I also upgraded my late 80's vintage 3D Maglite with an LED emitter, but I splurged and bought a 3 watt emitter that had the voltage regulation circuitry in the bulb. It's a big light but the throw with a focused beam is fairly impressive. I did the same with my newer 2D Maglite but with that I used a 1 watt emitter and then put it in my truck.
The emitters were not cheap, but it was a one-time thing and now they are very useful lights as long as you aren't carrying them. For a lightto keep on your belt (as I do when I walk the dog at night), AA and 123A lights rule.
One thing D cells give is a lot of run-time before a battery change is required. Since these are both back-up lights, I hope for the batteries to hit their expiration date (March 2018) before the light dims.
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Better is the Enemy of Good Enough.
Okay, what’s your point??