A bad output cable fault on the Manager30 means the unit has detected a voltage difference between the charger assembly and the battery sensor, usually caused by wiring issues.
Common culprits include loose or high-resistance connections, faulty fuse protection, undersized cables, or poor grounding. Diagnosing requires using a multimeter to compare voltages at key points, cycle the BMS into charging mode, and test individual wire runs for voltage drop.
Any drop greater than 0.5V indicates a problem that must be fixed. For systems with RedVision, extra checks are needed to isolate faults introduced through the TVMS connections.
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
This information is applicable to the following products:
- Manager30 Battery Management System (BMS12030S2, BMS12030S2-xx, BMS12030S3, BMS12030S3-xx)
Seeing the bad output cable fault on your Manager30 indicates that the unit has detected a voltage difference between the charger assembly and battery sensor.
Common issues
There are several common issues that can contribute to this fault condition. These include:
- Poor, loose or high resistance connections
- Faulty fuse protection (blade fuses and circuit breakers can often be the culprit)
- Undersized cable
- Poor earth return connection
These step-by-step instructions walk you through using a mustimeter to identify the issues within your system wiring.
Establish base voltage readings
Start by measuring key voltage points to compare values and identify discrepancies.
- Measure the auxiliary battery voltage at the battery terminals.
- Measure voltage between pin 1 and pin 3 on the green phoenix connector of the Manager30.
These values will form the basis for comparison during fault diagnosis.
Cycle the BMS to trigger charging
To force the Manager30 into its Boost Charging Stage, complete the following steps:
- Hold multimeter probes on pins 1 and 3.
- Cycle the system from Touring Mode to Storage Mode, the back to Touring Mode.
- Watch the output screen to verify the unit is delivering 25 – 30A charge output.
If the battery is at 100% state of charge, apply a load to simulate demand and force charging behaviour.
Identify voltage drop location
To help located the fault, the below testing will allow us to test each length of wire separately to identify voltage drop. When testing for voltage drop, we would expect to read 0v for each test. 0v indicates there is no voltage drop on this length of wire.
If we were to measure a voltage, for example we measure 6.2V, this identifies we have a 6.2V drop on this length of wire. Voltage drop is commonly caused from a poor connection or undersized cable which needs to be resolved for correct operation. Any more then 0.5v drop would be considered excessive and need to be rectified.
Checking pin 1 (positive supply)
Measure voltage between pin 1 and the auxiliary battery positive terminal:
- Voltage present: Cable has voltage drop (issue detected).
- 0V reading: Power cable is functioning correctly.
Checking pin 3 (earth circuit)
Measure voltage between pin 3 and the GND side of the battery sensor
- Voltage present: voltage drop in earth return (issue detected).
- 0V reading: earth cable is functioning correctly.
If readings are inconsistent or unclear, re-check voltage between pin 1 and the auxiliary battery positive terminal, and between pin 3 and the battery sensor GND. Consistent voltage drop confirms a wiring fault.
Additional checks for RedVision installations
If your system includes a RedVision TVMS, a few extra voltage drop tests are recommended:
- Between pin 1 and TVMS positive.
- Between TVMS and auxiliary battery positive.
- Between pin 3 and TVMS negative (ground).
- Between TVMS negative and the battery sensor GND side.
These checks assist in isolating faults introduce through RedVision integration.
