I hope you have a nice neighbor with jumper cables. If you are in a garage, invest in a battery minder to keep the battery charged.

It is always possible that the brushes in the voltage regulator are worn down and no longer producing 14.4V. If the headlights are always on when the engine is on, your battery will not charge at idle. Also when the heater blower is trying to warm up the cabin at the same time.

Taking the car to an auto parts store had having them do a 'load test' on the battery and alternator is also a good idea.

Shovel that snow away!!!!

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Keeping it running is better than buying new

Unhook the battery negative terminal. With everything off in the car, measure
DC current between the negative battery terminal and the lead you just removed.
You should measure very low DC milliamps 25+- fluctuating. That's to power
the computers. It will be higher since your battery is discharging.

Pull fuses one by one to find the guilty circuit. When the current drops to
the DC .025A +- (25 ma) you found it.
Likely you will find the problem circuit this way.

If you don't find the guilty circuit that is draining the battery after
pulling every fuse. Look for unfused items, maybe shorted alternator rectifier diodes.
If the short is in an unfused circuit then you start looking for
pinched wires, and it gets tricky.

WARNING: When measuring DC current with your multimeter:
The ammeter is connected in series with the battery and total load of the car.
Don't let anyone run the window motors or anything while you measure current since
you can damage your meter or blow a meter fuse.
Start on the highest current scale with your meter and work down to read the expected low values.

Post back with your results, Bill

What kind of battery is it?

A NEW BATTERY is sort of a false assumption. these days as many auto batteries are rebuilt.

Since rebuilt parts may have a poor record compared to new parts, I also think that you should have the battery checked.

Disclaimer: I have no specialized knowledge of S80’s. Just a few thoughts.

Glovebox light on? My 850’s glovebox light stayed on all the time until I fixed it. Could anything else possibly be on?

I know it is new, but have you had the battery tested? The battery is still under warranty. More likely there is a short somewhere else.
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Will I buy another Volvo??? We'll see....