As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU NO START, 2 ATTEMPTS WITH FAULT BOTH TIMES. APU VERY SLOW TO SPOOL, ABORTS AT 19 PERCENT ON 3 TRIES. REPLACED APU BATTERY, WAS READING LOW VOLTAGE 21 BEFORE START & 11 VOLTS DURING START. REPLACED APU BATTERY IAW AMM, CHECKED GOOD. APU STARTS & RUNS NORMALLY.