Load shedding solutions

With the current state of our local power utilities the necessity to power all your gadgets and devices during our infamous loadshedding has left us all trying to find a solution to our constant lack of electricity. We’ve put together a guide on all you need to know to find the energy solution for you.

What is an inverter actually?

Let’s start off with a simple explanation of the word every South African has recently heard way too much. Simply an inverter is a system that converts DC to AC, but what does that actually mean, well batteries provide their electrical energy in the form of a direct current that flows in a loop across a circuit, however the energy supplied by Eskom at your wall socket looks a little different, it comes in the form of alternating current particularly that in the form of a sine wave, but enough big words, this isn’t an electrical engineering lecture, we’re going to make this simple to understand. Effectively an inverter makes a battery appear exactly how Eskom would to your devices, except, it actually works.

How do I know what capacity solution I need?

Without going too much into the explanation of the electrical engineering behind these numbers we’ve built up a simple guide on the rough estimated consumption of common devices.

What do I need to get an inverter set up?

The fundamental components you’re going to need, don’t worry we’ll help you in selecting each of these in the paragraphs ahead:

Batteries.

DC high current rated wiring (with crimping).

DC fuse.

AC output wiring with junction.

AC input wiring (with a plug for a free-standing unit).

The inverter unit itself (hybrid inverter unit).

Batteries

The most important component in this equation. Batteries come in different chemistries, capacities and voltages, but we’re here to walk you through it.

Chemistries

The most important factor in determining the lifespan of your batteries is selecting the chemistry suitable for you. First off, it’s important to select a deep cycle (sometimes referred to as marine cycle batteries) for your inverter, this differs from a crank battery in its ability to slowly deliver a steady current to your devices over a long period of time, as opposed to a crank battery like you’d find in a car -optimized to send a sudden rush of current as needed in the starting of a car engine as an example.

Flooded Lead Acid Batteries

A common type of deep cycle battery is the flooded lead Acid chemistry. These batteries are relatively cheap but require regular maintenance and have a limited lifecycle making them unsuitable for high intensity loadshedding with heavy usage. They vary in terms of lifespan typically inversely proportional to the depth of discharge of each cycle (DOD), with an estimated 200 cycles at 100% DOD, an average of around 500 cycles at 50% DOD, and 1300 cycles at a 30% DOD. These estimates assume an end lifespan of around 50% rated capacity. In layman’s terms this means you can expect to perform that number of discharge/recharge cycles before the batteries can only deliver half the capacity they could when they were new.

Sealed, maintenance free batteries

These include gel, AGM, sealed lead acid classes to name a few, but the general idea is the same, they require little to no physical maintenance. They generally allow for a greater depth of discharge than their flooded counterparts, and thanks to a lower internal resistance these batteries are better suited to deliver higher current in sudden bursts of power to your devices as they need it during temporary increases in current including device startups. AGM batteries typically support a depth of discharge around 80% meaning they can safely be drained to 20% of their rated capacity before sustaining significant damage to the cells. They compare similarly to the depth of discharge patterns seen with the flooded cells with about a 20% to 30% improvement on the number of cycles achieved. The main disadvantage of both flooded and sealed batteries is their lifespan and charging rates.

Lithium, LIPO4, lithium phosphate batteries

Currently the best available battery chemistry, offering a significant step up in virtually every way to the other chemistry options but coming in at a significantly higher price range. These batteries can be charged up significantly faster and drained to a significantly greater DOD, while sustaining the majority of their rated capacities over a much longer period, potentially exceeding a decade depending on the usage intensity. The high price is typically seen as worth it in our country and more as an investment, as with high intensity loadshedding the other options could last as little as under a year before needing replacement, and Lithium batteries being usable for around 10 years in the right conditions.

Capacities

Batteries come in many different capacity ratings, but in order to understand what they are referring to its a good idea to familiarize yourself with the units of measurement of electrical capacity. The most common capacity terms are Ah (Ampere hours), and Wh (watt hours). Since batteries are DC devices the power unit used in describing the active rate of energy transfer is watts and revising over a tiny important formula referred to as Ohms law, you’ll see that a watt is equal to volts multiplied by amps. So, to convert between watt hours and amp hours just enter the voltage rating of your battery into the equation to find the unknown variable. Simply to get Wh you would times Ah by the known voltage, and to get Ah you would divide Wh by the known voltage. But what is a watt hour and amp hour? It’s simply the amount of current or power you’re using times by the time you’re using it. For example, 100AH would be enough to supply 100 amps over a 1-hour period, or 50 amps over 2 hours, or 200 amps over a half an hour, as 100 times 1 = 50 times 2 = 200 times 0.5, which are all equivalent to the same overall capacity. Similarly with watts: a 1000Wh battery could power a 1000W (also known as 1 KiloWatt) microwave for 1 hour, or 2 1000W microwaves for a half an hour. Selecting capacity comes down to what average power draw you use times by the number of hours you would need it. But remember that you never want to drain a battery to 0%, and the less you drain a battery the longer it will last, so draining your battery to a greater depth of discharge is generally a worse idea for battery longevity so select your capacity accordingly. It’s generally recommended that one drains a flooded battery no lower than to 50% its rated capacity, an AGM battery to around 35% capacity, and lithium around 20% capacity. Effective capacity will diminish over the lifespan of the batteries depending on the depth of discharge during each of its charge/discharge cycles.

