Diagnose

Battery keeps dying

PSE pumps that never sleep and trunk lamps that never go out are the usual thieves. Measure before you replace the battery twice.

Check

After the car goes to sleep (10–20 minutes), what is the current on the negative cable?

A healthy R129 sits around 30–70 mA. Over 200 mA is a hunt. Over 1 A is a lamp or a pump.