a little more information would be a good thing to get more correct information back, like a serial number... maybe the type of controller.
I am going to ASSUME this truck haas an EV100 lx controller.
these are all what we refer to as; "static return to off" codes, and they indicate an improper start up, or that the operator presence was not correctly detected.
Look for wires loose on the brakes and or seat switches. even just a little loose can throw these types of errors.
to put a load on the battery you only need to stall the hydraulics (lift all the way up) and read the voltages be sure to read the voltage "at rest" first.
these are not usually battery related codes.