To optimally control the charge and hold cycle for sealed lead acid battery, UC2906 series of battery charger controllers is used by all of the necessary circuitry. These integrated circuits control and monitor both the output voltage and current of the charger by way of three separate charge states; a precision float-charge, or standby state, a controlled over-charge, and a high current bulk-charge state.
Dual step current charging scheme is used by this this lead acid battery charger. When a large string of series cells must be charged, The dual step current charger is used to guarantee equal charge distribution between the cells, the holding-charge state maintains a slightly elevated voltage across the batteries with the holding current, 1H. The dual step current charger is different from float charger because at the bulk-charge state, no over-charge state occurs because Pin 8 is tied high at all times. Mean of current sense amplifier is used to regulate the holding current. In some applications, a series resistor, or external buffering transistor, may be needed at the current sense output to prevent excessive power dissipation on the UC2906. For more information about this sealed lead acid battery charger circuit design, please refer to the UC3906 application info here.
