SpeedTek RC 8,800uf 20V 2x2 capacitor pack can handle a maximum of 4s. It is proven to perform! We use these caps on all of or drag racing & speed run vehicles. They are also less than 1 1/2" square and use high flex/temp wire. 
 
The packs comes with an overall wire length of 4" and the option of terminating without a connector or a male/female XT90, EC5, XT60, Deans, Tamiya, EC3, or Traxxas connector.