5000 Watt AC Inverter by Wagan Tech
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User’s Manual—Read before using this equipment
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For example; if a 20 AH battery is discharged at a 1 amp rate, is will take 20 hours to
discharge that battery. The terms “charged” and “discharged” relate to actual battery
voltage. This means that the output voltage of a nominal 12 volt battery starts at 13.2 volts
(fully charged) then drops to 10.6 volts (discharged). If the load on the battery causes
the battery to discharge faster than the 20 hour rate, the capacity (AH) of the battery is
measurably reduced (derated). Derating is a major run time factor. The curve below can help
to determine what the battery bank can deliver under load. The results are used to estimate
how much additional battery capacity is needed to achieve the desired run time.
The left vertical numbers of the curve represents percentage of the battery capacity at the 20
hour rate. In this example, the user needs a one hour run time. If the example battery is 220
AH (20 hour rate), and the load is 220 amps that is 100% (horizontal number) of the AH (20
hour rate), starting at the 100% horizontal point and looking up to the curve the results are
that only 56% of the battery capacity is available. This means that a higher battery capacity
is required to get the desired run time: one hour. The curve also shows that a load of 200%
of the 20 hour rate yields only 31% of the battery capacity. The installer must carefully plan
the capacity of battery bank or the run time may be seriously affected. To the inexperienced
installer, several trial battery capacities may be required to make sure a large enough
battery capacity is available to achieve the desired run time.
The curve can be applied to any lead acid battery under load providing that it has an AH
rating at the 20 hour rate.
Continuing with the previous example, the 150 amp load will need to run for 10 hours, so
we begin configuration with a 1,500 AH battery. If the vertical is 1,500 and the horizontal
is 150 amps, the percentage of load on the battery is 10%. The curve shows that the 1,500
AH is derated to 90% of maximum. This means that the battery will have to be 16,500 AH
for the full 10 hour run time. It is important to add some extra battery capacity, because as
the batteries age they will lose AH capacity.
CONFIGURATING THE BATTERY BANK
Six volt, 220 AH “golf cart” batteries were selected for these illustrations because they are
generally readily available and relatively inexpensive. They are deep-cycle type and with
regular recharging they have a relatively long life. These batteries are “flooded” type; they
freely vent hydrogen and oxygen while under charging and heavy discharge. They must be
vented to outside air to prevent accumulation of explosive gases.
Fusing Requirements
NOTE: It is important that for this 5000 watt inverter has two ANL 400 ampere or
equivalent main battery fuses be added to the positive (+) battery cable as close as possible
to the battery bank’s positive terminal. The fuse amperage rating must be sized to allow
simultaneous operation of all the AC appliances to be powered, allowing for the momentary
high startup current requirements of inductive loads. Use the recommended fuse block (fuse
holder) and fuse, or an electrical equivalent. ANL type fuses and fuse holders are readily
available from marine supply dealers.
The fuses are very important to protect equipment, batteries and personnel. The fuses protect
against battery explosion if the cables that connect to the inverter accidentally short.
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