Hybrid Vehicles Part 2


Series Links: Part 1 Part 2 Part 3

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The back of the Prius rear seat consists of nothing more than a foam rubber seat cushion separating the interior of the car from the trunk area. Exposed to a fire within the passenger compartment, this seatback will burn and melt away, letting the battery pack in the trunk be exposed to the fire.

What emergency procedures should be taken at a fire involving a hybrid vehicle?

A fire involving a hybrid vehicle can be handled by following normal vehicle firefighting procedures. In a typical vehicle fire incident, the engine compartment, interior of the vehicle or trunk area are burning. By following generally accepted fire suppression guidelines, crews attack the fire with an adequate water flow rate, working from a safe position of approach. Self-contained breathing apparatus (SCBA) is worn throughout the fire incident. The wheels of the vehicle are chocked to prevent forward or rearward movement as soon as safely possible.

There are potential fire situations involving a hybrid that can present unique concerns. Any fire where there is direct flame impingement on the high-voltage battery pack would be one example. A fire that has originated within the battery pack itself or an electrical fire that begins somewhere within the high-voltage electrical system would also require special precautions.

The back of the Prius rear seat consists of nothing more than a foam rubber seat cushion separating the interior of the car from the trunk area. Exposed to a fire within the passenger compartment, this seatback will burn and melt away, letting the battery pack in the trunk be exposed to the fire.

Radiant heat could cause the plastic modules inside the high-voltage battery to melt just as any plastic material would when exposed to high temperatures. If heated sufficiently, it is possible that the plastic module casings could melt down, exposing the inner components of the high-voltage battery.

The fire service already has experience with lead acid batteries melting down during fully involved engine compartment fires. Unlike the meltdown of a 12-volt battery, however, responders who encounter a melted nickel metal hydride (Ni-MH) battery may want to notify the nearest Toyota or Honda dealership and ask that designated battery recovery specialists be notified so they may properly deal with the damaged battery after the fact.

Where a fully involved hybrid vehicle fire is encountered, copious (large and sufficient) amounts of water will generally be the extinguishing agent of choice. This will eliminate the radiant heat and begin cooling the metal battery box and the plastic battery cell modules inside the high-voltage battery pack itself. Fire suppression crews will not be shocked or electrocuted during direct attack on a hybrid vehicle fire, even if flames are impinging on the battery pack itself.

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The high-voltage battery pack cells are sealed and protected by their metal battery cover. All high-voltage circuits are protected from accidental contact within a shielded cable covering and a plastic conduit. All high-voltage circuits and plugs for this system are marked, color-coded orange and posted with warnings to advise of their presence. No emergency responder should ever disassemble or remove the metal cover of the high-voltage battery pack.

Ni-MH battery pack fire. For advice on extinguishing a fire where the high-voltage battery itself is the source of the fire, we turn to a major user of Ni-MH batteries. In the Ni-MH Product Safety Data Sheet from Moltech Power Systems, responders are advised that virtually all fires involving Ni-MH batteries can be controlled with water. This information sheet also recommends,

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