Switch Mode Lead Acid Battery Charger

More efficient lead acid battery charger can be implemented using switch mode circuit. A switch mode for lead acid battery charger can be constructed using bq24105 battery charger controller. The bq24105 was originally designed to charge single-, two- or three-cell Li-ion and Li-polymer battery packs. Its features doesn’t include the control for lead acid battery charger termination. Here we add external circuitry to enable this controller to charge lead acid batteries. Although the circuit becomes more complex, this circuit provide high efficiency, switching mode charging method for lead acid batteries. Here is the schematic diagram of the circuit:

Lead-acid battery charging system design specification:

• Battery voltage Vbat: 12-V lead-acid battery
• Input power source Vin: 17 ± 1 Vdc
• Battery bulk voltage regulation: 14.8 V
• Fast-charge current: 0.5 A for Vbat ? 13.5 V, 1 A for Vbat > 13.5 V
• Battery refresh voltage: 13.6 V
• Termination current: 0.9 A
• Precharge current: 0.45 A

[Schematic diagram source: Texas Instrument Application Report]