Racers Edge 7.4V 30C 4000 Race Battery hardwired W/TRX HC Plug. Racers Edge battery is lighter than traditional Ni-Cd or Ni-Mh batteries while offering improved performance and run times. It uses the same balancing connection as Align or Electrifly chargers. Be sure to use a voltage cut off if your speed control doesn't come equipped with one. ONLY USE A CHARGER SPECIFICALLY FOR Li-Poly cells!!!