No more speed

[Deshawnj]

Hi guys, I have someone that brought me a 99 EZGO non pds cart. They would press the accelerator to the floor and the cart barely moves. They changed the micro switch under the floor, the throttle sensor under the floor. They put a new solenoid and new forward reverse switch set and now you press the pedal to the floor it barely moves. If you press it half way it will slowly come up to speed.

The batteries will make 3 years old in March. I double checked the connections.

He said it happened all of a sudden one day.

Can anyone help me figure out what it may be. I have a voltmeter. I can post any results I get and would really appreciate it.

Edit, after the charger kicks off my pack voltage measures 38.0 each battery is between 6.33 and 6.38

[cgtech]

Carefully plug your volt meter leads into the charger port & report back to us how low the voltage drops when trying to drive.

[Deshawnj]

At a stop the charge receptacle reads around 37.89

Slowly depressing pedal it drops to as low as 34. Something

Pressing the pedal to the floor from a stop goes as low as 31. Something

[cgtech]

Is that 31 when the cart is going fast, or just barely crawling?.

[Deshawnj]

Barely crawling, it will slowly go faster and come up in volts to about 34

[Deshawnj]

I charged the cart full charge and put the rear of the cart on jack stands.

When I press the pedal the rear wheels spin no problem.

When I press the pedal all the way to the floor, the wheels spin as fast as they can go for as long as I want. Nothing out of the ordinary.

Put the cart on the ground and press the pedal slightly or all the way and the cart barely moves, while moving it shakes constantly.

Could my motor still be bad?

Or does it point to my controller?

Thanks,

[JohnnieB]

Sounds more like a battery issue.

It only takes a few amps to spin the tires when they are off the ground, but it takes a lot of amps to accelerate the cart from a standstill.

The battery pack voltage dropping less at partial throttle than it does at full throttle indicates the batteries might not be in good health and well maintained batteries in Louisiana only have a typical life expectancy of 2.5 to 3.5 years, so the 3 year old batteries in the cart are either passed their expected EOL or approaching it, depending on the location in the state. See attached map of battery life by climate zones.

I suspect the voltage of one (or more) of the batteries is dropping under load more than the others. Measure the battery pack voltage during a full throttle acceleration from a standstill and note the lowest the pack voltage goes to. Divide that by six to get the average voltage under load.

Then measure what each individual battery drops to under load. All six should be within 0.1V of the others, but I suspect several will be higher than the average while one or more will be significantly under the average.

[Deshawnj]

Thanks JohnnieB you helped me years ago fix my Powerwise charger and I greatly appreciated that.

Can I measure the battery voltage with the cart on stands or do I need to do it while the cart is on the ground and has resistance?

I'm at the southern tip of Louisiana it gets hotter than hell here. Thanks for that image.

[JohnnieB]

Tires on the ground.

Measure the voltages accelerating (or at least trying to accelerate) over the same stretch of ground.

Try to keep everything the same for each battery.

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I've got DVMs that have a Min/Max function that is the perfect tool for testing batteries under load. Just clip the leads to whatever you want to measure, set the Min/Max function and hit the pedal. The lowest voltage reached is captured. Comes in handy for a lot of other things also.

[Deshawnj]

Thanks JohnnieB over half the batteries were bad. My total pack voltage would drop to 30v when trying to drive the cart.

A new set of batteries and I am all good. Thanks again.