Power outage can interrupt your work and take away comfort of your home, so buying the best inverter and battery is the solution to this problem.
But which inverter and battery to buy, that will last for years to come?
Let’s answer that question by learning everything important about inverter and batteries.
So that you can make an informed buying decision.
By the end of this post, you will know everything you need, all in one place.
Here is what you will know in this guide.
- Know some basics, and how inverter and battery system works.
- Determine your total load requirement (to buy correct inverter and battery).
- Find inverter VA requirement for your load.
- Find battery Ah and voltage requirement (suitable for your inverter).
- Solution for longer power cut (connecting batteries in parallel).
- Types of inverter, and features to look for.
- Types of inverter battery.
- Battery warranty and after sales service.
1. Know some basics, and how inverter and battery system works.
(Skip this if you already know.)
Brush up your basics.
Electrical energy is supplied by the combination of current and voltage.
Voltage (also known as electric pressure) is the potential difference between two points, that will give one joule of energy when one coulomb of charge passes through those two points.
Potential difference is the difference in amount of energy that a charge carrier has.
Charge carrier will have some amount of energy at point A.
When it passes to point B it will have some amount of energy at point B.
The difference in this amount of energy between these two points is Potential difference.
Measured in volts (V).
V = Potential energy / Charge.
Potential energy is energy held by an object, here it is because of its electric charge.
Current is the net rate (one coulomb/second) of flow of charged particles through a conductor.
Measured in ampere (A).
(Note: 1 ampere = 1 coulomb = 6.241509074×1018 electrons worth of charge.)
Electric power or Wattage is the rate at which electrical energy is transferred by an electric circuit.
It is measured in Joules/second (J/s) or watt (W).
That is, Power (W) = Voltage (V) x Current (A).
In Direct Current (DC) electric charge flows in one direction.
DC does not have frequency.
In Alternating Current (AC) electric charge reverses its direction periodically.
Electric power is delivered to residences in AC form at different voltage (110 V to 240 V) depending on the country.
So, check your country’s residential voltage.
The frequency of AC is usually 50 Hz or 60 Hz.
How inverter and battery system works?
Battery stores and supplies DC current, but home appliances work on AC current.
So, inverter converts DC current to AC current.
When mains power cuts, the inverter transfers load to battery.
It then takes DC current from the battery and converts to AC current, which is used by electrical appliances.
When mains power comes back, it stops using power from battery and switches to mains electricity.
Meanwhile, it also charges the battery and prepares for the next power cut.
2. Determine your total load requirement (to buy correct inverter and battery).
Make a list of all essential appliances you will run during a power cut.
We need to calculate total load, by adding the load of each appliance.
(Note: You can find your appliance load on the compliance label or user manual of the appliance, which will usually be in watts (W). Remember, this power rating is the maximum power the device can use under normal conditions, but it can use less power than this [the power here refers to Real power].)
We will need this total load in a minute, to calculate your requirement.
Here is the table of common electrical appliances and their default load in watt.
| Ceiling fan | 75 |
| Cooler | 185 |
| LED light bulb | 10 |
| CFL light bulb | 14 |
| Incandescent light bulb | 60 |
| Fluorescent tube light | 43 |
| LED tube light | 16 |
| Desktop Computer | 60 to 300 |
| Wi-Fi router | 6 |
| Phone charger | 5 |
Example: If you want to run 2 fans, 3 LED tube lights and 2 LED light bulbs, then your load will be, (2 × 75) + (3 × 16) + (2 × 10) = 218 watt.
3. Find inverter VA requirement for your load.
When you look for inverter in the market, you come across inverter rating of 800 VA, 900 VA, etc.
But what inverter VA do you actually need?
Let’s get to the answer by understanding some important concepts.
Take some time to read on, as it will really help you to clear your doubts.
For simple DC circuit (like LED connected to battery).
Watts (W) = Amps (A) x Volts (V), will give you the load of the device.
But when it comes to mains power, we are dealing with AC current, and with AC not all the power is used to do the actual work.
Understanding Real power, Apparent power and Reactive power.
The portion of power which is not used to do the actual work is known as Reactive power.
So the above equation will give you Apparent power, but not Real power.
Apparent power = Amps (A) x Volts (V) = Volt-Amps (VA).
It is the power that flows through the electrical appliance.
Or to put it differently:
The power that electrical appliance consumes, but not necessarily converts all of this power to actual work.
When it comes to AC Current, the load we calculate must be Real power (also known as Active power, True power).
Which includes Power factor as well.
Real power = Amps (A) x Volts (V) x Power factor = Watt (W).
This is the power that is used by appliance running on AC current to do the actual work.
But it draws more power, which is Apparent power.
Power factor of the appliance.
Power factor is a measure of how efficiently an electrical appliance uses power supplied to it.
The closer the Power factor is to 1, the greater the efficiency.
Normally it is 0.7 or 0.8, but it depends on the appliance itself.
For example:
Most electric heaters convert all electrical power to heat (all power is converted into work) so will have a Power factor of 1.
This is an example of purely Resistive load.
In this case, Apparent power = Real power = VA = watt.
Pumps, fans, or any device that uses a motor will have a Power factor less than 1.
This is the example of Inductive load.
Now the load you calculated above is in watt, which also has Power factor already multiplied in it.
So it is Real power.
But the appliance consumes Apparent power (VA), which will be greater or equal to Real power depending on the Power factor of the appliance.
So to get your load in VA, you must divide it by Power factor.
Now you can not know the Power factor of every appliance, as it is different for every appliance, depending upon type of load.
So you can assume and divide your load by 0.7 or 0.8 of Power factor (use 0.7 to be on the safer side).
Let’s say your load requirement is 700 watt.
Dividing 700 W by 0.7 gives 1000 VA.
