Well i just performed a lowering mod on my car yesterday... i cut off the tab then lowered it and crazy glued it on.... after that it ran for a bit then stopped.... so i take off the cover and the car ran fine for a bit then stopped.... now after a full charge it wont even move, with a body on it or without.... and i just replaced the batteries 3 days ago!
Try taking the battery out of the chassis . Put your car
on the charger and run it . If it runs , your
wire connections should be ok , I would then focus
on the battery or the tabs that hold the battery .
If your car doesn't run , check your wires . or simply
replace the batteries again . New doesn't always
equal good .