As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU ARRIVED AT GATE WITH AN APU WEAK BATTERY MESSAGE AND APU CHARGER MESSAGE. BATTERY VOLTS AT 24 VDC, CHARGER NO MORE THAN 1 AMP CHARGE. FOUND FAULTY CHARGER. REPLACED APU BATTERY CHARGER AND APU BATTERY, REF MM 24-31-06 AND MM 24-31-05. OPS TEST OK.AC OK FOR SERVICE.