Battery degradation

[Phximiev]

As a follow-on to my previous post, I am still interested in the exact Mfgr and type of battery used in our iMiev packs as well as whether they have been tested as set out in the article and video. Hence, my question to Ben, as he seems to be the only person who has actually seen the "prismatic" cell of the iMiev.

Also, for those with their manuals out, referring to page 1-10, instructions are set forth there for in driving in intense heat. Perhaps for most of you, the ambient temperature will rarely or never exceed 104 degrees. Here in Phoenix, however, it is routine in the summer. My wife and I will see in the near future if anything described in the manual occurs. As far as charging, we charge in the garage where it is significantly cooler than outdoors. But this changes during the summer also and the ambient temperature regularly exceeds 104 degrees during the summer and well into the evening in the garage. And sometimes, it exceeds 113 degrees.

So perhaps an evap cooler for the garage.

 

[siai47]

If you look at some of my older posts you will find some more information on the battery in the I-MiEV. They are GS Yusa LEV-50 cells assembled into 10 eight cell modules and 2 four cell modules in the battery pack. The cells are unique to Mitsubishi as they were developed by a joint venture with GS Yusa. They are similar to the design of the 75 amp hour cells that were used in the Boeing Dreamliner packs that caught fire. Our cells have two 25 amp hour windings and the Boeing cells have three. Poor quality control and manufacturing processes were blamed as the cause of the fires in the cells and I think that it might have had an effect on the production (and recall) of some Mitsubishi vehicles overseas and the delay in the introduction of the PHEV Outlander in the US. That being said, I would assume the problems have been corrected and really don't concern our I-MiEV's. You will find discussions about battery temperature control and be assured, the I-MiEV does not have a active battery "cooling" system and will suffer the same fate as the LEAF in high temperatures. The cells in our vehicles are happiest at about 77 degrees. Any lower reduces range, any higher speeds up the degradation of the battery pack. Summer temps in Phoenix will get you if you don't have a cool place to store and charge the vehicle. The pack has a lot of mass and takes a long to time heat up and an equally long time to cool. In Florida summers (which aren't anywhere near as severe as Phoenix) I store my vehicle in a air-conditioned garage with the temperature maintained at 75 degrees. There is information on how to cool the pack with a simple modification found on other threads and would stress that you make the change if you are operating in hot climates.

 

[Phximiev]

Hey, thanks for the info. Also, where are the posts re the change to promote the cooling of the batter?

 

[Phximiev]

Ok, I did a quick internet check for the LEV 50 battery and could not find the design chemistry for the battery. So is it a lithium manganese design or something else? The Leaf apparently is a lithium manganese design and does appear to have battery issues during the summer.

Inquiring minds would like to know.

 

[Phximiev]

Ok, sorry to be answering my own questions, but the following appears to help, see the link:

http://atip.org/atip-publications/atip-news/2009/7804-gs-yuasas-commercial-lithium-ion-battery-for-ev.html

The link describes: (a) two different temperature testing scenarios, and (b) that the battery is lithium manganese oxide with an improvement to the cathode to prevent degradation.

It does make me wonder if the Battery University has tested this battery. I think I will ask them.

It does reinforce the notion that higher temperatures will affect battery life cycle.

Hope this is of interest.

 

[PV1]

Hey, thanks for the info. Also, where are the posts re the change to promote the cooling of the batter?

http://myimiev.com/forum/viewtopic.php?f=23&t=2324

On Page 2, I posted a picture of the servo. There are two screws that hold it in place. Unless you plan on quick charging, you should be able to unplug the servo as well (I always leave it plugged in when I manually flip the damper, which has only been twice the entire time I've had the car). The velcro holding the two small wires on the left support bracket won't be there. That's something I added to my car (LED footwell lighting).

Remember to direct the air to the floor to push cool air into the pack.