I have a basic question that i just cant seem to find the answer to.
I understant that if you run a P7 direct drive with 3 Nimhs, you get a peak voltage at the start of 4.2 v, which drives the led higher than its rated 2.8 amps and therefore it gets hot but rund brighter until the batteries drain to the normal voltage.
but i want to current control the circuit, and this is where it gets interesting for me and my newbie maths...
I also understand that, if you use a 2.8a current limited driver to run it, itll get its optimum 2.8amps until the batteries fall below the voltage required to power the driver to 2.8 amps, at which point it falls out of regulation.
I was wondering what happens to 4 cells being used with a 2.8 amp driver. Do you get a longer burn time at 2.8 amps since it takes longer for the cells to fall to below regulation voltage? any way of calculating how much extra you get out of a set of cells?
so, for 3 x 5000mAh cells, at 2.8A, im calculating almost 1hr 40mins. using the normal equation, for a 4.8v, 5000mAh pack, i also get 1hr 40 mins. What does the extra cell do, or am i missing something.
the thing is, i have 12 cells available, 5Ah capacity. i can either rig 3 cell or 4 cell packs, but using these calculations, i pretty much 'waste' a cell in each 4 cell pack- since i cant see where the extra power goes.
I hope that ll makes sense. Please help!