Introducing electric trucks into a fleet changes workshop risk more than it changes workshop work. The physical tasks are fewer, but the consequences of getting one wrong are severe, and most established diesel workshops have no procedure for them at all. This guide covers high-voltage safety and inspection for the SAGMOTO i9 platform — applicable across both the light-distribution configuration (96 kWh LFP pack, 167 kW peak motor, approximately 12,000 kg GVWR) and the heavy-distribution variants (246 kWh and 350 kWh packs, 26,000 kg GVW) — and sets out the procedures, protective equipment, test methods and inspection intervals a fleet should implement before its first electric unit arrives.
Understanding the i9 High-Voltage Architecture
The i9 nominally runs a traction battery in the 500-600 V DC band, delivered through a permanent magnet synchronous motor rated at 167 kW peak and 120 kW continuous with 1,100 Nm peak torque from standstill, supported by LFP (lithium iron phosphate) chemistry chosen for thermal stability and long cycle life — typically 3,000-4,000 cycles to 80 percent capacity. This is a moderately high DC voltage with very high available fault current, which is precisely why conventional automotive electrical practice does not transfer to it.
| Subsystem | Characteristic | Safety Relevance |
|---|---|---|
| Traction battery pack | LFP chemistry, IP67 enclosure, liquid-cooled | Stores energy even when the vehicle is shut down |
| Main contactors | Removable service disconnect isolates the pack | Primary isolation point for all HV work |
| Inverter / motor controller | Converts DC to AC, contains DC-link capacitors | Capacitors retain charge after isolation without correct discharge |
| DC-DC converter | Steps pack voltage to 24 V systems | Part of the HV network; not safe because it is "low voltage output" |
| On-board charger | AC input stage | Isolate from mains supply before HV service |
| Orange-sheathed HV cables | Colour-coded to standard | Never assume colour alone; test before touching |
| Insulation monitoring device | Continuously measures isolation resistance | First diagnostic reference during fault investigation |
Personal Protective Equipment Requirements
PPE requirements should be set by the fleet's own risk assessment and aligned to local electrical safety regulation, but the following baseline is standard practice for HV work at these voltages:
- Insulating gloves: Class 0 minimum for systems at i9 voltage levels, inspected before each use and periodically re-tested per standard schedule. Leather over-gloves for mechanical protection.
- Face shield and arc-rated protection: HV faults can arc with significant energy.
- Insulated hand tools: Rated for the working voltage, regularly inspected for damage.
- Insulating matting: Standing surface rated for the system voltage.
- Test equipment: A CAT III 1,000 V rated multimeter at minimum, with functioning leads and a verified proving unit.
- Warning signage and barriers: Marking the work area prevents third parties switching systems back on.
- Lockout/tagout devices: Physical prevention of re-energisation, applied by the person doing the work.
The De-Energisation Procedure
Every fleet should publish a written procedure and require its completion checklist to be recorded. The following sequence is the standard approach for the i9 and should be adapted to the specific variant being serviced, using the official service documentation as the authority:
- Position and secure: Park on level ground, apply the parking brake, chock wheels, and confirm the drive-ready indicator is off.
- Isolate external supplies: Disconnect any charging connector and verify the on-board charger is de-energised.
- Switch off low voltage: Isolate the 24 V system as specified, recognising that this also drops HV contactor control.
- Remove the service disconnect: Following the documented procedure, withdraw and secure the HV service disconnect — this is a physical isolation, not merely a software command.
- Apply lockout: Locks and tags applied by the individual technician, not by a supervisor.
- Wait for discharge: DC-link capacitors require a defined waiting period; consult service literature rather than assuming a universal time.
- Verify: Test for absence of voltage between HV positive and chassis, HV negative and chassis, and across HV terminals — using a meter proven live immediately beforehand.
