## Calculate Size of Inverter & Battery Bank

October 2, 2015 34 Comments

Calculate Size of Inverter for following Electrical Load .Calculate Size of Battery Bank and decide Connection of Battery.

**Electrical Load detail:**

- 2 No of 60W,230V, 0.8 P.F Fan.
- 1 No of 200W,230V, 0.8 P.F Computer.
- 2 No of 30W,230V, 0.8 P.F Tube Light.

**Inverter / Battery Detail:**

- Additional Further Load Expansion (Af)=20%
- Efficiency of Inverter (Ie) = 80%
- Required Battery Backup (Bb) = 2 Hours.
- Battery Bank Voltage = 24V DC
- Loose Connection/Wire Loss Factor (LF) = 20%
- Battery Efficiency (n) = 90%
- Battery Aging Factor (Ag) =20%
- Depth of Discharge (DOD) =50%
- Battery Operating Temp =46ºC

Temp. °C |
Factor |

80 | 1.00 |

70 | 1.04 |

60 | 1.11 |

50 | 1.19 |

40 | 1.30 |

30 | 1.40 |

20 | 1.59 |

__Calculation:__

__Calculation:__

**Step 1: Calculate Total Load:**

- Fan Load= No x Watt =2×60=
**120 Watt** - Fan Load=(No x Watt)/P.F=(2×60)/0.8=
**150VA** - Computer Load= No x Watt =1×200=
**200 Watt** - Computer Load=(No x Watt)/P.F =(1×200)/0.8=
**250VA** - Tube Light Load= No x Watt =2×30=
**60 Watt** - Tube Light Load=(No x Watt)/P.F =(2×30)/0.8=
**75VA** **Total Electrical Load=120+200+60 =380 Watt****Total Electrical Load=150+250+75= 475VA**

**Step 2: Size of Inverter:**

- Size of Inverter=Total Load+(1+Af) / Ie VA
- Size of Inverter= 475+(1+20%) / 80%
**Size of Inverter= 712 VA**

**Step 3: Size of Battery:**

- Total Load of Battery Bank= (Total Load x Backup Capacity) / Battery Bank Volt
- Total Load of Battery Bank=(380 x 2) / 24 Amp Hr
**Total Load of Battery Bank= 32.66 Amp Hr**- Temperature Correction Factor for 46ºC (Tp)=1
- Size of Battery Bank=[ (Load) x (1+LF) x (1+Ag) x Tp] / [n x DOD] Amp/Hr
- Size of Battery Bank= (32.66 x (1+20%) x (1+20%) x 1) / (90% x 50%)
**Size of Battery Bank= 101.3 Amp/Hr**

**Step 4: Connection of Battery:**

__If We Select 120 Amp Hr , 12V DC Battery for Battery Bank:__

**Series Connection:**

- Series configurations will add the voltage of the two batteries but keep the amperage rating (Amp Hours) same.
- Condition-I :
**Selection of Battery for Voltage = Volt of Each Battery <= Volt of Battery Bank**- Selection of Battery for Voltage =12< 24
**Condition-I is O.K**- No of Battery for Voltage = Volt of Battery Bank / Volt of Each Battery
- No of Battery for Voltage =24/12 =
**2 No’s** - Condition-II :
**Selection of Battery for Amp Hr = Amp Hr of Battery Bank <= Amp Hr of Each Battery**- Selection of Battery for Amp Hr =
**3<=120** **Condition-II is O.K**- We can use Series Connection for Battery & No of Battery required 2 No’s

- In Parallel connection, the current rating will increase but the voltage will be the same.
- More the number of batteries more will be the amp/hour. Two batteries will produce twice the amp/hour of a single battery.
- Condition-I :
- Selection of Battery for Amp Hr = Amp Hr of Battery Bank / Amp Hr of Each Battery <=1
- Selection of Battery for Amp Hr =101/120 = 0.84=
**1 No’s** **Condition-I is O.K**- Condition-II :
**Selection of Battery for Voltage = Volt of Battery Bank = Volt of Each Battery**- Condition-II :Selection of Battery for Voltage for Amp Hr =
**24<=12** **Condition-II is Not Full Fill**- We cannot use Parallel Connection for Battery as per our requirement But If We do Practically It is Possible and it will give more Hours of back

- Connecting the batteries up in series will increase both the voltage and the run time.
- Condition-I :
- Selection of Battery for Amp Hr = Amp Hr of Each Battery <= Amp Hr of Battery Bank
- Selection of Battery for Amp Hr =120<=101
**Condition-I is Not Full Fill**- Condition-II :
- Selection of Battery for Voltage = Volt of Each Battery <= Volt of Battery Bank
- Selection of Battery for Voltage = 12<=24
**Condition-II is OK**- We cannot use Parallel Connection for Battery

__If We Select 60 Amp Hr , 12V DC Battery for Battery Bank:__

**Series Connection:**

**Selection of Battery for Voltage = Volt of Each Battery <= Volt of Battery Bank**- Selection of Battery for Voltage =12< 24
**Condition-I is O.K**- No of Battery for Voltage = Volt of Battery Bank / Volt of Each Battery
- No of Battery for Voltage =24/12 =
**2 No’s** - Condition-II :
**Selection of Battery for Amp Hr = Amp Hr of Battery Bank <= Amp Hr of Each Battery**- Selection of Battery for Amp Hr =
**3<=60** **Condition-II is Not Full Fill**- We can use Series Connection for Battery

**Parallel Configuration**

- Condition-I :
- Selection of Battery for Amp Hr = Amp Hr of Battery Bank / Amp Hr of Each Battery <=1
- Selection of Battery for Amp Hr =101/60 = 1.63=
**1 No’s** **Condition-I is O.K**- Condition-II :
**Selection of Battery for Voltage = Volt of Battery Bank = Volt of Each Battery**- Condition-II :Selection of Battery for Voltage for Amp Hr =
**24=12** **Condition-II is Not Full Fill**- We cannot use Parallel Connection for Battery as per our requirement.

**Series-Parallel Connection****:**

- Condition-I :
- Selection of Battery for Amp Hr = Amp Hr of Each Battery <= Amp Hr of Battery Bank
- Selection of Battery for Amp Hr =120<=60
**Condition-I is OK**- No of Battery for Amp Hr = Amp Hr of Battery Bank / Amp Hr of Each Battery
- No of Battery for Amp Hr = 120/60 =1.68 =
**2 No’s** - Condition-II :
- Selection of Battery for Voltage = Volt of Each Battery <= Volt of Battery Bank
- Selection of Battery for Voltage = 12<=24
**Condition-II is OK**- No of Battery for Voltage = Volt of Battery Bank / Volt of Each Battery
- No of Battery for Voltage = 24 / 12 =
**2 No’s** - No of Battery Required = No of Battery Amp Hr x No of Battery for Voltage
- No of Battery Required = 2 x 2=
**4 No’s** - We can use Series-Parallel Connection for Battery

__Summary:__

__Summary:__

- Total Electrical Load=
**380 Watt** - Total Electrical Load=
**475VA** **Size of Inverter= 712 VA****Size of Battery Bank= 101.3 Amp/Hr****For 120 Amp/Hr , 12V DC Battery : Series Connection & 2 No’s of Battery or****For 60 Amp/Hr , 12V DC Battery : Series-Parallel Connection & 4 No’s of Battery**

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