CHAPTER
2
Testing Batteries,
Charging Systems, and
Starter Circuits, and
Measuring Voltage Drop
O
f all the areas marine electricians or boatowners must deal with, batteries, alterna-
tors, and starter motors, along with their related circuitry, are among the most
critical. Boats rely heavily on the integrity of their DC electrical system; on most
boats, if the batteries go dead, you’re simply out of luck—you can’t walk home!
The electrical system is one area where our automotive counterparts have the advan-
tage. You bring your car into the repair shop, and the technician hooks it up to a diagnos-
tic center. This electronic masterpiece produces all kinds of useful data, everything from
which cylinder is misfiring to the amount of poisonous emissions coming out your
tailpipe. It will also evaluate the performance of your battery, charging system, and starter
motor circuits.
Unfortunately, it’s impossible to drive your boat into the diagnostic bay at your local
auto shop and get the same sort of checkup. But let’s face it—most boatowners today
expect this same level of efficiency and technical capability. After all, if they can get it for
their $40,000 Lexus, why not their $400,000 Sabre sloop?Catalysts for Change
Enter the microprocessor. As we all know, microprocessors are continually becoming
smaller and more powerful. With these improvements have come changes in instrument
technology that are closing the gap between marine and automotive technicians. Instru-
ment manufacturers today can produce smaller diagnostic equipment with increased func-
tionality, and at prices that many boatowners and marine technicians can afford, or—in
the case of the pros—cannot afford to be without.
In addition, advances in battery technology have driven the development and modifi-
cation of testing instruments. In the old days, we removed the caps from the battery cells
and visually inspected the fluid level of each cell. Then—if we had the tools—we used a
hydrometer to measure the specific gravity and determine each cell’s state of charge, and aCopyright © 2007 by Edwin R. Sherman. Click here for terms of use.