Dr Kiwi nailed this one. I had a simular problem with my shockflyer setup. I ordered the Axi 2208/34 and tried using a thunder power 2 cell battery with it. I think it was a 760mah or so. I couldn't get much out of it before it cut out even with my pheonix 10 set to 2 cell low voltage cutoff. So I said, hey I'm going to use a 3cell. So I bought a thunder power 3cell 730mah, set my pheonix 10 to 3 cell and experienced the same problem. The problem is that these batteries only have like a 6C rating meaning they will only produce 6 times the listed amp hour rating in this case 4.3A. Pull any more current than that and the voltage starts to drop considerably. Then the low voltage cut off kicks in like it's supposed to and that's it your done.
So I bought a Tanic 3cell 850mah 10C rated battery. This thing will provide a constant 8.5amps if needed. Needless to say I haven't had any problems since, and have a ton of straight up power. It prop hangs about 1/2 throttle.
If you think this battery is a little heavy for the shockflyer, your right! It does seem a litte heavy when gliding in with no power.
I went to the Kokam site and it looks like they have high output 20C batteries now. A smaller one of those might be the hot ticket.
I am going to keep what I have cause I'm tired of buying batteries.[
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