I just looked at my battery aggain and sure enough it has the three
columns in the back of it with the balls inside. I didn't notice that
before. I don't think I've ever seen a battery with them built in. Usually
we used a Hydrometer to suck out part of the electrolyte and test it. It's
This is, of course, a built-in hydrometer.
a large syringe with a clear plastic or glass tube in
it and has 3, 5 or 7
balls inside the tube. The ratio of sulphuric acid to water in the
The battery-testing hydrometers we use in the UK have a special float
with a calibrated stem. The height it floats at depends on the density of
the electrolyte. It's normally housed in a glass tube with a rubber bulb
on the end to suck up some of the elctrolyte...
electrolyte changes depending on the state of charge
of the battery. As the
acid/water ratio changes the specific gravilty of the solution also
changes. The different balls in the hydrometer have different specific
gravities so more of them will float when the charge is higher and there is
more acid in the solution. Most LA batteries sold in this country in the
past 25 years are now sealed and are SUPPOSED to be maintenance free so
And if you believe that you believe anything :-). Car batteries still
seem to benefit from being topped up with distilled water from time to
time...
very few people know how to check one any more.
-tony