User guide

User Guide
9
3.4 Charging
The 12 volt and ground terminals on the power supplies are for supplying power
to the datalogger or other 12 volt devices. A lead is supplied fitted with an in-line
connector to connect to such a device. The in-line connector is the method of
turning off power to the datalogger.
The two terminals labelled ‘CHARGE’ are for connecting an AC adapter or solar
panel to charge the lead-acid batteries. The charge input can be either AC or DC,
and it does not matter which terminal is positive or negative. The voltage input
must be within the range 16 to 26V DC, or 16 to 26V AC RMS. A transzorb
provides transient protection to the charging circuit. A sustained input voltage in
excess of 40V will cause the transzorb to limit voltage.
Some solar panels and AC adapters are supplied fitted with a connector. This
connector must be cut off so that the two wires can be inserted directly into the
two CHARGE terminals.
The red light (LED) on the charger unit comes on when an external charging
supply is connected.
Illumination of this LED does not guarantee that there is sufficient
charge entering the battery to stop the battery discharging; it only
indicates successful connection of the charging source.
If the battery is fully charged first, it may be stored for up to six months.
A battery that has been stored without charging should be given a ‘top-up
charge’ by charging it in its carrier/charger unit from an AC source for
one day before being placed into service.
There are inherent hazards associated with the use of sealed lead-acid batteries.
Under normal operation, lead-acid batteries generate only a very small amount of
hydrogen gas. This gaseous by-product is generally insignificant because the
hydrogen dissipates naturally before build-up to an explosive level (4%) occurs.
However, if the batteries are shorted or overcharging takes place, hydrogen gas
may be generated at a rate sufficient to create a hazard. Campbell Scientific
therefore makes the following recommendations:
A PS100 or any supply equipped with lead-acid batteries
should never be used in applications requiring
intrinsically safe equipment and should not be housed in
a gas-tight enclosure.
Campbell Scientific’s ENC 10/12 and 12/14 enclosures are supplied fitted with a
porous vent plug in a cable gland on the base of the enclosure. It is recommended
that this is left in place when using a lead-acid battery as it will prevent pressure
build-up in the event of gas release from the battery.
It is recommended that the battery voltage is monitored using the appropriate
datalogger programming instruction. Add this instruction to your programs to
keep track of the state of the power supply. If the system voltage level consistently
decreases, some element(s) of the charging system has failed or the charging
source is not providing adequate current. It should be noted though that the
terminal voltage of lead-acid batteries varies with temperature.
NOTE
NOTE
WARNING