[alfa] Alternator overcharging problem

["John Fielding" <johnf@xxxxxxxxxxxxxxx>]

Hi All,

With all this talk about boiling batteries I thought this little piece of information
might prove useful for our Alfa's.

Here is something I picked up whilst doing some research for a book I am writing.

The GM series of vehicles equipped with AC-Delco alternators changed the battery type
sometime in the 1980's from a vented case to a sealed case.  The technology of the new
battery is slightly different because of the construction of the plate material.  The
battery manufacturers website I used for data on the new battery technology warned about
fitting the newer GM alternator regulator when an old fashioned battery is used & vice
versa as a new regulator on a old fashioned battery would cause over-charging.

When GM changed the battery type they also changed the cut-off voltage of the alternator
regulator.  The new regulator had a higher cut-off voltage to ensure the battery reaches
an adequate state of charge. The newer regulator had a higher voltage, approx. 0.5V .  The
vented batteries are not as tolerant to over voltage as the newer sealed types and will
suffer from excessive loss of electrolyte due to the higher charging voltage.

Here is the comment I found about the newer batteries:

"If you replace a sealed maintenance free battery in a GM vehicle, such as an AC-Delco,
with a non-sealed lead-antimony or lead- antimony/calcium low maintenance battery, you
will need to check the electrolyte levels more often. This is because GM sets their
voltage regulators at higher charging voltage, 14.6 to 14.8 volts, to recharge the sealed
maintenance free lead-calcium/calcium batteries".

The point is, make sure the cut-off voltage of an aftermarket regulator is correct for
your battery type!

John
Durban
South Africa
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