...and cyberwraith spake unto the tribes of Usenet, saying...

If all the cells were similar, I'd say it was either a charging or earthing
problem.  The fact that some of the cells are lower than others suggests the
battery itself is faulty.  If it's got some warranty on it, take it back.

If the starter is getting low voltage then the engine will be slow to
crank over - and diesels don't like starting when cranked too slowly.

This could be dirty connections, faulty battery or a faulty starter.
You need to check all the connections between battery and starter,
especially the earth connection.  It's probably also worth checking the
current draw of the starter - unless you've got a clamp style ammeter
that reads to about 500A you'll probably have to get a garage to check
it for you.  I'm sure someone here will have a sensible figure for tdi
starter current - my books are miles away so I can't look it up but my
gut feel is ~250A.

Also the uneven sg of the battery cells doesn't sound great so it may be
worth getting it properly tested with a view to claiming on the
warranty.  Be aware however that a new battery may have sufficient extra
power to initially overcome a fauly starter problem, but as the battery
ages the problem may reoccur - it's probably well worth checking the
starter current just to be sure that all is well.

My policy with car batteries is always try and fit the biggest "size"
battery as possible, these new designs don't account for cold weather, and
in all the years I have been driving it is always the 2 to 3 year old bat
which is sized just about to cope with the car its fitted to which lets you
down in the depths of winter. there is no substitute for cross sectional
area of plate or layers, this can only be achieved with a physically big
bat. This is what I do and touch wood have not had any problems in the cold
also you can get away with leaving your side lights on and still start the
car..

Rich
--
To reply remove " spam "

does sound iffy if some cells are down more than others.

another thing to check is glowplugs.  Although a good TDi shouldn't *really*
need 'em, if the battery is up to it.  The 300 TDi here only once failed to
start, when its original battery gave up at about 8 years old (!).

The Ford Di in the minibus doesn't seem to have any, and it's started so far
this year.

See other thread about batteries for discos though.  You can put a biggun on
it, 643 or 644 - need a minor mod to the battery clamp and IIRC move a cable
from the side of the engine bay to get it in.  Gives peace of mind that the
battery is big enough, and they tend to be cheaper to boot.

If you need to know which number, I'll look it up tomorrow.

Take it to a proper garage/battery specialist with a load tester if it is
dodgy it will take a charge and appear ok  for a day or so but not maintain
the charge That on a hyrometer test may appear similar to a battery which is
just not being charged sufficiently. A load tester will show up any
deficiency by stressing the battery the same way starting does have a look
at
http://www.marcspages.co.uk/tech/5104.htm answering a different question but
covering your concern
Derek
( we used to check individual cells before progress sealed them away)