[SwissXC90]

Here's some more math:

A car battery in the 2015 XC90 is a 80 or 95 Ah rated AGM battery, depending on model

An alternator in a XC90 is typically about 210A

Thus we can see that running 210A alternator for 1 hour will easily fully charge a 95Ah battery from nearly flat to full.

However many other factors also come into play:
The full alternator output is not available until around 2000 RPM
At 1000RPM, most alternators are at about 50% output

The amount of electrical load on the car will increase the time to fully charge the battery, as less power is available for charging

Assuming 50% of power is used for running the car, and then engine is running at 1000 RPM, the the available current to charge the batter is 210A x 50% x 50% = 52A. On a short run of only 15min every day, you can only put 50-ish amps into the battery for 15min, which is the same as 12Ah (50A for 15min = 12A for 1 hour), and if the battery is already depleted, you may find over time that this is insufficient to maintain a full charge.

Hence my recommendation for a smart battery charger

NOTE: The 2015 and newer XC90 use AGM batteries, your charger must be capable of charging AGM batteries. The charging parameters are different.