To enhance the performance of an electric bicycle lamp using ultra-bright white LEDs, it's essential to power the LED with a constant current supply. This ensures that the brightness remains consistent regardless of fluctuations in battery voltage. For optimal light concentration, choose white LEDs designed for focused illumination rather than diffused lighting.
Most electric bicycles still use traditional incandescent bulbs, which are inefficient and prone to dimming when the battery voltage drops. This not only reduces visibility but also poses a safety risk during nighttime riding. Replacing these with high-intensity white LEDs can significantly improve both brightness and reliability.
Battery voltages can vary widely—36V batteries may reach up to 45V, while 48V batteries can go beyond 60V. To protect the LEDs from overcurrent damage, a constant current source is necessary. The LM317 can be used as a simple and effective constant current regulator, providing around 60mA. Each white LED typically operates at 3.1V to 3.5V, so for a 36V system, you can connect 9–10 LEDs in series. These groups can then be connected in parallel to ensure even distribution of current and maintain consistent brightness.
If an LM317 isn't available, a high-power transistor can be used instead to create a similar constant current circuit. In this case, a red LED (with a forward voltage of about 1.8–1.9V) can serve as a reference. The transistor’s beta (current gain) should be above 100 for stability. If it's lower, adjust the resistor value accordingly to maintain a steady 60mA output.
Replacing the original bulb involves modifying the existing housing. The power supply input is usually around 15V, while the output is set to 5V at 4A. With a 10V voltage difference, the power transistor can dissipate up to 40W, making proper heat management crucial. A suitable aluminum heatsink with a thermal resistance of 0.75°C/W is recommended to keep the system cool and efficient.
Once the LED and circuitry are installed, the original reflector can be retained for better light focusing. The total power consumption stays under 3W, yet the luminous output exceeds 100 lumens. This makes it a long-lasting, energy-efficient lighting solution ideal for electric bikes.
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