DC motor noise in radio on Golf Cart

[danchalf14]

I have a 36 volt EZ GO Golf Cart and have installed a radio across 2 of the 6 6v batteries, my question is what is the best way to build a noise filter to get the motor noise out of the power to radio?

 

[MikeMl]

Get a 12V ~7AH SLA, and charge it with a $10 Charger from Harbor Freight

 

[ronv]

Are you sure it's on the power? I can hear them drive by my house and I don't share the power with them. But having said that I have seen it only as a power problem. Hook it to the car and try the cart near by.

 

[danchalf14]

It is spark noise from the motor brushes as soon as you let off from the accelerator it stops even as you are coasting and it never occurs until you power the motor.

 

[ronv]

The standard fix for brush noise is a .1 ufd. ceramic across the motor leads and one from each motor lead to frame ground. At least 3x the motor voltage. Inside the motor is best but short leads outside should help.
You may not be able to twist the motor leads but if you can tape them together it would help reduce the inductance just in case it is the PWM.

 

[danchalf14]

Do you mean across the Armature leads then the Stator leads, you don't mean also from an armature lead to a stator lead do you? These are 36 to 48 volt Series motors. Also in the golf cart world a frame ground is a real NO-NO. The 36 dc voltage is floating. It's just the battery bank across the motor with one leg broken and controlled by a mosfet controller for speed. If one of the Battery bank legs were to become grounded to the frame , no problem, but if one already is and the other would happen to be chafed and go to ground you could have 6 very powerful batteries under your seat go off like a shotgun. I seem to remember a resistor/capacitor filter , but can't remember the formula. Would a GE MOV ( metal oxide varistor ) work? I don't want to short anything out. The radio has the noise in it directly proportional to the speed of the motor. although the CD player and Mp3 input with iPod connected are ok. Maybe a filter on the Antennae input? Just a thought

 

[MikeMl]

...Also in the golf cart world a frame ground is a real NO-NO. The 36 dc voltage is floating. It's just the battery bank across the motor with one leg broken and controlled by a mosfet controller for speed. If one of the Battery bank legs were to become grounded to the frame , no problem, but if one already is and the other would happen to be chafed and go to ground you could have 6 very powerful batteries under your seat go off like a shotgun. ...

So if you hook a car stereo into the golf cart, doesn't that force you to ground the battery bank to the golf-cart frame? How do you "float" the case of the radio, the antenna base, etc?

 

[danchalf14]

The radio works great without grounding the the neg. side,sound is very clean without the motor running. if you think of a car on rubber tires the antennae is grounded to the frame, mine is too.I think I have a bad ground to the frame, but why would it receive Am and FM clearly, I am going to drill a hole in the windshield frame for a better ground. I got a thread from a guy that said to put a .1mfd. capacitor across the power into the radio , I am going to try that, but first off to the Dentist with a Broken Tooth,there goes
about $1000 for a crown. Won't be buying Cart Parts for awhile.

Dan

 

[ronv]

Brush noise

Just across the armature leads and to the frame of the motor. Keep the leads as short as you can. It would still take 2 failures to make a problem and even then the caps would just be a small fuse.