Runtime on 5 AA's

Got a Mag 4D with a tle-6ex in it. I'm a bit over the 1.1kg weight so ditched the D's and stuck 5 AA's inside for weight reduction. Now weighs 360grams less and feels just right for a light of it's size. Any idea of how long a runtime I might get, my guess would be 5-6 hours or should I just turn it on and start the timer?
Got another 4D Mag I'm going to endow with a SSC-P7 running 4 D's. Any idea of a runtime for this setup? D's aren't cheap and I don't want to waste them just finding out how long it will run for. Also how many lumens (approx) I might get out of the 4D SSC-P7 combination. I'm using alkalines at this stage because I've got no more hobby money till after New Year. "What was that dear? No I'm not spending any more money on flahslights (yet)".

Jash said:

Got another 4D Mag I'm going to endow with a SSC-P7 running 4 D's. Any idea of a runtime for this setup? D's aren't cheap and I don't want to waste them just finding out how long it will run for. Also how many lumens (approx) I might get out of the 4D SSC-P7 combination. I'm using alkalines at this stage because I've got no more hobby money till after New Year. "What was that dear? No I'm not spending any more money on flahslights (yet)".

Click to expand...

If you direct-drive off 4 alkaline D cells, the P7 will start at or about 3A (lumens depends on the flux bin of P7 you're using), and roll off rather steeply -- even D cells can't really handle that sort of current. The runtime depends on where you chop the (approximately) exponential rolloff; IIRC, 50% is in the neighborhood of 2 hours. But dropping in 4 NiMH D cells will seriously overdrive it; I'd expect the bond wires to blow instantly, but maybe it would just cook itself with 10A or so. Either way, not workable.

If you use a linear regulator (like two 4xAMC7135 boards -- what my 4D P7 uses), the alkaline characteristics are almost unchanged, but it'll also run fine on NiMH D cells. You'll get about 2.75 hours regulated runtime out of 10Ah cells, and then a fairly steep dropoff over about a half hour more to the 50% mark. IMHO a really nice setup, although I need to get some LSD cells for it.

And if you use a buck convertor, you should get you the longest regulated runs on NiMH, but the Alkalines will still fall over at 3A, and (assuming your buck driver reverts to direct drive for low voltages) will again have a similar characteristic.

I'm a novice at all this so I bought a kit. It's got a P7 with a C-bin and a regulated driver that is limited to 2800ma. It also comes with a fairly weighty copper heat sink which I am told is the goods. I'm getting an aluminium o/p reflector for it simply because I prefer a smooth, floodier beam to a throwy hotspot.