What options are there for converting 2AA’s to Series in a D cell size holder?
In total I’m wanting 6 AA’s totalling 7.2v (NiMh). Is there an easy way to do this?
It would have to be custom made. Not impossible if you have a hobby shop with a ‘Plastruct’ rack in the store. But you’d have to have a jumper in each D-size adapter. A custom battery carrier to hold all the cells at once would be idea.
I ordered this 3x AA to D converter about a week ago, I’ll let you know how it is.
Edit: Sorry, the ones I linked to are in parallel.
Use two 3AA to D series holders and a D size dummy.
http://kaidomain.com/product/details.S003294
These tend to have a lot of resistance, though, but good for low current apps.
Use 6 x 1/2 D cells?
http://www.batteryjunction.com/powerizer-half-d-cell-nimh.html?gclid=CPLeiZb_sLwCFcdQOgodCGMA6g
Lol it’s actually to replace a dud MagCharger pack that uses these as standard. But have you seen the price. And they aren’t LSD. About $42 + shipping.
There is a user here which has nice selfmade adapters which look better than any of these plastic boxes…
what current will you be running??
Thanks Werner. 
BTW I got some revised 3AA PCBs in the other day, but I have not had a chance to assemble them yet.
Chicken Drumstick, good idea to replace the MagCharger guts with AA’s. Have you considered just building a 6s1p pack of LSD NiMH AA, placing a spacer on one end, and then adding bottom and top contact plates? Soldering a 6s1p pack that fits in a MagCharger should be pretty easy, even if you are not capable of end-to-end soldering the cells. There is so much space you can solder on tabs, bare wire, or whatever you need. Once it’s assembled and installed, you’d just use the stock charger.
MAG-LITE says that the Mag Charger lasts two hours on high. If the stock NiMH Mag Charger battery is 3.5Ah then we’re probably talking about a peak of at least 2A current draw on unrested, fresh batteries. I’d say 2A is high for a low-end plastic carrier such as the Fasttech one linked earlier in this thread (until someone demonstrates otherwise :zipper_mouth_face: ). I guess it must settle into something like 1.5A in order to achieve 2hr.
I don’t use any flashlights with a charging cradle, but if I had a Mag Charger and used it in that fashion I would certainly be tempted to purchase a NiMH replacement for ~$30-40. That way when I pull it off the cradle I know I’m good for 2hr!
What’s the inner diameter of a Mag Charger anyway? The battery pack pictures make me wonder if it isn’t 35mm+. Do you think you could fit a 6s2p pack in there? If you can fit 12 loose AA cells inside it then that’s the ticket! That would net you more capacity than the stock pack, and it would be LSD.
Your OP asked for easy, not economical. 
Thanks for the replies.
Not really sure on plans yet. The MagCharger is stock, but I’ve read good things about running the stock bulb at 7.2v I also have another bulb (forget what it is now, but it likes more volts).
That said, I may opt for a LED conversion at some point on it. I have considered just getting new NiMh factory pack for it, but they are expensive and not LSD which puts me off if I could achieve similar performance from Eneloops for less money and have it LSD.
On a different note, I have two spare 2D’s that I’d like to mess about with. One has a huge heat sink in it and was the basis of a doomed project. But I’d like to revisit it. I’m not keen on running alkaline cells, so again, if I could get some Eneloops in there, then the better. Although to be honest as these are 2D’s, then a 3xAA to D cell converter seems the way to go. But with the MagCharger 9xAA’s in series is too much voltage.
No idea if this will work, but I ordered some of the 3xAA holders from FastTech and some dummy AA cells. Will try it out when it arrives.
Chicken Drumstick – Can you do a bit of DIY, solder, glue etc? If yes I have something for you. Some time ago I purchased a few kits of these from Kevin at Lambda lights - http://www.lambdalights.com/parts.html scroll down to bottom of the page.
Once built they make 6AA (7.2V) holders. They just don’t look very nice! If you want one drop me a PM with your address and I’ll post a kit to you as I have no use for it now.