Cutter has a thing called "7-up" that has 7 Cree XR-G R5 LEDs on it. Slap that on a thick chunk of aluminum with the 7 LED optics and wire it all in series. Throw a big resistor in there to drop a couple of volts since the thing has a forward voltage of 22.2V when the LEDs are running at 700mA. Maybe add an 8th LED for a forward voltage of 25.4V at 700mA and 26.4V at 1,000mA each.
For electric bikes "24V" can mean several different voltages from 26V will freshly charged lead acid to 28V for LiFePO4. If you can get a step-down (buck) regulator that pushes 500 to 700mA, the 7-up with 7 XR-G R5's will bark about 1,400 lumens out the front. That should be bright enough.
