Serial A814N02928B

This is a 48 volt unit. Has new battery and new charger. Both set up correctly. Customer ran unit extremely dead. got battery charger and equalized and unit will not run on 48 volts only 36 volts. When on 48 volts it reads voltage too high. had controllers inspected and they passed. hooked up handset and tried adjusting function 15 with no change. looked all over truck and unable to find any sort of dip switches. are there any dip switches in the controllers? is there something Im missing? or any other tests I can do? thanks for any input