A cold-chain distribution warehouse reported that an EP EFL181 80-volt lithium-ion electric counterbalance forklift developed intermittent power loss. The operator described the fault as a sudden loss of drive power that lasted 2 to 3 seconds, accompanied by a "Battery Undervoltage" warning on the dashboard. The truck would then recover to normal operation without operator intervention. The fault occurred unpredictably-sometimes multiple times per hour, sometimes not for an entire shift-and was more frequent when the truck was working in the cold-storage area (at -18°C) than in ambient dock areas.
The technician first connected the diagnostic tool and retrieved several historical "Battery Undervoltage" and "BMS Communication Timeout" fault codes. He checked the lithium-ion battery pack's state of charge and individual cell voltages-all cells were within specification and well-balanced, with no signs of a weak or failing cell. He then monitored the live CAN bus traffic between the Battery Management System (BMS) and the truck's main controller. Every few minutes, the CAN bus would drop into a "Bus-Off" state for 2 seconds, then recover-matching the operator's description of intermittent power loss.
He traced the CAN bus wiring from the main controller to the BMS module mounted on the battery pack. At the CAN bus junction block, where the main controller's CAN harness terminates at the battery's BMS CAN connector, he found a sealed junction containing the "120-Ohm CAN Termination Resistor." The junction block's grommet had been cracked by a previous cable-routing error, allowing condensation from the cold-storage environment to ingress. The termination resistor's solder joints were heavily corroded, with green copper-oxide residue on the connections.
The corroded termination resistor created an intermittent electrical connection on the CAN bus's termination point. Without proper bus termination, the CAN signals reflected back along the wire and interfered with subsequent data frames, causing periodic communication dropouts. When the main controller lost BMS communication, its fail-safe logic forced the traction controller into a 2-second derate-and-recover sequence-the power loss the operator was experiencing. The cold-storage environment accelerated the corrosion, explaining why the fault was more frequent in the freezer area.
The repair involved replacing the corroded CAN bus junction block with a new IP67-rated sealed unit, replacing the 120-ohm termination resistor with a new soldered component, and re-routing the CAN bus cable away from the area of cable-bending stress that had cracked the original grommet. Dielectric grease was applied to all CAN bus connectors to prevent future moisture ingress. The BMS's CAN communication error counter was reset, and the forklift was operated continuously for two full shifts-including repeated cold-storage cycles-with zero fault codes and no intermittent power loss.
