Posted by David Sheman on Monday, July 05, 2004 at 3:45PM :
In Reply to: why 24 volt posted by Steve Pellock on Monday, July 05, 2004 at 3:26PM :
Standardization is the main part of it, but why standardize on 24 volts? The main reasons are that it should be a multiple of 12V for convenient use of batteries, and that it should be the highest voltage that does not present a shock hazard in order to minimize the size of wiring needed. Doubling the voltage allows one to push twice the amount of power through the same size wires, thus saving weight and cost of copper. 30 volts is generally considered the safety limit for shock hazards. If your skin is wet, you might be able to feel 28 volts, but the amount of current that flows through you will not kill you. Above that voltage (48 volts, for example), it's possible to get electrocuted. Of course you can still get badly burned if metal jewelry shorts out a 28V (or 12V) source. Standardization isn't just a matter of being able to use the same starter or regulator or light bulbs on different equipment. It's very handy to be able to power an aircraft radio on vehicle power if need be or to jump-start any vehicle from any other vehicle without resorting to risky tricks. Frankly, since I have so much surplus equipment, I wish it was easier to convert my civilian vehicles to 24V.