2005 Precedent: power cut at full throttle

[Toddavid]

When I give it throttle, everything is good until I go full throttle and then it suddenly drops to like half power. If I back off, full power seems to come back for a little, and then drops off again at full throttle.

I would have thought a bad battery cell, but batteries appear fully charged, and I checked each cell with a specific gravity tester and all were within spec.

Ideas?

[Volt_Ampere]

You need to "Load Test" the batteries. It's likely that they are sagging under load. Specific Gravity isn't going to tell you much. You need resting voltage vs under load voltage.

[Cartmaster]

I could be wrong, but it may just be your speed sensor. Release the brake and push the cart. Does it roll freely with no bleeping or do you feel resistance and hear a bleeping after a couple of feet of movement.

As Volt ampere said, it could be failing batteries or a poor / corroded connection on a battery lead or any other high current lead between batteries, controller, solenoid, motor etc.

[Toddavid]

Cart rolls freely with brake off.

Battery terminals are clean.

Will drop from 54v to 50v under full throttle on a flat road, but feels like 3/4 speed.

To make matters worse I just checked and cleaned the motor terminals and now the cart won’t move in reverse. It makes a click noise from solenoid, moves a fraction of an inch forward, and then clicks and stops. I did terminals on motor one by one so they are definitely in the original spots…

[SV1]

Marking to follow thread

[WalterM6]

I just checked and cleaned the motor terminals and now the cart won’t move in reverse

Did you make any sparks cleaning those terminals?

[Volt_Ampere]

I hope you did not do that with the battery connected. If you did, you may have killed your controller.

[Toddavid]

Originally Posted by Volt_Ampere

I hope you did not do that with the battery connected. If you did, you may have killed your controller.

Well, yes, I think that’s what happened. Cart was key off, neutral, tow mode, which was a wrong assumption that battery power was killed to motor. Must have inadvertently shorted something along the way. I’ll use one of highly rated eBay refurb services to repair, unless you guys have a different suggestion.

Regardless, any insight to my full throttle power issue? Doesn’t seem to be a battery load problem.

After a full charge, I get one or two throttle applications before it goes into this “limp mode”. It still powers smoothly, just at a reduced volume.

[Toddavid]

Ok, finally can update this thread.

Sent my controller to a high rated repair service that I found on eBay, and indeed my reverse circuit was fried. They repaired it for $125.

Meanwhile I ordered up a speed sensor.

I installed the controller today, and had forward and reverse gear back, but still the power cut at full throttle.

I then installed the speed sensor and new magnet, 15 minute job, and all my power is back.

Would have been a cheap fix for $18 if I hadn’t fried the controller.

Lesson learned: always disconnect the batteries when working on the cart…

[SV1]

Thanks for taking the time to share the fix. It helps a lot of us learn.