©
2020 Sensata Technologies
Page 53
Appendix B – Battery Information
B-5 Battery Bank Sizing Worksheet
Complete the steps below to determine the battery bank size required to power your AC loads:
1. Determine the daily power needed for each load
a) List all AC loads required to run; and
b) List the Wattage for each load (see Table C-1 for common loads/wattage); and
c) multiply by how many hours per day (or a fraction of an hour) each load will be used; and
d) multiply by how many days per week you will use the listed loads; and
e) divide by seven =
Average Daily Watt-Hours Per Load
.
Average Daily Watt-Hours Per Load
AC load
Wattage
(x) hours per day (x) days per week
(
÷
7) = total power
4. Determine how deeply you want to discharge your batteries.
• Divide the
Storage Amp-Hours
by 0.2 or 0.5 to get the
Total Amp-Hours:
a) 0.2 = Discharges the batteries by 20% (80% remaining), this is
considered the optimal level for long battery life; or
b)
0.5 = Discharges the batteries by 50% (50% remaining), this is
considered a realistic trade-off between battery cost and battery life.
2. Determine the total power needed each day for all the loads.
• Add all
Average Daily Watt-Hours Per Load
=
Total Daily Watt-Hours
.
Total Amp-Hours
3. Determine the battery amp-hour capacity needed
to run all the loads before recharging.
• Divide the
Total Daily Watt-Hours
by the nominal
battery voltage of the inverter (i.e., 12 volts); and
Multiply this by # of days the loads will need to run
without having power to recharge the batteries
(3 to 5 days of storage) =
Storage Amp-Hours
.
x
___
=
(days of storage)
÷
___
=
(inverter battery voltage)
Temperature
80F/27C
70F/21C
60F/15C
50F/10C
40F/4C
30F/-1C
20F/-7C
Multiplier
1.00
1.04 1.11
1.19
1.30
1.40 1.59
Additional compensation:
Low battery temperature:
If the batteries are installed in a location that will be exposed to low
temperatures, the available output will be less. In these instances, you will need to determine
the lowest temperature the battery bank will experience and multiply the
Total Amp-Hours
by the
multiplier below.
Inverter effi ciency:
When used in a back-up power application the inverter ef
fi
ciency will not be a
large concern; however, if the inverter is the primary AC source for the calculated load, the
Total
Amp-Hours
should be multiplied by 1.2 to factor in an average 80% inverter ef
fi
ciency.
Total Daily
Watt-Hours
