battery getting drained while driving

What is the ground (negative) cabling from your battery? How is that connected, through the chassis? And do you have a large cable from the chassis up front to the engine block?

What is the symptom that all the juice is being sucked from the battery? Does it fail to start after running for a while. Have you measured the battery voltage non-running when it does this?

It does not make sense that you have 14.7 volts at the battery when running at high idle but that the battery is being discharged. Are you measuring from battery + to battery -? Or are you measuring the 14.7 volts up at the starter?