There's something else going on aside from just not driving it for 5 days. I've left my Jeep to sit in the garage for 2 weeks in the winter, and it still started up just fine.
You don't have anything plugged into the accessory outlet (used to be the cigarette lighter), do you? Most cars don't kill the power to that outlet just because the car is off. I nearly killed a battery because I left my CB radio on.
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"I feel like my world was classier before I found cyclocross."
- Mandi M.