An applicability study of LV battery on-board chargers for high power EVs

This paper analyzes an 11kW three phase on-board charger in case of prospective high power electric vehicles powered by low voltage traction battery (LV, e.g. 24V or 48V). The charger design is compared to the one in present-day electric passenger vehicles that use high voltage batteries (e.g. Tesla Model S). The analyses show that the main difference appears in the design and operation of the output stage of the isolated DC/DC converter, whereas performance of the PFC stage in both cases is comparable. First, the assessment of differences in the topology choice and in related design considerations is given. Consequently, the selection of semiconductor components for an exemplary topology is presented, followed by the efficiency-to-cost ratio analysis. Although no significant cost change is to be expected in case of LV battery chargers for high power vehicles, the LV system introduces distinguishing advantage by eliminating the need for an isolated HV to LV DC/DC converter, followed by the possibility for the space, loss and cost reduction.