The rapid growth of the Electric Vehicle (EV) deployment contributes to zero-emission transport but puts great pressure on the power grid. This paper proposed a Vehicle-to-Vehicle (V2V) energy trading platform for EV charging that allows EVs with surplus electricity to provide electric energy for the exhausted batteries of other EVs. The platform applied the Double Auction (DA) mechanism allowing multiple vehicles to conduct energy transactions simultaneously. The price, availability and amount of the traded electricity can be continually adjusted with high flexibility. The final trading price was determined by the k-factor rule so that balances the profits of all participants. A case study was performed by using the EV data collected from a public car park in the UK. The financial benefits of all participants were increased significantly and the energy consumption from the power grid was reduced by using the proposed trading mechanism. These potential reductions in EV running costs encourage the development of the EV market.