![]() ![]() Construction and testingĪ single-side PCB for the 12V battery absorb and float charger circuit is shown in Fig. The charger is on floating voltage (13.6V) now and it can be kept in this charging mode forever. ![]() Fully charged status of the battery will be indicated by glowing of LED3.ĭo not worry if you forget to switch off the charger. If neither of these light up, check the connections battery could be dead. Switch on S2 one of the LEDs out of LED2 and LED3 will light up (most likely it would be LED2). Connect the 12V battery under charging (BUC), with correct polarity, at CON2. With these settings, TP2 should read 14.1V when there is low voltage at test point TP3, and 13.6V when there is high voltage at test point TP3. Adjust VR2 to read 14.1V at test point TP2. Adjust potmeter VR1 to read 0.5V (difference of 14.1V and 13.6V) at test point TP1. Adjust potmeter VR3, so that LED2 begins to glow. While setting the charging voltage, remove the jumper and connect it back after calibration.įor initial setup, remove jumper J1, switch off S2, switch on S1 and adjust potmeter VR2 to get 13.6V at test point TP2. ![]() Jumper J1 is used for calibration (set-up). Capacitor C4 should be as near as possible to pin 1 of IC2. LM358 is a dual-operation amplifier that is used here to control overcharging of the battery. The basic circuit is a regulated power supply using LM317, with a control on output by changing resistance at adjust pin 1. This voltage is given to the input of LM317 for regulation. The 230V AC primary to 15V-0-15V, 1A secondary transformer used in this circuit steps down mains voltage, which is rectified by diodes D1 and D2 and smoothened by capacitor C1. It is built around step-down transformer X1, adjustable voltage regulator LM317 (IC1), op-amp comparator LM358 (IC2) and a few other components. 12V battery charger circuit Fig1: 12V battery charger circuitĬircuit diagram of the 12V battery absorb and float charger is shown in Fig. These values are to be set as specified by the battery manufacturer. For safe working and to avoid overcharging of battery, absorption voltage is selected as 14.1V and floating voltage is selected as 13.6V. Absorption and floating voltages are dependent on the type of battery.įor this charger, voltages are set for a sealed lead-acid (SLA) 12V, 7Ah battery, for which absorption voltage is 14.1V to 14.3V and floating voltage is 13.6V to 13.8V. This 12V battery charger circuit charges the battery at a particular voltage, that is, absorption voltage, and once the maximum charging voltage is attained, the charger changes the output voltage to float voltage for maintaining the battery at that voltage. ![]()
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