->         Go to eBay and look for "Prismatic" type of cells. They are
->         NiCads and not too many suppliers will stock them. Most of all
->         laptop cells are of this type. Some suppliers will make up a
->         pack for you when you tell them the unit that it will power.
->         about 50% of the original cost.

 I perfer LI-ion type of cells because of their higher Power Density.
Of course you pay a premimum price.            
The batteries in my Gateway LI-ion battery pack are 4800 mAh Sanyo
cells.
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