[george_tlc]

One last comment before the dead horse icon needs to be used...

Just because something appears to work doesn't mean that it is the right way to do things - ESPECIALLY if you don't understand the design of the equipment (at the circuit level).

Lower input voltage (especially in many modern pieces of electronic equipment that use switching supplies in various parts of the design) mean that input currents have to be higher to generate the same output power. Manufacturers, e.g. Yaesu, specify minimum input voltage (an max of course) to ensure that input currents are within spec for the operating mode. Most of the rigs will limit output power if the input voltage is too low to prevent damage.

Obviously the real issue is during transmit when high current is being drawn - when you can't hear if your signal is cr@p. A cigarette lighter is a rather pathetic power connector and to rely on it to provide stable power to high power electronic equipment is not a particularly good choice. Voltage losses across smaller gauge wiring in addition to poor connections (higher resistance) all mean lower and possibly out of spec voltage reaching the rig during transmission.

Running lower input voltages can often mean higher input currents that can stress electronic components. Efficiency is also lower leading to higher heat dissipation in many of the active devices that is never a good thing.

Finally, I use 40% efficiency as my seat of the pants figure for transmission power versus input power. i.e. if you have 50W output I assume at least 125W at the input. That means around 10A during transmit. Just 0.1ohms of resistance along the entire battery to rig wiring means 10 x 0.1 = 1V voltage drop.

My >2c as an electronics engineer that still actively designs rather than manage...

cheers,
george.