Alkaline batteries are 1.5v while all the rechargeables I use are 1.2v. This company has Nickel-Zinc batteries that output 1.6v.

http://www.powergenix.com/products.php

Currently they only offer AA batteries.

http://en.wikipedia....ckel-zinc_battery

Nickel Zinc cells have an open circuit voltage of 1.6 volts. This makes NiZn an excellent replacement for electronic products that were designed to use alkaline primary cells (1.5V). NiCd and NiMH both have open circuit voltages of 1.2v, which may cause some electronic equipment to shut off prior to a complete discharge of the battery because the minimal operating voltage is not provided.