In article ,
"Dave Plowman (News)" writes:
My experience with car batteries says they last no longer these days than
they did 40 years ago. BMW battery - made by Bosch - exactly 3 years. Just
enough for the car warranty. On my old Rover, which I've had for over 15
years, again 3 years or so regardless of make. And modern car charging
systems should be kinder to batteries than dynamos were.

I'd say they design the separators to self destruct at this age.

Not my experience. My last two cars were Fords brought new, and
neither has needed a new battery in the 8 years I kept them
(ignoring one which needed a new battery after 2 days because
it had been dropped and the acid drained out through a crack).

Battery life could easily be affected by the quality of alternator
used. Long after most cars had switched from dynamos to alternators,
some 20 years ago Citroens were using a funny hybrid -- an alternator
without the semiconductor voltage regulation, with an external dynamo
relay control box. Those went through car batteries quite fast,
probably due to crappy charging voltage regulation.

--
Andrew Gabriel