12V 7.2Ah Sealed Lead Acid (SLA) batteries are very common. However a few factors should be kept in mind while charging them through a power supply. There should be a charging circuit which roughly charges the battery with a certain charging curve.

• Charging Curve for each cell (2.1v nominal)
  

• Charging Modes

  • Bulk Charge: Constant current mode - The maximum current is written on the body of the cell, most of them can take upto 1.2A (keeping temperature in mind). However, as a rule of thumb, it is a good practice to keep the charging current at 1/10th of the rated current. So, in this case charging current would roughly be 7.2A/10 = 0.72A = 720mA.

  • Absorption: Constant voltage mode - The cycle charge voltage (i.e., 14.2 - 14.4v, or roughly 2.4v per cell) is the voltage to be kept during absorption, for approx. 5hrs.

  • Float (storage): Voltage should be dropped to 13.7 - 13.9v) (max. 2.3v per cell) and current should be capped at 1mA.

• A closed loop system which the desired current at the output, set by a threshold value.

• A closed loop system which the desired voltage at the output, set by a threshold value.

• Linear current source
  • Simple - Less components
  • Very little efficiency - heat dissipation

• PWM
  • Involving a microcontroller would be most effective
  • needs more components (like an inductor of a certain value etc.) to achieve precision
  • Very efficient

Commercial usage is strictly disallowed.