I had my first breakdown in 35 years yesterday.
I drove a 8 mile trip with the usual auto start stop warning on despite battery is only 2yrs old. I went into a shop came out pushed the button it struggled to turn over. After a few attempts battery had barley enough tp power the lights.
My missus came out and we tried jump leads from her Jazz. Not much to do, I borrowed her car and went to Halfords. I showed them battery receipt 2yrs and a few days old 700 cranking amps. Told them the storey and ashed to borrow a booster starter. They obliged and gave me a N0C0 Boost HD 2000a unit. I went back to my car connected it but it just turned over slowly. I the hit the extra power button and it fired up. We tested to charging at idling voltage 14.4V so we knew it should have been charging fine. Battery tester said all good but this last week I've done 204 miles with just 2 short 4 mile trips to the shops. Even though the fella said unit was showing in good condition 470cA it might be dodgy.
I've not been out today to test it but will be getting a new battery on guarantee when I do.