Electrical Systems
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5•154
EXECUTIVE
5. Freezing:
When the electrolyte freezes, ice formed dislodges the active material
from the plates. The battery case may crack and the electrolyte will leak out
when thawed. It is especially important to keep a battery at full charge in cold
weather to prevent freezing. The high specific gravity of a fully charged battery
doesn’t freeze as easily. Never attempt to recharge a frozen battery. Warm it up
first.
6. Corrosion:
Corrosion from spilled or splashed electrolyte form deposits that can
conduct electricity and cause battery drain. Clean off all corrosion, especially
around the battery terminals and on the top cover of the battery. Prevent
accumulation by coating the terminals and the exposed metal cable connectors
with high temperature grease.
7. Overcharging:
Overcharging rapidly converts water to gas and decreases the electrolyte’s
water content as the water evaporates. The electrolyte level drops and becomes
more acid in content. This subjects the plates to a higher concentration of
sulfuric acid and results in early battery failure.
NOTE: Anytime you add more than one or two ounces per-cell
per-thousand miles driven, check the motorhome charging system
for overcharging. Prolonged overcharging generates excessive heat
inside the battery, which buckles the plates and destroys the bat-
tery. It is a fact that over 50% of battery failures are caused by
overcharging.
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Why does the voltage on a discharged battery measure the same as a fully
charged battery, until the loads are applied? The simple answer to this might go
as follows: A battery creates electrical power by converting energy from a
chemical reaction into electrical energy. As this reaction slows down, the bat-
tery voltage will drop. In a lead acid battery the electrolyte conductivity (how
well electrical current can flow through it) changes. The same current may be
available but the rate of the reaction decreases, causing a voltage drop.
Another way of looking at this is to use the analogy of a water pump
(a battery is an electric pump). The pressure in PSI (pounds per square inch)
that a pump delivers is like a battery’s voltage. The volume of water in GPM
(gallons per minute) is like the electrical current. Let’s look at a 12 PSI pump
with no loads (the pump is running but the outflow valve is turned off). The
pump will run and the internal pressure of the pump will build up to some
point higher than 12 PSI. Once the valve is opened and the water is free to
flow into the loads, the pressure will drop to the rated output pressure of 12
PSI, but only if the load is not too big. If the pump is designed to maintain 12
PSI at 15 GPM, and a load demanding 20 GPM is connected, the pump will
not be able to keep up and the pressure will get sucked down to a lower PSI.
Battery Voltage &
Current
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