Power lithium-ion batteries are the core energy storage components in new energy vehicles, energy storage systems, electric ships, drones and other fields. Their insulation and withstand voltage performance, electric breakdown resistance, and internal short-circuit risks directly determine the safety, cycle life and long-term reliability of batteries. Cell withstand voltage testing is a mandatory test item in the R&D, mass production inspection, incoming inspection and safety evaluation of power lithium-ion batteries, including power-frequency withstand voltage test, DC withstand voltage test, insulation resistance test, electrochemical breakdown test, and insulation variation test before thermal runaway. It can effectively screen defective cells with internal separator defects, electrode burrs, electrolyte impurities and poor packaging, preventing unsafe cells from entering the market and causing thermal runaway, fire, explosion and other safety accidents. The multi-channel high-voltage power supply is the core power unit of the cell withstand voltage test system, providing independently controllable high-voltage outputs for mass cell testing. Its channel quantity, synchronous control accuracy, crosstalk suppression between channels, output stability and safety protection performance directly determine the efficiency, accuracy and safety of cell withstand voltage testing. Current mainstream standards require the output to cover DC 0~5kV and AC 0~3kV; production line equipment needs 16 to 128 independent channels with separate parameter setting, start-stop and protection. The synchronous trigger accuracy between channels is ≤1ms and inter-channel crosstalk ≤0.1%, with comprehensive short-circuit protection, arc detection and leakage current monitoring to avoid equipment damage and safety accidents caused by cell breakdown. Traditional single-channel and centralized multi-channel power supplies suffer from difficult channel expansion, severe inter-channel crosstalk, low synchronous accuracy, and overall system failure induced by single-channel faults, failing to meet high-volume, high-efficiency and high-safety testing demands. The design strictly complies with GB/T 38031, GB/T 31485, GB/T 16927.1, IEC 62660 and other national and international standards, while supporting automation, mass testing, high safety and traceability. Targeting key application demands and technical challenges, this methodology establishes a full-process framework covering modular multi-channel topology design, synchronous control optimization, inter-channel crosstalk suppression, mass testing adaptation and comprehensive safety protection. It supports full withstand voltage testing for cells, modules and battery packs, providing standardized guidelines for the localization and performance upgrading of domestic lithium battery test equipment. Addressing core challenges including independent multi-channel control, high-precision synchronization, low crosstalk and mass testing, the solution adopts the main architecture of independent single-channel modular design + distributed synchronous control + full optical fiber isolated communication, combined with inter-channel electromagnetic shielding and independent protection. It overcomes traditional limitations such as severe crosstalk, low synchronization accuracy, poor expandability and wide fault impact, realizing 16~128 independent controllable channels, microsecond-level synchronous triggering, ultra-low inter-channel crosstalk and isolated single-channel faults, fully adapting to automated mass cell testing. Five core principles are defined. First, the independent single-channel modular topology achieves complete electrical isolation to eliminate coupling and crosstalk, enabling flexible channel expansion. Each channel is equipped with an independent high-voltage module containing inverter, boosting, rectification & filtering, closed-loop control, sampling and protection circuits, with separate power input and high-voltage output and no shared power components. Each module adopts a quasi-resonant flyback topology with simple structure, few components, high boost ratio and soft switching for low loss and low EMI, covering DC 0~5kV and adapting to full load variation from no-load to short-circuit breakdown. An independent power-frequency inverter integrates AC 0~3kV 50/60Hz sine output for combined AC/DC testing. All modules adopt fully sealed metal shielding for physical and electromagnetic isolation, with seamless channel expansion from 16 to 128 channels. Faulty modules can be replaced without affecting other channels, improving maintainability and testing continuity. Second, the distributed high-precision synchronous control adopts a two-layer architecture of main system controller + slave channel controllers with full optical fiber synchronous bus. The main ARM+FPGA industrial controller manages human-computer interaction, process control, parameter configuration, synchronous triggering, data storage and upper computer communication. Each channel integrates an independent FPGA slave controller for closed-loop regulation, sampling processing, protection execution and synchronous command response. Optical fiber communication with delay ≤100ns realizes synchronous triggering, voltage ramping, sampling and shutdown with accuracy ≤1μs, ensuring complete electrical isolation against high-voltage interference. Hardware timing control inside FPGA eliminates software delay, supporting both synchronous mass testing and independent asynchronous testing for cells of different specifications. Third, full-link inter-channel crosstalk suppression optimizes architecture, hardware, wiring and grounding to keep crosstalk ≤0.1%. Architecturally, fully independent power, control and grounding loops eliminate conductive coupling fundamentally. In hardware, each channel adopts dual-stage EMI filtering and isolated DC-DC power supply at the input, plus independent RC filtering and high-voltage isolation diodes at the output to prevent reverse current coupling during cell breakdown. Independent power rails eliminate power-induced crosstalk. For shielding and wiring, each module is installed in an independent 1.5mm cold-rolled steel shielding cavity with shielding efficiency ≥60dB; double-layer shielded high-voltage cables with separate routing suppress capacitive coupling. A star single-point grounding structure unifies power ground, signal ground and shielding ground at the main busbar, eliminating ground loops and potential difference crosstalk. Fourth, high-precision output and sampling adopt dual-stage coarse/fine regulation and differential shielding sampling. 