There are two diode lamps on the MCU:
The green diode lamp indicates that 
there is a 12 V supply to the PCB.
As long as the monitoring circuit is intact, the MCU ensures that a small 
12 V relay remains connected. The 12 V relay supplies all remaining 
units which take energy from the battery, e.g. the key switches, main 
and pump relays.
The MCU monitors the cell circuit. If the circuit is broken, the red diode 
lamp ashes. After 10 seconds, the relay is disconnected and the red 
diode lamp lights up. 
The MCU is disconnected if the main switch is disconnected.
The red diode lamp indicates that the 
monitoring circuit is broken, i.e. that 
there is a problem with at least one of 
the cells.
MCU diode lamps
A break in the MCU circuit can be caused by a cell with excessively 
low voltage. If this is the case, recharge the battery. Press reset button 
briey. 
Resetting the MCU
Insufcient cell voltage
Open main switch If there is a break in the MCU circuit caused by the main switch having 
been opened, just press the reset button briey. The truck does not 
need recharging.
If the MCU is triggered during charging, the charging voltage may 
be too high or the battery imbalanced. Try pressing the reset button 
repeatedly. 
If one of the red cell sensor diode lamps lights up much earlier than the 
others, the voltage in this cell is too high. The cell may be damaged.
If the cell is damaged, contact GMR maskiner a/s. 
Excessive charging 
voltage or imbalanced 
battery
Stama trucks with no reset 
button (after 2014)
Stama trucks which do not have a reset button are tted with a simple 
BMS, in which the MCU is replaced by a simple BMS relay, which 
requires no resetting. If all the battery sensors light up green, the 
BMS relay is activated and the machine can be started. If just one of 
the sensors does not light up green, the relay is not activated and the 
batteries will not be excessively discharged.