I'm building a flashlight comprised of 18 x XML-T6 LEDs. The battery bank can be configured as 2 or 4 x 26650 batteries 7.4 or 14.8 volts input. What kind of driver could power these 18 x T6 in terms of output voltage and amps? I tried two drivers HX-1175b which is DC3V-18V 7A LED Driver for CREE SST-90 and 1-Mode 3V-18V Flashlight Driver Circuit Board Cree XM-L T6 XM-L2 U2 U3 and nether appear to work. BUT when I connect 12V DC straight, the leds flicker.
I assume the LEDs are wired in series. This means you will need a boost driver with an output of about 70V.
It depends on how much current. The max current will be determined by the thermal management. These LEDs get very hot. Without an additional heatsink I estimate this board will handle about 250mA which will take the PCB temperature to about 80°C. Too keep the temperature down to where it will not burn skin (50°C) you'd have to reduce the current to under 100mA.
If you were to use a Li-po battery pack with a 3.6V output you'd have an easier time finding a boost driver.
An good alternative is to break the LEDs in to smaller strings and use a multiple output buck step down driver. e.g. three drivers each with 6 outputs like TI's LP8552 High-Efficiency LED Driver.
After much experimentation with DC DC converters, the array lights up at 21V. 3 batteries 16V in, 21V out. It turned out to be a five dollar fix. Keep in mind that drivers need to be small enough to fit into casing.