If you are planning to design for a standalone home solar power system, the most crucial thing you need to take into account is the battery bank and the inverter. We need to make sure all the DC energy that can be stored into our battery bank. By wiring to the inverter where the DC electricity is converted to AC (alternating current) electricity.

How to calculate Home appliances’ total wattage usage needed:

Step 1: List out all the home appliances or devices’ load power in watts that consume in daily use

( total hours per day )

Note : Some appliances may take more than its rated power at start-up.

Step 2 : Multiply the wattage of each devise by its run-time to get the energy in watt-hours per day.

Step 3 : Add up all values to get a total watt-hour

Step 4: Multiply by a value of 1.5 in order to get a rough idea of the real value with system loses caused by temperature increases.

**Example :**

**Total watts consumes :**

Use 2 units of Fluorescent lights 40w and a TV 21” 60w :

40w x 2 + 60w = 140watts

Daily Power consumption ( watt-hour):

Run Fluorescent lights for 6 hours /day , TV runs for 2 hours/day :

Total watts consumption : 80w x 6hrs + 60w x 2hrs = 600watt-hours

600 x 1.5 = 900 watt-hours

Decide how many days you plan you can store your extra energy power for back up purpose. Generally can be 2-5 days depending your power system design.

At this step, we can calculate the minimum battery AH capacity. You can take the watt-hours per day and multiply by the number of days you decided and again multiply by 2 (cos estimate a 50% depth of discharge on your batteries). Finally we need to convert the kwh result into Amp-Hours(AH) by dividing with battery voltage.

**Example :**

from step 1, we have a total of 900watt-hours /0.9kwh per day

from step 2 , we need at least 3 days without recharging on the battery bank

Total capacity of Battery bank needed : 0.9 x 3 x 2 = 5.4kwh

To convert the value into AH, we need to divide by your system voltage ( 12,24 or 48) ;

if you design to use 24v, the minimum AH capacity is : 5400/24= 225 AH.

Lastly if you divide by your battery’ rating, you will find the number of batteries that you sure use. This will we a crucial part of the power system. There are 2 methods of wiring in a circuit – parallel and series.

As you can see from the diagrams, we can notice that in a parallel circuit the battery voltage remain the same but the current adds up; but on the other hand, voltage in series circuit will adds up, but current remain the same. You can eventually design and combine your battery wiring in series and parallel circuit that you require.

Battery wiring design plays an important part in your power system. A good wiring configurations can boost up your energy power performances to meet up with your voltage and AH requirements. So do always design and plan ahead before buying the right size inverter and batteries for your home power system.

For more info on battery wiring, you can read more at HERE

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Battery Bank always refer to a group of batteries that wired together in Series or Parallel circuit.

**Series circuit wiring** is made by connecting one pair of opposite terminals of different batteries together as per shown at the diagram. Series circuit wiring practically will increase the total voltages of the batteries but on the other hand, the amperage capacity still remains the same.

The below diagram is a string of 4 batteries connected in Series wiring. Each battery is 6V with rated 250AH capacity, thus the nominal voltage of this string is 24V with remain of 250AH capacity.

**Parallel circuit wiring** whereby is made by wiring with 2 or more same terminal batteries together (usually positive to positive terminal and negative to negative terminals). A Parallel wiring on the other hand can increase the amperage of the string batteries increase while keeping the total voltage the same as one of the batteries.

Series circuit wiring practically will increase the total voltages of the batteries but on the other hand, the amperage capacity still remains the same.

The diagram shows two 12V batteries rated 350AH each are wiring in parallel circuit. Thus the total voltage of these string batteries is remain in 12V with a AH capacity of 700AH.

Battery Banks often also is connected together by using both Series and Parallel circuit as per diagram shown below. Each battery is in 6V with 250AH capacity, then each string has a voltage of 24V (4 batteries with 6V) and 250AH. The two series strings are then wired in parallel which can increase the amperage capacity to 500AH.

It is important to make sure the voltage of your inverter and charge controller must same as your batteries bank voltage whether 12v, 24v or 48v.

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