You can load test a battery with resistors & a DVM. for a 48 v battery I used three 5 ohm 250 w resistors series (I had for PA amplifier tests) and a DVM. Two batteries would not sustain >40 v even with the 3 amp load that provides. Do this test outside on concrete, LiIon batteries can catch fire and the only extinguisher is piles of dirt.
If battery is okay, then you look for a controller. No way you are ever going to match a controller by number, if Pedego stiffed you. You can maybe match up the connectors to the motor, motor hall effect sensors, brake switches, throttle, and PAS sensor. I've recently found connectors to the sensors from 2018 are totally unavailale on ebay or amazon. Since my 2018 controller quit, to use a controller I can buy I've had to replace the throttle for one with a rectangular connector, give up the PAS sensor ( since scooter controllers don't have them) and I still haven't found the square plastic connectors for the brake handle harness. I also had to jimmy an input for a "door switch" which is some kind of scooter gizmo that works like an ignition switch. The juli connector motors I'm buying now require a converter harness to the 6 pin rectangular hall effect connector on the controllers I can buy. Plus the 3 bullet connectors for the phase wires (available from dorman at most auto supplies like oreillys). I found could buy a kit of rectangular connectors on ebay that I could solder instead of crimping. Juli connectors are molded, totally impossible to modify the pinout. Happy shopping.