There are many different formulations of lithium batteries, most familiar probably are the ones used in laptop computers. These formulations try to achieve high energy density so the manufacturer can claim greater battery life per charge. Problem is, their capacity is reduced with age whether you use them or not. At 3 years of age or so one may need to buy a new battery even if the original saw few or no discharge cycles. Too, typical lithium batteries are subject to explosion hazard in the rare case that a cell is shorted or a charger runs amok. Lithium-iron-phosphate formulations show much more resistance to decline in cell capacity with age or discharge cycles, and they are not subject to explosion. This technology was, and still may be, sought by Toyota to displace their NiMH batteries in their hybrid vehicles. My understanding is the manufacturing capacity for the new cells, and therefore cost-effective availability, was a sticking point for Toyota. Out only a few years with the technology, I chose to roll the dice that Dewalt made the right choice. Brand new, their lithium cells don't quite measure up to the competition, something like 2.3 Ah instead of around 3.0 Ah in the competition's cells. After a year or two of use the Dewalt cells will likely trounce the competition's batteries of the same age. Time will tell, but my oldest cells are now around 3 years old and I don't notice any difference between them and my newest cells only 6 months old. In the meantime, Dewalt's tools are still pretty darn good and bare tools are readily available once an adequate stockpile of batteries is achieved.
I'm surprised Dewalt doesn't brag up their batteries more, but I'm just a silly farmer from Iowa.
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