I'm thinking that all else left alone, it probably doesn't matter which way the shaft of an automobile alternator is rotated since the machine produces ac which is then rectified to create a polarized dc output.
Am I right about that?
The question came up just now when eldest son and I were kibitzing about this week's "Car Talk" puzzler:
And all my 120 volt drills turn only CW. (That tells ya how olde they (and I) am.
Son just pinged me to say that if you ran the alternator belt over the alternator pulley and then over the drill chuck you could point the drill in the appropriate direction. That may be the answer the Car Talk guys are looking for, as it's not likely there'd be enough room under the hood to connect the drill through a socket directly to the alternator shaft nut.
But, you could always unmount the alternator and.......
I wonder if hat's the correct approach. In my cars, the alternator pulley ratio apears to be at least 3:1. So at idle, the alternator is spinning at around 2400 RPM. My drill won't do anywhere near that speed. And running the belt over the chuck will turn the alternator pulley slower than the drill.
I'd just take the extension cord and/or jumper cables and wire the generator in series with the alternator output. The alternator diodes will rectify the AC. Then, throttle the generator up slowly. At a low RPM, its voltage output will be low enough to charge the battery.
My answer is first look for a DC output from the generator. Many have them.
Either direction will do; with the hood open and the engine off the generator will be in a far cooler enviroment.
I wonder how hard you can push it anyhow. A 100A car alternator is outputting ~1.5KW. [15v*100A] It needs say 2KW in to deliver that. That means the drill would need to produce 2KW. It would draw say 2600 watts. Can YOUR drill produce that? For how long? (I think it more likely you can get 600 watts ergo 20A out.)
So I think it fair to say that while you can spin the alternator and get some charge out of it; it's going to take you a while.
The other question is how to connect it up. Given we have a roll of duct tape... wrap the pulley and the chuck in same; and use friction drive? If it's a flat belt, you could drive it from the chuck...maybe.
On Mon, 04 May 2009 16:46:10 -0400, the infamous jeff_wisnia scrawled the following:
Electrically, you're probably right. But the brushes I've seen during rebuilds of most brands (in my previous life) were usually situated to run in one direction only and they'd self-destruct in minutes if run the opposite direction.
"Some kind of builder" wasn't very bright, was he? ;)
I'd run the genset to power up the drill to turn the alternator to charge the battery, even if I had to drill a hole through the radiator support and/or grille to do it with a branch extension and the duct tape.
-- The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage. --Mark Russell
So he's gonna build a cabin with an electric drill and a socket wrench? Must be an erector set scaled up, or maybe a metal pole building. Not what I visualize when I think "cabin", but these are modern times.
I wasn't anticipating standing there with the drill long enough to fully charge the battery, just long enough to get the engine to turn over. Yeah, leaving it there long enough to really charge would do it...
I am a professor; you'd need to ask my students whether I'm a teacher :)