Single tube constant current charger circuit diagram

As shown in the picture is a practical single-tube constant current charger, in which the transistor VT1 plays the role of constant current, and its constant current value is determined by the voltage of the voltage regulator tube and R2. Generally, the voltage regulator tube is selected to be around 3.3V, and the resistor R2 is (30~60 ohms)/(1W~2W). At this time, the charging current is about 50mA~80mA. R3 (200~500 ohms) and LED form a charging indication circuit. As long as the rechargeable battery is connected as shown in the figure, the LED will light up. If the LED does not light up, it means the battery contact is poor. This circuit can charge 1 to 4 AA nickel-cadmium batteries, and the charging time is 12 to 14 hours. Transistor VT1 can be used with 3DD15 or DS11 (plastic-sealed) power tubes. During installation, a radiator should be added to the VT1 tube.

Both chargers do not have a charging control circuit, so the charging time should be mastered when using them to ensure safe charging.

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