Why You Need It

Load shedding is a common phenomenon in South Africa where electricity supply is temporarily cut off to certain areas to prevent the national grid from collapsing. This occurs when the demand for electricity exceeds the supply, and it can have severe consequences for individuals and businesses alike.

However, a small home inverter can make a big difference in such situations. An inverter is a device that converts direct current (DC) electricity into alternating current (AC) electricity, which is the type of electricity that is supplied to homes and businesses. By using a small home inverter, households can continue to use essential appliances, such as lights, wifi routers and televisions, even during load shedding.

There are many all-in-one systems already out there but it is not difficult to create your own modular basic system, whereby you can mix and match the components to suit your needs.

Creating Your Own Inverter System

To create your own small inverter system, you will need the following components:

Inverter: This is the central component of the system and is responsible for converting DC electricity from the battery into AC electricity that can be used by your appliances. Choose an inverter that is rated for the power output you need for your specific requirements.

Battery: This component stores energy that can be used by the inverter during load shedding or power outages. Lead-acid batteries are commonly used in small inverter systems, but other types of batteries, such as lithium-ion batteries, can also be used.

Battery charger: This component is used to charge the battery during periods of normal electricity supply. A battery charger that is designed specifically for your type of battery is recommended to ensure maximum battery life and performance.

Suggested Products:

12V Car & Home Inverter 350W-500W

8 Amp 6/12V Battery Charger - Bch8

Battery - 630 (Exide)

A Look at the Numbers:

Assuming that a system is composed of the above three components, namely a 38Ah battery, a 350W inverter, and an 8-amp battery charger. If the intended usage involves two rooms with 11W low energy light bulbs, a TV and DSTV consuming 160W, and a 15W WiFi router, the total power consumption of the system is estimated to be 197W.

However, considering the typical efficiency of inverters, which is 80%, the actual power required from the battery is 246W, calculated as 197W divided by 0.8. The relationship between power, voltage, and current can be represented as P = IV, where P is power, I is current, and V is voltage. Therefore, for a 12V battery, the current required to produce 246W is 20.5 Amps, calculated as 246W divided by 12V.

A 38Ah battery can potentially provide 1.85 hours of power to this system, calculated as 38Ah divided by 20.5 Amps. However, to maintain the battery's lifespan, it is not recommended to discharge the battery beyond 75%. Thus, the actual available capacity is 28.5Ah, and the system can last for approximately 1.4 hours, calculated as 28.5Ah divided by 20.5 Amps.

What can I run for 2.5 hours?

We can also do the calculation in reverse. Let us start with the required runtime of 2.5 hours, which is roughly what the current loadshedding periods are. If the desired runtime is 2.5 hours during a load shedding period, the current must not exceed 11.4 Amps, calculated as 28.5Ah divided by 2.5 hours. The corresponding usable power is 109.4W, considering the 80% efficiency of the inverter. Therefore, the sum of appliances used in the system must consume less than 110W.

Have a look at the graphic below and see the typical power consumption values of small home appliances. Then see which appliances you can add together to reach a sum of a total of 110W.

If possible, it is recommended to look at the actual power rating of the appliances at your home rather than relying on average values or charts, as these can vary between different models and brands. The actual power rating can usually be found on the product specification label, the manual, or on the manufacturer's website.

Time Required To Recharge The Battery Between Loadshedding Periods

Finally, the time required to charge the battery from 25% to full capacity is estimated to be 5 hours, considering 40% power loss during the charging process. The calculation is performed as T = Ah ÷ A, where T is time, Ah is the battery capacity, and A is the charging current. In this case, T is calculated as 28.5Ah divided by 8A.

Useful Formulas:

The formulas used in the above article are:

P = IV

This formula represents the relationship between power (P), current (I), and voltage (V). Power is equal to the product of current and voltage.

I = P/V

This formula calculates the current (I) required to produce a given power (P) at a specific voltage (V). Current is equal to power divided by voltage.

T = Ah ÷ A

This formula calculates the time (T) required to charge a battery with a capacity (Ah) and a charging current (A). Time is equal to battery capacity divided by charging current.

The symbols in these formulas have the following meanings:

P: Power, measured in Watts (W)

I: Current, measured in Amperes (A)

V: Voltage, measured in Volts (V)

Ah: Battery capacity, measured in Ampere-hours (Ah)

T: Time, measured in hours (h)

A: Charging current, measured in Amperes (A)