Maybe something like this might help? It's 23$
http://www.amainhobbies.com/product_...ducts_id/13151
This is the Lipo Shield from Common Sense RC. Lipo Shield is a low voltage cutoff device which enables any ESC to be used with lithium battery packs. It installs easily between your receiver and ESC and provides a reliable 3.0V per cell soft cutoff to prevent over-discharge damage to your expensive lipo packs.