Does a 2.7v - 9v driver exist?

I'm still pretty new to flashlights, so there's a lot of stuff that I don't know/understand yet.

I have been thinking of trying to build my own p60 dropin. I have no idea what LED I want to use yet, but if it's possible, I want to build a dropin that can take 1 or 2 18650s. Many of Solarforce's dropins accept an input voltage of 2.7 - 9 volts. Having a dropin that can make use of my Solarforce body extensions sounds like fun.

Can I start planning a dropin based on the batteries I want to use?
Then figure out what kind of LED will work with the driver?
Or am I going about things backwards?

I'm not sure about a driver that will ACTUALLY work down to 2.7 volts but there are quite a few Buck/Boost drivers that have a range of 3.4 to 16 volts. The biggest problem I have experienced with these types of drivers is once the input voltage falls below the minimum Vf of the LED being used the drivers shutdown, become unstable or worse. Just stop working. Permanently. What you have to ask yourself is how much current in a buck/boost driver are you seeking? Most are right around 1 amp (1000mah) but they can be found up to 1500mah and will work with many XPG or XML type LED's. I use quite a few of them in a year with my Ebay business so if you would like some choices let me know.

They exist, but don't expect them to supply currents in excess of 700mA at those levels. For boost drivers the switch current is typically higher than the output current. In really low voltages, your output could be 300mA but your switch current as high as 1.8A

Illum said:

In really low voltages, your output could be 300mA but your switch current as high as 1.8A

Click to expand...

Man are you ever right about this. At least with alkaline 1.5V's they just kind of give up the ghost. With lithium cells like CR123's and L91's the amps can really start to soar. I've pulled L91's at 0.77V out of a boost light and they're too hot to hold.

I'm not very concerned with the low side of input voltage. I was hoping that there is a driver that will work with something as small as one CR123 and as much as 2x 18650s.

mtnelectronics has a 5.2v-12v driver, but that would force me to use two 18650s.
their LD-4B buck driver takes 3v-16v. I didnt think I really needed that much input voltage.

Perhaps I need to study a little more before diving in and ordering parts.