Follow up on my original post, thanks to everyone for the input! The batteries were Concorde's. The solenoid tested ok, the battery held a charge of 26 volts even after being off the battery minder for several days. If I then turned on the battery one switch, voltage at the battery dropped to around 4V and nothing came on in the cockpit. Turn batt 1 switch off, voltage back to 26. Changed out the battery and all is fixed, so must have been a bad cell within the battery. Can't complain too much since looking at the logs, the batteries were put in in 2009, unfortunately for me, I just bought the plane in August! Anyway, thanks to all for the advice, at least I learned a little more about the plane and the electrics!