Direct driving an MC-E, 3 vs 4 AA Nimhs

[swiftwing]

I currently have an MC-E modded 1D Maglite that's being direct driven through a d2flex board. Its currently being powered by 3AA eneloops in a mdocod 3AA to 1D adaptor.

I'm very happy with the brightness of the MC-E on 3AAs but i'd like to get abit more runtime. My Mag host is bored for a 4AA to 1D adaptor, so that's what i'm looking.

As far as i understand, for direct driven LEDs, the higher the driving voltage, the more current it will pull, so going from 3AAs to 4AAs will give me a brighter light since i'm now driving it at 4.8V nominal instead of 3.6V. What 'm wondering is 2 things,

1. Am i overdriving the MC-E with 4AAs direct drive?
2. Will the extra capacity of the 4th AA give me more runtime even after accounting for the increased current draw due to driving at 4.8V instead of 3.6V?

 

[mdocod]

Hi swiftwing,

4AAs will just burn out the MCE within moments. Especially cells with relatively low resistance like eneloops. So, one could say that it would make your runtime very short

For 4AAs, you would likely need a regulator of some sort, the result may or may not actually translate to more runtime, because in the 3AA configuration, you are experiencing steadily dimming output, which extends runtime, whereas on 4AA cells with a buck regulator, you would have steady full output through the run, which could actually translate to less runtime.

-Eric

 

[swiftwing]

Hi swiftwing,

4AAs will just burn out the MCE within moments. Especially cells with relatively low resistance like eneloops. So, one could say that it would make your runtime very short

-Eric

Ah, bummer. I was afraid of this. I've got nowhere near the skill required to add some sort of buck circuitry to nailbender's exquisite creation, still, this gives me an excuse to get another light . This makes me worry about my idea of running it on 3 Energizer L91 Lithiums. I'm thinking that even with the voltage sag at the high current draw, i'm still looking at 4V minimum? Dave did say i could make the light crazy bright by feeding it 2xCR123 primaries though, i should give that a try sometime. I do realise that CR123s sag like mad when subject to a high load and i may not be getting much more voltage out of a pair of them than my 3 eneloops, which seems quite sag resistant even at 3A draw. Oh well, looks like my best be at extending my runtime would be to go back to the 2700mah Sanyo.

Now assuming one would like to make a regulated MC-E light powered by 4AAs. Which driver should i be looking at? I've been looking at the drivers from taskled but nothing jumps out at me. The one buck regulator that can drive a 2.8A current needs a 4.5V minimum input (i think its the hipflex, can't check since taskled.com is down at the moment)