SCR Battery Charger
Build an SCR battery charger using BT151 thyristor for controlled DC charging. Suitable for 12V/24V batteries in DIY electronics and hobby projects.

SCR battery charger BT151
A battery charger is a type of SCR-based battery charger that regulates charging current to DC batteries by using BT151. Current is switched in a controlled way by the BT151 thyristor, with adjustable and efficient charging possible.
BT150 thyristor charger circuit
The SCR Battery Charger with BT151 is a controlled charger for DC batteries (e.g., 12 V or 24 V lead-acid batteries). The BT151 SCR is a switch that controls the amount of current flowing to the battery to ensure a safe and efficient charging. The project is suggested to hobbyists, students, and other electronics enthusiasts who want to have a simple battery charging solution that is based on SCR. The charging current could be adjusted with a potentiometer. Diodes are used to convert AC to DC, and resistors are used to restrict the current and to shield the SCR. The status of charging can be indicated by an LED. The circuit is small and can be fitted on a PCB board or breadboard. An SCR will provide a fine level of control and minimize chances of overcharging, which improves battery life. This charger is ideal for low-voltage battery projects in DIY electronics projects, small solar system,s and education projects.
Work / Installation (Inputs β Outputs)
- AC Input β 12V/24V AC supply.
- Rectifier Diodes β Convert AC to DC.
- BT151 SCR β Switches DC current to the battery.
- Potentiometer & Resistors β Adjust and limit charging current.
- Output Battery β Receives controlled DC charging current.
- Installation β Assemble on PCB, connect AC supply, rectifier, SCR, resistors, potentiometer, and battery. Adjust potentiometer to set desired charging current.
Testing & Final Adjustments
Once assembled, connect the battery and the AC input. Tilting slowly the potentiometer regulates the charging current. Monitors the LED indicators of charging. Ensure that the voltage of battery increases gradually without going beyond the limit. Make sure that SCR and diodes are oriented properly. Check with a varied battery capacity to ensure good working. However, with proper testing, there is safe and controlled charging and elimination of overcharging and overcurrent. Protection is added by using a fuse. To be used in the long run, mount components shall be placed in an insulated enclosure and heat dissipation provided to the SCR. This will ensure efficient charging and extend the life of the battery and other components.
Frequently Asked Questions - SCR Battery Charger:
What is BT151?
BT151 is an SCR (thyristor) used to switch and control DC current.
Voltage supported?
Suitable for 12V or 24V batteries.
Can current be adjusted?
Yes, using a potentiometer in series with the SCR.
Is it safe for batteries?
Yes, ensures controlled charging with proper current limiting.
Applications?
DIY battery charging, hobby electronics, small solar systems.
Do I need a rectifier?
Yes, to convert AC to DC for charging.
Is it beginner-friendly?
Yes, with careful component placement and assembly.
Can it charge multiple batteries?
Yes, within voltage and current limits of the circuit.
Fuse needed?
Recommended for protection against short circuits or overcurrent.
Heat dissipation needed?
Yes, the SCR should have a heatsink for safe operation.
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