I think you had a lucky save with that. 10.5 Volts suggests the battery had a damaged cell or had been run flat possibly by issues with the cars computers, keep an eye on it over the next few days to make sure all the computers are shutting down properly and not causing a drain on the batteryNo joy
Checked battery today, 10.5v! Replaced battery all good now.
Certainly possible, they often say to have additional power supply if suspect. Not that it is much help now.