DC Brush motor as genny
By PEdoubleNIZZLE, Section Mechanical Posted on Tue Aug 16, 2005 at 11:31:32 PM MST
RPM and volts

I am about to acquire a 24 volt DC PM brush-type motor. My question is: If it spins at 500 RPM @ 12 volts, then will it generate 12 volts if you spin it at 500 RPM? (not accounting for resistance.) It seems to make sense to me that if the motor's resistance was negligeable, it would work this way. Any thoughts? Thanks, Josh

DC Brush motor as genny | 10 comments (10 topical)

Re: DC Brush motor as genny (3.00 / 0) (#1) by techwolf on Tue Aug 16, 2005 at 09:11:23 PM MST

yep, you can do this, I did a while back and it made enough power to run an auto headlight,

Re: DC Brush motor as genny (3.00 / 0) (#2) by ghurd on Wed Aug 17, 2005 at 07:46:08 AM MST

I'll say don't count on the first one working very well. I have quite a few smaller motors that peak out in voltage at 20-60% of the rated motor voltage, say 3 to 7V for 12V automotive type motors.   Guessing it is due to weak magnets. Never did find one that reached charging voltage from a car. The coil resistance limits charging current more than it seems it should at first glance.  Like a 24V 2A PM brush motor that only puts out about 200ma at 12V at double the name plate speed. My experience with them says the smaller the motor, the less chance it will work. Big fun even when they don't work! G- Ghurd.info

Re: DC Brush motor as genny (3.00 / 0) (#3) by Norm on Wed Aug 17, 2005 at 12:04:38 PM MST

One of the neatest things to do is hook the motor something like this: http://www.los-gatos.ca.us/davidbu/pedgen.html  something like this only use a multigroove serpentine belt....make the front pulley a little smaller and the small pulley from paraticle board also ...about 20 to 1 ratio should do it, 25rpm on the crank pulley should spin the motor about 500 rpm...... Now have a switch hooked directly to the 12 volt battery connected to the motor...when you switch it on the motor will spin about 500rpm.    A multimeter hooked onto the battery terminals to see the voltage change....    This is the fun part....   you'll see like 12 volts on the multimeter.... turn on the switch to the motor you'll see the voltage drop...start pedaling....you'll see the voltage come back up to 12 volts as you pedal just fast enough to just barely keep ahead of the motor....as you pedal harder you will notice the voltage going up....theory ...I guess the harder it is to raise the voltage the better the motor....    Anyway something like this: Yeah...that shiny chrome socket is the crank handle.                         ( :>) Norm. for more detail go to.... http://www.fieldlines.com/story/2005/3/23/225230/317 ( :>) Norm

Re: DC Brush motor as genny (3.00 / 0) (#4) by techwolf on Thu Aug 18, 2005 at 06:41:01 AM MST

Interesting feedback here, in the last picture I posted you can see a headlight on and I had both the high and low beams powered. Now this was only in a good wind, at lower wind speeds I could run the low beam only with out stalling the mill. still, given that a headlight is rated at 65 watt thats 65/12= 5 amp, not bad for a mock up mill with a 4 foot blade. it was the 2nd blade I tried as the first was running too slow, this one would really spin.... I mean stand back... when a good wind hit this one you would not want to be too close. but the trade off was hard to get started. in a slow wind I'd give it a spin by hand and then it would keep going. It would self start in a good wind.

Re: DC Brush motor as genny (3.00 / 0) (#5) by ghurd on Thu Aug 18, 2005 at 07:29:30 AM MST

What kind of motor did you use? Everything you can remember about it would be great. G- Ghurd.info [ Parent ]

Re: DC Brush motor as genny (3.00 / 0) (#6) by techwolf on Thu Aug 18, 2005 at 10:50:33 AM MST

if memory serves me, I think it was a pmg with brushes from a auto heater fan. this was direct coupled to the rotor. I dont know what car its from as I bought it surplus when I saw it. It seemed to have some cogging when i turned it by hand and thats when the bulb went on in my head. Wind Power...gota try it.

Re: DC Brush motor as genny (3.00 / 0) (#7) by ghurd on Thu Aug 18, 2005 at 01:17:57 PM MST

Wow! Norm and I wish you had a manufacture's part number! We, or at least I, had no luck. http://www.fieldlines.com/story/2004/12/28/192456/26 It was a 12V motor? G- Ghurd.info [ Parent ]

Re: DC Brush motor as genny (3.00 / 0) (#8) by PEdoubleNIZZLE on Thu Aug 18, 2005 at 03:21:29 PM MST

by heater fan, do you man the cooling fan for the radiator, or the blower for the cabin heat? (or climate heat, whatever you wanna call it) I'm the P-E-double-NIZZLE fo Shizzle [ Parent ]

Re: DC Brush motor as genny (3.00 / 0) (#9) by Norm on Thu Aug 18, 2005 at 08:48:42 PM MST

Neither one...the blower for the heat or air- conditioning... in a car...12 volt the older ones work better...less power smaller wire...higher voltage I guess it   You have to spin it pretty fast but for me they're free...at least the first dozen was.....              ( :>) Norm. ( :>) Norm [ Parent ]

Re: DC Brush motor as genny (3.00 / 0) (#10) by Norm on Thu Aug 18, 2005 at 08:56:13 PM MST

I'm all mixed up  past my bedtime...kinda disregard most of this if it doesn't make any sense...car heater blower motors do work okay if you can spin em fast enough ...                  ( :>) Norm. ( :>) Norm [ Parent ]

Login

Make a new account Username: Password:

Total Views

88 Scoop users have viewed this posting.

Related Links

· Also by PEdoubleNIZZLE