[Oeva-list] Lithium Ion Batteries

Kevin Fairham-Wheeler Kevin.Fairham-Wheeler at pgn.com
Fri Dec 9 12:47:01 PST 2011


Gary, 

Thanks for your measured response, words of caution and the benefit of your experience. As a newbie to the OEVA I really value the information that others can offer to make this new adventure safe & fun for me. I had talked to a few other members to see if there were educational offerings from the club that could help newbies like myself better understand terms and systems. 

I've been told that previously the club offered EV 101 breakout sessions in the regular meetings  to try to bring the newcomers up to speed on the technology. In my experience the life blood of any volunteer organization is the newcomer. I can't think that anyone would want to be a part of an organization that they could not understand. 

It is also key to reach out for new members to gain interest. A part of that could be educating the public in forums beyond EV Celebrations and monthly meetings. Even with my limited range of knowledge I've been out to an events and high school classes to give presentations on electric vehicles and my company's take on how it will affect their grid. 

It was heartening to be pelted by questions by engaged teenagers. The greatest point was to watch them all aghast that the vehicle was quiet when turned on. They were in greater shock when I backed the Leaf up and pulled it forward (the instructors moved the kids away from the back and front of the car first)and there was again very little  noise. 

I'd like to encourage our members to resurrect the old EV 101 curriculum, knock the dust off it and see if we can not only train our members, but also look at educational opportunities for the general public as well. 

Regards,

Kevin 

Kevin Fairham-Wheeler


-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On Behalf Of Gary Graunke
Sent: Friday, December 09, 2011 11:02 AM
To: oeva-list at oeva.org
Subject: Re: [Oeva-list] Lithium Ion Batteries

All,

There are many kinds of Li batteries, so it is important, especially for us amateurs, to be very selective when considering Li batteries for our conversions. Since major companies have more resources, they may mitigate some of the dangers by careful design, cooling systems, etc. However, even then in an accident is should be common sense that one should carefully dismantle damaged packs and remove the energy source from charged batteries and, more importantly, damaged cells and interconnects.

Many advanced batteries require redundant, reliable thermal management for safety reasons. These are not for amateurs, and might be wise to avoid by consumers as well.

Li cells with Cr have the highest energy density, but are subject to thermal runaway, and the electrolyte is explosive when in contact with air. 

I have been using A123 LiFePO4 cells for 4.5 years now in my Insight conversion, and again in a plug-in Prius. They are extremely safe, and require no thermal management. Initially, I had cooling and logged temperature before concluding that I did not need those systems. My cells are cylindrical, and this permits air cooling of the cells. They also have expansion room in case a cell pops as required by A123 guidelines. 

The A123 systems cells lost out to the LG Chem cells because A123 did not make prismatic (rectangular) cells to permit less pack volume, and perhaps other reasons. However, the Navistar truck uses newer prismatic A123 cells, so they may be more suitable for the Volt. 

In another case, the OSU solar racing team lost their vehicle due to a fire which may have originated in the batteries--the driver, who escaped with 2nd degree burns, reported a popping sound and quickly exited the vehicle. The OSU solar racing team in their first vehicle used A123 LiFePO cells upon my advice for their successful race from Austin to Calgary, and after the fire approached A123, who is now their battery sponsor.  

So unless you really know what you are doing (more than GM), stick with lead or LiFePO cells!
Pay attention to thermal issues and monitor pack temperatures, and design your battery boxes to mitigate battery fires or starting adjacent materials on fire when the batteries are extremely hot, such as when you have a loose connection!
I have melted plastic on lead battery cases due to an over-tightened interconnect that stripped the nut on my S10. If I had had a temperature sensor, I would have stopped in time to prevent further damage. Now I check the pack after a first short run with an infrared thermometer to verify connections are tight. Someday I'll get one that provides an image.
Even aging lead batteries may do thermal runaway when charging, so this is not an issue restricted to lead. I have also had this happen in my Insight conversion when I used old lead batteries, but no consequential damage due to good battery box thermal isolation. Best to have a system to shut off charging for hot batteries!

Generally, if you are paying attention to battery care issues, you will have a good start on the safety issues as well.

And, of course, it is best practice and worth repeating ad-nausea to isolate both plus and minus leads from the pack with appropriate contactors for an emergency disconnect, and use only DC-rated high voltage fuses, such as the Bussman FWH or Littlefuse KLKD in the pack itself to prevent plasma fires.
Keep in mind there is enough energy there to move a heavy vehicle a long distance--we don't want it to be released quickly!  

Electricity is much safer than gasoline in many ways, but has its own issues. These deserve our respect and attention.

Gary

-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On Behalf Of gfifield at onlinenw.com
Sent: Friday, December 09, 2011 7:32 AM
To: oeva-list at oeva.org
Subject: [Oeva-list] Lithium Ion Batteries

Bloomberg Businessweek article
GM Buys Batteries Less Volatile Than Volt's for Spark Model
http://www.businessweek.com/news/2011-12-09/gm-buys-batteries-less-volatile-
than-volt-s-for-spark-model.html



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