Hello everybody I am direct driving a P7 3D mag. It starts out bright and dims after about a second, it is barely noticeble but I was thinking it might be the gauge of wire I am using. Since I am using 3 12 amp CTA batteries what gauge of wire would you guys suggest for around 36 amps continuosly?
You don't need wire for 36A, because if there would be 36A, your LED would go in seconds.
Your led might go dim because of unproper heatsinking or to high voltage...
What batteries are these, never heard of them?
When you say the P7 "starts out bright and dims after about a second, it is barely noticeble (sic)", do you mean that the P7 dims so much that it is barely noticeable or that the amount of dimming is very slight and thus barely noticeable?
If it is the latter, that's probably because the NiMH cells, like all cells, have voltage sag under load. Thus, you get an initial peak brightness, followed by a decrease to a steady state. That's the nature of direct drive. The drive current to the LED follows the discharge curve of the cells you use.
If it is the former, then most likely your NiMH cells are bad. I assume that these "12A CTA" cells are 12mAh NiMH D cells? If they are alkalines, then that may be the reason. Alkalines can't deliver the 2.8A that would otherwise drive the P7 at max output. Alkalines will sag dramatically, although not to "barely noticeable" light output levels.
Last edited by Justin Case; 07-20-2009 at 04:18 PM.