So the compart for the battery is small. If you don't know what im talking about then u may have the wrong forum! These compartments are tight... I have a solution! Because whining w/o a fix is part of the problem So i have the basic onyx 2s 5000mah 25c battery and that will fit TIGHTLY but im really wanting to find the largest mah 3s lipo that will fit. However, i have a fix, if you want the 3s power to test or a cheap way to keep you running i have been using small 1 18 scale batteries to keep the granite hard. Just tonight i got about 30 min runtime out of a 1300mah 3s going about 40mph for about half the time. This is not only cost effective but it allows me to have a better scale of time vs heat vs speed because of the lack of MAH. Just be careful a totally drained lipo will expand and explode so make sure you have a cutoff set up and you don't try to start moving again after it stops. Been doing it for weeks but now my rc18 wants it gogo juice back So whats the largest mah 3s that you guys have installed?