5.0 APPENDIX
58 ©2000 Xantrex Technology Inc.
Battery Bank Sizing (continued)
Example
Complete the following steps to calculate the battery bank capacity requirements. Use the blank
table on the next page to enter the values for your system. An example table is shown below.
* Refrigerators and ice-makers typically run only about 1/3 of the time, therefore the running wattage
is 1/3 of the total wattage of the appliance. Divide the total wattage of the appliance by 3 and enter
it in Step 2.
Step 1 Determine the loads the inverter will power and list them in the Step 1 column.
Step 2 Enter the running wattage of each appliance in the Step 2 column.
Step 3 Determine the number of hours (or fraction of hours) the appliance is used each day.
Enter this figure in the Step 3 column.
Step 4 Determine the number of days the appliance will be used during the week. Enter this
figure in the Step 4 column.
Step 5 Divide the number (entered into each row of the Step 4 column) by 7 to obtain the
AVERAGE DAILY WATT-HOURS REQUIRED figure. Enter these figures in the Step 5
column.
Step 6 Add all the figures entered into the AVERAGE DAILY WATT-HOURS REQUIRED (Step 5)
column and enter this number into the TOTAL DAILY WATT-HOURS REQUIRED (Step 6)
column in the second table.
Step 7 Multiply the TOTAL DAILY WATT-HOURS REQUIRED (Step 6) figure by the number of
days of autonomy (days between recharging expected, usually between 1 to 5. The
examples use 3). Enter this figure into the AUTONOMY BATTERY SIZE (Step 7) column.
AC Appliance
Step 1 Step 2 Step 3 Step 4
Appliance
Running
Watts
(x) Hours Used
Each Day
(x) Days Used
Each Week
(÷ 7 =) Average Daily
Watt-Hours Required
Microwave 600 0.5 7 300
Lights (x 4) 40 6 7 240
Hair Dryer 750 0.25 3 81
Television 100 4 7 400
Washer 375 1 2 107
Refrigerator* 480/3 = 160 24 7 3840
Vacuum Cleaner 1200 1 1 171
Total Daily Watt-Hours
Required
Autonomy
Battery Size
Rough Battery Size
(Watt-Hours)
Safe Battery Size
(Watt-Hours)
Safe Battery Size
(Amp-Hours)
5,139 15,417 30,834 37,001 1,542
975-0012-016
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