The unit requires at least 4V to detect a connected battery, so if an auxiliary battery is too flat, it must first be boosted with a jump starter or mains charger before the BCDC will take over.
The charger displays fault codes through LED flashes, such as under-voltage (caused by poor fuse holders) or output over-voltage (often due to solar wiring issues or another charger). The LEDs also indicate charging stages: Boost, Absorption, and Float.
Correct diagnosis involves checking voltages at the start battery, auxiliary battery, BCDC input, and BCDC output to identify voltage drops and confirm charging performance.
REDARC recommends seeking the support of a qualified auto electrician or technician.
Important
For your safety, REDARC recommends installation by a qualified auto electrician or technician. Our trusted REDNetwork is made up of professional auto electrical businesses certified by REDARC to install the complete of REDARC solutions. Find Your Local Installer
REDARC answers some common questions from customers about the BCDC range of in-vehicle battery chargers.
The BCDC will not start charging because the battery is too flat
One of the most common inquiries we get is when a battery has been over-discharged and the BCDC won’t start charging because the battery is too flat. The BCDC needs to see at least 4 volts in the battery to identify that a battery is actually present. This is a safety feature.
So, if your auxiliary battery has been discharged too far, perhaps from leaving a light or a fan on, you’ll need to apply a higher voltage to that battery in order for the BCDC to recognize it. This can be done with a jump starter pack, by jump starting from your start battery, or by applying another charger such as a mains battery charger. Once that’s done, when you start the vehicle, the BCDC will recognize the battery and take over charging.
Common BCDC fault codes explained
The BCDC has six fault codes that it can display by flashing all of the LEDs, with a three-and-a-half second delay between flash rates.
If all LEDs flash five times, it indicates input under-voltage. The most common cause is using an incorrect fuse holder. Blade fuse holders or circuit breakers are not recommended. Instead, MIDI or MR-style fuses should be used.
If all LEDs flash four times, it indicates output over-voltage. This is often caused by a solar panel wired in reverse polarity to the BCDC, or if the auxiliary battery is being charged by another charger that’s supplying too high a voltage.
BCDC charge profiles explained
On the front of the BCDC there are seven LEDs that indicate its function, and they can also help identify faults.
The profile LED shows which charge profile is selected, which is set during installation via the orange wire. When the charger is in standby, the profile LED flashes slowly. When the vehicle is running and the charger is active, the profile LED goes solid.
Depending on the power source, the vehicle LED, the solar LED, or both will illuminate solid. The stage LED shows the stage of charge:
In Boost, the LED is solid.
In Absorption, it flashes twice every two seconds.
In Float, it flashes once every two seconds.
Testing for correct voltages
When testing to ensure the BCDC is receiving the correct voltages, it’s important to check at four locations:
At the start battery. With the vehicle off, this should be below the BCDC’s turn-on voltage.
At the auxiliary battery across the positive and negative terminals. This shows the resting circuit voltage of the auxiliary battery.
At the input wire (red wire) of the BCDC.
At the output wire (brown wire) of the BCDC, referenced against the black ground wire.
Comparing these voltages allows you to see if there’s a significant voltage drop between the batteries and the BCDC. If so, there may be excessive voltage drop in the wiring that needs to be checked.
Measuring battery voltages with the engine running
With the engine running, the start battery should show better than 13.8 volts. The auxiliary battery will then see the BCDC charging voltage. If the auxiliary battery is very flat, its voltage may still appear lower than expected. In this case, measuring the current flow from the BCDC into the auxiliary battery will confirm charging. For example, here we can see around 20 amps going into the auxiliary battery.