Why has the battery in my car failed after just three years?

What type of stop/start battery is fitted to my Mercedes B-Class and why has it failed? The car is less than three years old and the mileage is 28000.

Asked on 26 November 2019 by Allan Monk

Answered by Honest John
It will be an 020 Bosch AGM Stop Start Battery S5A15, costing around £230. The usual reason for failure is not driving the car far enough often enough, though, as you rightly suggest, 28,000 miles in three years should have been enough to keep the battery fully charged and at full capacity.
Similar questions
My stop-start engine stopped, as per normal, at a set of traffic lights - but then wouldn't automatically start again. Why's that?
I bought a Toyota Auris from a main Toyota dealer a week ago. The car is a 16 plate, with only seven miles on the clock when I bought it. The car was a Toyota fleet car, so was unused for over a year....
I own a 2019 1.6-litre diesel Vauxhall Astra. When I'm in in traffic or at traffic lights if I lower the clutch in gear the stop-start mode operates. I have to higher the clutch then lower it again for...
Related models
Loads of cabin space front and rear, excellent safety kit, good range of efficient engines, classy image.

Value my car