What must be done if the battery voltage is found to be below 22 VDC?

When the battery voltage is found to be below 22 VDC, replacing the battery is often the necessary action to ensure proper functionality and safety of the aircraft's systems. A battery with low voltage may not be able to provide sufficient power to start the engines or operate essential electronic systems, posing significant operational risks.

In situations where the voltage falls below this threshold, the integrity and reliability of the battery can be compromised, meaning it may not hold a charge effectively even if recharged. Thus, replacement ensures that a fully functional and reliable power source is provided, which is critical for the operation of the C-130J.

While recharging the battery might seem like a viable option, it is not guaranteed to restore full functionality if the battery has reached a point of deterioration. Adjusting the voltage wouldn't be applicable, as batteries need to be capable of reaching and maintaining a specific voltage level for safe operations. Checking the connections is important for troubleshooting but won’t resolve the fundamental issue of a battery that cannot hold sufficient voltage. Therefore, replacement is the definitive solution when confronted with low voltage readings, as it guarantees reliability and safety in aircraft operations.