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Why aren't car batteries more deadly?

I will throw a wrench in the works on this one, while the 12v systems are safe the new hybrids have more than enough energy in the orange wires to turn a person into worm food. There are also the electric power steering systems found in newer cars that have enough voltage to cause injury.

Yep, 202V on the Prius is nothing to mess with.

The IEC standard for acceptable leakage current by equipment in contact with patients is in the hundreds of MICRO-amps. Once you bridge the upper dermis layers, several hundred micro-amps of current at the right frequency and across the heart can easily fibrillate your heart and kill you.

Back when I started designing patient data monitors (ex: ECG), we were using milli-amps of leakage as a standard. Come to find out years later than was an order of magnitude above what could be lethal.

There is wide variation in skin types and conditions (hereditary issues, disease related, medicine induced etc) that contribute to wide variation in skin impedance. I would have no concern about soaking my hands in water and then grasping the terminals of a traditional 12VDC car battery. The fact it is DC and low potential means it has no possibility of adversely affecting me whatsoever.

“There are also the electric power steering systems found in newer cars that have enough voltage to cause injury.”

These are only in hybrids, which have a source of high voltage to step down to 48V or less.

The latest generation (non hybrid) Corolla has electric PS.

Non-hybrid electric power steering systems are very common now and use 12V motors.

Even the power to the power steering motor on my Insight hybrid comes directly from the 12V battery through a 60 amp fuse.

Electric power steering may not actually use 12v at the motor. It may have an inverter to boost the voltage so the motor can keep up. Current is torque, voltage is speed. The motor may not spin fast enough to keep up without a boost.

The first generations of electric power steering used 12 volts for the motors. The newer systems for Toyota/Scion use the steering ecu as a boost converter and power to the motor varies from 4 to 35 volts and can spike as high as 90 volts. Most other manufactures have gone the same route using a boost converter for higher voltages on non-hybrid cars.

Steve