# Calculate Size of Inverter & Battery Bank

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

• 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:

• 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:

• 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

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

Parallel Configuration

• 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

Series-Parallel Connection:

• 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:

• 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

Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical) from Gujarat University. He has more than 14 years experience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He is Freelancer Programmer of Advance Excel and design useful Excel Sheets of Electrical Engineering as per IS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India" Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

### 30 Responses to Calculate Size of Inverter & Battery Bank

1. علي سراج says:

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

2. kass says:

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

3. Robert Baluku baleke says:

Thanks

4. electroninz says:

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

>

5. ravindrababu uba says:

how to prepare single line diagram,slection of panels

6. S.Prashant says:

Thank you sir, these calculation is realy very useful.

7. Vikas G says:

Thanks Sir.

It is a great help.

Regards, Vikas Gupta.

Vikas Gupta.

8. vilas harlapur says:

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

9. Ajanta Mahanta says:

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.

10. Renjith Kumar says:

nice calculation use full for normal man thangs

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

t

11. Andrea AP says:

Thanks for sharing

12. B.D. says:

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 …

13. A.Balan says:

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.

14. prathap singh says:

dear sir
how to desired amp hr of battery bank in series connection 3
and parallel connection 101

15. prathap singh says:

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

16. prathap singh says:

hi there

17. M.THIYAGARAJAN says:

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

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

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

20. Baiju says:

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

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

22. Bas Karan says:

i am creating a android application for this “inverter bank size selection “. will it useful for you.

23. Bas Karan says:

i am going to create a android application this ” inverter battery bank size selection” will it useful for you?

24. raj khating says:

Essy skal the problems

25. sudip says:

how you get this formula

26. Joven says:

A good illustration.

27. Mangesh Parab says:

Its really useful calculation…………….
but how to decide Depth of discharge, battery aging factor, loss factor and efficiency……….??

28. Amna Ali Butt says:

Why is it suggested to use a fuse with lthium sulphate battery?