Thanks all for being so helpful with my question last night and this morning. Here is one last one before I start building.
I have this cool little key switch that my kid found and we want that to be our main power. I found what I think is the same part online and I think maybe it can just barely handle the power on our robot. We're right at the rating and that is assuming I'm not mistaken about what part it is and that's a 50:50.
So I don't want to push everything through that switch, but it has to cut the main ground to the battery, again that's 7 - 18V. The bot pulls somewhere in the neighborhood of 10-12A at the most at 7V and far less at 18V. Probably in the neighborhood of 80W if everything is locked up at full stall current. Most of the time it will be far far less than that, but those are the worst case with a little safety built in numbers that I'm working towards.
I have a relay that I can use for sure. But I wondered if a transistor solution might be nicer. I have a few NFET transistors laying around from other projects.
I was thinking something like this:
I have this huge transistor with a big honking heat sink on it. I know it can take the current:
FCA47N60F - 47A - 600V. It may be way overkill. Even so I prefer overkill to buying something else.
Or do I?
It's another case of if I can build with what I got. I've got all kinds of resistors and caps and stuff here. But that's about all I got for FETs. If I can't do it with this then I'll just use the relay.
If it's a bad idea for whatever reason, please school me. That's why I came here today was to learn about switching power. Consider this me turning in my homework.