OK. This is going to sound crazy but I SWEAR, it's true...
Two weeks ago, I was flying my De Ja Vu and I pushed from inverted to vertical. Half way up the line, the plane cuts off. So, I swing around quickly and head for the runway. On approach, I'm able to "refire" the motor by turning the motor switch off and back on from the transmitter. The motor comes back to life but you can hear it cutting on and off. I land safely and take it to the pits. This was a fully charged 50 flight battery and I was only in the first 1/4 of the sequence.
Since this has happened before on my Passport, I was thinking it was the Anderson Pole arming plug. I removed the plug to look at the metal contacts and the positive side seemed like it was about wore out. Removing the arming plug from the plane and plugging the battery directly into the ESC, I checked again and the problem was gone. I marked it up to the arming plug and used the remaining two batteries to fly the rest of the day without the plug.
Fast-forward to yesterday. I had replaced the Anderson Pole plug with Dean's connectors as they actually handle high voltage much better. I stuck in my Sky Lipo 4400 mah pack and took off, turned downwind and flew out of the box for my turn-around to enter the box and begin the sequence. I pulled vertical and half way up the line, the plane dies again in exactly the same fashion. Needless to say, I was a little beside myself. Once again, no problem getting the plane back to the runway and on to the pits. I thought to myself that maybe I hadn't done a good job wiring although I'm pretty maticulous when it comes to electronics. I had one of the guys hold the plane up vertcially and I ran up the throttle. The first time, everything worked fine but then he did it again and the plane cut off. I checked all my wiring and thought oh boy, now I have to come up with another ESC. I decided to try it again with a different battery pack and could not get it to repeat no matter what I did. I even had the guy shake the airplane with the throttle up and it wouldn't even hesitate. It's the battery! But how...how is this possible? It did this before switching out the arming plug.
It then dawned on me. I had the same pack (1 of 4 packs I have) in it both times this happened. The reason it didn't repeat the first time after removing the arming switch is I didn't use that battery again for the day. When I tested the first time, two weeks ago, I had switched the battery out at the same time I removed the arming switch. Here's where it gets really weird.....
I took that battery and put a volt meter on it. The battery was laying horizontally and the voltage was correct. I, literally, stood the battery up and the voltage started jumping all over the place. I laid it back down on the table and the voltage stabilized and remained. This time, being very careful not to move discharge leads, I stood the battery up again and had the same thing happen! We decided that it was the clunk line in the battery and to discard it as normal.
I can only attribute this to some connection between the cells inside the battery shorting out. It still made very little sense though.....taking a battery (especially in a plane) and changing it from horizontal to vertical should not have this type of thing happen. It seriously was like a stuck clunk in a fuel tank. I guess I"m not really looking for anything since it was just a Sky Lipo as far as answers but it does bring up speculation that you may have fun with. Two things though: A. You get what you pay for (50 flights out of both my Sky Lipo packs and they're dead vs. 125+ flights so far on my F3A Unlimited packs or 300+ from my Hyperions). B. NEVER change two things at the same time when trouble shooting. Yes, I should have known that. I was just certain it was the arming plug since this happened on my Pass-Port a few years ago and the fact the Anderson plug on the positive side looked so worn out. Still, the battery thing makes zero sense especially when strapped down inside the aircraft. I checked for moving wires as well. Just weird I guess.