Now you can buy inverter slightly more than 1000 VA, but not less than this.
4. Find battery Ah and voltage requirement (suitable for your inverter).
Take your total load requirement (must be in VA and not in watt).
Multiply it by the number of hours you will run this load.
Example: 1000 VA x 4.5 hours = 4500 VA-h.
Now here comes the voltage of the battery.
The battery in market is usually available in 12 V, 24 V, etc.
But the inverter you choose dictates what voltage the battery must have.
Let’s say your inverter requires 12 V battery.
Now to find the Ah of the battery divide 4500 VA-h by 12 V
4500 / 12 = 375 Ah
Just like the limited options you have for battery voltage, battery Ah options are also limited.
Usually it comes in 150 Ah, 200 Ah, etc.
But here we need 375 Ah battery, how do we solve this?
The answer is connecting two batteries of 12 volts and 200 Ah in parallel.
(Note: Ensure your inverter supports multiple battery setup.)
This will give you 12 volts and 400 Ah of battery system.
When you connect two batteries in parallel, current gets added, but voltage remains same.
(Note: To add current and keep the voltage same, we connect the batteries in series.)
To connect batteries in parallel, you need to connect positive terminal of one battery to positive terminal of another battery.
Do the same with negative terminals.
Finally, connect the positive and negative of the final battery to the inverter.
This also gives us a solution to our next problem.
5. Solution for longer power cut (connecting batteries in parallel).
Depending upon your load and number of hours, you can calculate your battery Ah.
Let’s take your load as 1000 VA.
Based on your inverter requirement, let’s take battery voltage as 12 V.
Number of hours you need the power, let’s take 6 hours.
Therefore, 1000 VA x 6 h = 6000 VA-h.
Dividing this by voltage, gives battery Ah.
6000 VA-h / 12 V = 500 Ah.
So the solution will be to connect three batteries of 200 Ah and of 12 volts each in parallel.
Which adds up to 600 Ah.
(Note: Connecting two different Ah battery [one with 150 Ah and other with 200 Ah] in parallel is highly discouraged as this setup will cause charging problems. Always connect batteries with same Ah and voltage.)
6. Types of inverter, and features to look for.
Types of inverter is based on output waveform the inverter can produce.
Square wave inverter.
This inverter produces a square wave output.
This type is not suitable for sensitive appliances.
You must not buy this type, because most appliances are designed to use sine wave.
Sine wave inverter.
This type of inverter is best suitable for all appliances, and its output is very similar to the mains, so is widely used in residences.
You must buy the inverter that has pure sine wave in its specifications.
Pure sine wave means the output sine wave will have very low percentage of THD (Total Harmonic Distortion).
Features of inverter you can look for.
(Remember, the more features the inverter has, the higher will be the price tag.)
Mode of operation.
Normal Mode (also called as Eco mode).
If you are not using a computer where sudden power failure will be a problem, then use this mode.
UPS Mode (Uninterrupted Power Supply).
If you are using a computer, then use this mode. This mode will also regulate the voltage suitable for the computer.
Front display.
Normally, all display panels of inverter will at least give you some basic info like,
Mains on, Charging, Mode, Low Battery, Overload, etc.
But what will be beneficial here is, if it also indicates:
Battery water topping.
So that you can maintain battery water level without having to check the level every now and then.
Maintaining good water level will improve overall battery life.
Battery’s remaining time of discharge.
This will help you to turn off some unwanted electrical appliances to increase the backup time, in case of longer power cut.
Number of batteries and type of battery it is compatible with.
Number of batteries will depend on your need as discussed earlier in this post.
But if you bought two batteries, and your inverter spec says you can only use one, then it will be a problem.
Also check whether it supports different types of batteries like Flat plate, Tubular, Sealed Maintenance Free (SMF), etc.
This is the reason you must buy the inverter first, before buying the battery.
Other useful features.
Bypass switch.
This will come handy when there is a fault in your inverter or battery.
Using this switch you can directly connect to mains power, bypassing the inverter until your technician diagnose and repairs the fault.
Temperature management system.
To avoid overheating of the inverter and maintaining optimum temperature level.
There are many other features, but the inverter you buy must at least have above-mentioned features.
(Note: Inverter must at least have two years of warranty, and make sure to read the conditions of the warranty.)
7. Types of inverter battery.
Flat Plate inverter battery.
If you are on a low budget, buy flat plate battery.
But the disadvantage will be shorter battery life.
So might cost you more in the long run.
These batteries perform poorly under heavy load.
Water must be topped frequently.
Tubular inverter battery.
This type of battery is best suitable for inverter.
It has longer battery backup and battery life.
Tubular batteries perform well under heavy load.
Best suitable if you have power cut for longer duration.
Does not require you to add water frequently.
SLA (Sealed Lead Acid) battery.
These batteries are also known as VRLA (Valve Regulated Lead Acid) battery.
VRLA are of two types.
Absorbent Glass Mat (AGM) and Gel cell (Gel battery).
These are maintenance free battery, meaning there is no requirement of maintaining water level.
But these have shorter battery life, and are mostly used for portable electrical devices.
8. Battery warranty and after sales service.
Usually the battery warranty will be of 36 months.
The longer the warranty duration, the costlier the battery will be.
After sales service will depend on which company’s battery you bought.
Buying from reputed company will give you sense of trust, but make sure to read the reviews of the company.
Check what people have talked about the company’s after sales service quality.
You can search online like this:
“Company-Name” after sales service review.
Also check reviews (of verified purchaser) on major e-commerce platform like Amazon.
(Tip: Read review of those who gave 3 to 4-star rating.)
Conclusion.
Hopefully this cleared your doubts and answered the questions you had.
So whether you decide to buy it online or offline, now you are equipped with the information, to select the best inverter and battery for your home.