2.0INVERTER APPLICATIONS
Aside from issues of supplying power to higher wattage appliances, inverters must be supplied with a constant source of high current 12VDC from a bank of batteries. At full watt load, the DC input requirements are up to 15 amps at 12VDC.
Read and comply with the following applications, and your inverter will give you years of reliable service.
WARNING: Never connect the inverter’s AC output to an
AC distribution system.
2.1 UNINTERRUPTIBLE POWER SUPPLY (UPS)
Inverters can be operated as uninterruptible power supplies that continuously provide AC even if outside AC is interrupted. This function continuously operates the inverter from a battery bank, simultaneously replacing the charge to the battery bank with an AC-powered 12 volt battery charger. Charging can also be by means of a solar charger system. (See FIGURE 3). The charger must be selected to operate continuously in order to fully replace the charge on the battery as the inverter operates. In this configuration, the battery "floats" on the DC from the charger, not really supplying power or being charged. When out- side AC fails, the inverter continues to power the appliances for the life of the useful charge of the battery bank. When outside AC is restored, the batteries are charged as the inverter continues to operate. Battery charging must be sized to replace the average current supplied by the inverter plus a little more current. Another requirement is that the battery charging rate cannot exceed 10% of the Ampere Hour (AH) rating of the battery bank, otherwise the life of the batteries can be dramatically reduced through overcharging. Most modern battery chargers automatically adjust the charging rate based on the state of charge on the batteries they are charging. For this type of operation, use deep- cycle batteries and avoid charging at too fast a rate.
Common unattended applications for the UPS (floating battery) include power- ing: sump pumps, safety lighting, communications equipment, burglar alarm systems and computer systems.
Figure 3 – Uninterruptible Power Supply
