User`s manual

page 18
Actual Current Draw
Approximate 12 volt current draw is the load in watts divided
by 10. Thus a 60 watt light bulb plugged into the inverter will
draw 6 amps (60 / 10 = 6) from the 12 volt supply.
Batteries are rated in several different ways:
Peak cranking amps - Not a useful number for inverter use.
Battery reserve capacity - How long a battery can supply a
given current, typically 25 amps, before the battery reaches a
low voltage. A battery rated at 200 minutes reserve can
deliver 25 amps for 200 minutes before it is discharged.
Ampere-hour capacity - How many amps a battery can deliver
over a period of time, typically 20 hours. A 100 amp-hour
battery can deliver 5 amps for 20 hours (5 x 20 = 100).
Actual operating time will depend upon the current draw
from the battery. A battery will deliver less total power
(energy) as you draw higher amps. A 100 amp-hour battery
can deliver 5 amps for 20 hours (100 amp-hours) but it will
only deliver 50 amps for 1 ½ hours (50 x 1.5 = 75) or 75
amp-hours at the higher rate.
Also remember, battery life is decreased if the battery is
discharged fully. Lead acid batteries have the longest life,
if they are kept fully charged.