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Power Back-up Systems

Choosing a Home Backup System

You do not need to be without power when Umeme load sheds you. You can have a reliable and economical power backup system. Before choosing a home backup system for your needs, we recommend that you read this information. This will help you understand some basic functions, capabilities and limitations of the system units and why some cost more and others less. These definitions and explanations apply to all makes of backup system components whether they are supplied by us or not.

Why Inverter and not Generator?

You can use a generator as a backup system and you won’t need an inverter but we recommend that you consider using an inverter-based system. The following are some of the reasons why you should consider an inverter rather than a generator:

  • No fuel is required to run an inverter and maintenance costs are very low. The cost of the inverter and batteries can be recovered with savings in fuel and maintenance costs required to run the generator.

  • Depending on the load, the inverter draws only the required amount of power from the battery. The fuel consumption in the case of the generator is more or less constant irrespective of the load. The inverter is therefore more economical.

  • The inverter gives you ease of operation. It automatically changes over to inverter mode and vice-versa during power failure. Since a generator runs on fuel, it has to be refueled manually and in most cases has to be started and shut down manually.

  • There is no noise or environmental pollution in case of an inverter whereas a generator is noisy and pollutes the environment.

  • An inverter can be installed anywhere in the house whereas a generator has to be installed outside the house and requires more space.

If the grid power is so unreliable, you may consider installing solar power to give backup charge to the batteries if the load is not too big or get a generator for use in such emergencies.

Why you need an inverter

A backup electric power system with storage battery, which stores power in the form of direct current (DC) needs an inverter to convert DC to AC, and also to change the voltage. This allows a battery-based independent power system to run conventional appliances through conventional home wiring. There are many ways to use DC power directly, but if you need to power AC appliances that are normally supplied by the utility grid, you will need an inverter.

Inverter Power Rating

The inverter size you choose depends on the total power in watts of the appliances/equipment you want to run. You need to know both the continuous rating and the peak/surge rating in watts. Without this information any further calculation is not possible.

Inverters are rated in continuous power and peak/surge power. Continuous power is the total WATTS the inverter can support indefinitely while peak/surge power is the amount of power that the inverter can provide for a brief period, usually when the equipment/appliance starts up. So, for example, if you want to run a continuous load of 1150 Watts and a peak load of 3450 Watts, you would need an inverter with a continuous rating of approximately 1500 watts and with a peak/surge rating of approximately 3500 watts.

Inverter Power Quality

Some inverters produce "cleaner" power than others. The quality of the AC power that the inverter produces in waveform, frequency, and voltage, determines the types of appliances and equipment it can operate. Two types of inverters predominate the market - modified sinewave (quasi sine wave) and pure sine wave inverters.

The Modified sinewave inverter has an inferior waveform. Though inexpensive compared to the pure sine wave inverter, it has limitations. It is adequate for many homes with simple needs, but some sensitive electronic equipment will malfunction. Generally a modified sine wave inverter reduces the reliability of appliances (as does poor quality grid power). The pure sine wave inverter gives the best output waveform you can get out of an inverter and all appliances are able to run off it without interference or overheating. However, it is more expensive. Its output voltage waveform is a pure sine wave that is the same (or superior) as the distribution mains supply

What Type of Batteries Should I Use?

Batteries are the fuel tank of your backup system and are a key component that all other components rely on for operation. Motor vehicle starting batteries can be used but do not really have the capacity for continuous service with many charge/discharge cycles. We recommend that you use lead acid industrial type batteries which have much thicker internal plates that can withstand many deep discharge cycles.

How Long Can I Run the Appliances from the Inverter?

This depends on the battery size selected and the type of batteries used. Deep cycle (e.g. solar) batteries generally have the highest reserve ratings. They are specifically designed to withstand repeated drains of power and recharging. If you parallel two such batteries this will generate twice the amp-hours of a single battery; three batteries will generate three times the amp-hours, and so on. This will lengthen the time before your batteries will need to be recharged, giving you a longer time that you can run your appliances.

The lifespan of a battery is closely related to the frequency of use, how deep the battery is being discharged, the quality of the battery charger and how it is maintained. Vehicle start batteries should not be discharged below 90% charged state, and solar deep cycle batteries should not be discharged below 50% charged state. Doing so will shorten the life of the battery based on most battery manufacturers’ recommendations.

Battery charging features

Some inverters have a built-in battery charger that will recharge the battery bank whenever power is applied from an AC generator or from the utility grid (if the batteries are not already charged). A good battery charger should have charge control features including accommodation of different battery types (flooded or sealed) without the risk of overcharge. It should have sufficient charging capacity for the installed battery capacity. A multi-stage intelligent charger will maximize battery capacity and lifespan.

You get what you pay for

A good inverter is reliable and able to handle a wide variety of loads without wasting lots of energy. It is well protected from surges from nearby lightning and static, and from surges that bounce back from motors under overload conditions. A good inverter is an industrial quality device that is proven and certified for safety, and can last for decades. A cheap inverter may soon end up in the junk pile, and can even be a fire hazard. Consider an inverter to be a foundation component. Buy a good one that allows for future expansion of your needs.

A correctly sized bank of good quality batteries is also essential for the proper functioning of your system. Compromising on the battery bank can lead to poor performance and dissatisfaction with the entire system. A good quality inverter combined with a good quality battery bank installed by a competent technical team will give you reliable and trouble-free service for many years.

Preventive Maintenance Contracts

Power backup systems, especially larger systems, require maintenance. We offer countrywide service agreements, ranging from basic maintenance to full service contracts. Please enquire. These services help to extend the inverter and battery life span.

Seek professional help

Safe and effective system design is critical. It is best to seek professional help if you are not sure before you buy one. We are just a call away.

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