- Re-verify: Repeat the verification after the test and before commencing work, and whenever the work area has been left unattended.
| Common Procedural Failure | Consequence | Control |
|---|---|---|
| Testing without proving the meter | False "safe" reading on a live system | Prove-then-test-then-prove-again protocol |
| Assuming key-off means de-energised | Live HV present with the vehicle shut down | Physical service disconnect removal required |
| Working alone | No rescue capacity following shock | Two-person rule for all HV work |
| Refitting disconnect before completing work | Re-energisation during a repair | Disconnect held by the technician with personal lock |
| Insulating gloves stored loose in a toolbox | Micro-damage invisible to the eye | Dedicated glove bag, visual and inflation check before use |
Inspection and Test Programme
| Interval | Task | Acceptance Criteria |
|---|---|---|
| Every service visit | Visual HV cable and connector inspection | No chafing, cracking, corrosion or loose fasteners |
| Every service visit | Diagnostic scan for insulation monitoring values and stored HV faults | No stored isolation or contactor faults |
| Every 20,000 km | Coolant level and leak check on the battery circuit | Level within specification, no evidence of weeping |
| Every 20,000 km | HV enclosure seal and breather inspection | Seals intact, breather functional |
| Annually | Insulation resistance verification | Above manufacturer minimum; trended, not just passed |
| Annually | Contactor and service disconnect condition | No arcing damage, clean mating surfaces |
| Per manufacturer schedule | Coolant replacement on the HV thermal circuit | Correct specification — never generic automotive coolant |
Insulation resistance deserves particular attention. Rather than simply checking that today's reading passes, record each measurement and trend it. A reading declining gradually over successive services indicates moisture ingress or insulation degradation long before it becomes dangerous, giving the fleet a chance to act during planned maintenance instead of after a roadside isolation fault.
Battery Thermal System Interface
HV safety intersects with thermal management because the same technicians who open HV enclosures will also work on the liquid cooling circuit. The i9's battery pack operates ideally within roughly 15-35 °C, with active chiller cooling engaged above about 35 °C and pre-charge heating when packs fall below roughly 10 °C. Following coolant service on this circuit, an incorrect refill or an air lock can produce localised overheating that degrades cells and, in the worst case, precipitates a thermal event.
- Use only the specified coolant type and mixture.
- Follow documented filling and bleeding procedures — this circuit cannot be treated like a diesel radiator.
- After any thermal circuit service, verify operation across cooling and heating modes before returning the vehicle to duty.
- Record service actions, since battery warranty claims often depend on demonstrable adherence to maintenance requirements.
Emergency Procedures
- Shock or arc incident: Do not touch the person while they remain in contact with a live conductor. Isolate at the service disconnect where safely possible, otherwise at the main supply, then call emergency services and begin appropriate first aid.
- Suspected battery damage or thermal event: Evacuate the area, maintain distance, call emergency responders, and inform them that a lithium battery is involved. Battery fires behave differently — they can reignite long after apparent extinguishing.
- Immersion or flood: Treat any flooded or submerged pack as compromised. Do not attempt charging or startup; isolate and contact technical support.
- Collision damage: Assume HV compromise after any structural impact. Isolate, secure the vehicle outdoors away from combustibles if safe to move, and await technical assessment.
Technician Qualification Requirements
Fleets should formalise who may touch what. A practical structure distinguishes three levels:
- Awareness level: All workshop staff — recognise HV components, understand danger, know who to call. No hands-on HV work.
- Supervised level: Trained technicians performing defined procedures under supervision and to checklist, up to and including isolation verification.
- Authorised HV technician: Formally qualified, documented training, refresher at defined intervals, authorised for full HV diagnostics and repair.
Training should be refreshed on a defined schedule and re-delivered whenever the fleet adds a new variant. Records of qualification should be kept centrally and verified before work allocation — a control that costs nothing and prevents the most likely cause of serious incidents, which is simply that someone assumed they were working on a diesel truck.
Conclusion
Electric truck operation is not inherently dangerous; unmanaged electric truck maintenance is. Fleets that implement written de-energisation procedures, require verified testing rather than assumed safety, specify and inspect PPE properly, trend insulation resistance rather than merely passing it, and maintain clear qualification boundaries run i9 fleets safely and with lower maintenance cost than comparable diesel operations. Shaanxi Fenghan Trading supports i9 operators with HV safety procedure documentation, technician training coordination, genuine HV components and diagnostic support, and can review existing workshop procedures before first delivery. Operators evaluating electric platforms across the range can also review our SAGMOTO new energy electric trucks overview.