Wow, first thanks to all the forum posters here. Many of the articles on controller modifications and learning about brushless DC motors helped me with this modification.
The scooter is fantastic to drive now. The acceleration is great and I am going an unconfirmed 42 miles an hour. It's unconfirmed because it's hard to tell how fast your really going with the gauges.
First, I picked up this scooter used, very cheap at ($200.00). This included a brand new 48 volt charger. Given my current financial state I could not afford to drop thousands on a new electric scooter.
I could only acheive a top speed of about 28 m/hr. This was disapointing as most of the roads I need to drive on the speed limits are 45 to 35 m/hr.
I went about taking the controller apart and making the following modifications:
1.) Add a 1.5 inch length of pollished "coat hanger" to the current shunt.
2.) I added solder to the positive and negative traces that feed the FETS to add to their current carrying capacity.
3.) I replaced the capacitor across the FETS.
4.) I added an additional wire to the positive and the negative input DC power wires. This was to increase current
carrying capacity and reduce voltage drop.
After making the modifiation to the current shunt I noticed a wonderfull increase in acceleration. I would highly recommend this modification to anyone interested in increasing acceleration.
I was very concerened about the trace thickness and their ability to supply adaquate current to the fets and not burn up a trace when excessive current is present. It is imperitive that if you make the shunt modification that you check to see if the traces can handle it.
In the 60 volt mod of the Panterra Freedom the FETS are only rated for 75 volts. Your charged battery voltage is around 66 volts and all brushless DC motors have a certain amount of back EMF (Electromovive Force). This is esentially Enery in the motor winding that is released and can cause a voltage spike across the FETS and damage them.
In order to be sure my FETS rated at only 75 volts were not damaged I replaced the 63 volt 2200uF capacitor with one much, much larger. A 100volt 15000uf cap. This cap is physically much larger and had to be mounted outside the controller.
The DC power wires of the controller that supply the 60 volts and current to drive the motor are very under sized. The wire from the batterys is a legitamate 10 gauge stranded, but the wire going into the controller would be lucky to be a 14 guage stranded. I added a wire to the positive and negative input, thereby increaseing the current capacity and reducing voltage drop.
In this cheap scooter it is essential that wire guage be increased and connections be improved with solder and elimination of high voltage loss connectors. Voltage = speed = RPM's. Minimizing voltage drop is key.I believe the large capacitor is also providing a valuable service to the controller by providing the quick energy needed so the contoller can quicly respond to throtel demand and provide excellent protection to the FETS when running so close to their rated maximum voltage.
This scooter flys now and is usefull to me on the busy streets. It is a testiment that you don't have to buy an expensive scooter, but definattly need to know how to modify one.