Battery Bank Sizing Example & Worksheet - Trace Engineering LEGEND II Manual

Battery Bank Sizing Example & Worksheet
Complete the steps that follow to calculate your battery bank capacity. No two installation will require
exactly the same battery bank capacity. The example that follows will provide a guideline for
determining your needs. Read through the example and then complete the worksheet on the
following page.
Step 1: Multiply the number of hours (or fractions of hours) you will use the appliance each day by
the wattage of each appliance. Total these Daily Watt-Hours to determine your Daily Energy
Required ;
Step 2: Multiply the Daily Energy Required by the number of anticipated days of autonomy (days
between charging, usually one to five) to determine your Rough Battery Estimate (example used
three);
AC Appliance
Microwave
Lights (x4)
Hair Dryer
Television
Washer/Dryer
STEP 1
STEP 2
STEP 3
STEP 4
INVERTER
Step 3: Multiply your Rough Battery Estimate (Step 2) by two. This allows for a maximum 50%
normal battery discharge and an additional 50% for emergency situations. Multiply this figure by 1.2
to allow for an efficiency of 80%. This number is your Safe Battery Size in watt-hours.
Step 4: Convert Safe Battery Size in watt-hours to amp-hours. The formula is Safe Battery Size
(Step 3) divided by DC system voltage (example used 12-volts). This is the Amp-Hours Required
each day from your battery bank without recharging.
Inverter: This is the minimum inverter size required. Add together the appliances that will run at the
same time from Column 3 (Appliance Watts, listed above). You will need an inverter with this many
watts or more.
WK
Hours of Appliance
Daily Usage Watts
0.5 600
6 40
0.75 750
4 100
1 375
Daily Energy Required
Rough Battery Estimate
Safe Battery Size (watt-hours)
Amp-Hours Required
Minimum Inverter Size Required
Daily Watt-Hours Used
300
240
563
400
375
1878
5634
13522
1127
2000