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Wiring a car alternator to work as a lawn mower generator? Answered

I have a car alternator that I picked up form my local pick N pull. I also have a lawn mower! Now how to put it together? How do I wire the alternator to charge a battery? it has one main cord that i assume is the negative,  a circular plug that has 3 wires coming out of it: black and yellow, blue and white, and yellow and blue. I also want to wire in a switch to start and stop power production. HELP ME! Thank you in advance!


How many HP is the lawnmower?

Alternator’s are notorious for only being 50 to 60% efficient so you need 2 HP for every 754 watts roughly.

I could not get the power rating for your alternator but I would not go less than 3.5 to 4 HP.

Now if I have it right (black and yellow wire) and (Blue and white wire) go to power, and the (Yellow and blue wire) go to the warning light or the charging indicator.

OK you have plenty of power.

From a battery connect a wire to the switch.

From the Alternator connect the (black and yellow wire) and (Blue and white wire) to the other side of the switch then cap or connect the (Yellow and blue wire) to a warning light or charging indicator.

Were do I get a charging indicator or Warning light? I checked on Amazon and nothing came up. Also what gauge wire do I need? And what type of switch? Like a light switch or something more industrial?

how exactly are you planning to spin the alternator?

I recommend using the CS-130 alternator for your project.
It is found on many older GM vehicles and is said to have a higher
output at lower rpms than many other alternators.
If you do a search for CS-130 you will even find a repair / hookup manual
for it . Plus there is a rebuild video for it on You Tube.

You can do a quick google search and find out how to wire the alternator to the battery. But first you need to identify the alternator itself. What model and year vehicle did it come from. This may or may not make a difference as to which wires go where and how much power it can produce.

This may help.


5 years ago

As you see the alternator frame is the Negative
and the main heavy gauge wire is the Positive !

Put the switch in series with the Rotor Field coil ( green wire in pic )
You do know the alternator needs a regulator
which is a relay that connects the field to the + aux 
when more voltage is needed
and connects the field to minus to lower the voltage

Because the the alternator mass makes the voltage change slowly
a relay was initially used regulate the field.

You should find yourself a regulator.



The alternator is a BBB 13384 from Napa auto. It was pulled from a Lexus (That's what the sticker says. I googled it and it says it is internally regulated. as for your pic, I can not understand any of it. Thanks Though!

Sorry for misunderstanding.  Your question asks how to wire an alternator !

Have a look at my 50 cycle alternator generator for background.

All alternators are basically rotating transformers.

The stator in that pic is the stationary ( non-moving ) part of the three phase transformer
that's why the three windings are drawn separated by 120° just as they are in the machine itself.
The Rotor ( armature ) has a rotating magnetic field spinning in the center distributing shifting flux
energy to the stator windings, where those black arrow-bar Diodes change the transformer AC
Alternating Current to DC Direct Current which is what you need to charge a battery.

A regulator controls the rotating field and in most alternators this is accomplished by
passing electricity to the rotating wire coil by using two conducting metal rings that are
always spinning with the rotor.
Electrical connection to these slip-rings is made through two stationary carbon-brushes
sliding 24-7 while engine turning on the slip rings.

Hope this helps you a little bit  :)