Where to now?

I recently was given a remote control golf cart. It had been stripped of it's circuitry except the two 180 watt wheel motors and battery. I thought that I could salvage this cart by converting to battery powered by wiring it up with a PDM. I tried a small PDM (12v-40V-10A) but kept blowing fuses. The battery is a 12V-80ah. My only guess, at this point, is that PDM I chose is too small in capacity, Is there something else I should be considering. I don't want to ruin the motors , s they are working fine. What's to do? I need , obviously, some method of speed control. Any suggestions?

Welcome to the forum.
You could measure the max current consumption then get a controller double that.

By "controller" do you mean PDM?

If you did mean PDM, it would be for 2- 12v dc @23Aand 180Watt motors each running at the same speed Could I possible harm the motors by going to -say- a 40AMP PDM?

You will only damage the motors if you give them too much voltage. It is OK to have the current rating of motor speed controller higher than what the motors need. They will only draw the current they need to run at X speed under load. If each motor can draw 23 amps, then you want a controller larger than tnd the sum of the two currents. I would say 50Amps minimum. But I would probably go 70Amps or higher.

PWM (Pulse Width Modulator) is the term used for most motor speed controllers.

A 12 V 180W DC motor has max current of 15A but at stall or max torque or reverse acceleration the current can be more than 5x or 75A. The current surge follows OHm's Law for Ipk= Vbat/(Rs+RdsOn) for motor coil DCR, Rs and total bridge FET resistance (RdsOn)
The current is directly proportional to acceleration until max speed friction is reached.

Normally I choose RdsOn to be 10% of the motor coil Rs. Logic level FETs make the job easier but you strill have to ensure deadtime to prevent shoothru.

Use PWM to regulate the Voltage and monitor current if you want to limit that and the torque.

Your probably way underpowered. Take a look here: **broken link removed**

These are much higher voltage motors.

Is the steering accomplished with the wheel motors at different speeds?

Try the manufacturer for some specs.

In any rate, you could put the wheels off the ground and measure the noload current easily.

Use a starter solenoid and direcly connect it to the battery, that way the sparks are elsewhere.

Use a shunt such as this one **broken link removed**

You may need to use a 9V battery. Be aware that most of these ebay ammeters put the shunt in the negative supply.

Your controller is 10A *12V which is 120 W, not 180 . 180W would not be high enough because the motor needs a LOT more current to start.

You could estimate this if you knew the DC resistance of the winding.

Assuming, you don't have a 5-wire ohmmeter and don;t live near me, you can measure the resistance by measuring the current through the motor (shunt) and the voltage across the motor. Maybe a couple of D cell batteries and use that as your max current.

Be careful choosing the wire gauge too.

To back me up, here **broken link removed** is some DC motor theory. The stall and starting current is the same V/R.

So, you have to find the motor resistance.

The controller may also implement braking.

So, you have
Direction=FWD/REV
COAST
BRAKE
SPEED which is generally a NOT ENABLE signal for the PWM.

and you could have steering as the relative speed of the two motors and slow start. Regenerative braking is also possible. That's where braking charges the battery.

So, you may have a lot more going on.

BTW: Welcome to the forum!

I was thinking pwm not pdm too.

Thank you guys for the info and excuse the pwm-pdm confusion on my part. I have located a reasonably priced PWM rated @ 60 A. This will just be a straight forward battery powered golf cart with no excessive load requirements. "Turn the knob to match your pace" type of thing. Hope it helps my game.

You can get thumb throttle controls for electric pushbikes, might be more suitable, and safer, if you trip the cart stops instead of running away on its own, ought to be failry simple to hack one.

That's a good suggestion but a bit more than a typical golf cart would require. I would like to put a an ON-OFF switch some where but can't decide if it should be before the PWM or on the motor control wires. With a 60amp PWM I don't think I need to be concerned. Right?

Your on/off switch should be between the battery and the PWM.

One reason for that, is that PWM controllers will still draw some internal operating current, even when their output is off.

This **broken link removed** is outside the US and with a "replacement part" flare, there are no specs. The operation needs to be rated continuous and it will be your safety to pull out all of the stops. i.e. disconnect the battery or at least the propulsion. Using the URL because it was the first find.

These were used on older vehicles to start cars.

Make it a good switch. We wouldn't want to read about the golfer who was chasing his runaway cart.

Thanks so much for the support and insight. The cart is up and running and I'm off to lower my handicap. For a "jerk" I've over come. Thanks again.

Cool. Glad we could help.

Brilliant.
You can stop at the 19th now and spend some of the money you saved.

I got my cart all wired and applied the pwm. All seems fine but I'm wondering if I have it wired in series versus parallel. I have the B+ wire to the B+ wire on one motor and the B- wire of that motor wired to the B+ wire on the second motor with B- wire connected to the B- destination. Should I have the B+ wire connected to both B+ connections on both motors and the B- wire connected to both B- wires on both motors? The speed and performance , as I said, seem ok but this has me wondering. As you can tell, I know dip about this stuff. Am I missing performance.

Well, all you said, I think is two 180 W motors. yes, you do have them in series, not parallel. (2*180)/12 or 30A, so you should be OK with a 60A controller providing the motors are indeed 12V.

Thank you again!