E021
EVBox
Local Load Balancing Communication Fault
Charger shows E021; load balancing between multiple EVBox units fails; charging current not shared correctly.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Broken or miswired RS‑485/CAN bus between chargers, Incorrect master/slave configuration, Termination resistor missing or duplicated, Faulty communication port on one EVBox
How to Fix / Troubleshooting
Safety: Work on communication wiring only with power off to avoid accidental shorts.
- Check topology: Verify that the EVBox units are wired according to the local load balancing diagram (daisy chain, correct polarity).
- Inspect cables: With power off, check the twisted pair communication cable for damage and ensure correct A/B polarity at each unit.
- Termination: Confirm that termination resistors are installed only at the ends of the bus, not at every unit.
- Configuration: In the installer interface, ensure one unit is set as master and others as slaves, with unique addresses.
- Isolate faulty unit: Temporarily disconnect one unit at a time to see if E021 clears, indicating a defective communication port on a specific charger.
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Repair Difficulty
Hard
4/5
Required Part
EVBox RS‑485/CAN Communication Port
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