EZGO Marathon 1993? Low torque!

[Codum]

My Marathon has lost torque. It was running fine then all of a sudden like flipping a switch torque was cut in half and is smells like and electric short. Each battery has 5.7 volts and I have 34.2 total. Also when in reverse the back up horn cuts off once load is on motor. How do I tell if it's the motor that is bad and not something else. I also had like 27.4 volts at the two terminals on the rear side of the device between the batteries under the plastic cover. I am thinking it could be a bad cable. Any suggestions. Thanks.

[dougmcp]

It is definitely a bad cable or bad/loose/corroded connection.
Take a look at your connections for any place that shows heating, discoloration, melting etc.
Give all your cables a tug and make sure they are not broken inside.
Check all connections from the batteries to the F-N-R switch to the solenoid to the motor.
5.7v in each battery is essentially dead, they need to be above 6.3v to be any good.
When you apply power to drive the motor, as the battery voltage goes down the amperage goes up. With low batteries the increased amperage is putting an extra strain on your connections.

[Codum]

Thanks, I am charging the batteries now. I have checked the connections at the batteries and motor all seamed ok. Once charged, can I check the voltage at the post on the motor. What should that voltage be? Should it be the same as when checked at the batteries 37 or more with no or little voltage drop. If I do have voltage drop then does that ensure I have a bad cable or bad connection. Thanks.

[dougmcp]

Is your cart a resistor cart or controller cart?
Voltage drop won't necessarily indicate a bad cable, you could have a bad battery or something that is not allowing the power to flow like a throttle, resistor, controller or even brakes dragging.
Get the batteries charged up and then take an individual reading of each battery after the batteries settle down from charging (a couple of hours).
Attach your voltmeter to the pack and take the cart for a ride, if it drops more than 15%-20% (31v-32v) under full throttle, you have a battery, connection or cable issue.

[Codum]

Out of curiosity I checked the voltage while charging. All but one battery shows 6.3 volts. The one that is first from the negative side is showing 9.5 volts. Seems like they all should be the same. The total volts while charging is 41.9-42 volts. Does any of this mean anything? Thanks.

[dougmcp]

Generally the battery that shows the highest voltage while charging is the weakest battery of the bunch.
After you disconnect the charger, let the batteries settle down, preferably overnight but at least a couple of hours then take individual readings of the batteries. You will probably find that the one that was charging the most has the lowest retained voltage.
You may want to get a hydrometer and check that battery or load test it.

[Codum]

Thanks, also it has a controller I think. It has three devices between the batteries under on cover. One has linkage to the gas pedal. One looks like a solenoid. The other is a square box 3"x5"x8" approximately. I think this is the controller. How can I test the controller or be able to rule it out? Thanks!

[dougmcp]

That is the controller but they rarely fail partially. If you have a cart that moves and is somewhat speed controllable, I would rule that out as a problem.
You probably have a 0-5K throttle assembly that can occasionally be a problem and they need to go smoothly from 0-5K ohms.

[Codum]

Looks like you were right. The battery that was showing the 9+ volts while charging is now this morning 4.2. All the others are 6.1-6.2. When I drive it yes the volts drop to 34 volts and if on a slight incline it will barely go up hill plus it starts to vibrate. Once back on level ground it will go just no torque. I will get another battery tomorrow. My batteries are 4 years old so I will try to get a good used one. Then in another year or two replace them all. I read somewhere that it was not good to put a new battery in with a group of old ones. Thanks for the help.

[dougmcp]

Good plan to replace that 1 battery and start saving for a whole new set.
Glad you got your problems sorted out and thanks for letting us know.

[Codum]

Got a good used battery today. $35.00 Problem solved. Thanks dougmcp!

[dougmcp]

Glad it working well now!
It's all good!