If the voltmeter reading is .5 volts or above, there
is high resistance at the battery cable connection. This
indicates that the battery connections need to be
cleaned. A good, clean battery will have less than a .5
BATTERY VOLTAGE TEST.The
voltage test is done by measuring total battery voltage
with an accurate voltmeter or a special battery tester
(fig. 2-8). This test determines the general state of
charge and battery condition quickly.
T h e b a t t e r y v o l t a g e t e s t i s u s e d o n
maintenance-free batteries because these batteries do
not have caps that can be removed for testing with a
hydrometer. To perform this test, connect the voltmeter
or battery tester across the battery terminals. Turn on
the vehicle headlights or heater blower to provide a
light load. Now read the meter or tester. A well-charged
battery should have over 12 volts. If the meter reads
approximately 11.5 volts, the battery is not charged
adequately, or it may be defective.
CELL VOLTAGE TEST.The cell voltage test
will let you know if the battery is discharged or
defective. Like a hydrometer cell test, if the voltage
reading on one or more cells is .2 volts or more lower
than the other cells, the battery must be replaced.
To perform a cell voltage test (fig. 2-9), use a low
voltage reading voltmeter with special cadmium (acid
resistant metal) tips. Insert the tips into each cell,
starting at one end of the battery and work your way to
the other. Test each cell carefully. If the cells are low,
but equal, recharging usually will restore the battery. If
cell voltage readings vary more than .2 volts, the
battery is BAD.
Figure 2-8.Battery voltage test performed with a battery
Figure 2-9.Cell voltage test.
BATTERY DRAIN TEST.A battery drain test
checks for abnormal current draw with the ignition off.
If a battery goes dead without being used, you need to
check for a current drain.
To perform a battery drain test, set up an ammeter,
as shown in figure 2-10. Pull the fuse if the vehicle has
a dash clock. Close all doors and trunk (if applicable).
Then read the ammeter. If everything is off, there
should be a zero reading. Any reading indicates a
problem. To help pinpoint the problem, pull fuses one
at a time until there is a zero reading on the ammeter.
This action isolates the circuit that has the problem.
BATTERY CAPACITY TEST.A battery load
test, also termed a battery capacity test, is the best
method to check battery condition. The battery load
test measures the current output and performance of
the battery under full current load. It is one of the most
common and informative battery tests used today.
Before load testing a battery, you must calculate
how much current draw should be applied to the
battery. If the ampere-hour rating of the battery is
given, load the battery to three times its amp-hour
rating. For example, if the battery is rated at 60 amp-
hours, test the battery at 180 amps (60 x 3 = 180). The
majority of the batteries are now rated in SAE cold-
cranking amps, instead of amp-hours. To determine the
load test for these batteries, divide the cold-crank