Xantrex Technology 120 VAC/60 Battery Charging With Multiple Inverters, Operation, Page

OPERATION

BATTERY CHARGING WITH MULTIPLE INVERTERS

The inverters can operate in parallel as battery chargers from the same AC source connected to the same battery. The AC input terminals and DC terminals would all be in parallel. The inverters will synchronize individually to the AC source and then connect.

When multiple inverters are connected to the same battery and operated as in battery charger mode, the settings of the inverters are best set to the same settings. Only when a system is being operated in automatic generator control mode should staggered settings be used.

The most significant problem with multiple inverters charging the same battery is the voltage ripple caused on the battery. This causes the chargers to not reach their full output - two battery chargers on the same battery may not provide twice the charging rate to fill the battery in half the time. The higher the charger rate and/or the smaller the battery, the more pronounced this problem would be. The only way to reduce the problem is to individually cable each inverter and to connect them at opposite “corners” of the battery bank. Keeping the cable size as short as possible also helps.

Since the inverters will all be charging the same battery, one inverter may taper off first and finish the bulk stage before the others. When a single inverter has reached the float stage, it is best to turn off the generator at this time. It may take a longer period of time for the remaining inverters to reach the float stage. Running the generator to only power an inverter that is float charging is very inefficient and should be avoided.

If multiple Battery Temperature Sensors are installed, ensure they are all connected to the same location (battery). This will also help prevent one inverter from tapering off first.

AUTOMATIC GENERATOR CONTROL WITH MULTIPLE INVERTERS

Several considerations must be taken into account when using the automatic generator controlling system with multiple inverters. The inverter that controls the generator – referred to as the “generator controlling” inverter - along with the other inverter which does not control the generator - referred as the “non- generator controlling” inverter - must be programmed differently to achieve the best results. The two inverters should be programmed with the same BULK VOLTS DC and FLOAT VOLTS DC settings, but with the ABSORPTION TIME on the “non-generator controlling” inverter to a longer setting. This will ensure that the charge current is shared between the two inverters more equally during the absorption stage by preventing one of the inverters from switching to float before the other. When the inverter that controls the generator reaches float, it will shut down the generator.

The same consideration should be made if you are trying to equalize the batteries. The two inverter/chargers should be programmed with the same EQUALIZE VOLTS DC settings, but with the EQUALIZE TIME on the “non-generator controlling” inverter to a longer setting. When you are ready to start the equalization process (either manually or automatically) you must select EQ from the SET GENERATOR menu item on both inverters (accessible by pressing the green GEN MENU button on the Control Panel). This will allow both units to help bring the voltage to the EQ voltage level. During the equalization process, the BULK LED will flash slowly on each inverter to indicate that the EQ position has been selected from the SET GENERATOR menu item.

If you manually equalized your batteries – by using a manually started generator or utility power - the FLOAT LED will come on to indicate that the equalization process has finished. You must return the cursor to the OFF position in the SET GENERATOR menu item on both inverter/chargers once the equalization period has been completed.

If the automatic generator control system is used to equalize your batteries, the equalization process will begin during the next - automatically started - generator run period. When the equalization period has been completed, the generator will automatically stop and the cursor under the SET GENERATOR menu item will return to the AUTO position on the “generator controlling” inverter. At this time, you must manually return the cursor in the SET GENERATOR menu item on the “non-generator controlling” inverter from EQ back to OFF or you will allow this inverter to charge up to the EQ voltage the next time the generator comes on.

 2001 Xantrex Technology, Inc.	Telephone: 360/435-8826	SW Series Inverter/Charger
5916 - 195th Street N. E.	Fax: 360/435-2229	Part No. 2031-5
Arlington, WA 98223	www.traceengineering.com	Rev. C: February 2001

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