Vehicle power supply system

A vehicle power supply system comprising:

• a plurality of battery modules each having a plurality of high-voltage batteries;
• a case for accommodating the plurality of battery modules;
• and
• a cooling circuit having a radiator, a cooling pump, a plurality of battery cooling units for cooling the plurality of battery modules,
• the case being disposed below a floor panel, wherein:
• the plurality of battery modules include a front battery module which is disposed under a front seat, and at least two rear battery modules which are disposed under a rear seat;
• the front battery module is laid out flat under the front seat;
• the at least two rear battery modules include an upper rear battery module and a lower rear battery module, which are superposed vertically under a front of a seat cushion of a rear seat;
• the front battery module has a battery capacity which is smaller than a total of battery capacities of the at least two rear battery modules;
• the upper rear battery module has a battery capacity which is smaller than that of the lower rear battery module;
• in the cooling circuit,
• the plurality of battery module cooling units are connected in parallel by piping;
• the radiator and the cooling pump are disposed outside the case;
• the plurality of battery module cooling units, the piping, a branch portion which is provided to an upstream side of the plurality of battery module cooling units, and a merging portion which is provided to a downstream side of the plurality of battery module cooling units are provided inside the case;
• and
• a first flow rate control device is disposed at an upstream side or a downstream side of a front battery module cooling unit for cooling the front battery module;
• and a second flow rate control device is disposed at an upstream side or a downstream side of an upper rear battery module cooling unit for cooling the upper rear battery module.