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What do I need to do if my battery goes into Battery Under-Voltage or Cell Under-Voltage
Protection Mode?
• To begin the recovery process, connect the RV to an external 120VAC (up to 30A) power source, and
ensure that the inverter/charger power switch is in the “ON” position.
o For a Protection (hard fault), the protection mode will need to be cleared by allowing the cell
voltage to reach the recovery and restarting the battery.
• When the unit is depleted below 10% SOC, this can cause the SOC% and voltage levels to be out of
calibration, the only way to recalibrate the BMS is to charge the unit to 54.4V which will re-calibrate the
SOC to 100%.
NOTE: If a battery is allowed to let the minimum cell voltage to be lower than 2000mV, it
is unlikely that the lithium battery can be recovered.
Why is the SOC% (State of Charge) not showing o
n the Firefly Screen?
• When the unit is depleted below 10% SOC, this can cause the SOC% and voltage levels to be out of
calibration.
• There are times when you will see that this system’s total voltage is either increasing or decreasing but
the SOC% may appear to be locked on a certain percentage. The BMS (Battery Management System)
can fall out of calibration over time.
• When this occurs, change the inverter #9 setting to 54.4 and fully charging the battery with shore
power. It will recalibrate the battery BMS.
NOTE: After calibration, it is recommended to re-set Inverter setting #9 back to 54.0V.
Troubleshooting Guide
Attempt to turn on
battery, but reset
button doesn't
initiate startup
sequence - nothing
happens
The reset switch may be installed
backwards
Unplug the switch and verify the tab lines up with the
latch, and the terminals of the switch line up with the
terminals in the connector
Battery or Cell under-voltage
protection
* Connect the unit to an external 120VAC power
source, and ensure that the inverter/charger power
switch is in the “ON” position.
battery, but screen
turns off when let
go of reset switch
or all information
Battery internal fuse may have
blown
Replace internal fuse - contact Dehco (See Must Read
Before Operating section on page 2)
The battery turns
on, but there is no
48V power
Fuse in the battery may be blown
Replace fuse/BDU - contact Dehco (See Must Read
Before Operating section on page 2)
The contactor in the battery may be
stuck open
Replace BDU - contact Dehco (See Must Read Before
Operating section on page 2)
The battery turns
on, but there is no
12V power
Fuse in the battery may be blown
Replace fuse/BDU - contact Dehco (See Must Read
Before Operating section on page 2)
The contactor in the battery may be
stuck open
Replace BDU - contact Dehco (See Must Read Before
Operating section on page 2)
The DCDC converter may be
defective
Replace BDU - contact Dehco (See Must Read Before
Operating section on page 2)
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