I was yesterday's age, when I discovered that a 2008 Mustang GT, with a tuned/CAI but otherwise stock 4.6 3V and TR3650 could run approx. 25 minutes on 10.8 volts of battery-only power. First, I got this in a parking lot 12 miles from home:
I have a lighter-plug phone holder/charger, that happens to have a digital voltmeter, in the dash...so could monitor the debacle, in real time. I also had documentation that the previous owner had the alternator replaced in 2017 (at 77K) and the real-world experience from members of this forum that the reman alternators were crap, which proved to be true with me, as well:
This heaping pile of dung lasted a whole 45K miles. However, armed with the impeccable knowledge of this forum's members, I had already purchased a replacement and upgraded cable, in anticipation of what exactly happened:

Removing and replacing both was very straightforward and the only detail not covered by the multitude of YouTube videos was the separation of the 3-pin harness from the factory positive cable and reusing it with the upgraded one, pictured below:
All in all it only took about 90 minutes, from start to finish, including cleaning the battery terminals and zip-tying everything to tidy up the (now separated) cables. 14.2V at the battery when running (had been mid-13s, previously) and the added energy seems to be noticeable in the SOTP dyno, as an added bonus...