USER’S MANUAL — Please read before using this equipment.
© 2007 Wagan Corporation.
All Rights Reserved.
Wagan and Wagan.com are trademarks used by Wagan Corporation.
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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 220AH (20hr rate), and the load is 220 amps that is 100
percent (horizontal number) of the AH (20hr rate). Starting at the 100 percent
horizontal point and looking up to the curve the results are that only 56 the
percent 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 percent of the 20 hour rate yields only 31 percent 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 the 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.
Derating Curve Lead Acid Batteries
L
8000W Power Inverter
By Wagan Tech
www.wagan.com
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Continuing with the example above: The 150 amp load will need to run for 10
hours, so we begin configuration with a 1500 AH battery. If the vertical is 1500
and the horizontal is 150 amps the percentage of load on the battery is 10 percent.
The curve shows that the 1500 AH is derated to 90 % of maximum. This means
that the battery will have to be 16500 AH for the full 10 hour run time. It is
important to add some extra battery capacity, to compensate for battery age.
CONFIGURATING THE BATTERY BANK
Six volt, 220 AH deep cycle “golf cart” batteries were selected for these
illustrations because they are generally readily available and relatively
inexpensive. With regular recharging they have a relatively long life. These
batteries are “flooded” and vented types; 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.
If the batteries are to share a compartment with the inverter, then use sealed lead-
acid batteries that are available in gel cell and AGM varieties. Both sealed battery
types will not spill liquid electrolyte (acid) when overturned or punctured.
Battery Bank diagram
