Changan BenBen EV Traction Battery Pack Disassembly and Assembly Guide

Fault Background

The Changan BenBen EV (1781 manual) traction battery pack is located under the vehicle floor. Service disassembly and assembly are divided into two levels: complete battery pack removal (using a lift and hydraulic cart) and disassembly of 23 internal components (sealing plate → top cover → reinforcement bracket → high-voltage electrical box → busbars/relays/BMS/PTC/modules). The manual specifies three hard rules: ① When removing the battery mounting bolts, first loosen all bolts, then remove the 4 front and rear bolts, and finally remove the left and right side bolts (M12 socket + pneumatic wrench); ② The 46 mounting bolts and 2 nuts of the battery top cover, as well as the bolts connecting the busbars to the modules, must not be reused once removed—replace with new parts; ③ After tightening the module long bolts with M8 hex thin nuts to 12 N·m, mark with a white paint line (extending from the bottom contact surface to the side of the fastener). This article is organized as a disassembly/assembly guide following "complete removal → internal 23 items → module assembly process".

Complete Battery Pack Removal Procedure

1. Raise the vehicle to a certain height, and raise the lift platform cart to support the bottom of the battery pack—first use the hydraulic cart to support the bottom surface of the battery, positioning the cart as close to the rear of the battery as possible, and ensure the battery is symmetrical left-right on the cart;
2. Disconnect the front and rear connectors of the battery pack;
3. Remove the battery mounting bolts: first loosen all bolts → remove the 4 front and rear bolts → then remove the left and right side bolts (M12 socket + pneumatic wrench).

Installation is the reverse of the removal procedure.

Disassembly of 23 Internal Battery Pack Components

BMS four-piece set: Battery state manager assembly I (24S, 2101220-AM50), state manager assembly II (36S, 2101230-AM50) ×2, battery management controller assembly (2101210-AM50)—position diagram uses different markings to distinguish, removal method is the same (disconnect connectors + 4 mounting bolts).

Module Assembly Process (A301 Module)

Block Assembly: A Block consists of 2 battery cells (44Ah cells); place the module base plate on the turnover cart in the correct orientation → align the positioning holes of the side insulation covers with the base plate → install the heat dissipation aluminum plate onto the Block (Block frame positioning pins align with the heat dissipation aluminum plate positioning holes) → sequentially install the heat dissipation aluminum plate, Block, and inter-Block insulation plate (insulation plate fits into the Block frame mounting holes).

Long Bolts and Torque: Long bolts pass through the module from top to bottom; the 6S side uses 13S module long bolts, the 7S side uses 14S module long bolts, with M8 hex thin nuts tightened to 12 N·m at the bottom, and mark with a white paint line on the nut (extending from the bottom contact surface to the side of the fastener).

Internal Series Busbars: Install sequentially according to the part numbers (Module 1: 11; Module 3: 15; Modules 4/5/6: 12), pre-tighten each busbar with M5 hex flange floating nuts; before installing the module series busbars, confirm that the Block tabs are visible at the corresponding positions, and install the series busbar covers according to left/right side requirements.

Finishing: Secure the sampling harness with cable ties to the first tie hole from the bottom of the module frame, and route the harness inside the module frame; verify module insulation cover height ≤ sheet metal upper cover height; affix the module customer traceability code, module positive/negative labels, and module traceability code to the module top plate.

Safety Warnings

• This article is for technical reference. Traction battery disassembly/assembly is high-voltage work and must be performed by qualified technicians (electrician certification + company training authorization) in accordance with OEM specifications. Before work, power down the vehicle and verify no residual voltage on the busbar.
• When using the hydraulic cart to support the battery, keep it symmetrical left-right and close to the rear of the battery; during lifting, confirm the lift safety locks and never allow personnel under the battery pack.
• Single-use fastener discipline: The 46 top cover bolts + 2 nuts and the bolts connecting busbars to modules must not be reused after removal; replace with new parts, otherwise there is a risk of increased contact resistance, heat generation, and burning.
• Torque discipline: Module long bolts M8 thin nuts 12 N·m, mark with white paint line for anti-loosening; series busbar M5 floating nuts pre-tightened, then final torque per procedure.

Maintenance Insights

The most important takeaways from this disassembly manual are the two iron rules: "reverse order" and "single-use": All 23 components are reassembled in reverse order of removal, with no exceptions; and the busbar bolts connecting to modules and the top cover bolts are "single-use fasteners"—this is not a cost consideration but an electrical connection safety consideration. Reusing old bolts/nuts increases interface contact resistance, creating localized hot spots under high current. There are also two easily overlooked operational details: When removing the battery pack bolts, you must "loosen all first, then front/rear, then left/right"—wrong order can cause the pack to tilt and jam; Module long bolts come in 13S/14S two specifications, and using the wrong one on the 6S side or 7S side can cause the plate to not seat properly—separate them by position before removal. Finally, the 12 N·m white paint line: the start and end points of the line are specific (from bottom contact surface to fastener side), and this is the cheapest anti-missed-inspection method in the workshop.

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【This article is for reference only】