GM Announces Enhancements to Chevrolet Volt

[SanDust]

How significant, is conjecture, not fact.

Nissan also could have extended battery (undoubtedly much more significantly, for the vast majority of LEAF owners/leasers) by life by limiting available battery capacity, as did GM.

Nissan couldn't limit the percentage of the battery used since it would have resulted in too little range. The Leaf's range is 73 miles. If you used 60% rather than 80% of the available 24 kWh you would have a range of 55 miles, and an EV with a range of 55 miles is simply not marketable. Why do you think Nissan overhyped the range as being "100 miles".

Nissan's recommendation to use the "long life" mode and only charge the battery to 80% of the 80% used does in fact limit the percentage of the battery used to almost exactly the same percentage as GM does in the Volt. I suspect this is not a co-incidence.

FYI the fact that temperature affects battery life is fact. Tons of research proves this. Raising the discharge temperature from 25C to 45C more than doubles the capacity loss.

 

[palmermd]

FYI the fact that temperature affects battery life is fact. Tons of research proves this. Raising the discharge temperature from 25C to 45C more than doubles the capacity loss.

Please, when making statements like this, cite a reference. It is a pet peeve of mine that people say there is lots of research behind their statements, and then don't cite any references. I agree with you on general grounds, but i'd like to see some reference to Lithium Manganese based cells which the Leaf uses (with or without the cobalt and nickel and other enhancing ingredients). I'm not picking on you, but there are lots of times people cite these things and are either not talking about Lithium batteries at all, or they are referring to another lithium chemistry (LiFePO4 for example) which may or may not apply. References help to answer these questions and support your argument.

Sorry for the rant...carry on with the conversation.

Glad to see the Volt battery crash story is nearing a conclusion. Seems like a simple solution which is always good.

 

[linkim]

FYI the fact that temperature affects battery life is fact. Tons of research proves this. Raising the discharge temperature from 25C to 45C more than doubles the capacity loss.

Please, when making statements like this, cite a reference. It is a pet peeve of mine that people say there is lots of research behind their statements, and then don't cite any references. I agree with you on general grounds, but i'd like to see some reference to Lithium Manganese based cells which the Leaf uses (with or without the cobalt and nickel and other enhancing ingredients). I'm not picking on you, but there are lots of times people cite these things and are either not talking about Lithium batteries at all, or they are referring to another lithium chemistry (LiFePO4 for example) which may or may not apply. References help to answer these questions and support your argument.

Sorry for the rant...carry on with the conversation.

Glad to see the Volt battery crash story is nearing a conclusion. Seems like a simple solution which is always good.

I think the MNL forum is very useful for finding information on the LEAF and Li-ion batteries, but it is not a place where the discussion is comparable to a scientific paper where references are cited. Much of the discussion may be based on information gleaned from the internet, news articles, etc., but not from scientific/engineering studies. A big problem is retrieving the reference even if one had read it, because most of us are not very organized. I personally experienced this situation during my career in research.

Well back to the point, and not wanting to be too judgmental, there is a discussion of the effects of temperature on battery life in Wikipedia - Lithium-ion battery. Not specific to a battery chemistry but chemical reactions that lead to cell degradation generally follow similar rate equations (with temp. as a variable). The result is degradation rates that vary with battery chemistry, but at different rates.

There are scientific papers that reported on the effect of temperature on the dissolution of the LiMnO spinel, but it would take me some time to find them since I stopped working in the field.

 

[evnow]

I think the MNL forum is very useful for finding information on the LEAF and Li-ion batteries, but it is not a place where the discussion is comparable to a scientific paper where references are cited.

I don't think so. When challenged the person should be willing to provide references.

I spend a lot of time searching for references and posting them when people challenge me.

 

[surfingslovak]

FYI the fact that temperature affects battery life is fact. Tons of research proves this. Raising the discharge temperature from 25C to 45C more than doubles the capacity loss.

Please, when making statements like this, cite a reference...

There are scientific papers that reported on the effect of temperature on the dissolution of the LiMnO spinel, but it would take me some time to find them since I stopped working in the field.

Incidentally, I remember posting something on this topic a few months ago. Here is it again. It's from a report on LiMn2O4 cells from Park, et al (University of Michigan).

 

[linkim]

Incidentally, I remember posting something on this topic a few months ago. Here is it again. It's from a report on LiMn2O4 cells from Park, et al (University of Michigan).

Thanks George for the reference and paper. I have visited Prof. Sastry's lab on several occasions in the late 1990s. She is a very talented engineer with extensive experience in mathematical modeling, and has established a a great reputation in the battery field. She is the founder of Sakti3, another in the long list of battery startups, receiving funding from a Sandhill Road VC with an emphasis on cleantech.

 

[Herm]

That first graph shows accelerated degradation with higher temperatures, one big thing that we worry about the Leaf.. what I would like to see is relative capacity per temperature going down to below zero.

 

[GRA]

That first graph shows accelerated degradation with higher temperatures, one big thing that we worry about the Leaf.. what I would like to see is relative capacity per temperature going down to below zero.

I too would like to see some curves on LiMn2O4 capacity loss at low battery temps, but the discussion was about why battery pack thermal management was important for pack longevity in high pack temp conditions, and this chart directly answers _that_ question. It will be interesting to see what level of degradation Leaf owners in places like Texas and Arizona experience over the next couple of years versus those in more temperate conditions, and compare them to Focus or other BEV owners with the same or different chemistries in the same areas.

If anyone has it, I'd like to see info on how Coda arrived at their claim of only 7% loss to pack capacity after 100,000 miles for their LiFePO4 chemistry. Anyone know what the conditions were, who did the testing, etc.?

