# Calculate Size of Inverter & Battery Bank

October 2, 2015 23 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**

Good

I think thise calculetions its very good , ,therefore l will depend on this calculetions in future.

this is wow, good work. I have been trying to calculate the size of an inverter, but now u make me know the calculations. thank you

Thanks

Hi Mr. Parmar,

This is the first time I actually follow and review the content of your mails. There’s a lot of error here.

Firstly, you won’t be able to get 712VA with your formula of 475 + (1+20%) / 80%, unless you multiply 475 to rests of the equation, not add.

Secondly, total load of battery bank is 31.66 Ah, not 32.66.

Thirdly, the unit for size of battery bank should remain Ah not Amp/Hour.

I did not finish the rest of the article. There’s probably more error down there.

Thanks for the effort, anyway.

Best regards, Ben

>

how to prepare single line diagram,slection of panels

type-2 cordetation chart

Thank you sir, these calculation is realy very useful.

Thanks Sir.

It is a great help.

Regards, Vikas Gupta.

Vikas Gupta.

Dear sir, will be there any major problem if one battery of 12 70 Ah in a bank of 15 batteries (series parallel combination) is repalced by 12 V 75 Ah battery. with regards,

vkh

Dear Sir,

As directed for expert/OEM opinion i am jotting down the schemes in which the 1×1.5MW Myntriang Small Hydro Electric Project(MSHEP) run.

*1st Scheme:* Originally 2×1.5MW MSHEP grid oriented machines get synchronized in the 33KV side. The 33 KV evacuation line is 8Km which feed this 3MW power from the generating station to 220KV grid substation through a 220/33KV Station Resesrve Transformer(SRT).

*2nd Scheme:* Due to non-availability of 220/33KV SRT this 3MW power of MSHEP was synchronized with another 33/132 KV grid substation. this 33/132KV grid substation is around 40Km away from MSHEP. this 40Km, 33 KV line passes via two numbers of 33/11Kv distribution substations. The faults of this 33KV line is very frequent.

whether the *2nd scheme *of evacuation for this particular 2×1.5MW MSHEP machines is proper. Kindly suggest some measures to run the machines in *2nd scheme *smoothly.

With regards, A.Mahanta DM,APGCL.

nice calculation use full for normal man thangs

*Thank you for your kindness and consideration*, RENJITH PILLAI

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Thanks for sharing

This post is very helpful, though the calculations done for condition I and II are quite confusing like

for 60 Ah 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

How ? it does not fulfills "Amp Hr of Battery Bank / Amp Hr of Each Battery <=1"

There are lot more …

Thanks for a nice explanation. Like to second confirmation with your permission for the following :-

1) parallel connection with similar Ah and same Voltage of each battery:

(a) Ah is increased&Voltage is same

2) Series connection for the batteries as(1):

(b) Ah is same&Voltage is increased

Clarification :

The lowest Ah should be taken in to an account for DIFFERENT Ah with same / similar voltage batteries to the above(1) & (2). Advise me with diagrams pl.

dear sir

how to desired amp hr of battery bank in series connection 3

and parallel connection 101

please explain

dear sir

this is very excellent explanation. but how to desired amp hr of battery bank in series connection 3 and parallel connection 101

hi there

Thanks sir, this will help me in deciding the size of solar power installation projects to government buildings.

Diagram series parallel connection Output NO (240 AH, 24V), YES (120 AH, 24V)

Why Temperature Correction Factor for 46ºC (Tp)=1?

Single phase UPS taken 16A input current which capacity MCB need in input

Hi,

my doubt on this topic is that why starting KVA for the computer load has not been considered?