1. Lead acid batteries
12 V
24 V
48 V
A lead acid battery is made up of individual cells. A 12 V battery is made up of six 2 V cells. The cell voltage of 2 V is a nominal value, not the actual voltage.
The capacity (C) of a battery is usually expressed in ampere-hour (Ah). The capacity of a lead-acid battery is usually determined by measuring the average load current during a discharge test that lasts a specific duration and brings the battery voltage down to a preset end value at which the battery is considered to be completely discharged. When the capacity is determined using a test that lasts 20 hours, it is designated as the capacity C20.
A lead-acid battery rated for 200 Ah (10 A X 20 h) will deliver 10 A of current for 20 hours under standard temperature conditions.

2. Anything above 2.15 volts per cell will charge a lead acid battery, this is the voltage of the basic chemistry. However, most of the time a higher voltage is used because it forces the charging reaction at a higher rate.
As you increase the voltage to get faster charging, the voltage to avoid is the gassing voltage, which limits how high the voltage can go before undesirable chemical reactions take place. The typical charging voltage is between 2.15 volts per cell (12.9 volts for a 6 cell battery) and 2.35 volts per cell (14.1 volts for a 6 cell battery).
The lead acid chemistry is fairly tolerant of overcharging.