Just a little guess here, but it sounds to me like the motor you're working with is a GWS IPS-DX 2S. Motor maybe 1/2" dia. x 1" long or so? I have a few of these, and they work great for me . It sounds (I am by no means an expert) like the voltage cutoff was kicking in on the speed controller, cutting the motor off. This happens to me sometimes with my nicad packs; I was able to diagnose it with my multimeter. Cycling the packs should help with the voltage depression...If this is the motor I'm thinking of, http://www.gws.com.tw/english/produc...system/ips.htm has specifications on this and all their products if you poke around a bit. I hope this info helps you.