Block Diagram Operation Manual Electrical Specs. Mechanical Info.
Transfer Switch: This is a solid-state switch that connects the PCB output to one of two sources. If the Input Supply is above 21.6VDC, the switch uses this as the source and the external battery is disconnected from the output circuit breaker. If the Input Supply is below 21.6VDC, the switch uses the external battery as the source and the Input Supply is disconnected from the circuit breaker. The transfer from the Input Supply to the external battery takes less than a millisecond. Circuit Breaker: To protect the unit, a solid-state circuit breaker trips at between 3.5A and 7.0A. This completely disconnects the PCB Output Power terminal. The circuit breaker latches in this state until the input power is removed and the enable terminal disconnected from ground (briefly). When the circuit breaker trips, Signal F (fault) goes high to indicate the fault. uP - Controller: The unit's microprocessor-controller is powered by either the Input Supply (if present) or by the unit's external battery (if enabled). This device controls the various solid-state switches, monitors the external battery voltage, and generates the LED signals. Signal C (charging) has two functions. When the Input Power is above 21.6V, this signal is on whenever the battery charger is charging the battery and goes off when the charging is complete. When the Input Power is less than 21.6V, the microprocessor monitors the battery and reports its voltage by flashing on and off. Please see the Operation Manual for a detailed description of this. Signal P (power) is on when the Input Power is above 21.6V and off otherwise. Battery Charger: This is a switch-mode, buck/boost, enhanced 3-mode unit that can generate the proper battery charging voltage over the complete Input Supply voltage range. When the Input Supply is at a normal 24V system voltage (or higher), the charger can supply approximately 0.75A. The charger continues to operate at Input Supply voltages down to 5V. However, its current output drops considerably as its input voltage is reduced (0.15A at 5V input). Because the charger continues to operate down to 5V input, it can contribute its output current to the PCB Output Power terminal. This, even when the internal battery is connected to the output (as it would be if the Input Supply dropped to 5V). Battery Disconnect: This also is a solid-state switch and has two functions. When the external battery is connected to the PCB Output Power terminal, the microprocessor monitors the battery voltage. A SLA (sealed lead-acid) battery can be damaged if its open-circuit voltage is allowed to drop below 21.6V. Should this happen while the battery is connected to the Output Power terminal, the microprocessor signals the Battery Disconnect switch to disconnect the external battery and shutdown the PCB. Applying a proper voltage the the unit's Input Supply terminal restarts the PCB and allows the battery to be reconnected and recharged. The second function of this switch is to allow long-term storage of the PCB/battery when not in use. When the enable terminal is disconnected from ground (and the supply voltage is less than 21.6V), this switch disconnects the battery so that the long-term storage time is limited only by the battery's internal leakage current.