Reply to post: Re: standard operating procedures

Tesla driver dies after Model S hits tree

Anonymous Coward
Anonymous Coward

Re: standard operating procedures

The voltage is not the most important thing. From an electrocution point of view there is a difference between SELV (Safety Extra Low Voltage), ELV (up to 50VAC/120VDC) and low voltage (up to 1500V maximum excursion, i.e. 1000VAC and 1500VDC). SELV can sustain an arc under suitable conditions, and I used to have the melted spanner to prove it. Lead acid vehicles and telephone systems are almost all SELV, but even so they can produce hazards; lack of ventilation can result in hydrogen explosions, for instance, and the Boat Safety Scheme expects conductors connected to batteries to have (I think) a minimum of 25 sq mm cross section to prevent shorts from setting everything on fire. On the other hand, a domestic 230VAC supply with RCBOs is pretty damn safe even though it can deliver nearly 10kW on the cooker circuit, whereas a 48V battery circuit driving a 10kW motor at around 200A requires considerable knowledge to design for safety.

Electrocution can occur with SELV under wet conditions.

It is all about standardised design, familiarity and training. Lots of people have been looking at electrical safety since Kipling described early electricians splicing live wires, but large lithium batteries in road vehicles along with all the electronics and electrical machines are very new, and the body of knowledge presumably isn't widely disseminated yet. At the moment electric cars, in terms of numbers and familiarity, are something like petrol cars were before WW1, and I imagine fire brigades had a lot of trouble with them.

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