Alternative power Inverter backup - Battery charger, the weakest link An inverter backup system is made up of an inverter, a battery charger (integrated or dedicated) and of course a battery bank. A properly sized inverter will handle any selected loads and a fully charged battery bank will provide backup to the loads for the autonomy calculated. This means that you can have your home or office powered by an inverter backup system when regular power fails for say 3hrs, 24hrs or more depending on the state of charge of your battery bank. However, a battery cannot generate energy, it stores energy that is released due to chemical reactions. So, there must be a charging system that must properly charge the battery or a bank of batteries (battery bank) for the end user to enjoy the backup time calculated prior to buying and installing the inverter backup system. You can either over charge a battery, under charge it or properly charge it. The first 2 options will gradually but eventually destroy the battery while the last option will ensure that the battery lasts as long as the battery is designed to last. In Nigeria today, we have quite a number of people that have tried and regretted ever using inverters in their homes or offices. While the problem may come from the service provider, the end user or even both I will be focusing on the hidden problem caused by the charging system in some inverter backup systems. It is important to note that backup systems are rarely the same as regards the autonomy as Mr A may prefer a 12hra backup while Mr B may prefer 24hrs backup for the same loads while using the same inverter but with different battery banks. Technically and in reality the same inverter will work for both Mr A and Mr B but there is no way Mr B will enjoy a 24hrs backup by simplying doubling the battery bank of Mr A if the charging time is not increased because he will be requiring at least twice the number of hours it takes to charge Mr As battery bank to charge his own battery bank. Unregulated charging (whether over charging or under charging) will harm your battery bank and without a charged battery bank your inverter backup system is pretty useless. Even regulated charging that over charges or under charges your battery bank will ultimately lead to the same problem. For best results the charging system must take into account the capacity of the battery bank, there is certainly no other way to guarantee proper charging of your battery bank. Back to Mr A and Mr B, if the inverter unit (remember they are using the same inverter) has a charger that takes about 8 hrs to fully charge say 4 nos batteries for his 12 hrs backup then Mr B will require 16hrs to fully charge his 8 nos batteries to provide the 24hrs backup. If they both live in the same area and in any given 24 hr period regular power is available for 10 hours then Mr A will enjoy his inverter backup system while Mr B will not because his battery bank will always be under charged and this will lead to premature battery failure and he will simply become another statistic in the list of people with bad experiences as far as inverter backup systems are concerned. So, it is possible for an inverter backup system to be setup and from day 1 the battery bank will never receive full charge until the day the batteries give up because the charger cannot fully charge the battery bank due to the number of hours required for proper charging. By the way a generator can be used to charge a battery bank. You can have the best inverter in the world (microprocessor based PWM Sine Wave inverter) and the best batteries (deep cycling capability) in the world, without a properly sized charging system your whole backup setup could be another failed project. The only place where such problems do not manifest (even though they exist) is the backup for ATMs and the reason is simple, these ATMs usually depend on the Banks for power and over 80% of the time for most banks you have either regular power or generator running. Most of the time that the banks are closed for business the ATMs are not fully active especially at night (say from 10.00pm to 6.00am) so in reality the backup for the ATMs may be active for less than 25% of the time when either regular power or generator is not available. Such backup systems last longer and are very reliable. The charging system of inverter backup systems must be built to properly charge a given number of batteries in a reasonable time and the power supply in the user location must be factored in. When next you are discussing the possibility of an inverter backup system make sure that the service provider is taking into consideration your total loads (determines the capacity of the inverter with some buffer factored in), the number of hours you are expecting for the backup (this determines your battery bank) and the average power supply in a 24hr period in your home or office (this will help in designing a battery charger that will be able to charge your battery bank in a reasonable amount of time). Inverter systems work regardless of the bad experiences out there, homes and offices have backup systems from as little as 3 hrs to up to 48hrs.
Posted on: Mon, 01 Dec 2014 22:34:45 +0000