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:
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
- 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
- Power Unit
The electrical propulsion circuit must be isolated from other (auxilliary)
circuits in the vehicle. Systems such as lights and brakes must operate
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
- 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
- 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
- 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.