Alkaline battery charger circuit schematic

Photocoupler

description:

This circuit is specifically designed to charge alkaline batteries. In the respective charging circuit, the special connection method of the transistor causes it to oscillate continuously, and the charge accumulated in the capacitor is transferred to the battery in this way. When charging a 1.37V battery, the orange LED flashes approximately 5 times per minute. For a completely unfilled battery, the flashing will be faster, but the more the battery charges, the slower the flashing will continue until it stops. You can leave the battery in the charger, it will be charged at a small current and maintained at around 1.6V. In order to set the correct voltage, you need to connect a new, unused battery and adjust the capacitor until the oscillation starts, then stop until no oscillation occurs, and the circuit is ready for operation. Please use the specified transistors, color LEDs, Zener voltage and rated power as they will determine the final voltage through the battery.

This circuit is also a simple 9V charging circuit: it will charge to approximately 9.3V and maintain a small current charge: the green LED will go out when charging, and the green LED will be on when the battery is near its final voltage.

A 2.5V transformer can charge up to 4 batteries at the same time, although only 2 are shown on the chart. In order to minimize the interference between the circuit and the circuit, they are different except for the transformer. In order to balance the load of the transformer, half of the charging components will adopt a positive sine wave and the other half will adopt a negative sine wave. Use a high frequency common emitter current gain transistor such as BC337-25 or better BC337-40. Sometimes the scattering parameters of a transistor may make it unable to oscillate. Use a weak high-frequency Zener voltage: 7.5V instead of 6.8V or a green LED instead of an orange LED.

All types of alkaline batteries can be recharged: it takes one day to charge a fully discharged AA or 9V battery, while a large D-type battery will take several days. The best way is to not completely discharge the battery or battery, but often charge for a short time, although this is not easy to do. Do not attempt to charge a fully discharged or slightly damaged battery.

I successfully tried to charge the NiMH battery. Although the charging index of such batteries is different from that of alkaline batteries, the circuit seems to work well. Don't leave the battery in the charger forever, because it may be overcharged, especially for smaller batteries. The power transformer must be suitable for the available voltage in each country: typically 230Vac or 155Vac.