New 500A controller causing problem

[danzapata9]

I just added a 500A controller to my 1991 ezgo marathon. I believe I swapped it out correctly but the cart now jumps when hitting the accelerator. Any thoughts on why this is happening?

[golfcartg]

Let's start with some general troubleshooting steps. Firstly for safety, placing the cart on jack stands. Next, we'll want to check the potentiometer (pot box) to verify it's functioning correctly. The pot should measure 0-5k ohms through its travel. To do this, disconnect two wires from the pot to the controller and insert the test leads of a Digital Voltmeter (DVM) into the wire connectors. Set the DVM to 20k ohms (this setting is usually indicated by the symbol Ω on the DVM), if you're unsure how to set this, look for a dial labeled with resistance values, and select the 20k ohms option. Now, depress the pedal and observe the meter reading. The reading should rise smoothly to 5-6k ohms as you press the pedal.

The POT box serves as the throttle control mechanism, translating the movement of the accelerator pedal into electrical signals that regulate the speed of the cart. Inside the pot box is a potentiometer, a variable resistor that changes resistance as the accelerator pedal is depressed or released. As the resistance changes, the potentiometer sends corresponding voltage signals to the motor controller, instructing it to adjust the speed of the electric motor accordingly. In essence the pot box acts as the intermediary between the driver's input on the accelerator pedal and the motor controller. Any issues with the pot box, such as wear and tear or malfunction, can lead to erratic acceleration or other performance issues.

To test the controller's functionality, start by placing the test leads of the Digital Voltmeter (DVM) on the B- (Battery Negative) and M- (Motor Negative) terminals on the controller. With the cart safely elevated on jack stands, press the accelerator pedal until you hear the solenoid click. At this point, you should read the full battery pack voltage between the B- and M- terminals on the controller. As you continue to press the pedal down, observe the voltage on the DVM. You should see the voltage gradually decrease, indicating that the controller is successfully powering up and delivering voltage to the motor as the pedal is depressed. This test helps confirm that the controller is functioning correctly throughout its range and is capable of supplying proper power to the motor for smooth propulsion.

Understanding how the cart was running before the controller upgrade and why the upgrade was undertaken could provide valuable context for troubleshooting. Any information on the cart's performance issues or limitations prior to the upgrade, as well as the specific goals or improvements sought with the new controller, could help pinpoint potential causes with the jumping motion.

[danzapata9]

golfcartg thank you for the response that is going to be a lot for me to make happen but I will try to work through that advice. The cart was maxing at 12mph and the hope was to get it a little quicker to be on the street. It was running fine for the week I have had it just slow

[danzapata9]

golfcartg the cart jumping feeling happened immediately after swapping out the controller. Drove it about 50 ft turned around and parked it.

[golfcartg]

Thankfully in this scenario, the POT box appears to be functioning properly. This removes one potential worry from the troubleshooting process. Try reaching out to the controller manufacturer directly for instructions on how to program the controller for your setup. Additionally, keep an eye on your Forward/Reverse (FNR) switch to make sure it doesn't overheat. If it does, consider temporarily reducing the controller output until further upgrades can be made.

Actually, you can maintain your current motor and original controller and still achieve a 25% increase in speed through a few simple modifications. Firstly, upgrade all your cables to 4 gauge and clean the connections well for improved electrical conductivity. Next, consider increasing your rear tire diameter from the stock 18 inches to 20 inches (without requiring a lift kit), which can provide a slight speed boost. Another option is to add an additional battery in the center, near the FNR switch to upgrade to 42 volts. Keep in mind that this will necessitate a new charger compatible with 42 volts unless you opt for the cheap way and use an automotive charger for the extra 6 volt battery. Your original controller should be suitable for the task depending on its specifications. For instance, many of the original Curtis 36 volt controllers have the capacity to handle up to 42 volts without any adverse effects.

[danzapata9]

golfcartg when you say all the cables do you mean the ones from the motor that attach to the controller? Or does that include the ones that are connected to the batteries as well?

[golfcartg]

Thicker gauge battery cables along with squeaky clean connections offer lower resistance to electrical flow, allowing for more efficient power transmission from the batteries. This improved conductivity can lead to slightly better acceleration and enhanced torque. Swapping out the cables that connect to the motor can also contribute to gains by improving power delivery efficiency. These cables deliver power from the controller to the motor, and upgrading them to thicker gauge options can further reduce resistance, resulting in improved responsiveness, particularly during acceleration and uphill climbs.

Pairing the upgraded battery and motor cables with increased tire size can lead to a noticeable improvement in torque and speed on a golf cart when on a budget. When you increase the tire size, you effectively change the gear ratio of the cart. Larger tires cover more ground with each revolution compared to smaller ones, akin to shifting gears in a car. This alteration in gear ratio allows the motor to operate more efficiently, translating into better speed performance. However, this change in gear ratio can sometimes lead to a loss of torque, particularly during acceleration or when climbing hills. The upgraded cables help to compensate for this potential loss of torque by allowing more electrical power to reach the motor more efficiently. This helps to offset any reduction in torque caused by the larger tires. As a result, the cart maintains its ability to accelerate and climb hills, even with the altered tire ratio.

[danzapata9]

golfcartg thank you all the info. Would the motor/controller cables be the same as the battery cables? Or do they differ in some way other than length?

[danzapata9]

golfcartg hello again. I have replaced 5 of the battery cables but have not attempted to replace the two that go into the charging port. Would these two need to be replaced as well to improve the speed or do they not impact the carts driving performance?

[Michael Eddie]

Figured I'd chime in, when upgrading your battery cables for improved performance it's generally recommended to use 4 gauge cables for all high current connections. This includes cables such as those from the battery to the solenoid, from the solenoid to the controller, from the forward/reverse switch to the motor and controller, etc (see pic). However, the wires that run from the charger port to the batteries don't fall into this category. These wires handle a different type of current and typically don't impact the cart's driving performance.

[danzapata9]

Michael Eddie thank you I was hoping that is the case. I am not an expert with this stuff and messing with the charging port was not something I feel confident messing with.