An AA5B pilot on an IFR flight lost electrical power and communication capability just as he exited IMC into an area of VMC. He proceeded VFR to a nearby airport where he contacted ATC to advise of his safe arrival.

Narrative

I was northbound a few miles south of an enroute airport at 8;000 in IMC. At this time I noticed that the portable Garmin 296 GPS in the aircraft announced that it had lost ship's power and was switching to battery operation. In response; I adjusted the power connection between the GPS and the auxiliary power outlet (cigarette lighter). This appeared to solve the problem. A few moments later; the aircraft exited the clouds into an area of VMC several miles wide in all directions with an overcast layer at approximately 9;000. Shortly thereafter; ATC advised me that there was higher traffic at 9;000. I was unable to reply. I checked the headset connections; the radio; and the circuit breakers and tried the ship's microphone. The ammeter indicated that the electrical system was operating normally with no discharge; as it continued to do throughout the flight. A moment later; all of the electrical displays in the cockpit blinked on-and-off and began to display erratic numbers. At this point; I decided that I was having a serious electrical problem; that I was flying under emergency authority; and that neither the communication; transponder; or navigation radios were reliable.Given that I was in VMC and had ground contact for several miles; I decided to proceed VFR. I set the transponder to 7600; in the hope that ATC would understand that I could not communicate. This appeared to be successful as the Controller asked questions to which I tried to reply with the 'ident' function. I believe that this form of communication was at least partially successful based on the Controller's questions. To avoid entering the clouds again; I began a descending turn to the right and looked for the closest airport. Once I had descended to about 5;500; I could see part of the area and that the bases of the lowest cloud layer were high enough to allow VFR flight. From the charts; I knew that the enroute airport was in a position that would allow me to land VFR; so I continued my descent. I was able to copy a request to call ATC on the telephone. However; within a couple of minutes; during the descent; all of the ship's communication and navigation displays went black which was no longer a problem given that I was VFR. To inform ATC of my situation; I changed the transponder squawk code to 1200. I am not certain at this point whether the transponder was transmitting and if so what it was transmitting; but the display appeared to be functioning most of the time. Shortly thereafter; the transponder display also went black. The NORDO flight and landing to the enroute airport was uneventful except for the lack of electrical power to lower flaps. But given that I regularly practice no flap landings; this was not an issue. After landing I advised ATC that I was safe and on the ground. The supervisor told me that at first they had been worried because of the other traffic and they could not tell whether I was climbing or descending and they did not know that I was VMC and not disoriented.The electrical system malfunction was apparently caused by an intermittent short in a cable connecting the battery system to the alternator. According to two A&P's this sort of break sometimes causes the symptoms that I experienced; the intermittent and scrambled operation of electrical equipment and the discharge of the battery without an ammeter deflection. I was surprised to learn that the battery could discharge without any warning. This had not been part of my training. I had learned that I would see an ammeter deflection if the alternator were to fail and that this would provide approximately 30 minutes of advance warning before total electrical failure. Evidently; this is not always the case.I recommend that a voltmeter be required in all aircraft with similar systems. A voltmeter would have displayed a decrease in electrical potential that would have warned me of the problem. I intend to install a voltmeter as soon as possible. Also; I recommend that a procedure be adopted for IFR pilots to squawk 1200 following a communications failure to advise ATC that they are OK; are operating VFR; and no longer require emergency assistance (as 7600 implies).