Masterclass: How to build a battery backup

On December 22, 2018 Mathy Mpassy Isinki, founder of Energy One Africa gathered 23 people for a masterclass on how to build a battery backup. The battery backup masterclass took at ISIC in Mont Ngafula, Kinshasa. During the masterclass, in addition to how battery backup works, Mathy shared a step by step guide on how to specify  the appropriate inverter, select the batteries and  size and configure the battery bank.

A power backup system is a standby power systems which supplies electricity to a load in case of mains power  failure. A battery based power backup system is made of two main components:

  • A battery bank storing energy and;
  • An inverter converting battery bank DC electricity into AC, inverters used for backup systems usually have inbuilt battery chargers for charging the battery from the mains power source. A separate battery charger is required when the inverter does not have one inbuilt. 

Battery based backup systems are an alternative to generators. Their advantage over generators are:

  • Silent and non polluting operations
  • Instantaneous change over when mains power fails or come back
  • Low running cost; just limited to the necessary power to charge the batteries. 

Their main drawback compared to generator is that they only supply power for a predetermined amount of time and, the backup time decreases as the load increases. Therefore, the battery bank should be properly sized to meet the load requirements.

In a backup system, energy is stored within a battery bank for use during periods of mains failure. It is recommended to use deep cycle batteries.Deep cycle batteries have the capacity of being charged and discharged hundreds of times before they wear out. Lead-acid batteries are the most used.

Car batteries which are also lead-acid type are not recommended. However, because they are cheap, they are sometimes used for small backup applications but, their operational life is likely to be short: their thin plate do not allow them withstanding the deep discharge experienced by batteries in backup applications.

On the other hand, the inverter must provide enough power to start and run the connected load.To maintain continuous power supply to the load, backup systems are installed between the mains AC power supply and the load.

The full guide is accessible here: