Advantages of 6AA as a retrofit for 2D.

Battery adapters that have 3AA in series to replace 1D cell exist. I’m not going to post links since they quickly expire. Many people have bought these thinking they are 3AA in parallel. The higher voltage allows the use of buck regulators which are around 90 percent efficient compared to boost regulators which are around 70 percent efficient. A simple calculation 2.300AH*1.2V*6**.9=14.9WH compared to 10.000*1.2V*2**.7=15.6WH. This is very close and the 6AA batteries will cost around half the price of 2D batteries. Of course bulb manufactures will not tell you what kind of regulators they use but many of them will give you the lumens and amps these draw. You used to be able to buy travel chargers that would work with 2D’s these are getting hard to find so I’m switching. I will be buying 4 of these and a lantern light that has an adapter for 4D batteries and a PR flange bulb that is rated to 28 volts.

I have used the three AA in parallel to D adapters in my Fenix TK50 stock light and they work well. About 3 hours run time at maximum with 6 AA 2000 mAh Eneloops. Not a light modifier yet though I do have some lights hopped up by RMM of Mountain Electronics. The Chinese three parallel AA to D adapters work well at reasonably low currents but not sure how they will do at higher currents due to steel contact plates and springs used in them. I have seen the Chinese three AA in series adapters and they appear to be of similar construction so not sure how well they will work if you try for high current draw.

Sounds like a good plan to me. If you bore out the battery tube just slightly, you can go 4AA carriers.