MOSFETS overheating

[WingZER0]

I just remembered something that completely slipped my mind. Some time ago the 249 burned out it's fuse when I was running a 7.2 1700 mAH battery when it was still stock wired. That was right before I began rewiring for a MOSFET.

It was a 30A fuse IIRC.... would this have any bearing?

[green_ninja]

Originally Posted by mcguyver

Mnay FETs will heat up horrendously under load, even a small load. A heatsink is the solution, to increase the effective mass and surface area of the FET when.....
....specify whether you had a fuse in the system, but if you had one it likely would have blown already or shown signs of thermal damage.

I tried making a mosfet for myself, but to order the mosfet semi-conductor itself, you can only buy them in bulk (like 1000's). Screw that, so I found hhairsoft to make me one. Turned out to be a very efficient and sleek design, but after reading how these buggers like to heat up, I modded it with a heatsink from a useless videocard. It also helps to put a bit of thermal grease between the mosfet and the sink. Turned out great, and works fine!



FET increased my ROF by 27% from 840rpm to 1140rpm w/ no major sign of heat after full auto of 10-15 sec, running w/ 9.6v battery; at ~340fps w/ .20g. Do the heatsink if you get mosfet! highly recommend.

[mcguyver]

The best compound to get would be some heatsink compound. I don't know exactly what's in it, but it's white and uber-sticky, great for transferring thermal energy. Even a small heatsink is a huge benefit. Look at the metal back on a TO-220 size FET and see how little surface area and mass is there, for passing so much current.

[green_ninja]

Yes, that's what I used, same sh!t from underneath the CPUs, works great eh?! yeah, there's direct contact b/w the metal backing of my mosfet and heatsink, should have better heat dissipation.