On Thursday, May 23, 2013 1:00:50 PM UTC-5, Eric Greenwell wrote:

The Becker AR4201 is a "modern" radio, meeting the standard requirements to transmit and receive at 10 volts. But, if a 12 volt battery has dropped below 11 volts, it has so little energy left, it may not be able to operate the 4201 in transmit mode; however, it should still receive properly. If it won't receive with voltages between 10 and 11 volts, it isn't operating properly, and I would send it in for repair. The Cambridge computer and Nav can work on even lower voltages than the 10 volt specification for a transceiver, so they would work longer than the radios. The AR3201 is also a "modern" radio, and has the same voltage operating specifications as the AR4201. Ditto for the ATR500. The Microair, at least the earlier versions (don't know about the latest), is not a "modern" radio, and has a much more limited voltage operating range than the ATR500, AR3201, and AR4201. Many thousands of pilots have (and still are) successfully operated these very popular radios on 12 volts for over two decades. Since you've had problems with all three radios that thousands of other pilots don't, perhaps your installation was causing it; Possibly, your 12 volt battery capacity was inadequate (battery too small or in poor condition), and you simple ran out of charge. Adding a 14 volt battery to a marginal 12 volt system would increase the battery capacity, allowing you run longer. -- Eric Greenwell - Washington State, USA

I also have Terra TX-720s (I know. ANCIENT. But, they work). I also know that most people running 12 volt batteries carry a second and even a third 12 volt battery as "backups". Some have even more than that. I have a single 14 volt battery in most everything I fly. And my one 14 volt battery is lighter than your two or three or four 12 volt batteries. I would much rather have one system that is reliable and will work all the time than several that will work, but must be changed during a long flight.

All of the above noted radio crap-outs have been lack of transimission from one of those radios hooked to a 12 volt battery some time into the flight. They all still receive just fine. Not all have been me personally. So, my crappy wiring isn't the fault in all of these instances. :-)

Feel free to continue enjoying the added security you feel with multiple 12 volt batteries and the associated wiring, switches, fuses, etc. Just like so many people need to have backup loggers becasue what they have sometimes fails. Me? I have a Cambridge Model 20. Has never failed. Other things are newer, and some may be better, but none that I am aware of have had fewer bugs or lockups in flight.

My favorite quote about a backup system, and maybe it was just how I chose to read it, was from A.J. Smith. Talking about the AS-W12 and the addition of a second drag chute, in case there was an issue with the primary. He said "That way, you get TWO failures per flight."

Now, lets all just get our batteries charged and get ready for a fun weekend of flying, OK?