314 | Section 8 Electrical System ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------- Monarch SE 2004
When the tank is full it is capable of feeding more “pressure” to the pump inlet
due to gravity, and the pump always has enough water available to
maintain its rated pressure and volume. However, if the water tank gets low
the pump will not have enough water volume coming in to maintain 12 psi at 15 GPM.
If the loads are removed from the pump by closing the valve on the outflow, even
with low pressure in the tank the pump will eventually pressure up to 12 psi. It
will just take it longer to get there. When the valve is opened the pump will sustain
12 psi for a brief period, but since the tank is no longer feeding the pump as fast as
needed the pressure will eventually drop. This analogy can be restated by replacing
the pump with a battery, pressure with voltage, volume with amps, outflow valve with
a switch, water with electricity and the water tank with the battery electrolyte.
The level of the tank could be thought of as the rate of the reaction occurring in
the electrolyte. When the battery is fully charged the electrolyte has an excess of
reactions taking place to feed the battery terminals. This tapers off with time as the
electrolyte is spent, so maintaining voltage becomes possible. With no loads, the
discharged electrolyte is capable of producing close to the rated voltage, but only
after a period of time has elapsed for enough of a reaction to take place to bring
the voltage back up. This explains why a battery measured at rest can indicate
close to its rated voltage, but will not run a load.
Calculating Run Times:
Calculating run time figures when operating 120 Volt AC electrical items with
an inverter can be exponential. This is due to battery characteristics. Flow
characteristics of electrons vary with different battery types and chemical
compositions. Deep cycle batteries are generally designed to slowly release a
majority of their charge capacity. Deep cycle batteries are rated in amp hours
(Ahrs) with the discharge occurring over an extended period of time before the
battery is charged. Engine starting batteries are designed to quickly release large
amounts of current for short durations, without depleting battery reserves.
Commercial type batteries bridge the gap of deep cycle and engine batteries.
Commercial batteries release medium amounts of current over a longer period of
time but they are not designed to cycle their charge capacity.
The working range of a deep cycle battery is between 50 and 100% state of
charge (SOC). Deep cycle batteries should not be cycled below 50% state of charge.
Discharging a deep cycle battery below 50% state of charge shortens the life of the
battery. Deep cycle batteries use an amp hour rating which is usually calculated
over a 20 hour discharge interval. For example: A deep cycle battery with a rated
capacity of 100 Ahrs. is designed to release current at the rate of 5 Amps per
hour. Multiply a 5 Amp load over a 20 hour discharge period equals the rated 100
Ahr. capacity. These discharge figures are calculated with the battery starting at
100% state of charge with the battery at 80º F when the discharge cycle begins.
Battery Charge Time
& Consumption Rate
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