Tech Info: Safety Considerations

 

Australian Guidelines for EV Conversions

The following PDF documents outline the official Australian National Code of Practice for Light Vehicle Construction and Modification. The first one covers general information for Alternative Power Units, the second, specific Guidelines for Installation of Electric Drives in Motor Vehicles:

NCOP13_Alternative_Power.pdf NCOP14_Guidelines_Electric_Drive.pdf

A brief summary of the document:

  • Structural strength
    Modifiers must take care not to compromise the structural strength of the vehicle, in particular the seat anchorages and occupant protection. In general it is best to avoid modifying any part of the original chassis and body.
  • Braking Systems
    Large increases in vehicle mass, alteration in the centre of gravity or weight balance and changes to the brakes' power assistance must remain within Australian Design Regulations.
  • Battery Restraint
    The batteries that power the vehicle must be in a fixed position so they will not easily break free in a crash. The battery restraint system should be designed to withstand 20Gs (i.e 20x the battery weight).
  • Containment of Wet Cell Batteries
    All batteries that contain liquid or give off gases (read: flooded lead acid batteries) must be contained in a corrosion resistant, sealed box with ventilation only to outside the vehicle. Forced ventilation is sometimes required.
  • Power Unit
    The electrical propulsion circuit must be isolated from other (auxilliary) circuits in the vehicle. Systems such as lights and brakes must operate independently.
  • Controls
    A master switch for isolating the power supply to the motor and its control apparatus must be located within easy reach of the driver. It must be a mechanical switch, i.e contactors don't count - you actually have to have a mechanical switch. Circuit breakers with a manual trip are a good option.
  • Electrical Installation Standards
    All electrical installation work must be designed and executed in accordance with accepted codes and standards. (Read section 2.7 of the PDF for full details!)
  • Weight Considerations
    Vehicles must remain within their Gross Vehicle Weight rating after conversion, including at least 81.6kg per passenger. Historically, EVs using lead acid batteries were significantly heavier than their petrol counterparts, but with lithium batteries it is usually not too much trouble keeping inside the GVW.
  • Brakes and Steering
    If the original vehicle was fitted with power assisted brakes or steering, an alternative system must be fitted. The capability of the new system must remain within the legal capacity requirements.
  • Electrical Safety
    Any voltages above 32V should be considered dangerous. The vehicle should include automatic power disconnection device(s), and have a master switch that is readily visible to/identifiably by persons outside the vehicle. Negative cables should be black, positive under 32V should be red, positive above 32V should be orange.

 

Some Other General Advice

  • Design safety systems with some redundancy, if possible, e.g we usually recommend people run fuses connected close to each battery pack, and a master circuit breaker, and a contactor.
  • If possible it is also a good idea to have an inertia switch which will trigger isolation of the battery pack in the event of a crash.
  • Make sure your cables are big enough to handle the power you're pulling. Check out the current ratings of the guage you are working with, or ask for advice on an appropriate cable size.
  • Cables passing through panels should always have grommets to prevent damage to the insulation and possible shorts.
  • Double insulation recommended whenever high voltage lines need to travel more than half a metre, e.g put cables in PVC tubing.
  • Always disconnect the battery when working on the vehicle, unplugging Anderson-style connectors are the usual solution.
  • Don't use the car body for negative lines. It works OK for the vehicle's 12V auxilliary power systems, but the main drive circuit carries far too much power.

 
 

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