Well, in essence, a cap is a battery, just one that stores more power and discharges it very quickly. If your amp isn't on, it shouldn't be draining the car's battery to recharge the cap. I'm at a loss on this one. If you have a meter or test light, hook it up to the REMOTE wire and - terminals on the amp with the radio OFF. There should be 0 volts, or no light on the test light. If there is either, the amp is drawing power and killing your battery, keep up posted, well get to the bottom of this!