As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOTH AFT (L2 AND R2) EMERGENCY BATTERIES TEST BAD. GROUNDED - YES. REMOVED AND REPLACED LEFT AND RIGHT AFT BATTERY PACKS AND POWER SUPPLIES, S/N 414761 & S/N 412851. OPS CK GOOD IAW B737-900 AMM 33-57-06-960-805 STEPS 4.E(1-3(E))(4-6), F(4) AND AMM 33-51-06-960-806 STEP 5.E(1-3(E)), (4-5), F(4).