You should look into these lipos, they are so darn affordable now:
only $19 for this 100a cont. lipo, 2s -
http://www.hobbycity.com/hobbycity/s..._20C_Lipo_Pack
Or 3s for $29 -
http://www.hobbycity.com/hobbycity/s..._20C_Lipo_Pack
Your 8.4v nimh will not do justice to that ESC/motor setup, and you will possibly be disappointed.[
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