High Current Battery Options

I'm planning on modding a Maglite with an XM-L drawing 3 amps. The current will be regulated and the host will be a 3D Maglite.

What are some recommended battery configurations that would give good runtimes? I was thinking Li-ion or NiMH.

Thank you

EDIT: Maybe I should've posted in the batteries forum... excuse me

some suggestions:

1) AMC 7135 driver (2.8A) on 3D nimh
You won't get full regulation throughout but you should get 2.8A with freshly charged batteries.

2) AMC 7135 with 4C nimh and spacer tube. You may need to modify tailcap to make it fit but you will get full regulation.

3) Taskled H6CC driver on 9 x AA (or 12 x AA with quad bored host)
A bit more expensive but will maintain full regulation. Adjustable current up to 6.7A.

4) Taskled H6CC driver on 3D li-ion. D li-ion tend to be a bit longer than regular D, so you will need to do the tailcap mod.

building on what monkeyboy said in his first option, you could get 3 (3AA to D) battery holders and wire them in parallel. Although that would have less run capacity (and thus less run time) than 3 decent D NiMH. This should give you full regulation over pretty much the whole discharge of the batteries if you use quality AAs.

furthermore, I would expect D batteries to be able to hold a decent voltage for most of the charge cycle when oonly giving 3 amps and thus stay in regulation for nearly their whole capacity.

If you use a battery sleeve (I use schedule 40 PVC and bore out the middle with a paddlewheel bit), you should be able to fit three 26650 cells in a 3D mag. Some modification to the tailspring might be needed. The cells I got from 4sevens were 3.7v and 4000mAh each so three of them would be able to handle a 3amp draw for a reasonable amount of runtime.

I've decided to go with an AMC7135 driver (2.8A) and four C NiMH.

I'm looking into Li-ion for future builds; some 26650s in a D size Mag.

Thanks for the suggestions.