Electrical Systems - House
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DIPLOMAT
8•224
The battery cable to battery terminal connections should be metal to metal.
Periodically check the batteries for corrosion. Look for cracks and check the
vent plugs. Replace them if they are cracked or missing. Keep the top of the
batteries clean. The accumulation of electrolyte and dirt may permit small
amounts of current to flow between the terminals, which can drain the battery.
WARNING: Liquid lead acid batteries produce hydrogen gas
while being charged. This is highly explosive. Do not smoke
around batteries. Extinguish all flames in the area. The hydrogen
gas may explode resulting in fire, personal injury, property
damage or death.
There are several ways in which a battery can be tested and monitored.
The motorhome uses a monitor panel, located in the hall area, which shows
the status of the house and chassis batteries at a quick glance. Pressing and
holding the test button, the power level will be displayed on the battery scale.
The illustration shown explains in more detail the scale and indications.
A more efficient way of testing the batteries is to check the electrolyte
solution. The only way to test a battery’s electrolyte solution is with a
hydrometer. Many styles are available, from types with cylinder graduation
(shown here) to types with floating balls. Hydrometers can be purchased from
most auto parts stores. The hydrometer tests the battery’s electrolyte solution
which is measured in specific gravity. Distilled water has a specific assigned
gravity of 1,000. The hydrometer is calibrated to this mark. Pure sulfuric acid
has a specific gravity reading of 1,840. The acid is 1.84 times heavier than
water. The electrolyte solution is about 64% water to 36% acid (fully charged
battery). Hydrometers with cylinder graduation are graphed and the exact
state of specific gravity can be determined.
Temperature and recent battery activity (charging or discharging) affect the
hydrometer readings. It is best to check the battery when it has been “at rest”
for at least three hours, although readings taken at other times will give a
“ballpark” figure. When using the hydrometer, draw the electrolyte solution up
into the tube. Allow the hydrometer to attain the same temperature as the elec-
trolyte solution. Note the reading for that cell. Complete the same test for the
rest of the cells on that battery bank.
The hydrometer is calibrated at 80° F. Temperature affects the hydrometer
readings. The higher the electrolyte temperature, the higher the specific gravity
reading. The lower the temperature, the lower the specific gravity reading.
Add or subtract four points for each 10° variance from the 80° F chart.
Readings between cells should not vary more than 50 points.
If one cell in a particular battery bank being tested is at a 50% state of
Testing the Battery
Temperature Correction Chart
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