Are the Prius batteries made with conventional lead plates and sulfuric acid with multiple cells rated at about 2 volts per cell?

Which model Prius? NHW10, NHW11, or NHW20?

Which battery? The 12v accessory battery is a standard conventional lead-acid battery, but it is an AGM about the size of a motorcycle battery. It is only used to power the computers and run the accessories (radio, clock, fans, etc.). Once the computers are on, they flip a relay which connects up the hybrid traction battery. The hybrid traction battery is what starts the gasoline engine through one of the electric motor-generators, and also provides power for electric propulsion.

The hybrid traction battery is NiMH (nickel-metal hydride), NOT lead-acid. They are built by Panasonic EV Energy Corp. in Japan: http://www.peve.jp/e/shouhin.html

The differences in the battery pack designs and voltages are highlighted on this page:
http://john1701a.com/prius/prius-history.htm#Generations
The author calls the NHW10 model the "Original," the NHW11 model the Classic, and the current NHW20 model the "Iconic."

You may want to read more through the Toyota training document "Hybrid03 High-Voltage battery.pdf" found at http://www.autoshop101.com/autoshop15.html#Hybrid

For the NHW11 and NHW20 Prius (the models sold internationally), the hybrid battery pack is comprised of many prismatic modules (28 or more). Each prismatic module is made up of six 1.2V individual NiMH cells, so each module is 7.2V.

Toyota is experimenting with lithium-ion LiO packs for future Prius releases, but none are commercially on the market yet…