Newbie with some MagLight questions

Hi, all-
I'm new to this whole flashlight thing- to me, a flashlight has been- at best, a MagLight- at worst, plastic flashlights at work with dead batteries!
Discovered the world of 'better' flashlights, and find it interesting!
I've ordered 3 different lights (LED type), but tonight, it dawned on me- that I have 2 MagLights that might benefit from some improvements- even if only better batteries, preferably rechargeables.
I have a 3 D-cell and a 2 C-cell MagLights… what would be a good upgrade on batteries over the typical Duracell's I throw in them? Are rechargeables suitable- due to the lower output voltage from an alkaline cell?? Are there other simple mods that I could do to start with?
I'm totally unfamiliar with the process and concepts of modding flashlights… I've been reading through material on here- some of the basics- trying to figure out the terminology,etc, so I at least have an idea of what's IN these things! I'm an electronics technician by trade, in and working for the Navy for 47+ years- and a certified micro tech, so the soldering issues are non-issues for me. I just don't understand the theory and block level operation of the driver/regulator circuitry- I assume there's a bit of electronics in the MagLights as well?? (Mebbe' not!)
Anyway, better batteries would be a starting place for the MagLights.
Thanks for any advice!
Wes

First of all, :welcome:

To begin with, some basics: in the simplest terms, you just need batteries and an LED to get light. LEDs have a forward voltage rating, known as Vf. This is the approximate voltage the emitter is driven at when driven at a certain input, usually 350mA. As voltage goes up so does the input current. Get the voltage right and the emitter lights up. Too much voltage will destroy the emitter. Too little voltage and it won't light. What does this mean to you? Wire an LED, say a Cree XM-L, to both of your MagLites (on a proper heatsink, please), in what is known as direct drive (no driver board, I'll get to that later), and the result will be somewhere around 50 lumens from the 2D and 700 or so lumens from the 3D, assuming you're using NIMH cells (interestingly, you'll get slightly more light from the 2D using alkaline cells but less light from the 3D cells because of the higher voltage on the 2D but the higher current draw will cause the voltage to sag on the 3D). As the cells drain and the voltage drops, so does output from the light. On the 2D that'll happen fairly quickly as the battery voltage will drop below the operating voltage of the emitter fairly quickly.

So, why use a driver? A driver regulates the voltage and/or current going to the emitter which should give you more predictable results, longer run times, and more even light. There are three basic types of drivers: boost; buck; and linear. Which one you use depends on the voltage of your power source. If the power source is less than the Vf of the emitter(s) then you need a boost driver. If the voltage of your power source is more than the Vf of the emitter(s) then you need a buck driver. If your supply voltage is slightly more than the Vf then you can use a linear driver (there are also boost/buck drivers that will operate as a buck driver until the supply voltage drops to the same as the Vf then will become a boost driver until the voltage drops too low). In the case of your two lights, you should use a boost driver for the 2D and a linear driver for the 3D.

What you want to do with your two lights depends on how much effort you want to put into them and how much light you want out of them. If you want more than 100 lumens, you should use a heatsink to prevent damaging the emitter from heat. If you want more than 200 lumens then a heatsink that's connected to the body of the light to allow the heat to be dissipated to the atmosphere is required. The more output you want the more important this is. Below 100 lumens and you can get away with minimal heatsinking. Think of it this way, a Cree XM-L driven at 1W will produce 1W of heat and about 120 lumens out the front. At 2W you're getting 2W of heat and about 200 lumens (emitters are less efficient as they're driven harder). Drive this emitter at 8W and it's producing a bit more than 7W of heat. That's where the heatsink comes in.

Having said all that, if 50 lumens is sufficient, which is more light than your incandescent 3D light makes now with fresh alkaline cells, then I'd suggest getting the Nite Ize 1W PR flange drop-in. It's an LED bulb that replaces the incandescent bulb in your existing lights. The same bulb will work in both lights and will have slightly less output in the 2D. In the tail cap I'd put the much dimmer Nite Ize 1/2W drop-in for crazy long run times. It produces about 15 lumens and will give you about a week of continuous light (turn it on and a week later it'll dim and turn off on its own).

For 80 to 150 lumens, you can try tracking down the now discontinued MagLED drop-in. They produce about 80 lumens out of the package and can easily be modified to about 150 lumens by swapping in a current emitter like an XM-L. They are made specifically for 2, 3, or 4 cells, and their output drops as the module heats up, but, your eyes would not be able to tell.

If you hang around here long enough you'll see that there are lots of posts about stuck and/or leaked alkaline batteries. NIMH is the way to go.

The choice of military and professionals is the Malkoff drop-in; a quick and easy bulb replacement that will get you far more output and runtime, and even make your Mag more durable than it was before. Highly recommended.