Loss of power

[Adawg]

Hi guys, I have a 2001 PDS cart with a lift and 22" tires. I have yet to replace the controller and solenoid, but I did install new batteries and 2g wires. It has been working fine but this weekend I was driving through some trails at a slow rate of speed and then had an occasional loss of power. I had to stop, wait a few seconds and then I was off again. When I got home I noticed the cover to the controller was warm to the touch. I know I need more upgrades still but do you think the slow driving speed was the culprit?

[BobBoyce]

Originally Posted by Adawg

Hi guys, I have a 2001 PDS cart with a lift and 22" tires. I have yet to replace the controller and solenoid, but I did install new batteries and 2g wires. It has been working fine but this weekend I was driving through some trails at a slow rate of speed and then had an occasional loss of power. I had to stop, wait a few seconds and then I was off again. When I got home I noticed the cover to the controller was warm to the touch. I know I need more upgrades still but do you think the slow driving speed was the culprit?

Yes. Driving slow works the motor harder, and larger tires makes it even worst.

[sltintexas]

how slow is considered too slow?

half throttle?

Quarter throttle?

A slow crawl?

[JohnnieB]

A sepex motor is capable of drawing more amps at lower RPM than it is at higher RPM and the efficiency at low RPM is dismal, so more amps are needed to produce the torque needed to propel cart at lower speeds, which in turn causes more heat buildup in both motor and controller.

The 22" tires creates a double whammy in the overheating department since the motor turns 22.2% slower for a given speed and and has to produce 18.2% more torque to maintain that speed.

I try to keep my motor turning at least 1000RPM when driving at low speed for more than a minute or so. That is 4.0 MPH with my 17" tall tires, 4.3 MPH with stock height (18") tires and 5.3 MPH with 22" tall tires.


If you want to drive at jogging speeds or slower for any significant length of time, upgrade to a higher ampacity controller, they have better heat dissipation properties.

Also, upgrading to a 42V or 48V battery pack (requires upgrading controller) reduces the amount of amps needed to produce that same amount of torque produced with a 36V battery pack and the amount of heat produced is the square of the amp flow. (P=I²R)