Monaco DIPLOMAT 2004, Руководство пользователя

Страница: 319 / 446

8 • 319
ELECTRICAL SYSTEMS - HOUSE
DIPLOMAT 2004
7. Overcharging:
Overcharging rapidly converts water to gas and decreases the elec-
trolyte’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: Any time more than one or two ounces of distilled
water is added per-cell per-thousand miles, check the
motorhome charging system for overcharging. Prolonged
overcharging generates excessive heat inside the battery,
which buckles the plates and destroys the battery. It is a
fact that over 50% of battery failures are caused by
overcharging.
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. 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. When 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. If
the load is reduced or removed the pump will catch up and return to its rated
12 psi pressure. If the pump has an infinite source of water, such as a lake or
the water utility (this is like the grid, no battery), the pump will never run out
of pressure. If the pump never runs out of pressure, and is operated at or
below its 15 GPM level, it will hold 12 psi. However, a pump that is con-
nected to a water tank with a finite capacity will start to lose the ability to
hold pressure as the level of water in the tank drops. Think of siphoning
water from a bucket. As the level of the water drops, the volume of water
exiting the siphon slows down.
Battery Voltage &
Current