How to ground/earth my BCDC or Manager charger to my vehicle or trailer

This information is applicable to the following products:

BCDC Classic Range (BCDC1225D, BCDC1240D, BCDC1250D)
BCDC Core Range (BCDCN1225, BCDCN1240)
BCDC Alpha Range (BCDC12025B, BCDC12050B, BCDC12050R, BCDC12100R)
Manager30 Battery Management System (BMS1230S3, BMS1230S3R, BMS1230S3-NA, BMS120S3R-NA, BMS1230S3R-EU, BMS1230S3-EU, BMS1230S3R-UK, BMS1230S3-UK)
Manager Alpha Battery Management System (BMS12050-AU, BMS12075-AU, BMS12100-AU, BMS12050-NA, BMS12075-NA, BMS12100-NA, BMS12050-UK, BMS12075-UK, BMS12100-UK, BMS12050-EU, BMS12075-EU, BMS12100-EU)
Smart Battery Monitor (BSEN500)
TVMS Prime (TVMS1280)
TVMS Rogue (TVMS1240)

One of the most frequently asked questions about REDARC’s Battery Management Systems, RedVision, and Smart Battery Monitor is how to correctly set up grounding. Below are some common queries our team receive on this topic.

If you require assistance, REDARC recommends seeking the support of an installer.

THE DISPLAY/APP SHOWS THE STATE OF CHARGING READING IS HIGH BUT MY BATTERY VOLTAGE IS LOW

HOW DOES THIS APPEAR?

The Display/App shows that the SoC is reading ‘100%’, but a ‘Low Battery Voltage’ fault code/warning appears.

WHAT CAUSES THIS FAULT?

It is likely that the system or sensor is not wired correctly. Specifically, the battery sensor or Smart Battery Monitor.
This means that the loads and devices that are drawing power from the auxiliary battery are bypassing the sensor/shunt, so the system is unaware that the battery is being drained.

HOW TO FIX THIS ISSUE

Ground/earth wiring needs to be inspected to ensure that the correct connections have been made to the ‘GND’ and ‘B-NEG’ sides of the sensor/shunt as required.

WHEN RUNNING WIRING FOR A VEHICLE INPUT, DO I NEED TO PROVIDE A POSITIVE AND NEGATIVE CABLE RIGHT TO THE START BATTERY?

Whilst this can be done, it is not necessary in all applications.

Utilisation of the vehicle or caravan/camper chassis is the better and easier method, primarily to reduce the amount of cable used and keep the length of the cable as short as possible.

HOW TO FIX THIS ISSUE

The Smart Battery Monitor and the ground connection from REDARC systems can be connected directly to the chassis or the nearest connection point. This may also be a factory ground point on the frame.

This tip can apply when connecting your loads to a ground point too – these can also utilise a chassis/ground point connection and minimise the length of cable required.

DOES MY AUXILIARY BATTERY NEED TO BE GROUNDED TO THE CHASSIS OR MY REDARC CHARGING PRODUCT?

Yes, connecting the auxiliary battery to the chassis ground is the preferred option as typically your REDARC charging product will also be grounded to the chassis too.

This ensures that the REDARC product can correctly reference the auxiliary battery, start battery and any solar panel voltage as a ‘common earth/ground’ setup. The REDARC products will then operate at optimum efficiency and with minimal voltage-drop.

CAN I USE A BUSBAR TO CONNECT MY GROUND WIRES TO?

This can be done and keeps the number of connections and lugs to a minimum and in a central location.

When wiring up REDARC’s battery sensor/shunt or Smart Battery Monitor, this can ease the number of cables connected to the ‘GND’ side of these units.

That way, you have all your main ground cables running to the busbar and then a single, thicker cable running to the ‘GND’ portion of these units.

WHAT IS THE BEST METHOD FOR CONNECTING MY NEGATIVE WIRING SO MY AUXILIARY BATTERY CONNECTIONS ARE BALANCED?

When you have multiple auxiliary batteries connected in parallel, the ground connections need to be setup as per the below diagram. This method ensures that each battery is drawn down and recharged equally when in use.

WHERE DO I GROUND TO THE START BATTERY WITH A VARIABLE VOLTAGE ALTERNATOR (VVA OR SMART ALTERNATOR)?

It’s important to know vehicle’s with VVA have a smart sensor which works just like the REDARC shunt, monitoring all current that’s passing through it. When you connect an accessory directly to the start battery negative terminal, you bypass this shunt.

Bypassing this will lead to the vehicle’s computer not compensating for power consumption that may lead to insufficient charge provided to the start battery by the alternator. Always connect your earth/ground wire to the vehicle chassis to ensure all current passes via the vehicles shunt.

It is important to ensure you have the REDARC charger, auxiliary battery and start battery all sharing a common chassis connection.

REDARC’s Battery Managment systems have a battery monitor (shunt) that monitors all current going in and out of your battery and allowing the battery percentage to be accurate on your display.

You need to ensure that all your devices all have the ground wire connected to the GND side of the shunt assembly or chassis.
You should only have one wire connected to the BNEG side of the shunt which will connect to the battery negative terminal. This will ensure all power travels through this shunt.

Ensure the cable from BNEG to battery negative terminal is a suitable size to carry all loads combined, inverter often being the largest load.