[Mgs] batteries and starting

Paul Hunt paul.hunt1 at blueyonder.co.uk
Tue May 26 05:29:25 MDT 2009


If a battery has gone flat you can often recover most of its apparently lost
capacity by giving it a boost charge i.e. charge it at a higher voltage than a
conventional trickle charger or even on the car, i.e. greater than 14.5v for a
couple of hours.  Some years ago Mercedes were having to select alternator
voltage regulators picking the ones that gave a voltage at the higher end of
the tolerance as the ones at the lower end were allowing the battery to
gradually lose capacity.

Whilst it's quite likely that the original tar-top batteries *are* original
technology inside, there is no reason why modern technology couldn't be or
isn't used, and I'm aware of at least three different styles of 6v battery for
the MGB.  The original capacity was 58Ah/250CCA and I have found that more
than adequate for the UK, although I don't use the roadster in temps below
freezing and it's garaged.  This capacity is available from a number of
suppliers, and Moss Europe have a 'heavy duty' 63Ah/295CCA as well.  Whilst
modern, physically smaller 12v batteries do have a greater CCA they tend to
have a lower Ah rate which means whilst they will have better cranking
performance i.e. for cold conditions they will go flat quicker under
conditions like stuck in traffic with lots of electrical stuff running, or if
you have to park anywhere with lights on.

Having to cut flanges off the case in order to make it fit will invalidate any
guarantee, cross your fingers and hope they don't spot it if you have to
claim.  You also need to change the hold-down arrangements for a 12v.

PaulH.
  ----- Original Message -----


  ... I
  charged and discharged the battery over a period of a couple of weeks
  and it actually recovered capacity.


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