I'm not sure what kind of motor you have, which is a 15 turn with a sealed endbell. I've heard of Dynamite basher 15 turn motors, but without verification on what you have, this is pure speculation. Here lies the problem with asking for help on the Internet from total strangers. You seek advice and tips, but cannot verify or clarify anything. Any input given to you can simply be disregarded or compromised by throwing a curveball back at us on these forums. We did not initially know you had a Nimh requirement. We did not know you had an old 15 turn sealed endbell brushed motor. We do not know the rule set you have to follow. We are curious as to how you are able to easily afford and procure carbon fibre components for such a shitty vehicle, yet lack the basic knowledge of how an rc car works (hacking/reverse engineering a 4wd into a rwd with locked diff, and then converting it back to "normal"). We don't even know if you are using a peak detection charger capable of 10 amps, or if you are using an old charger that has an analog egg timer on it (yes, many of us in this hobby started with the egg timer charger).
Please find an onroad rc club in your area, or seek the advice of a hobby shop so that you can get hands-on help and verification. At this point, nothing else we can tell you is of any measurable help or validity. You might as well start searching for unicorns. Without tangible information and parameters, we can only do so much to help or guide you over the Internet.