16-bit DAC achieves 0.1V resolution; 24-bit ADC with 100kHz sampling ensures accurate voltage and leakage current collection. FPGA-based full-digital PID control with 50kHz loop update delivers voltage accuracy ≤±0.2% FS, long-term stability ≤±0.5%/8h, line regulation ≤±0.1% and load regulation ≤±0.2%. Wide-range leakage current detection (0.1μA~100mA) with 10nA resolution identifies micro insulation defects and triggers rapid protection during breakdown. Fully differential sampling with double-shielded cables guarantees anti-interference capability in complex electromagnetic environments. Fifth, lithium battery test scenario adaptation embeds standard test templates for DC withstand, power-frequency withstand, insulation resistance, breakdown voltage and step-up testing, fully complying with national standards. Users can configure voltage, ramping rate, dwell time and leakage thresholds via upper computers for automatic unmanned testing. Dual modes (synchronous/independent) support mass testing of identical cells and parallel testing of different cells respectively. Full data recording binds test parameters with cell barcodes for full lifecycle traceability. Microsecond-level synchronous interfaces connect manipulators, scanners, fixtures and PLCs for fully automated production line workflows. Graded alarm and independent channel protection cut off high voltage within 1μs and release residual voltage rapidly upon breakdown, avoiding fault expansion without affecting other channels. Multi-channel synchronization and crosstalk suppression form the core of this methodology. High-precision synchronization adopts an optical fiber distributed bus with a constant-temperature crystal oscillator (≥100MHz) as the global clock. Phase-locked synchronization keeps clock deviation ≤100ns; hardware broadcast synchronous commands ensure triggering accuracy ≤1μs. Synchronous ramping, dwelling, discharging and sampling guarantee consistent test conditions and comparable data for defect screening. Asynchronous timing supports flexible independent testing. Full crosstalk suppression eliminates conductive, radiative, capacitive and grounding interference: isolated power and filtering suppress conductive crosstalk; sealed shielding cavities and optimized PCB layout reduce radiative emission; double-shielded separate cables minimize capacitive coupling; star grounding eliminates ground loops. Multi-device cascading via optical fiber extends channels to over 1024 with inter-device synchronization ≤10μs, adapting to super-large production lines with distributed data uploading to MES systems. High-precision measurement and cell safety protection define critical constraints. Dual-stage regulation achieves low ripple (≤0.5% FS); adaptive PID ensures full-range accuracy without overshoot. Auto-ranging leakage current detection with 10nA resolution identifies potential internal defects in advance; differential filtering improves signal stability and trend analysis predicts breakdown risks to prevent thermal runaway. A ten-layer dual hardware/software independent protection system for each channel includes overvoltage, overcurrent, short-circuit, leakage overlimit, overtemperature, breakdown fast protection, arc detection, high-voltage interlock, safety door interlock and emergency stop. Independent hardware circuits cut off output within 1μs and release residual voltage to safe levels within 50μs to avoid thermal runaway. Arc detection prevents fire hazards; high-voltage interlock and emergency stop ensure operator safety; dual redundant leakage detection avoids protection failure. Production line adaptation supports mainstream industrial protocols for unmanned automated testing, barcode-data binding, multi-spec parameter libraries, automatic defective cell sorting and real-time equipment self-diagnosis to reduce downtime. Reliability and compliance optimize full-lifecycle performance. All key components adopt Class I derating with strict stress limits; high-reliability semiconductors and long-life film capacitors ensure long-term operation with module MTBF ≥30,000 hours and system MTBF ≥20,000 hours. Hot-swap module replacement enables maintenance without production line shutdown. EMC design fully complies with GB/T 17626 with soft switching, three-stage EMI filtering, optical isolation and multi-layer PCB layout, meeting Level 3 anti-interference requirements for factory environments. The entire design conforms to national safety standards for electrical clearance, creepage distance, insulation withstand and grounding. In summary, this full-process technical framework solves core drawbacks of traditional multi-channel power supplies, including severe crosstalk, low synchronization accuracy, poor expandability and wide fault impact. Independent modular design suppresses crosstalk ≤0.1%; full optical fiber synchronization achieves ≤1μs triggering accuracy; scalable architecture supports flexible expansion and isolated faults; comprehensive safety protection guarantees absolute cell testing safety. Widely applied to withstand voltage and insulation testing for cells, modules and battery packs in new energy and energy storage industries, it provides core technical support for the domestic substitution and performance upgrading of lithium battery test equipment.