The Hidden Hazards of Converted Electric Vehicles

Globally, emergency responders are slowly becoming more familiar with electric vehicles, especially the common Teslas, Volvos, BYDs and Leafs.

But what happens when an EV doesn't look like an EV?

While rare, with only an estimated 200 on the road in Australia, converted EVs - vehicles that were originally manufactured as internal combustion engine (ICE) vehicles and later retrofitted with electric drivetrains - can present significant and under-recognised hazards, particularly in emergency situations.

A great example of this occurred on 20th August 2025, when a converted 1970 Mercedes spontaneously went into thermal runaway while driving along the Eastern Freeway in Melbourne. (All images Channel 10 News Melbourne.)

The driver, who is also believed to be the owner of the converted EV, pulled over after noticing smoke. After exiting the vehicle he went to inspect the area, suffering serious burns in the process. See video here.

What is an EV conversion?

An EV conversion typically involves removing a vehicle’s petrol or diesel engine and replacing it with an electric motor, battery pack, and associated electrical systems. These conversions can range from high-quality professional builds to informal, owner-led projects with varying levels of engineering oversight.

While innovation and experimentation have played a role in the evolution of electric transport, conversions introduce unique safety challenges that differ markedly from those of factory-built EVs.

Challenge 1: Identification by First Responders

Perhaps the most critical issue is identification.

Converted EVs may:

• Retain original ICE badging

• Lack EV-specific external markings

• Appear identical to petrol or diesel vehicles

• Have no accessible ERG, or one not written to ISO 17840

In an emergency, responders rely heavily on rapid vehicle identification to determine hazards such as high-voltage systems, stored energy, and fire behaviour. A converted EV that visually presents as a conventional vehicle can lead to:

• Delayed recognition of high-voltage risks

• Unsafe cutting or extrication actions

• Incorrect fire suppression strategies

• Increased exposure to thermal runaway or re-ignition

Challenge 2: Design and battery placement

One of the greatest challenges posed by converted EVs is the lack of standardisation on the location of the battery pack/s.

Manufacturer-built EVs follow established design principles:

• Predictable battery locations (often underfloor)

• Clearly defined high-voltage cable routing

• Standardised isolation points

• Comprehensive labelling and documentation

• Emergency Response Guides (ERGs) to ISO 17840, listed on ANCAP, EURO, EV Rescue or CRS apps

Converted EVs, by contrast, may have:

• Battery packs installed in boots, engine bays, rear seats, or multiple locations

• Non-standard or improvised high-voltage routing

• Custom enclosures with unknown crash or fire performance

• Varying battery chemistries and protection systems

• No ERG

For emergency responders, this uncertainty significantly complicates size-up, stabilisation, and suppression decisions.

In the case of the converted Mercedes, at least three battery packs were located in the former engine bay, with high voltage systems in the rear.

Challenge 3: Fire behaviour and suppression risks

Battery fires in converted EVs may behave unpredictably due to:

• Non-standard battery assemblies

• Inadequate thermal management

• Limited or absent battery monitoring systems

• Unknown state of charge at the time of incident

If responders are unaware that a vehicle has been converted, they may initially apply tactics appropriate for ICE vehicle fires, which can potentially place crews at risk and delay effective suppression.

Moving Forward: Awareness and Risk Reduction

Here's what we learned from this incident:

• The vehicle was originally built in the 1970s and retained original badging

• Therefore, it was easy to assume it had a petrol driveline

• It contained ~3 lithium-ion battery packs in former engine bay

• Packs were point of origin and in thermal runaway

• Vehicle not clearly marked as an ‘EV’, either on body badging or with the blue 'EV' badge on numberplates, which is mandatory in Australia

• While the vehicle was road registered, it is unclear how or when the conversion was completed and battery pack quality (ie. potentially harvested from a written off EV, therefore likely already damaged)

• The vehicle poses a serious risk of secondary ignition in following days, weeks or months and should be quarantined indefinitely

Given the clear appeal of rebirthing a classic car into an electric vehicle, converted EVs are likely to remain part of the transport landscape, particularly in niche, hobbyist, or commercial applications.

However, improving safety for emergency responders will require:

• Greater awareness among emergency services

• Clear, consistent external identification of converted EVs

• Improved guidance for converters on responder safety considerations

• Data sharing and inclusion of converted EV risks in training programs

Recognising the unique hazards of converted EVs is an important step in ensuring responder safety and effective incident management.

When we train emergency responders through our Electric Responder program, we talk about 'assume it's electric until proven otherwise', and this example proves the point!