I'm thinking of converting my D-Cell Mags to 32650 batteries in preparation for a JayRob XM-L drop-in.
I've got a 2D and 4D Mag. The 4D has a Terralux drop-in that I'm not ready to upgrade yet, but it still burns through batteries (albiet 4 every...year). It's the single emitter type TLE-6EX.
I thought about using rechargabe D-Cell, but those are just as pricey as the 32650 and require a new charger which itself isn't cheap.
I plan to run the 32650 on a 18650 charger with magnetic leads.
I'm wondering though...could I put 3x32650 in my 4D Mag body with a "spacer". This would give me 11.1 volts to my Terralux, which would be a slight voltage increase over its 9 volt list max (6 D-Cell).
I'm no expert, but I'll offer an opinion. I don't know how many amps that TerraLux drop-in draws, but I know the AA->D adaptors don't handle many amps. I would think you could take the adapter and hard wire from end to end with some large gauge wire just using the adaptor as a "spacer" and not to pass current through. You could use any adaptor (AA->D, 2AA->D, C->D) My next question would be if that drop-in can handle the 11.1 volts ok.
I'd personally go with NiMh cells and avoid the risk with 3 Li-Ions, but I guess that depends on how much you are going to use the light.
How about C size NiMh (around 5,000 to 6,000mAh) in a C->D adapter? Here's 6,000mAh for $5.50 ea. Of course you might need a new charger too.