Error 30 is a communication failure between the display and the controller. It could be either the display or the controller or the cable between them. Unplug all the connectors between the display and the controller and carefully inspect the connector pins. Sometimes a pin gets bent. Also check the length of the cable for any visible damage. If you still get error 30 after checking the connections, it's hard to know if it is from the display or the controller unless you have another one to test with.
Yes, the 52v controller will work fine as long as you have a 52v battery. The only real difference is the high/low cutoff voltages and the range of the voltage meter on the display.
Yes, the 52v controller will work fine as long as you have a 52v battery. The only real difference is the high/low cutoff voltages and the range of the voltage meter on the display.