BCU-NEV-XXC MANUAL
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3) If the battery voltage is below the minimum or above the maximum and the BMS cell loop
signals an error on one cell the relay will immediately open, no delay. Solid red LED.
If the relay is open and there is a solid red LED the system may be reset by switching the remote
enable line off and then on again. This will engage the relay for a short period to allow recharge.
The relay is a special type. It consumes no power when switched on. The downside of this is that it
can remain on if power to the BCU is removed or if the BCU fails for any reason. Check that the
relay is operating correctly occasionally by switching off and on the BCU.
!
SOME LOADS AND CHARGERS HAVE INTERNAL CAPACITORS
WHICH DRAW LARGE INRUSH CURRENTS WHEN CONNECTED. THIS MAY
CAUSE THE RELAY CONTACTS TO FUSE CLOSED. SUITABLE PRE-
CHARGE CIRCUITS SHOULD BE INCORPORATED.
!
DO NOT DISCONNECT POWER TO THE BCU WHILE THE RELAY IS
IN THE ON STATE or battery protection will be removed.
!
Reverse polarising the battery will cause damage to the BCU-NEV and void
warranty.
If the BCU cuts off the battery during discharge the battery is most likely nearly empty. DO NOT
RESET AND CONTINUE DISCHARGE!
Reset and charge the battery immediately.
Note that the low voltage cutoff threshold equates to approximately 10% remaining battery
capacity, more or less. The battery should be considered to be flat at this level to allow for a safety
buffer.
Note that even when switched off the BCU consumes a small parasitic current. It will take some
months to drain a full battery at this rate but it is best to either leave the battery on continuous float
charge or to disconnect the BCU if the battery is to be stored for long periods.
If the relay opens during charging it means either the charge voltage has gone to high or the cells
are unbalanced. Try reseting and charging a few times. If one red LED on the BMS cell modules on
the battery comes on long before the others then that cell is running too high. Contact EV Power for
advice in this instance.
In normal day to day use with charging and discharging one would leave the BMS and main battery
isolator switched on. It is not really possible to use a key switch with the button as such to switch
the BCU on/off.
There are two trimpots on the PCB. They are for adjusting the battery and load voltages and are set
in the factory. Only the LOAD trimmer is field adjustable to trim the displayed voltage (as
displayed on the monitor) to match the actual voltage. Please do not touch the battery voltage
trimmer.
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