Battery Swapping Stations (BSSs), which have a lot of batteries primarily for Battery Swapping Electric Vehicles (BSEVs), can operate as an emergency power supply with proper allocation of electricity. BSEVs can redistribute the stored energy between two BSSs through battery migrations, then, the difference of stored electricity among BSSs also can be minimized. Electricity is transferred from a BSS with a higher State Of Charge (SOC) to the lower one by BSEV. By the way, the effects of battery migrations appear with delays. In other words, it needs a time to appear the effects accordance with the distance between BSSs. Therefore, BSEVs perform migration consisting of loading/unloading a battery with an easy decision as of only start time, they put energy into destination BSS after equalization. This phenomenon incurs both of the unneeded inversions of high-low relationship and it makes wider the SOC gaps among BSSs. We propose two methods to decide migration considering transportation delay to suppress improper electricity transports. The proposed methods effectively narrow the gap of SOC between BSSs and restrain the fluctuation of SOC. The latter method also cannot take effect for proper judgement of migration with decreased estimation accuracy.