CHARGE CONTROLLER
Stevens features a float charger that can be used with PV arrays or power supplies having power
ratings as high as 40 watts (or larger under controlled conditions).
Battery temperature is sensed by a sensor installed at the terminal labeled “Temp Sensor” on the
controller. The float level of the changes by approximately –23 millivolt per degree C, colder
temperatures causing a higher float level. If the battery is located far from or in an area with
differing temperature, it is recommended to place the temperature sensor on the battery and extend
using standard low voltage wire.
The float threshold of is adjustable via an adjustment screw located on the top of labeled
“Float Adjust”. The 20 degree C float threshold may be set to any level between 11 and 16 volts. The
charge controller will charge a fully discharged battery at the full current output of the solar panel and
will automatically taper the charging current to zero as the terminal voltage of the battery approaches
the float level of the charger. The charger then supplies whatever trickle current is required by the
battery to maintain the battery at the float level, assuming sufficient sunlight. Any additional current,
due to the load on the battery, is automatically supplied as needed, so long as there is sufficient
sunlight to produce the current.
An LED indicator located on the top of the unit and labeled “Charge” indicates when the charger is
charging or holding the battery at the float level. The main purpose of this LED is to give an indication
that the charger and solar panel are functional. The LED is powered from the solar panel, and will not
be illuminated if there is no sunlight. A dimly lit LED will occur with low sunlight levels insufficient for
battery charging.
POWER MONITOR
Using SDI-12 commands, can be treated like a sensor, making measurements of Solar panel
voltage, Battery voltage, and Load current. Both instantaneous and averaged measurements can be
made. Measurement averaging sample rate and time period are adjustable with extended SDI-12
commands (see Appendix, SOLO SDI-12 Extended Commands for details).
To request measurement data using the SDI-12 protocol send aM! (where a is the address,
default 0). responds with a0006 to indicate 6parameters of data are available. These 6
parameters are Instantaneous Load Current, Instantaneous Input Voltage, Instantaneous
Battery Voltage, Average Load Current, Average Input Voltage and Average Battery Voltage.
Current is measured in amperes, voltage is measured in volts. All measurement are fixed point
with two digits to the left of the decimal and 4to the right. Instantaneous Measurements are
returned in response to the command aD0!. Average measurements are returned in response to
the commands aD1!. A typical response to aDn! is in the format:
