But you should leave the car for a while after driving before testing it to see if it holds its charge so I’d expect to see around 12.4-12.7 in a healthy battery.
I once left my Sat Nav connected to the cigarette lighter socket when I was overnight in Birmingham. My wife, myself, my Sister and hubby were due to set off for our hotel in Windsor the next morning. I took our suitcases out early morning, so had chance to realise my battery was flat and alert the RAC as I was a member. Their agent came out and connected my Mondeo up to his van using jump leads and stayed until I'd got sufficient juice in the battery to get me away. That was a salutary lesson and I ensured that the Sat Nav was fully disconnected every time I used it thereafter.
It does seem strange that it stood for a while and you were able to start it and drive it on Wednesday. Make sure you’ve not left the interior light on or something. That said, I assume your drive on wednesdsy included heater, windscreen wipers, heated rear window, etc. This could have put a lot of strain on the battery and not necessarily given chance for the alternator to put in a substantial charge. If the speedo, or lights inside don’t flicker... the battery could just be completely flat. Once again indicating that it could be something left on draining it. I would jump start initially, check for any left electrical things. Then if no joy invest about £10-15 quid in a battery charger, (some have a battery repair function that has worked for me in the past). Then it’s time to test or replace the battery. Good luck pal.
Had the same problem when down in Cornwall.Nothing on ignition just dead,breakdown came out and In the end it was the starter motor that had gone,so look into that too.
Agree with all this. My daughter had this last week, we jumped it, started ran for a day or so and then just completely cut out and wouldn’t start. Turned out because she only does short journeys and was having the heater etc on full blast, the battery had gradually drained to the extent it was knackered and every time she had too much on (heaters etc) it would struggle. Message from this I would suggest to the OP is if you manage to jump start it, still get the battery checked.