it is this reasoning discussed at length in the past.
"100 mile" BEV owners drive their ICE when they need to go farther or are are worried about bumping up against there range if it is close.

Also this thread: Volt Vs. Leaf practical range comparison
http://www.mynissanleaf.com/viewtopic.php?f=10&t=9576#p217161" onclick="window.open(this.href);return false;

 

[blackmamba]

EV's don't have tailpipes. If it has a tailpipe, its a hybrid.

Whatever you want to call it, both the Volt and the i3 tailpipe hybrids will give you more zero emission (electric) miles than a Leaf. Except of course if you take the tailpipe off the i3, which will reduce the zero emission miles.

Care to explain?
You can do 40-80km/charge in a Volt and you can do 100-160km/charge in a LEAF.
Your math doesn't add up as they say.

Maybe he mistyped, and meant to put an 's' at the beginning of 'miles'. :mrgreen:

 

[SanDust]

Care to explain?
You can do 40-80km/charge in a Volt and you can do 100-160km/charge in a LEAF.
Your math doesn't add up as they say.

If you're smart enough to do the math then it does add up. The Volt is the simplest case. To simplify, all the data available indicates drivers go less than 40 or more than a 100 miles a day. If you go 40 miles or less there is no difference in the zero emission miles from both cars. Over 40 miles you get X - 40 more miles on the Leaf, where X is some number between 40 and 70. Over 70 miles you get 0 zero emission miles for the Leaf since you're not taking it and 40 for the Volt. The empirical numbers from the drive cycle and very basic math say you get more zero emission miles for the Volt on days when you leave the Leaf at home and go over 70 miles (more like 100) than you get zero emission miles for the Leaf on the X-40 mile days. Your fallacy is just looking at the range numbers without considering the drive cycle. (You can't use opportunity charging to change the result because the Volt can opportunity as well as the Leaf. In fact we know empirically that Volt owners opportunity charger more often than Leaf owners, meaning if anything the X-40 days overstate how competitive the Leaf is in the zero emission mile race.)

The i3 shows a different reason why in practice vehicles with range extenders will get more zero emission miles than the raw numbers indicate. With a range extender you can go until the battery runs out and then beyond. Without a range extender drivers leave a buffer since they don't like the prospect of being stranded. This is why I've pointed out that the i3 with the range extender, which has only 80% of the electric range of the i3 without, has the same practical EV range as the i3 without the range extender.

 

[evnow]

To simplify, all the data available indicates drivers go less than 40 or more than a 100 miles a day.

What utter BS. Just look at the transportation suvery ...

 

[qwk]

Then by your judgment, the BMW i3 with Rex cannot be correctly termed an EV, or even correctly termed an Electric car with a gasoline-powered range extender. WHat is it, then? Are you going to call BMW a liar if they refer to the i3 Rex as an EV with extended range?

This is really simple to understand unless one has an agenda.

EV's don't have tailpipes. If it has a tailpipe, its a hybrid.

If it uses that tailpipe, sure. What if the Rex just sits there, unused? What if I stick a tailpipe on my Leaf? There is only one sure thing in life: there are no sure things...

If the rex sits there unused, then you bought the wrong vehicle.

 

[jackal]

[The i3 shows a different reason why in practice vehicles with range extenders will get more zero emission miles than the raw numbers indicate. With a range extender you can go until the battery runs out and then beyond. Without a range extender drivers leave a buffer since they don't like the prospect of being stranded. This is why I've pointed out that the i3 with the range extender, which has only 80% of the electric range of the i3 without, has the same practical EV range as the i3 without the range extender.

I think the reasoning is still flawed. The assertion for 'those days of >100' makes it sounds like it is as much as 'days < 100 miles'. Fact is people who bought leaf already knows the 100 miles limitation and thus likely deemed 95% of their of commute is less than that. If so, using your zero emission rationale, for 'those' 5% days, their zero emission will be 40 miles less. If we make an assumption of a 50 mile commute, over all, the zero emission numbers should overwhelm the Volt by a net of 150 miles for the other 95% days.

 

[qwk]

Care to explain?
You can do 40-80km/charge in a Volt and you can do 100-160km/charge in a LEAF.
Your math doesn't add up as they say.

