Installation Manual

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 Watt-Hours for each load (see Table B-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 Watt-Hours (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 the Average Daily Watt-Hours Per Load together = Total Daily Watt-Hours.

Total Daily WHrs

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, 24 volts); and

• Multiply this by how many days the loads will need to run

without having power to recharge the batteries (typically

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 the inverter is used in a back-up power application the inverter efﬁ 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 efﬁ ciency.