Voltages

Different inverters require different voltage input levels. This is listed as a spec on the inverter and in some cases even a setting required during installation. Using the same formula mentioned earlier you can convert between watts to amps times volts to find how many amps of current you would expect to be running through the dc part of the inverter system when using different amounts of power (W). This means to get a unit of power you can either have more voltage or more amps, but ideally the lower the current (Amps) the better. Higher current draw means thicker wires, and more opportunity for wasted energy as the components have to work harder to overcome resistances in the system. Batteries can be combined in series to add up to a larger voltage or connected in parallel to add up the capacities but keeping the voltage the same. But keep in mind the fundamental principle here is the higher the voltage the lower the current draw will be in proportion at the same power output.

What options do I have?

Hybrid Inverters

Hybrid inverters are the most common systems available, integrating all the systems required to simply connect a battery and be done. These are what most people are referring to when talking about inverters in South Africa.

UPS

Another word being thrown around a lot is a UPS (uninterruptable power supply), and while it’s not exclusively reserved for inverters an inverter can be configured to act as a UPS. However, the most common type of UPS is a simple DC to DC voltage converter acting similarly to a power bank capable of powering small DC based Electonics like WIFI routers and smartphones. An actual inverter would however still be required to power any AC devices.

Pure Sine Wave Inverters

Pure sine wave vs simulated or square wave inverters. While more expensive a pure sine wave inverter is almost always recommended to power sensitive electronic and inductive loads. The increase in cost is much worth the power efficiency improvements and safety benefits when powering sensitive devices, with some technologies outright refusing to operate correctly on simulated sine wave inverters, including neon lights and microwaves.

Parallelable

Parallel inverters are designed to be connected to each other summing up the power generation capabilities of the individual units. This also allows for later expansion where more power is demanded as an upgrade to an existing invertor installation.

What makes should I consider?

This is surprisingly both complex and simple to address, most hybrid inverter units available locally are all rebranded variants descending from the same company Voltronics manufactured under the original brand name Axpert. The main advantage of these units is the wide range of support available across the internet from many different countries and in many different languages amended and augmented by local retailers and enthusiasts. There are several other manufacturers available locally ranging from diy kits to fully assembled units. Just follow our spec guide and you’ll be on track to select the right product set for your household.

Axpert inverters are generally easy to identify visually, they have a very particular look to them but often feature custom branding by local retailers. However, all the equivalent models should perform near identically.

How do I set up my set up?

The first step to setting up an inverter solution is to decide whether you want to leave it free standing or integrated into your household wiring, we recommend hiring a professional for the later, but with basic precautions it should be simple enough to set up a free-standing system yourself.

Wiring

An important next step is determining the layout, the most important factor in this stage is reducing the length of the DC cabling as much as possible, not only for cost reasons, but namely for efficiency. Inverter trolleys and wall mounted setups are generally preferable to keep things organized but aren’t strictly speaking necessary. One highly recommended safety aspect is the installation of the DC fuse as reasonably close to the positive battery terminal as possible. Selecting a suitable DC cable is vital for the connections between the batteries and the inverter unit, by estimating the current according to the earlier mentioned Ohms law, you simply divide the maximum power rated by the inverter by the voltage of your battery bank to get the maximum expected current, take these numbers to your local cable store to find a fuse and some cable rated to handle your requirements. The DC wiring should be installed according to the supplied owner’s manual and under no circumstances should you allow both terminals of the battery to be connected directly. As for the AC wiring simply splitting an extension cord in two and wiring the respective connections to the input and output connectors of the inverter should do the trick for a free-standing unit.

Settings

Before flipping the switch on your new setup it’s necessary to read through the supplied owner’s manual to discover the available settings, and to consult with your batteries spec sheet to match the settings with what your battery requires. It may also be necessary to connect your batteries smart management connection to your inverter unit if it comes supplied with an integrated battery management unit.

Power factor and efficiency

One of the more confusing looking specs on an inverter spec sheet is the power factor, simply this is a ratio of the effective real power absorbed by the load connected to the system versus the apparent overall power produced by the system. The closer this number is to 1 the better and the more efficient your system will be. If that answer doesn’t satisfy you basically, what this means in simple terms is the real power in watts used by your devices isn’t the whole picture of what’s happening in the system, and as a result of certain reactive elements (what you may have heard referred to as inductive loads) the inverters experience a certain complicated kind of inefficiency. To make sense of this complex electrical engineering principle all you really need to know is the unit VA(volt amp) -professionally known as complex power- is equivalent to a W(watt) -known as real power- plus the imaginary reactive power component.

Battery management systems

Most non-Lithium batteries are capable of using the built-in battery management systems of the hybrid Inverters with no special interfacing; however, many lithium batteries communicate between their usually built-in Battery Managment Systems to the inverter to control charge and discharge states and rates.

Energy generation (solar panels)

The majority of inverters in South Africa are ready to support the optional addition of solar cells, with a simple reconfiguration in the settings and DC wiring input to support the cells connections.