If you're smart enough to do the math then it does add up. The Volt is the simplest case. To simplify, all the data available indicates drivers go less than 40 or more than a 100 miles a day. If you go 40 miles or less there is no difference in the zero emission miles from both cars. Over 40 miles you get X - 40 more miles on the Leaf, where X is some number between 40 and 70. Over 70 miles you get 0 zero emission miles for the Leaf since you're not taking it and 40 for the Volt. The empirical numbers from the drive cycle and very basic math say you get more zero emission miles for the Volt on days when you leave the Leaf at home and go over 70 miles (more like 100) than you get zero emission miles for the Leaf on the X-40 mile days. Your fallacy is just looking at the range numbers without considering the drive cycle. (You can't use opportunity charging to change the result because the Volt can opportunity as well as the Leaf. In fact we know empirically that Volt owners opportunity charger more often than Leaf owners, meaning if anything the X-40 days overstate how competitive the Leaf is in the zero emission mile race.)

The i3 shows a different reason why in practice vehicles with range extenders will get more zero emission miles than the raw numbers indicate. With a range extender you can go until the battery runs out and then beyond. Without a range extender drivers leave a buffer since they don't like the prospect of being stranded. This is why I've pointed out that the i3 with the range extender, which has only 80% of the electric range of the i3 without, has the same practical EV range as the i3 without the range extender.

Generalizing isn't smart at all. I drive about 30 miles 3 times a week, and over 120 miles the rest of the time. The Volt would make absolutely no sense in my case. Here is the kicker, I have burned exactly 0 gallons of gas driving even more than that since March. I could have done it in a Leaf, but it would have been a great inconvenience. That's why a car with over 200 miles of range has such great VALUE. Sure it's more expensive in the beggining, but over time, you get much closer to the cost of an ice; no other vehicle needed.

 

[SanDust]

What utter BS. Just look at the transportation suvery ...

Serioiusly? You don't think 20% is a bigger number than 12%? The data says 17% of daily driving days involve more than 100 miles and 2.9% of the days involve driving more than 75 miles. Compare that to 6.6% of the days that involve driving 50-75 miles and 13.8% that involve driving 30-50 miles. Note that the Leaf won't really go 75 miles, mine can't reliably go 55 miles, and, while I've split the daily driving of between 30 miles and 50 miles more or less evenly 30-40 miles and 40-50 miles, the reality is that 30-40 miles is probably two thirds of the miles. With those two adjustments the the split is more like 20% vs. 10%, at best.

Given that the Volt's advantage on those 20% of days is 40 miles and that the Leaf's advantage on those 10% of the days is, ON AVERAGE, a mere 12.5 miles, and it should be obvious that this is not a close call. If you think otherwise why don't you explain how you get a different number rather than just BSing. Here's the data. You don't even need to stress about finding it: http://www.fhwa.dot.gov/policyinformation/pubs/hf/pl10023/fig4_5.cfm" onclick="window.open(this.href);return false;

 

[SanDust]

Generalizing isn't smart at all. I drive about 30 miles 3 times a week, and over 120 miles the rest of the time. The Volt would make absolutely no sense in my case. Here is the kicker, I have burned exactly 0 gallons of gas driving even more than that since March. I could have done it in a Leaf, but it would have been a great inconvenience. That's why a car with over 200 miles of range has such great VALUE. Sure it's more expensive in the beggining, but over time, you get much closer to the cost of an ice; no other vehicle needed.

Actually the fallacy lies in failing to use the average. Anyone can come up with a scenario where any car works better than another. It's easy to "prove" that a PIP will use less gas than a Volt or a Leaf if you get to pick the numbers. The question at the moment, and the only relevant question really, is whether the average driver could get more zero emission miles from a Volt or a Leaf. That answer is very straightforward. They'd get more zero emission miles from a Volt.

If you think that spending $100K on an additional car is an answer to anything -- much less the nutty claim that this has "VALUE" in any economic sense -- then there isn't much to say other than religious people will believe what they want to believe.

 

[SanDust]

Couldn't the initial ~5% shortfall in the first test be partially or entirely due to alternate explanations, such as that the Volt Battery not being to spec when "new", or that the battery was charged and tested at lower temperatures by the DOE, than GM used (do we even know if GM used a discharge test, and if so, at what kW?) to set the 16kWh capacity spec?

I doubt they'd use a discharge rate of 3C. Probably 1C.