Stumped by my subaru

what could cause a 2003 subaru outback with 160,000 miles on it to die 100 yards down the road from my driveway, after idling fine for ten minutes before driving. there was no warning, or gradual failing, it was instantaneous. i rolled into a sidestreet, left it there for ten minutes, and when i returned, the battery was completely drained, to the extent that the power doors wouldn’t even open. i only drive this car about once a week, as it is my backup vehicle now. the question is: what would cause it to die without warning, and why would the battery get drained while it just sat there for ten minutes?? thanks for your help

A short in the wiring, battery, alternator. Now, your mechanic has somewhere to start.

The battery could be drained because it is a bad battery. YOu could have another problem that caused the car to die. Was the charge light on; does the charge light work?

Many things could have caused it to die suddenly, broken timing belt (if it has one), fuel pump, ignition failure of some sort. We can help you narrow this down if you are planning to try and fix it yourself. After charging the battery, first thing you need to do is check to see if there is spark and if there is fuel pressure.

The battery may have developed an internal short and I suspect it is not usable now. Before replacing the battery I would check the power system for a short before installing another battery. If there is a high current short it may be from the starter or alternator circuits.

Is that the original battery? If so, it may have decided to just give up its life because 6 years is really stretching it.
It’s also possible that you could have a dirty/corroded battery cable end or it’s quite possible a fusible link decided to pop.

There are several fusible links and power to everything on the vehicle runs through them except the starter motor current.
Sometimes a fusible link will pop simply due to age and the repeated heating and cooling cycles it goes through.