Battery Charging

[mrfrisky]

I have a windblue PMA connected to a 1/3hp 115V electric motor. I just want to be able to charge deep cycle batteries. I have two 12V 105 Amp hour deep cycle batteries wired in parallel. Using a 7" pulley on the motor, I'm getting a lot of rpm yielding 671 ACV from the back of the unit and 298 DCV with rectifier. I get stalling/stoppage of the motor/PMA combination once I hook up to battery. Is it the alternator or the motor? Would I need a voltage regulator, or higher capacity rectifier? I've seen videos on youtube where they use capacitors on the motor with this kind of setup. Any information will be greatly appreciated.
See http://www.merdist.com/DC540.jpg
and http://www.merdist.com/DC540setup.jpg

[WeThePeople]

Frankly, I'd put the smallest pulley on that motor you have,
you don't need that much speed for this task.

1/3-HP is much less than what that alternator is capible utilizing at full output,
reduction from a very small pulley should give that motor a better advantage.

Second, I see the meter is set to AC-volts, not DC-volts.

Your looking at open circuit AC ripple in that pic,
and indicating a DC measurment above too.

Open circuit voltage without load has little value.

Use a headlight bulb, or whatever you have hanging around to load it first.

I goes without saying you should be using a charge regulator btw...

[mrfrisky]

Received this suggestion also:

I think you may be turning the alternator too fast, most only need 1000 RPM to reach a good charging level. I am seeing the size of the pulley on the motor and it seems to be too big, lessening the torque to the alternator. I'd change the pulley size to make the alternator turn at only about 1000-1500 rpm. 1/3 hp will put out about 250 watts ( 1 HP = 746 watts)

Also you will need a three phase diode bank, if there is one in the alternator already it may have got fried from the high voltage. May need to replace it and the regulator. The internal diodes are usually only rated for 150 VDC.

Good luck!

Greg

[ewizard]

Yes most PMA's do not like high speed and can be damaged by spinning too fast. Check the specs for the one you have but as someone else mentioned it might have already caused some damage.

[WeThePeople]

perhaps you could tell us more ?

Which WindBlue-PMA alternator ?
Permanent Magnet Alternators

What RPM is the motor rated for ?

It was hard to guess if you had the external rectifier model,
or was testing from the AC-tap provided on one of the phases
of alternators to be reverse compatible for older applications.

They only show the fronts on the website,
and your pics are of the back, lol...

[mrfrisky]

Thanks,
Sorry about the delay, was out of town.

DC540, first one on your page.

I reduced the pulley to 3 1/2" and with external rectifier am now getting 138DCV. Still getting same problem when I connect to Deep Cycle battery.