28 Description TB9400 Installation and Operation Manual© Tait Limited March 20171.7.5 PMU Operation on DC InputThe operation of the PMU on DC input is controlled by three sets ofparameters:■ user-programmable alarms■ user-programmable startup and shutdown limits■ battery protection limitsThe voltage range for each of these parameters is provided in Table 1.2 onpage 29. Figure 1.9 on page 30 illustrates how these parameters interact,and how they control the operation of the PMU over a range of DC inputvoltages.Alarms User-programmable alarms can be set for low or high battery voltage(Configure > Alarms > Thresholds). The alarms will be triggered when theset voltage levels are reached. These limits are subject to the tolerances ofthe battery protection circuitry, as stated in “Battery Protection (Fail-safe)Limits” in Table 1.2.Startup andShutdown Limits The user-programmable startup and shutdown limits allow for adjustablestartup and shutdown voltages (Configure > Base Station >Miscellaneous). These limits can be adjusted for different numbers ofbattery cells, or for the particular requirements of the base stationoperation. Once the limits are reached, the PMU will shut down. Theselimits are subject to the tolerances of the battery protection circuitry, asstated in “Battery Protection (Fail-safe) Limits” in Table 1.2.Notice It is possible to set the startup voltage of the base stationbelow the nominal voltage of the battery. Continuing to use a battery forextended periods when it is below its nominal voltage will severelyshorten its service life. For more information on battery management,we recommend that you consult the battery manufacturer.Battery ProtectionLimits The battery protection limits are set in hardware at the factory, and cannotbe adjusted by the user. These limits will not be reached under normaloperation conditions, but are provided as “fail-safe” measures to protect thebattery from deep discharge. They also remove the need for low-voltagedisconnect modules.
