Programs
Telecom Sizing
The telecom sizing program was designed specifically for telecom applications. These applications typically have constant current discharges and have a runtime of 1 hour or greater. For discharges greater than 1-hour, end voltages are typically equal to or greater than 1.75 volts per cell. When entering runtime, please note that the runtime is specified in minutes.
UPS Sizing
The UPS sizing program was designed specifically for UPS applications. Loads are specified in terms of kVA of the inverter. Power factor and inverter efficiencies provided by the UPS manufacturer will convert kVA to the kilo-watts of the battery. Runtimes are typically less than 1 hour (i.e. 15-minutes) to an end voltage of 1.67 vpc.
Switchgear Sizing
The switchgear sizing program was designed for multi-load applications. This is typically seen in switchgear applications where the load profile changes during the discharge cycle. The program uses the IEEE-485 worksheet to determine proper battery sizing.
Definitions
Aging Factor
As a battery ages, the capacity declines. Typically a battery is replaced when the capacity has degraded to 80% of rated capacity. An aging factor of 1.25 (1/80%) should be used to insure the battery provides the required runtime at the end of life.
Amp Load
The load that the batteries must supply to the system for a specified amount of time. This is a constant current load specified in amps.
Cells per String:
The number of cells connected in series to provide the correct voltage window. For example, Unigy II cells float at 2.25 volts per cell. If a system is floated at 54 volts, the number of cells per string would be 54 volts / 2.25 volts per cell = 24 cells.
Connector Package:
The connector package is determined by the actual load required by the system and does not include aging or design margings. For multiple string systems, it is assumed that all strings are sharing the load. If it is required for strings of batteries to carry more of the load due to service and / or maintenance, please contact East Penn Mfg. to determine the correct connector package.
Design Margin
A factor of 10-15% is recommended to compensate for any unforeseen circumstances such as lower than expected temperatures or higher than expected loads.
Inverter Efficiency
Factor specified by the UPS manufacturer that converts kilowatts of inverter to kilowatts of battery. It is a ratio of kilowattsout / kilowattsin.
Inverter Power Factor
Factor specified by the UPS manufacturer that converts kVA to kilowattsout of the inverter.
Lowest Ambient Temperature:
As temperature decreases, capacity of a lead acid battery decreases. It is important to enter the lowest expected temperature the battery will see to insure that the battery can maintain the specified runtime at these temperatures.
Mimimum Cell Voltage
This is the cell voltage at which the system will shut down. It is important to include voltage drop through cables when determining minimum cell voltage. If this is not included, it may appear that the battery is failing prematurely when in fact, the voltage drop through cables from the battery to the system was never considered. If a system is designed to shut off at 20.5 volts and the cables from the system to the battery are designed with a .50 voltage drop, the minimum cell voltage would be (20.5+.5)/12 = 1.75 vpc.
Period
In switchgear sizing, there are typically multiple loads and various times during the discharge. Each period identifies a specific load for a specified time. It is important to follow IEEE guidelines when entering information for periods to insure the information entered is entered correctly.
Random Load
In switchgear sizing, a random load is a load that can occur anytime during the discharge. The sizing program will insure no matter when the load occurs during the discharge cycle, the battery will be sized properly.
Runtime
The length in time during discharge that the battery must support the required load. The program requires that the runtime be entered in minutes. If an 8-hour runtime is required, this must be entered as 480 minutes. If 8 is entered, the program will think the runtime is 8 minutes and not 8 hours.
UPS kVA Rating
The is the kVA rating of the UPS that the batteries are providing backup power to. The kVA rating is provided by the UPS manufacturer.
