well you might not be able to. I had an older mm that ran 14 cells great. ubec of course. then i smoked it after months of awesome use. It would thermal. then i added a fan and the temp barely broke 110. anyways the fan had stopped working, i drove it anyways, hit a jump and peged the throttle and when it landed. it smoked. So i sent it to cc with 50$ they sent me a brand new one. and it wont go on 14 cells. Runs fine on 12. but it wont run on 14. there are lots of threads about the difference's between newer one having fewer fets 12 i think than the older ones (15 fets). The the concences is the newer ones also have some sort of overvoltage protection. Some have said you can get around it by turning off the lvc, but that didnt work for me. Now 4s is lower than 14 cells nominal, so you still might get away with it. But i wouldnt be suprised if you couldnt.