Micha Solar MSR2-30 Charge Controller 800817-9.doc
Product Manual
Page 3 of 23 Document: 800817-9.doc Date: September 2017 www.micha.co.uk
3. MSR2-30 Control Unit Operation
3.1. Analogue Measurements
The MCU uses an A/D converter to read the battery voltage, the array voltages, the temperature sensor
and the array and load current if the metering option is included.
The battery voltage is read every 50ms (20 times a second). Where the unit determines a change of
mode or alarm status is necessary, four successive readings will have to be above or below the
appropriate setpoint (the exception is the High Volts Alarm) for the change to occur.
To obtain the true array voltages, the MCU needs to first disconnect an array from the battery (if
connected) and then read the array voltage. This is done approximately every 60 seconds
The temperature sensor is used to compensate the battery voltage. If faulty or disconnected, then the A/D
converter will return a value outside of possible air temperature limits in which case the regulator will
operate as if the temperature was sensed as being the Temperature Compensation Null Temperature (i.e.
zero compensation applied).
3.2. Battery Regulation
If the compensated battery voltage is less than the Reset-to-Boost voltage, the unit will enter the Boost
Mode. During this time the unit will connect the arrays to the battery if the voltage present on each array is
greater than the battery voltage by 2V. If the total array current is greater than the load current, the battery
will charge and the battery voltage will increase.
When the compensated battery voltage reaches the Boost voltage, the unit will enter the Equalisation
Mode. In this mode, the unit will disconnect and reconnect the arrays to the battery to regulate the battery
voltage at the Boost voltage for the Equalisation period. This ensures the battery reaches its optimum
state of charge.
After the Equalisation period, the unit will enter the Float Mode. In this mode, the unit will disconnect and
reconnect the arrays to the battery to regulate the compensated battery voltage at the Float voltage.
If the compensated battery voltage decreases below the Reset-to Boost voltage, the unit will enter the
Boost Mode.
When there is insufficient light to generate current (at night or on a day with poor light conditions), the
regulator disconnects the arrays from the battery to avoid the battery discharging back through the array.
This is the Night mode.
When the unit is regulating at either the Boost voltage or Float voltage, it will disconnect the arrays from
the battery when the battery reaches the required voltage. It will re-connect the array to the battery when
the compensated battery voltage falls below the required voltage by 0.15V(12V system), 0.3V (24V
system) or 0.6V (48V system).
3.3. Alarms Activation and Reset
If the compensated battery voltage is higher than the High Volts activation voltage, the array will be
immediately disconnected from the battery and the High Volts alarm relay and indicator will be activated.
If the compensated battery voltage is lower than the High Volts reset voltage, the High Volts alarm relay
and indicator will be immediately reset.
If the battery voltage is lower than the Low Volts activation voltage and remains lower for 2 seconds, the
Low Volts alarm relay and indicator will be activated. If the battery voltage is higher than the Low Volts
reset voltage, the Low Volts alarm relay and indicator will be immediately reset.
If the battery voltage is lower than the Load Cut activation voltage and remains lower for 2 seconds, the
Load Cut alarm relay and indicator will be activated. After the Load Cut switch delay period, the Load Cut
Switch and indicator will be activated. If the battery voltage is higher than the Load Cut reset voltage, the
Load Cut alarm relay and indicator and the Load Cut switch and indicator will be immediately reset.
If the voltage on either array does not exceed 2V above the Battery Voltage for a period of 24 hours then
the 24 Hour Alarm will be activated. The Auxiliary Alarm Relay can be programmed to activate for this
Alarm.
The Auxiliary Alarm Relay and indicator can be programmed (Menu 3) to activate on 24Hr Alarm,
Common Alarm (i.e. any alarm) or System Normal (i.e. active when they is no alarm). System Normal can
be used to ensure the charge controller is actually powered and operating correctly.
