I learned a lesson about battery voltage checking (under load). I have a small twin C160 that last week started glitching after take off. I checked my battery voltage and it showed 4.9 volts no load. I checked all the control surfaces etc. and flew it again, same thing happened and I barely got it down in one piece. Somebody at the field asked me if I checked the battery under load. Since I only had a non-load meter one of the guys loaned me his. Under a two amp load voltage dropped to 3.1 volts. This same meter on my other plane recorded 4.4 volts under the same load. Replaced my pack in my C160 and everything is fine. I just bought a new Hanger 9 volt meter with load selection! Good luck, Jerry.