Clean Republic has a new 36 volt battery

Can be used with existing Hill Topper kits! They described the chemistry as NCR.

"...Horizon Battery uses a similar type of cell, the NCR (Nickle Cobalt Rechargeable)."

Could be one of the following:

Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2)

Lithium nickel cobalt aluminum oxide battery, or NCA, has been around since 1999 for special applications. It shares similarities with NMC by offering high specific energy, reasonably good specific power and a long life span. Less flattering are safety and cost....

NCR Li-Ion batteries are a new standard in the Lithium ion world. This chemistry of these batteries are LiNiCoAlO2. They are referred to as "NNP" batteries.