When the UPS is connected to an appropriate DC source (10.8V to 32VDC), the source is connected directly to the output port of the UPS - and, presumably, to the application load. The application load may draw up to 3.0A - all of which is supplied by the DC input source.

While DC input power is supplying the UPS, an internal enhanced 3-mode battery charger recharges and maintains an internal 12V 5Ah SLA battery. This charger is a switch mode, buck/boost type which supplies the proper battery charging voltage over the complete DC input voltage range.

If the DC input power is disconnected from the UPS, the internal battery is connected to the UPS output in less than a millisecond. The application load may still draw up to 3.0A. However, since this current is now supplied by the internal battery, there is a time limit before the battery becomes discharged.

The battery's voltage is monitored by the unit's microprocessor. To protect the battery, if its voltage falls below 10.8V, the battery is disconnected from the output and the UPS completely shuts down. When DC input power is restored to the UPS, the UPS reconnects the DC input power to the UPS output port and starts to recharge its internal battery.

There are three signals available to power standard LEDs to indicate the unit's status. The C (charge) signal indicates that the battery is being recharged. The P (power) signal indicates that the DC input power is above 10.8V and is connected to the UPS output port. The F (fault) signal indicates that the UPS output port has experienced a gross overload - possibly from a short circuit in the application load.