Friday, October 12, 2012

First Run of Electric Go Kart and First Problem, Solutions

Here is a video of the maiden voyage. It worked perfectly for a few minutes before it died!

At first we thought the controller shorted out or the batteries died. When we opened up the engine cover we smelled burning plastic. The problem was that the connectors from the batteries to the controller and from the controller to the motor melted. The odd thing is that these connectors came with the controller. I actually thought that they cheaped out on the wires. I went to Home Depot and bought some heavy duty connectors and a crimping tool and we were back in business. When I called TNC Scooters the next day, they told me that sometimes the connectors are not rated for the right amperage. This was a $30 controller, I guess I should be happy it worked at all.

Original Connectors:

Battery/Motor Connectors (2-pin) from TNC Scooters
These melted after 5 minutes of use.

New Connectors:
These are 12-10 gauge (high current) connectors from Home Depot
These worked perfectly, no more problems.

Shortly after I installed the Dorman LED indicator light, it blew out. I quickly diagnosed the problem. The wiring diagram for the controller is as follows:
Wiring Diagram from TNC Scooters
I assumed that the power indicator would be 12 volts since most electronic components such as lights and accessories are 12 volts. I was wrong. The voltage is the same as the supplied voltage from the batteries, 36-39 volts. This is way too much for a 12 volt light. I searched for a 36 volt LED indicator light and could not find one. I ended up buying another 12 volt Dorman indicator light from and used a work-around technique which I will describe later.

After changing the connectors and using the go kart a few more times, I noticed problems with overheating of both the motor and controller. The controller seemed to heat up after a few minutes of use and stayed hot. Airflow over the controller from opening the mailbox door did not help. The motor only seemed to heat up when used at low speeds with high load such as driving around in the grass in circles. If you look on YouTube, you will see examples of overheating MY1020 motors:
On, there is a thread called How to Ice Your Motor which gives great ideas for cooling electric motors. Fetcher and Lessss post some great pictures showing Nidec centrifugal blowers attached to their electric motors. I checked Ebay and found that you can buy these types of fans for about $10 each. When buying Nidec fans, look at the voltage and amperage. Since I have a 36 volt system, I decided to buy one 12 volt fan and one 24 volt fan and string them together in series. Here are the fans I used:

Nidec 24 VDC 0.40 A fan. Link to fan

Actual pictures of Nidec fan:
Nidec Gamma32 Front
Nidec Gamma32 Back

Nidec 12 VDC 0.46 A fan. Link to fan on Ebay.
Nidec Gamma30
Once I had both fans wired to the power indicator connector on the controller and installed them properly, the overheating problem was completely resolved. Both the controller and engine stay cool at all times. The cost is a 15 watt draw on the batteries. This will result in less driving time between charges but I haven't noticed the difference.

Picture of Nidec Gamma32 blower attached to MY1020 motor with a plastic bag directing the airflow through the motor.

Here is a video showing the fan in action:

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