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Battery
Testing
can be
done in
more
than one
way. The
most
popular
is
measurement
of
specific
gravity
and
battery
voltage.
To
measure
specific
gravity
buy a
temperature
compensating
hydrometer
and
measure
voltage,
use a
digital
D.C.
Voltmeter.
A good
digital
load
tester
may be a
good
purchase
if you
need to
test
batteries
sealed
batteries.
You must
first
have the
battery
fully
charged.
The
surface
charge
must be
removed
before
testing.
If the
battery
has been
sitting
at least
several
hours (I
prefer
at least
12
hours)
you may
begin
testing.
To
remove
surface
charge
the
battery
must
experience
a load
of 20
amps for
3 plus
minutes.
Turning
on the
headlights
(high
beam)
will do
the
trick.
After
turning
off the
lights
you are
ready to
test the
battery.
| State of Charge |
Specific Gravity |
Voltage |
| |
|
12V |
6V |
| 100% |
1.265 |
12.7 |
6.3 |
| *75% |
1.225 |
12.4 |
6.2 |
| 50% |
1.190 |
12.2 |
6.1 |
| 25% |
1.155 |
12.0 |
6.0 |
| Discharged |
1.120 |
11.9 |
6.0 |
*Sulfation
of
Batteries
starts
when
specific
gravity
falls
below
1.225 or
voltage
measures
less
than
12.4
(12v
Battery)
or 6.2
(6 volt
battery).
Sulfation
hardens
the
battery
plates
reducing
and
eventually
destroying
the
ability
of the
battery
to
generate
Volts
and
Amps.
Load
testing
is yet
another
way of
testing
a
battery.
Load
test
removes
amps
from a
battery
much
like
starting
an
engine
would. A
load
tester
can be
purchased
at most
auto
parts
stores.
Some
battery
companies
label
their
battery
with the
amp load
for
testing.
This
number
is
usually
1/2 of
the CCA
rating.
For
instance,
a 500CCA
battery
would
load
test at
250 amps
for 15
seconds.
A load
test can
only be
performed
if the
battery
is near
or at
full
charge.
The
results
of your
testing
should
be as
follows:
Hydrometer
readings
should
not vary
more
than .05
differences
between
cells.
Digital
Voltmeters
should
read as
the
voltage
is shown
in this
document.
The
sealed
AGM and
Gel-Cell
battery
voltage
(full
charged)
will be
slightly
higher
in the
12.8 to
12.9
ranges.
If you
have
voltage
readings
in the
10.5
volts
range on
a
charged
battery,
that
indicates
a
shorted
cell.
If you
have a
maintenance
free wet
cell,
the only
ways to
test are
voltmeter
and load
test.
Most of
the
maintenance
free
batteries
have a
built in
hydrometer
that
tells
you the
condition
of 1
cell of
6. You
may get
a good
reading
from 1
cell but
have a
problem
with
other
cells in
the
battery.
When in
doubt
about
battery
testing,
call the
battery
manufacturer.
Many
batteries
sold
today
have a
toll
free
number
to call
for
help.
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