Need help understanding drivers

[rideandshoot]

Over on MTBR.com's DIY forum I received the following advice…

When using single 18650s the light will be more efficient if the 'driver' is 4.2 V max rather than 9V max (allowing 2xCR123s).

I am very concerned about run time so efficiency is a major concern.

What say ye…

Thanks

 

[old4570]

More to do with keeping the light in regulation [ Constant current to LED ]

Thats why some folk really like the higher voltage drivers , as output is maintained for a longer time .

A 1Amp buck boost driver [ 4.2v ] with a 18650 will also help in this regard .

 

[Lighthouse one]

I would say the info is correct....but so what? If you get 2 hours and 30 minutes instead of 2:45- it's a problem? How long does it take to change batteries? You shouldn't be heading out with only one light and no extra batteries or two lights. Having perfect regulation or the highest possible efficiency is fine, but not really a big deal in real time usage.

Buy what interests you...don't get hung up on perfection. I've built over 20 lights using DX drivers. many are for 3-6 volts. Some are 4.2 volts max. I've yet to fry a driver, and often switch between 2 123 primaries ( I use these to give away lights to friends) and 1 18650 which I use myself. THe drivers using the 2,3,or 4 7135 chips work great- and are very robust. I glue my drivers to the base of a heat sink with the thermal glue that DX also sells. THese are probably less efficient than some of the more expensive ones available, but they work great, and are easy to use, since they are very thin and flat. Kai Domain also sells a high/low driver that works great too. #4660 or 4659 I believe.