Lightweight composite accumulators are enabling a drive technology that provides better fuel economy, reduces harmful emissions and delivers more power at the same time

Steelhead Composites lightweight high pressure accumulators are a vital component in every hydraulic hybrid vehicle system operating in a stop-and-go drive cycle. In such vehicle, braking forces the fluid into the high pressure accumulator recapturing the energy which is then reused to help propel the vehicle from stop. Lightweight composite accumulators rated for high operating pressures help reduce the overall weight of the vehicle resulting in greater range for equal fuel consumption and provides added bonus of lowering carbon fuel emission.

The significance of using a lightweight high pressure composite accumulator in a hydraulic hybrid vehicle is best explained by the Ragone chart. Conventional batteries may provide excellent energy storage capabilities for the desirable driving range of smaller electric and electric hybrid vehicles. However they lack the ability to provide enough power (energy drawn instantly) to help propel heavier vehicles for a given mass. Accumulators and specifically lightweight composite ones provide the potent specific power so desirable for propelling these medium and heavy duty trucks and vehicles. It is the high specific power density of these accumulators that allows efficient harnessing of the energy stored by regenerative braking.

Plot courtesy of W. J. B. Midgley and D. Cebon, “Comparison of Regenerative Braking Technologies for Heavy Goods Vehicles in Urban Environments,” Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 226, pp. 957-970.


Steelhead Composite accumulators reduces weight of an essential component of the hydraulic hybrid drive system to a fraction of that of steel accumulators. The result is safer handling and much lower installation costs. 

Steelhead Composite accumulators are one-third to one-quarter the weight of traditional steel accumulators, while offering the same functionality. While traditional steel accumulators cap out at 15 gal (54 L), Steelhead Composite accumulators are available in sizes up to 30 gal (113 L) with pressure rating of 6000 psi (414 bar) to meet the needs of power and energy storage requirements of heavy duty hydraulic hybrid vehicles. The lighter weight in a single package helps with the installation in a retrofit system as well as easier and safer field maintenance of these hydraulic hybrid vehicles.