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velocity. Rolling requirements in construction and agricultural machines are related to the resistance due to tire deformation combined with resistance due to soil deformation [47, 48]. In the case of work vehicles, continuous variable transmission CVT could be used to determine the energy flow that reaches the transmission from each energy source (engine, generator, and motor battery) [49]. 3.3. Energy storage devices The energy efficiency of construction machinery is generally relatively low, and kinetic or potential energy is lost during operation [50]. Currently, batteries [51], super-capacitors, hydraulic accumulators, and flywheels are mainly used as energy storage devices in hybrid construction and agricultural machinery (HCAM), as schematically described in Figure 5. 3.3.1. Batteries Batteries are the most studied energy storage and are divided into three types: Li-ion [52], nickel-metal hydride [53, 54], and lead-acid [55]. Li-ion batteries are considered as a highly prospective technology for vehicle applications [56, 57] because of their larger storage capac- ity, wide operating temperature range, better material availability, lesser environmental impact, safety [58–60]. However, despite having the highest energy density, Li-ion batter- ies a shorter lifetime, higher vulnerability to environmental temperature, and higher cost compared with other energy storage devices. A comprehensive review examined the elec- trochemical basis for the deterioration of batteries used in HEV applications and carried out tests on xEVs, automotive cells, and battery packs [61, 62] regarding their specific energy, efficiency, self-discharge, charge-discharge cycles, and cost. The results indicated that Li-ion is currently the best battery solution, surpassing the other technologies in all parameters except charge speed, in which Pb-acid batteries showed a better performance. Over the last years, graphene and its applications have become an important factor in improving the per- formance of batteries [63]. Figure 4. Types of electric motors for HEV applications. Trends and Hybridization Factor for Heavy-Duty Working Vehicles http://dx.doi.org/10.5772/intechopen.68296 9