Hi Jim
On (16 Oct 97) Jim Dunmyer wrote to Alec Cameron...
 JD> I'm not sure that it's necessary to equalize an auto battery, is it?
 JD> Normal charging voltage is 14.5 volts, a bit higher than a float charge 
at
 JD> 13.8.
"Normal" varies between makers, and of course regulators are often drifted 
ff
spec. 14.5 is 2.41v/ cell plenty high enough for floating an ignored battery.
For a supervised battery [generating station, phone exchange] the makers used
to prescribe and debate, values in the range 2.25 to 2.35 per cell. One of 
he
objections to the higher figure is the rapid fall in voltage when load is
applied. "END CELLS" were used in sensitive applications to allow these to be
inserted/ cut out while on load in order to manage the discharge voltage.
When a battery is a long time on preset float voltage a cell [or cells]
behaves as the runt in the family, and its terminal voltage becomes a little
suppressed. This automatically causes the charger to pump more amps and the
healthy cells in the same battery oblige by raising v a bit, but still
ahead of the runt, and the charger current self limits to a small amps value.
In time a survey of that battery with a voltmeter, may show cell voltages
like:
2.15  2.45  2.45  2.45  2.40  2.60.  Total, 14.50v
The first cell looks very tired [2.15] and the last cell [2.60] looks very
old and may be sulphated and/or low [electrolyte]. Four cells look OK.
After topping up and boost charging at average 2.6 v/ cell, the cell
capacities will have "equalized" and back on float, a more even voltage cell
by cell will be found. The amp hours capacity will have increased. That cell
which was previously floating at 2.60 may need hospital treatment, hence the
use of single cell chargers.
                            
 JD> It probably wouldn't *hurt* anything, though, maybe I'll try it.
Just before winter, is a good time.  Cheers..........ALEC
... ........When I contemplate the moon, my head aches [Galileo]
--- PPoint 1.92
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