To charge
the cells, the 12 Volt plugpack supplied with the external receiver
may be connected directly to the PPS input jack.
This power is also passed through to the receiver, so that the
receiver can be used while the batteries are charging. A bicolor LED
on the front panel depicts the status of the charging cycle. Red
light means fast charging cycle is active, green light means the
batteries are being trickle charged (i.e. fast charge has finished).
Assuming the cells have been sufficiently charged, the receiver
may be disconnected from mains power without resetting. This means
that the receiver will continue to operate in the event of a loss of
mains power, therefore the batteries can act as a backup for remote
monitoring applications where there is not a reliable mains power
source.
When operating on battery power, there is a level test switch on
the front right of the unit. This switch applies a known load to the
cells in order to provide for the most accurate measurement of
remaining charge in the batteries. The charge is displayed on a
5-LED bargraph: the more LEDs are alight, the greater the remaining
charge. This graph is roughly calibrated in percentage of total time
remaining for a given set of usage conditions: 5 LEDs = 100%, 4 LEDs
= 80% etc.
When battery charge falls to a dangerously low level the bicolour
LED will flash yellow to indicate the cells are flat, and that the
unit may switch of at any time. This is a useful means to alert the
user to connect external power, without it being necessary to
manually check battery level. In continuous use, typically the
bicolour LED will light during the last 15 minutes of operation. If
external power is not connected before the cells are completely
flat, the PPS will internally disconnect the battery output, to
prevent a complete discharge of the cells which would shorten
battery life.
