Geely Emgrand EV Pro Traction Battery System Diagnosis and Disassembly Guide

Fault Background

The Emgrand EV Pro traction battery uses a ternary lithium battery (cobalt/manganese/nickel compound cathode + carbon material anode capable of lithium-ion intercalation + organic electrolyte), mounted under the vehicle body. Its internal structure is a clear functional chain: Cell → Module → CSC acquisition system → BMS (integrated inside the assembly) → B-BOX high-voltage distribution unit (mounted at the positive/negative output terminals). Key diagnostic knowledge points: Insulation faults are coded separately based on whether the high-voltage relay is closed or open (P154100/P154300); pre-charge diagnostics have two calibration thresholds: current >5A for 50ms and pre-charge time 600ms; balance diagnostics look at (SOC_Max − SOC_Min) > 30%. On the disassembly side, follow the sequence: "disconnect negative terminal → lift vehicle → disconnect DC bus → drain battery coolant → disconnect high-voltage harness connectors". Torque specifications: 78 N·m (battery pack) and M10x35 68~88 N·m / M10x20 35~55 N·m / M5x12 5~7 N·m. This article compiles the structure, working principles, DTCs, diagnostics, and disassembly into a reference guide.

System Composition and Working Principle

DTC Key Points (BMS Side)

Diagnostic Process Key Points

1. Routine inspection (appearance, connectors, foreign objects/water traces);
2. Measure battery voltage in ON mode: standard 9~16V, if not, replace battery or repair charging system first;
3. Fuse check: CF27 (interior) / EF03, EF18 (front compartment), if blown, repair circuit and replace with same capacity fuse;
4. Read BMS DTCs and classify per the above table;
5. Insulation category: distinguish "high-voltage relay closed/open" conditions corresponding to different codes;
6. Relay category: judge main positive/negative and precharge relays by three states: "stuck closed/not closed/not opened";
7. After repair, complete confirmation test per standard.

Disassembly/Assembly and Torque

Disassembly sequence: Wear insulating gloves as required → disconnect battery negative cable (follow battery disconnect warning) → lift vehicle → disconnect DC bus assembly (traction battery side) → drain traction battery coolant (prevent coolant overflow at outlet hose connection) → disconnect front compartment harness connector → disconnect traction battery high-voltage harness connector → move traction battery to platform cart, slowly lift and slowly move cart backward to remove assembly.

Installation sequence (reverse of removal): platform cart lift and align → tighten mounting bolts → connect high-voltage harness and front compartment harness connectors → connect DC bus → fill traction battery coolant → lower vehicle → connect battery negative cable.

Fastener specifications:

Safety Warnings

• This article is for technical reference only. Traction battery service must be performed by certified personnel per OEM specifications. Readers unfamiliar with the procedure must not attempt it themselves.
• When removing the traction battery assembly, insulating gloves must be worn as required; disconnect the battery negative cable and follow high-voltage operation warnings.
• After disconnecting high-voltage harness connectors, insulate them immediately; the traction battery is a high-voltage hazard, and improper handling can cause injury or death.
• Coolant draining/filling must prevent splashing onto high-voltage connectors; the assembly is heavy, so platform cart operation must be slow to prevent falling.
• Fasteners must be torqued per manual; bracket bolts and sealing plate bolts must not be interchanged.

Maintenance Insights

The most memorable points from the Emgrand EV Pro traction battery manual are the three "condition distinctions". First, insulation faults are coded by condition—P154100 is insulation fault with high-voltage relay closed, P154300 with relay open; when diagnosing, first confirm relay state then match code, which directly eliminates false alarms from relay not engaged. Second, two calibration values for precharge diagnostics—precharge current >5A for 50ms and precharge time 600ms; exceeding these triggers precharge codes, giving clear quantitative boundaries for "slow precharge/precharge failure". Third, balancing is judged by SOC difference—(SOC_Max−SOC_Min)>30% triggers imbalance, and with P152D00 (balancing circuit fault) you can distinguish "cell difference" from "balancing circuit fault" as root causes. Structurally, remember the four members of the B-BOX (positive/negative/precharge relays + current sensor + precharge resistor); relay DTCs' three-state judgment ("stuck closed/not closed/not opened") all revolve around them. On the disassembly side, two numbers: battery pack mounting 78 N·m, bracket M10x35 68~88 N·m.

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【This article is for reference only】