iPhone 6s battery terminal reading?

i recently bought a water damaged iphone to see if i could fix it. long story short, the motherboard turned out to be bricked so i bought new/used one of ebay. Today i received it, installed it, and would not turn on, not even when connected to power. I tore it apart and tested the battery terminal on the motherboard. (battery is disconnected) Obviously when tested it without the charger plugged in, i got 0 volts. but once i plugged the charge cord in, the reading is measily 0.9 volts. shouldnt it be closer to 5.0 volts? or does the circuitry ramp the voltage down for a charge? any help is appreciated.