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5916 - 195th Street N.E.

Arlington, WA 98223

Telephone: 360/435-8826

Fax: 360/435-2229

www.traceengineering.com

PS Series Inverter/Charger

Part No. 3597

Rev. D: November 23, 1999

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 start 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 other. 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 START WITH MULTIPLE INVERTERS

When using multiple inverter/chargers with the automatic start system, only one inverter/charger controls

the generator. The two inverter/chargers should be programmed with the same BULK VOLTS DC and

FLOAT VOLTS DC settings, but with the ABSORPTION TIME on the non-generator start inverter/charger

to a longer setting. This will ensure that the charge current is shared between the two inverter/chargers

more equally during the absorption stage by preventing one of the inverter/chargers from switching to

float before the other. When the inverter/charger 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 start inverter/charger to a longer setting.

Trace Engineering PS Series User Manual

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