I wonder if there was a batch of dud batteries in the system last year? My 5 year old battery was replaced in June 2021 and the new one failed in December. (The replacement in June was due to age related failure and I had no problem with that being done).
It took 3 months for the dealership to accept liability (in between patronising me with suggestions that I wasn't doing sufficient mileage - so how does that fit with charging the battery with an off board charger and it still not holding its charge?) and ignoring the log of starting/mileage events and battery voltages that I recorded during January and February. Eventually the dealership painted themselves into a corner and accepted liability under warranty, changed the battery and all has been well since.
Sadly, there seems to be an over reliance on electronic battery testers which only appear to measure battery voltage and the internal resistance of the battery and then calculate everything else from these readings. As far as I am aware there is no instrument on the market which can directly measure the capacity of a battery. The old on-load testing kit (with the glowing red hot resistance coil) which actually drew a heavy current from a battery under test is still the best indicator of the state of a battery but presumably the use of such equipment is no longer deemed safe to use thanks to H&S regulations
'Collect the evidence, marshal the facts and then present your case.'
Bob
