Xantrex Technology 1800i Automobile Battery Charger User Manual


 
7.2 Battery Size
Just as important as the type of battery selected for use
with your Xantrex Sine Wave Inverter is the subject of
battery size (capacity). There are a number of different
standards for rating battery capacity. Automotive
starting batteries are normally rated by cranking amps.
This is not a relevant rating for continuous use. Deep
cycle batteries are rated either by reserve capacity in
minutes or by amp-hours.
Battery reserve capacity is a measure of how long a
battery can deliver a certain amount of current—usually
25 amps. For example, a battery with a reserve capacity
of 180 minutes can deliver 25 amps for 180 minutes
before it is completely discharged.
Amp-hour capacity is a measure of how many amps a
battery can deliver for a specified length of time—usually
20 hours. For example, a typical marine or RV battery
rated for 100 amp hours can deliver 5 amps for 20 hours.
(5 amps x 20 hours = 100 amp hours)
You can expect performance from the inverter to suffer
with the use of a small, low amp-hour rated battery (for
example, 50 Ah). Even if your battery is in excellent
shape and fully charged you will likely experience
poor surge power performance and unsatisfactory
operating time with anything but a small AC load.
Xantrex recommends a minimum battery size of 200 Ah
for moderate loads (less than 1000 W) and greater than
400 Ah for heavy loads.
To determine how large a battery or battery bank you
require for equipment running from the inverter, simply
add together the power requirements for all electrical
devices that you will be running multiplied by their
approximate running times in hours between battery
recharges. Each device will be rated in either watts, volts
and amps, or VA. For this calculation, all three of these
ratings are equivalent (i.e. volts x amps = watts = VA).
The following example, based on battery recharging
every three days, illustrates the calculation:
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English 15
Xantrex Sine Wave Inverter Owner’s Manual