Powerboost hub

A series hydraulic hybrid system for a vehicle, comprising:

• a hydraulic circuit comprising a first hydraulic displacement unit in fluid communication with a second hydraulic displacement unit through a first main fluid line and through a second main fluid line;
• and
• a high pressure hydraulic accumulator in fluid communication with the hydraulic circuit and a low pressure hydraulic accumulator in fluid communication with the hydraulic circuit;
• a first pressure-actuatable shut-off valve selectively fluidly connecting the high pressure hydraulic accumulator with the first main fluid line;
• a second pressure-actuatable shut-off valve selectively fluidly connecting the high pressure hydraulic accumulator with the second main fluid line;
• a pressure actuatable proportional flow control valve fluidly connecting the high pressure hydraulic accumulator with the hydraulic circuit;
• and
• a pilot fluid line for piloting the first pressure-actuatable shut-off valve, the second pressure-actuatable shut-off valve and the pressure actuatable proportional flow control valve via the pilot fluid line.