Edit

Found this, although SciVerse is down for upgrades today so couldn't read the full article:

http://www.mendeley.com/research/cycling-degradation-automotive-lifepo4-lithiumion-battery-1/" onclick="window.open(this.href);return false;

Guy

 

[surfingslovak]

Thanks George for the reference and paper. I have visited Prof. Sastry's lab on several occasions in the late 1990s. She is a very talented engineer with extensive experience in mathematical modeling, and has established a a great reputation in the battery field. She is the founder of Sakti3, another in the long list of battery startups, receiving funding from a Sandhill Road VC with an emphasis on cleantech.

How fascinating, thank you for mentioning this, Kim. Both Sakti3 and Prof. Sastry's work is well publicized, and I referenced an article from last summer below. It features a video interview.

http://www.technologyreview.com/energy/37199/" onclick="window.open(this.href);return false;


Click to enlarge

That first graph shows accelerated degradation with higher temperatures, one big thing that we worry about the Leaf.. what I would like to see is relative capacity per temperature going down to below zero.

Herm, here is graph from an older NREL study (page 6), which I mentioned in a different thread last year. It's for Saft's 10-year old cells, and although I found the data sheet, the chemistry is not specifically called out. I believe that this implies lithium cobalt.

What's also interesting is that the nominal capacity of 6 Ah was achieved at 0 C. If I'm reading the graph correctly, the relative battery capacity was 15% higher at 25 C. For for what it's worth, I observed about 10% range reduction in the Leaf compared to the summer. I don't really use any auxiliaries, and the ambient temps are usually around 50 F, although they can drop close to or slightly below freezing at night.


Click to enlarge

 

[edatoakrun]

For those interested in Volt battery active thermal management, GM definitely has put a lot of effort into it, and it also seems to be a quite a complicated and lengthy topic of conversation:

From Friday's chat with GM engineer Larry Laws, I learned:
- the Volt starts heating its batteries at 32 deg F (0 deg C) (it used to be 25F, at least that's what we thought)
- the battery is designed to start the car at temperatures as low as -22 deg F (-30 deg C) (used to be -13F?)
- they try to keep the battery temps between 32F and 90F (used to be 25F - 72F?)

Otherwise the chat confirmed what I already have documented in the post in this thread and linked from the FAQ.

Once we get more data I'll post an update to that table here.

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band/page17" onclick="window.open(this.href);return false;

Some more of the management parameters are posted here, including:

...At extreme high temps, the ICE may come on to generate power for the TMS to work faster...

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band&p=48601#post48601" onclick="window.open(this.href);return false;

 

[DrInnovation]

For those interested in Volt battery active thermal management, GM definitely has put a lot of effort into it, and it also seems to be a quite a complicated and lengthy topic of conversation:

From Friday's chat with GM engineer Larry Laws, I learned:
- the Volt starts heating its batteries at 32 deg F (0 deg C) (it used to be 25F, at least that's what we thought)
- the battery is designed to start the car at temperatures as low as -22 deg F (-30 deg C) (used to be -13F?)
- they try to keep the battery temps between 32F and 90F (used to be 25F - 72F?)
..

Is there a place where the aforementioned chat what Larry Laws is logged? I've read the web-chat logs from friday and did not see that. Though I know there was also an internal web-chat at GM going on at the same time?


Edit: bit of searching and I found my own answer
http://www.chevroletvoltage.com/index.php/volt-blog/18-volt/2560-winter-driving-efficiency-tips-for-the-chevrolet-volt.html" onclick="window.open(this.href);return false;

(Note its from earlier in DEC.).

 

[GRA]

For those interested in Volt battery active thermal management, GM definitely has put a lot of effort into it, and it also seems to be a quite a complicated and lengthy topic of conversation:

From Friday's chat with GM engineer Larry Laws, I learned:
- the Volt starts heating its batteries at 32 deg F (0 deg C) (it used to be 25F, at least that's what we thought)
- the battery is designed to start the car at temperatures as low as -22 deg F (-30 deg C) (used to be -13F?)
- they try to keep the battery temps between 32F and 90F (used to be 25F - 72F?)

Otherwise the chat confirmed what I already have documented in the post in this thread and linked from the FAQ.

Once we get more data I'll post an update to that table here.

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band/page17" onclick="window.open(this.href);return false;

Some more of the management parameters are posted here, including:

...At extreme high temps, the ICE may come on to generate power for the TMS to work faster...

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band&p=48601#post48601" onclick="window.open(this.href);return false;

Thanks for that info.

Guy

 

[SanDust]

Please, when making statements like this, cite a reference.

Among others, Masanori Kitamura, GS Yuasa Corporation AABC 2008. Presenting data from Lithium Energy Japan.

Happy? Probably not. But I believe you can order the proceedings and check it out. While I appreciate that citations to online information is useful, keep in mind that this is not basic science, that a lot of battery work is done by private companies, and that even when these private companies present material at conferences and so forth they strictly prohibit republication.

 

[cwerdna]

http://finance.yahoo.com/news/government-closes-volt-probe-says-car-safe-224312565.html" onclick="window.open(this.href);return false;

 

[scottf200]

http://finance.yahoo.com/news/government-closes-volt-probe-says-car-safe-224312565.html

Here is the one from their actual site:
NHTSA Statement on Conclusion of Chevy Volt Investigation
FOR IMMEDIATE RELEASE
January 20, 2012
http://www.nhtsa.gov/About+NHTSA/Press+Releases/2012/NHTSA+Statement+on+Conclusion+of+Chevy+Volt+Investigation" onclick="window.open(this.href);return false;