Start up and throttle problems with my 3kw 48v golden motor

[Bill Parker]

Any help would be greatly appreciated
I built an electric go kart for the kids using a 48 volt 3kw golden motor with matching VEC200 controller. It is powered with a 51volt 40 ah LIFePo4 battery. I am using an FSC010 foot throttle to controller it. The problem that I am having is when the go kart is first starting off from a dead stop the motor make loud ring noises and bucks. However if I push start it or if it’s rolling it will take off pretty good. It also seems to accelerate pretty well.  Also the foot throttle seems to have a dead spot a full throttle.
Thanks in advance
Bill 

[Bikemad]

Hi Bill andto the forum.

I suspect the gear ratio between the motor and the driven wheels may be a bit too high, which could be overloading the motor during the initial startup period.

It might also be worth making sure that the "Maximum rated phase current(A)" is set approx. 30% higher than the "Battery Main current (A)".
E.g. If your "Battery Main current (A)" is set to 150A, then the "Maximum rated phase current(A)" should be set to 195A (150 x 1.3).

A bit more information would be very useful:

• What gear reduction ratio do you have? (Number of teeth on the front and rear sprockets?)
• What is the outer diameter of the driven tyres?
• What is its current top speed?
• Approximately, how many seconds does it take to reach maximum speed from a standing start? (After the slight push to start it moving.) 
• What is the combined weight of the go kart and rider?
• Can you post some screen shots (or photos) showing your controller settings?

Check out this thread for further details of a similar setup.

If the motor is cutting out at full throttle, this is probably caused by the throttle signal output voltage being higher than the "Throttle Maximum Allowed Voltage (V)" setting in the controller.

Try increasing the "Throttle Maximum Allowed Voltage (V)" (along with the "Throttle Upper Voltage Fault Exit Value (V)" and the "Throttle Maximum Valid Voltage (V)") and hopefully it will cure the cutting out problem.

Alan
 

[Bill Parker]

Hi Alan,
As for the “max rated phase current” and the “throttle max allowed voltage” do these two items require programing the controller? I am currently running the controller straight out of the box. Will I need a programing cable and software?
Additional info:
1)   Gear ratio is 5:1; 12 tooth motor sprocket and 60 tooth axle sprocket
2)   The tire diameter is 17 inches
3)   Current top speed is unknown; I have not measure it yet.
4)   Time to reach max speed is also unknown but I would guess about 6-7 seconds (short street we run out of room)
5)   Total combined weight is ; kart is about 300lb. and rider is 160lb. total is 460lb.
Hopefully this is enough info to help.
Thanks for your help
Bill

[Bikemad]

Hi Bill,

Unfortunately, without a programing lead (and the free programming software) it is impossible to check or adjust any of the controller settings, and I don't know what the default settings in the controller are likely to be straight out of the box.

I noticed  in one of your photos that the chain appears to have a fair amount of backlash in it, which might not be very helpful when trying to take off from a standstill, but I couldn't see any obvious means of adjusting the tension of the chain.

According to the data figures for the 3kW motor, it should produce 8Nm of torque @ 4073rpm.
With a 5:1 gear ratio, your go kart should produce 41.56lbs of forward force with 8nm of motor torque, and should theoretically be capable of ~41mph @ 4073rpm if the 41.56lbs of available thrust is sufficient to overcome the wind resistance at that speed. 

Below 15mph, the 5:1 gear ratio should still be able to produce at least 100lbs of forward thrust, provided your battery is capable of delivering 90-95 Amps and the controller current settings are set high enough.

I noticed that the PI800 programming software has a "Throttle Mode Selection" setting which allows either "SoftStart" or "Linear" to be selected, but I don't know which one would be the default setting, or even if these modes are applicable to the VEC200 controller.

The "Starting Phase Current (A)" and Motor Stall Settings could also affect the problem you are experiencing with taking off from a standstill.

I'm not sure what else to suggest, apart from purchasing a programming lead so you can find out what the existing settings actually are.

Alan
 

[Bill Parker]

Alan,

Thanks again for your help. I ordered the programming cable to see if I can tweak the controller’s performance per your suggestion. I will provide feedback once I learn more.

Bill