User guide

PS100, CH100 & BP-ALK Power Supplies
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The datalogger measures the voltage at its 12V port, not the voltage
of the lead-acid battery. External power sources must therefore be
disconnected from the charging circuit in order to measure the
actual lead-acid battery voltage.
3.5 Use of Backup Battery
The charger/regulator is fitted with two connectors labelled ‘BATTERY’. One of
these sockets is normally used for connection of the internal battery. The other
socket is provided mainly for the connection of a secondary backup battery, which
could be an alkaline battery pack. This pack would normally only be connected to
allow the internal lead-acid battery to be exchanged. The two terminals are diode
protected.
Under certain circumstances a larger lead-acid battery can be permanently
connected to one of these sockets, with the internal battery disconnected. You
should be aware that the charger circuit is designed for float charging relatively
small lead-acid batteries. Trying to recharge a discharged, large external lead-acid
battery may be successful but will result in a very slow rate of charge and a certain
amount of heat generation by the charger circuit. If the external battery is being
discharged at a significant rate, then current limiting circuits in the charger may
prevent enough charge reaching the battery to keep it fully charged.
3.6 Fuse Protection
A thermal fuse (1.85A) in the power circuit limits current flow from the battery to
the 12V terminal. If excessive current is drawn, the fuse gets hot, increases in
resistance, and limits the current. When the problem is fixed, the fuse cools and
the resistance decreases, eventually allowing current to pass. When excessive
current is drawn due to shorting the power leads together, for example, allow 10 to
15 seconds for the fuse to cool before reconnecting power.
4. PS100-A100 Power Supply with Null Modem Ports
The PS100-A100 12V Lead-Acid Power Supply with Charging Regulator and
Null Modem Ports (see Figure 1) is used when 5V is needed to power external
modems, in addition to the normal capabilities of the PS100. The PS100-A100
supplies 5V to pin 1 of two 9-pin null modem ports, which protrude from the side
of the case. Otherwise the capabilities and functions are identical to the PS100. A
common use for the PS100-A100 is in radio telemetry networks. The maximum
current drain on the 5V supply of the PS100-A100 is 150mA.
NOTE