Hello, I’ve been looking around the forums and was wondering what I could use as a base to power an LED with such a high Vf. It’s only going to be driven at 1A and used with a boost driver to bring it up to that 20V needed.
What sort of options are there for 3x or 4x 18650 in series to drive one LED (I think 2x would be pushing it).
Recommended max input current for the Max6Flex is 3A. If your emitter is 20w, the lowest input allowed is 7.41 volts. 3 Cells would work well and you could set the low voltage cutoff to fully drain the cells.
To determine the lowest allowable input voltage for a given wattage you just divide the total wattage by the max allowable input current, but the efficiency of the driver needs to be part of the total wattage, like so: 1A x 20V = 20W / .9 efficiency = 22.22W / 3A = 7.41V
7.41V / 3 cells = 2.47V minimum per cell. I’d set the shutoff voltage at like 8V, 2.66V per cell, if I was using Panasonic cells rated to 2.5V drain in a 3S configuration. It is important to know the actual voltage of the emitter at a given amperage if you are going to push the driver.
HBflex allows up to 7A max input and 3A output but it is a larger driver and seems less fitting to your particular application.
Thanks for the help everyone. I was also wondering if there are any flashlights that came in a 3 or 4 series configuration to drive one LED from the factory.
ICSK wrote:Thanks for the help everyone. I was also wondering if there are any flashlights that came in a 3 or 4 series configuration to drive one LED from the factory.
Hi ICSK. This 15 xml2 light has the emitters wired 5S3P on the emitters and can be used with 2 to 4 cells. I used mine for just a little bit before taking it apart. The driver seemed happier with 2S cells than 4S cells. Several people have had these lights fail on them (presumably the driver and assuming while using 4S cells).
If I come across the driver today, I will post a picture of it.