[shook1]

My wife has a 97 Mustang GT with two batteries. One is in the stock location under the hood, and one is in the trunk for use on a hydraulic pump system that raises the car. The battery in the trunk is connected from the front battery in parallel, and has an electronic device that ensures charging from the alternator without reverse draw towards the front battery. The battery under the hood has a lower cold cranking amperage than the battery in the trunk. My problem is, the front battery that actually starts the car keeps dying on me after a couple days of being parked. I'm wondering if the higher amperage battery int the trunk is draining the lower amperage battery under the hood, or if the issue is something else entirely. We thought it was a faulty battery under the hood last year, so we bought a new battery. It lasted a little while, but eventually died on us. The battery in the trunk hasn't given us much trouble.

Do two car batteries in parallel have to be the same amperage? If the draw is from the factory wiring, how do I isolate what is draining the battery?

Thanks in advance,
Luke