• Over voltage limit: the value at which the controller cut-outs out. A fault is set if the voltage
exceeds the cut-out voltage.
Under voltage
To prevent excessive battery discharge, set values for these parameters at 2C02
h
:
• Under voltage start cutback: the value at which the current drawn from the battery is reduced to
limit voltage decrease.
• Under voltage limit: the value at which the controller cut-outs out. A fault is set if the voltage drops
below the cut-out voltage for longer than the protection delay
• Protection delay: the time it takes for the controller to cut-out after the under voltage limit has been
reached (2C03h).
Battery Discharge Indicator (BDI)
CAUTION: When not in use ensure the BDI function is disabled by setting the Cell Count (in 2C30
h
, 6)
to 0.
Monitor battery voltage using Dragon8’s Battery Discharge Indicator (BDI). The BDI presents the
driver with a percentage remaining charge figure and has become an industry standard in recent years.
NOTE: The BDI is not a measure of the absolute battery charge remaining and therefore we recommend you
regularly check the absolute value in accordance with the battery manufacturer’s instructions.
To use the BDI, configure the following parameters at 2C30
h
in the Object Dictionary:
• Cell count: this is the number of battery cells and is normally half the battery voltage, as cells are
usually 2 volts each.
• Reset voltage (V): set this to the cell voltage when the batteries have just been charged. This resets
the BDI back to 100%.
• Discharge voltage (V): set this to the cell voltage when the battery is discharged.
• Cut-out level (%): this is the level at which the vehicle adopts the low battery drivability profile.
• Discharge rate (s/%): this is the rate at which the BDI remaining charge value discharges. Set to 0
to use default value of 16.8s to reduce by 1%. This default should suit most lead-acid battery types,
however, this can be increased/decreased for different battery technologies.
NOTE: Setting the warning and cut-out levels to 0% disables the warning and cut-out functionality
An additional table exists at index 2C31
h
which allows an initial BDI value to be specified at start up
based on the measured battery voltage. At start up, the measured battery voltage is taken, and the
corresponding BDI percentage remaining value is then used as the starting point for the BDI. After this,
the BDI remaining value operates in the standard way. Note, this function is only available if the
corresponding bit is set in object 2C30
h
sub 1.
Read the percentage remaining charge value from 2790
h
sub-index 1 in the Object Dictionary.
Battery Current Limit
Battery current is estimated from the measured motor currents and applied voltages. It can be limited
by the controller for the purposes of efficiency or to protect batteries that are sensitive to high levels of
current flow. Charge and discharge currents can be limited independently.
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