Hi! I am Ahmad. I hv a rc car. Lamborghini Aventador 1:8 scale with an nicd 6 cells battery of 700mah (7.2)volts. Now i want to buy a Lipo battery for it. Plz tell me the maximum amount of mah and volt of Lipo battery my car's motor can handle. Nd yh its not a hobby grade car its a normal car. It has a brushless motor.

nicd * 6 will be 7.2v, not 7.4v...
use same mah and 2s, you will be at tolerable voltage...if you need more runtime, use higher mah...

ND I WANT TO INCREASE A LITTLE SPEED TOO BY BETTER BATTERY TELL ME THE MAXIMUM VOLT AND MAH IT CAN HANDLE

well I cannot comment on the battery voltage without knowing your motor and esc etc. but yo should opt for maximum mah your car can accommodate to increase running time..

Your motor ideally should have the voltage rating specified on it ...if there is nothing written, there is little that can be predicted without some trial and error...or some more information about the current handling capacity and the wire quality and thickness... you havent even mentioned if its a brushless or a brushed motor...Assuming that it is a brushed motor, the easiest route would be to slowly increase the voltage and look for signs such as heated coils, increased screeching, anything about 60-80% of this top limit should be your ceiling...but all in all, difficult to predict...

PS:
You could try speaking like that to the motor, the speed might increase    ....you never mentioned what your intent was in the original post...
Please refrain from using all caps....

 
Its a brushless motor

In that case sire, the voltage is limited by your ESC, and it should have a clear indication of what is the maximum voltage that can pass through (2s/3s?)...Most 2s ESCs also support 3S but your motor might not, due to increased KVs and more current passing through...you will need some manuals/or be able to provide some pictures for further help...if that cannot be found, I'd recommend sticking to the existing voltage of 7.2v using a 2s lipo...It will take less than a microsecond for things to go poof!

1.  Please post the right boards.  Start by reading this :  http://www.rcindia.org/rc-india-forum/how-to-make-a-new-post-on-this-forum/

2.  To give you more informed answers, we need to know the exact model of your ESC (speed controller). Can you identify that, or post a link to the same ESC some where online ?