The main Types of Rechargeable Batteries are NiCd - Lead Acid - NiMH - Lithium ion. The Gel Lead Acid Battery is Termed Maintenance Free and may have to be treated differently for charging.
List of battery sizes - Wikipedia4.5 Volt - D - C - AA - AAA - 9 Volt - SR41/AG3 - SR44/AG13
Battery Charger Circuits and Resources
Solar charger for lead-acid batteries
The charger will stop charging once a pre-set voltage (temperature compensated) has been reached, and recommence charging when the voltage has dropped off sufficiently.
12 Volt Gel Cell Charger
When a discharged gel cell is connected, the charger goes into a fast charge mode at a fixed rate of 400 ma. After the chip detects the voltage leveling off or when 4 1/2 hours has elapsed.
Temperature Controlled NiCd Charger
This circuit is for a temperature controlled constant current battery charger. It works with NICD, NIMH, and other rechargeable cells.
Battery charger 150-1700 mAh with PIC16F876
This is the extension of the simple battery charger to different battery capacities. The software and the controller are largely identical.
Rechargeable Batteries and Chargers
There are three types of rechargeable batteries. They are Nickel-Cadmium (NiCd), which are the oldest type; Nickel-Metal Hydride (NiMH), which were developed around the same time that low-cost digital cameras were invented.