Monarch SE 2004 - Testing the Battery

Monarch SE 2004-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Section 8 Electrical System | 309
Deep Cycle Batteries:
Deep cycle batteries are best suited for use with 12 Volt operated lights,
appliances and inverters. Deep cycle batteries are designed to have a majority of
their capacity used before being recharged. These are available in many sizes and
types. The most common is a non-sealed, liquid electrolyte battery. The non-sealed
types have battery caps. The caps should be removed (monthly) to check the level
of electrolyte. When a cell is low, only distilled water should be added. Water
consumption will vary depending on many factors: how far the batteries are
depleted, how long the voltage is being applied to charge the batteries, how much
voltage is used and how often this occurs. Generally, the batteries should be
checked every two or three weeks when continuously hooked to shore power.
NOTE: Tap water contains minerals which can alter battery
chemistry and ruin the battery. Use only distilled water when
refilling the battery.
There are several ways that a battery can be tested and
monitored. The motorhome uses a monitor panel that shows
the status of the batteries at a quick glance. Press and hold the
test switch to display the desired battery bank voltage.
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. Hydrometers can be purchased
from most auto parts stores.
Many styles are available, from types with cylinder
graduation (shown here) to types with floating balls. 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 electrolyte solution. Note the reading for that cell. Complete
the same test for the rest of the cells on that battery bank.
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Testing the Battery