Hi Sean:

The type of question you are asking can best be answered by the battery 
manufacturer or the data sheet for the specific battery in question.

Lead Acid type batteries are usually specified based on a 20 hour discharge 
providing some number of amp hours.  The is called the  1 C rate.  At first you 
would expect that if you discharged at the 2 C rate the battery would last 10 
hours, but the capacity decreases at higher currents and increases at lower 
currents.  You need the spec sheet to find this type of thing.

A trickier question is how far should you discharge the battery.  It's a fact 
that you get more charge discharge cycles if you only partially discharge.  Say 
you discharge to only 50% and you get twice the number of cycles until the 
battery is shot.  But if you discharge to 100% of the capacity you're getting 
the same watt hours out of the battery, but at 100% discharge that battery 
looks twice as big as when using 50%.

There are losses (internal resistance and external wiring, etc.) that lower the 
efficiency both during charge and discharge.

The best book is probably "Handbook of Batteries" which goes into a lot of 
details for a number of chemistries.  But it does not address things like 
"Burp" charging which I think really works (at least on Ni-MH where I've used 
it).  I think this relates to books generally not covering topics that are the 
subject of patents.  More on "Burp" charging at:
http://www.prc68.com/I/BatChg.shtml#Burp

-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com

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