[Milsurplus] Can.military use of 14V/12V

[WA5CAB at cs.com]

As I've written (perhaps tongue in cheek) before, aircraft radios and other 
electrical equipment are typically marked (or called) 14V or 28V (the fine 
print on the dynamotors may actually give the performance at slightly 
reduced voltage but always above 12.6 or 25.2 volts).  Ground vehicular equipment 
at least into the late 40's was marked 6V, 12V or 24V.  This is because a 
truck or tank with its engine off will glide much further than an aircraft 
will.  :-)

In a message dated 11/16/2012 15:19:15 PM Central Standard Time, 
ka2ivy at verizon.net writes: 
> On 11/16/12 10:05 AM, Ralph Cameron wrote:
> >I am told by former Canadian military staff that 14V was often stated on
> >RCAF equipment because a fully charged 12V battery is 13.8V and that was
> >close enough to call it 14V. At some point in time it was renamed 12V as
> >being a nominal value and to conform to other services.
> >
> >Ralph
> >VE3BBM
> >
> Calling it 14 volts is a compromise. A fully and recently charged 12 
> volt lead acid battery will deliver about 12.7 to 12.8 volts under light 
> load. This will decrease to about 12.6 and remain fairly steady until 
> the charge nears depletion. Conversely, charging regulators adjust the 
> voltage for battery temperature to insure full charging. A battery at -5 
> degrees C. will need about 14.2 volts for a while. At about 5 degrees, 
> 13.8, dropping to about 13.2 at 30 degrees will assure a full charge. 
> Because aircraft batteries tend to be in cold locations, they usually 
> receive these higher voltages. Aircraft electrical systems were often 
> set for 14 volts, and if the battery life was shortened, it was just a 
> cost of operating the aircraft.  They tended to be at minimum size that 
> would start the engine for weight saving, and had to be as fully charged 
> as possible. It was a great source of batteries for me in high school, a 
> battery that would not start a Beechcraft Bonanza (or a DC-3!) on a cold 
> morning was still great for radios.
> 

Robert Downs - Houston
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