Yes, you will cause damage, not sure what the voltage of the caps would be but my guess would have been 100V. You can open up the controller and see what the ratings are for the caps and fets. You could probably check out the HKSUNWIN thread for the spreadsheet on 72V, mosfet #'s and cap #'s.
Shah said:
I have recently bought 2 60v 23ah battery discharge 80a and bought a series connector too. I was planning to make it to a 120v battery. I just want to test my freeload and maybe just a short ride to test its top speed. Will full throttling it melt my 72v controller? 48v-72v 80a yyk controller. There is a current and phase limit in the Bluetooth app. Will those help anything out to prevent the controller from being spoilt?
So it will probably run on 84 volts then, but about my Controller will it be able to handle it just for a minute or in a matter of seconds and it will be done