AC Inverter
™
8,000 Watt DC to AC Power Inverter by Wagan Tech
®
9
www.wagan.com
at 150 amps equals 1,500 amp-hours (AH). This answer is just a beginning because there are
other factors that determine actual run time. These include:
• AC appliance load and time in use (basic AH)
• Cable gage and length (cable losses)
• Charge level of the batteries (between use, chargers have to be able to fully charge
the batteries)
• Temperature of the batteries (colder batteries provide fewer amps)
• Age and condition of the batteries (older batteries lose capacity)
• Compliance with turning off unnecessary AC loads.
• Compliance with turning off unnecessary DC loads.
Derating the Battery Bank
Most lead-acid batteries have a rating expressed in amp-hours (AH). The most common rating of
AH is “at the 20 hour rate”. 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 percent (horizontal number) of the AH (20 hour
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.
Summary of Contents for 2403 AC Inverter
Page 19: ......
