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Razor ground force drifter troubleshooting

Hi,


I recently bought 2 used V4 Razor Ground Force Drifter karts about 2 weeks ago.  One worked, one didn't.   The dead one had a weak battery which I swapped out and it came to life.  Kids had tons of fun for about 5 sessions.


While I was at work, the kids drove the karts until both stopped working and said they were "out of batteries" (versus suddenly stopped working).  They charged them back up and I verified that each 12v battery measured between 12.8v and 13.1v.  However, next session, neither kart worked.  Power light lights up but both basically "click" and barely move (as in just a momentary thunk of chain tension and no actual movement.


Here are my troubleshooting results so far:

Kart A

Voltage across both batteries w/switch OFF: 25.4v

Voltage across both batteries w/switch ON (no throttle): 21.1v

Motor to controller connectors are melted and distorted, cannot disconnect

Directly connecting 12v battery to motor: rear wheels spin quickly


Kart B

Voltage across both batteries w/switch OFF: 26.4v

Voltage across both batteries w/switch ON (no throttle): 26.4v 

Motor to controller connectors are NOT melted, look fine

Directly connecting 12v battery to motor: rear wheels DO NOT spin at all


I cannot believe both karts died for different reasons on the same day in the same session.  I can't understand how the one with no apparent problems in the wiring has a dead motor, nor can I understand why the kart that worked fine with melted looking wires worked great but now shows a voltage drop when turned ON but has a working motor.


Any ideas?

Thank you for posting such comprehensive test results. They make diagnosis of the problems very easy.

Kart A: The test results show that the battery pack is old, worn out, or faulty and needs to be replaced.

Kart B: The test results indicate that the motor has failed and no longer works.

It is unusual that both karts would fail on the same day however thanks to your thorough diagnostic testing the reasons why are apparent.

Thank you for the quick response.


I'm curious, is the voltage drop I saw from simply turning on the power switch an expected symptom of a weak battery?  I ask because my kids have driven these karts for a minimum of 20 minutes (usually over 30 minutes) per session and all of a sudden, it stopped working.  There was no slow degradation of battery life.  Also, you didn't comment on the melted wiring I mentioned.  It's curious to me that the kart with the potentially weak battery would show the symptom of melted wiring, which I would equate to high resistance somewhere in the system.


Either way, tonight I will swap batteries and motors between the two to see if I can make a working combination out of the potentially good parts.


Thanks,


Joel

The Voltage drop from only turning the power switch on is a sign of a very weak battery pack, usually the Voltage drop occurs when the throttle is engaged and there is more of a load on the battery pack. Being that the Voltage drops when the power switch is turned on indicates a battery pack in very poor condition.

It is not common for a battery pack to work for 20 minutes one day and then to not work the next day. Usually they do wear out more gradually than that. It is possible that a manufacturing defect or high g-force event such as an accident or impact caused the failure of the battery pack instead of old age in this situation.

The melting of battery pack or motor wire's insulation is most commonly caused by an over-current condition created by going up a hill that is too steep, starting the kart when it is stopped against a curb, or traveling through high grass, mud, or sand which bogged the motor down. Melted wires could also be caused by a motor that has a short circuited coil or power wires which could be due to a manufacturing defect or overheating event.

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