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TECHNICAL INFORMATION
BATTERY BANK SIZING
EXAMPLE
Complete the steps that follow to calculate your inverter's battery bank capacity. No two installations will
require exactly the same battery bank capacity. The following example provides a guide for determining
your needs. Read through the example and then complete the worksheet on the following page.
STEP 1-4: Determine your Average Daily Watt-Hours Needed.
AC APPLIANCE
APPLIANCE RUNNING
Microwave
Lights (x4)
Hair Dryer
Television
Washer
Refrigerator*
480/3 = 160
Vacuum cleaner
STEP 1: Determine what appliances the inverter will power and enter the Appliance Running Wattage
of each appliance.
* -
Refrigerators and icemakers typically only run about 1/3 of the time, therefore the running
wattage is 1/3 of the total wattage of the appliance.
STEP 2: Determine the number of hours (or fractions of hours) you will use the appliance each day;
STEP 3: Multiply the number of days you will use the appliance during the week; this is your Weekly
Watt Hours Needed;
STEP 4: Divide your Weekly Watt Hours Needed by 7 to obtain the Average Daily Watt Hours
Needed;
STEP 5: Total Average Daily Watt Hours Needed to determine your Total Daily
Watt Hours Needed.
STEP 6: Multiply your Total Daily Watt Hours Needed (Step 5) by the number of
anticipated days of autonomy (days between charging, usually 1 to 5)
to determine your Autonomy Battery Size (example used 3 days).
STEP 7: Multiply your Autonomy Battery Size (Step 6) x 2 to allow for a 50%
maximum battery discharge in normal operation and an additional
50% for emergency situations to obtain your Rough Battery Size in
watt-hours.
STEP 8: Multiply your Rough Battery Estimate x 1.2 to allow for an efficiency of
80%. This number is your Safe Battery Size in watt-hours.
STEP 9: Convert your Safe Battery Size to amp-hours. Divide Safe Battery Size
by the DC system voltage (i.e., 12, 24 or 48 VDC; example used 24-
volts). This number is your Safe Battery Size in amp-hours, which is
the battery bank capacity needed before recharging.
2001 Xantrex Technology, Inc.
Page
5916 - 195th Street N. E.
102
Arlington, WA 98223
STEP 1
STEP 2
(X) HOURS USED
WATTS
EACH DAY
600
0.5
40
6
750
0.25
100
4
375
1
24
1200
1
STEP 3
(X) DAYS USED
EACH WEEK
7
7
3
7
2
7
1
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
STEP 4
( 7 = ) AVERAGE DAILY
WATT-HOURS NEEDED
300
240
81
400
107
3840
171
Total Daily Watt Hours Needed
5,139
Autonomy Battery Size
(Watt Hours)
15,417
Rough Battery Size (Watt Hours)
30,834
Safe Battery Size (Watt Hours)
37,001
Safe Battery Size (Amp Hours)
1,542
SW Series Inverter/Charger
Part No. 2031-5
Rev. C: February 2001
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