Re: [Phys-l] lithium batteries

["John SOHL" <JSOHL@weber.edu>]

I've been doing a lot of research on batteries and battery charging for a camping tent light product that I've developed called the "firefly" (patent pending). Charging and discharging batteries is a remarkably complex process. All chemistry is temperature dependent and battery behavior involves a lot of chemistry and physics. Here is an inside tip. If you charge your Li ion batteries in the garage or other cold (or particularly hot) environment, you might want to change that. Unless you know for a fact that your charger was designed for charging cold batteries, you should charge your batteries at room temperature. (An option that I don't have with a camping product. Thus, I've had to build in ambient thermal sensors and battery thermal sensors as part of my charging circuits.) 
 
One of the best web sites that I've found with general information at a level that is a fast and easy read is the Battery University. The page of interest for the discussion on battery storage and lifetime is:
http://batteryuniversity.com/parttwo-34.htm 
 
Note, battery composition is not a fixed thing. Different manufacturers use different balances and elements from each other. Thus, it might well be true that a particular battery is best stored dead, but everything I've been reading says you should store your Li ion batteries somewhere between 40% and 100% charged depending on how often you use the battery. 
 
John
 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
John E. Sohl, Ph.D.
Professor of Physics
Weber State University
2508 University Circle
Ogden, UT 84408-2508

voice: (801) 626-7907, fax: (801) 626-7445 
e-mail: jsohl@weber.edu 
web: http://physics.weber.edu/sohl/ 

> > > Jeff Radtke <jr@cloudchambers.com> 1/8/2008 8:55 PM >>>
According to these people, lithium-ion batteries are best stored at  
40% charge:
http://www.batteryuniversity.com/partone-19.htm 

The newer A123 lithium nanophosphate batteries are best stored at  
higher levels of charge, about 95%.
http://www.rcuniverse.com/forum/m_5048617/tm.htm 

The A123 cells are fantastic: best cycle life with highest discharge  
and charge currents.  I built a cyclemotor that uses them:
http://www.neodymics.com/drivetrain.htm 

-- 
Jeff Radtke
jr@cloudchambers.com 
www.cloudchambers.com 

Who stores all of his alkaline and zinc/carbon batteries on the fridge  
shelf, where they last at least twice as long.  See Fig 14.2.E in  
Horowitz and Hill's "The Art of Electronics."


Quoting Bernard Cleyet <bernardcleyet@razzolink.com>:

> New to me.  I'll query the PHYS-L crew
>
> T.K.Wang & Mary Brooks wrote:
>
> > According to the Canon instruction book, a lithium battery wears
> > itself out by being charged.  they recommend DISCHARGING a battery and
> > then storing it (when for a long time) and charging it the day of use.
> > Just the opposite of Nicads.
> > T.K.
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