Development of a control device of the traction battery operation

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The necessity of control of charge and discharge modes of lithium-ion traction accumulation battery (TAB) of electric cars and hybrid cars is shown. It is possible to fully realize the capabilities of the traction battery set by the manufacturer only if you strictly ensure the modes of charge and discharge, i.e. maintaining currents and voltages on each element of the battery within acceptable limits. These modes must be provided by a special control system BMS (Battery Manger System). This article is devoted to the practical implementation of a possible use of such a system. Because the TAB elements are connected in series, the current in them is common and is controlled by a battery current sensor. The voltage at each element of the TAB must be monitored individually so that no element has an increase in voltage when the charge is above the maximum allowable, or a decrease in the voltage when the discharge is below the minimum allowable. The onboard charger is practically realized on the microhybrid car on the basis of the Lanos pickup car. TAB of this car consists of 20 cans of lithium-iron-phosphate batteries WB-LYP90AHA, capacity is 90 Ah, maximum charge voltage of one can is 3.6 V. The functional diagram of the onboard charger with balancing and protection system is given. At the input, the charger contains a power factor corrector. The galvanic isolation is made in the form of a resonant half-bridge DC/DC converter. The controller of the onboard charger stabilizes the charging current and voltage. When in the process of charging the TAB voltage reaches a maximum value of 72V, the controller begins to reduce the fill factor, and hence reduce the charging current, preventing further voltage increase. However, before the maximum TAB voltage is reached, the maximum voltage of the individual TAB elements will be reached. For these elements, further charging becomes unacceptable, so the work of the balancing system is necessary. The electric scheme is given and the principle of work of the BMS board is described.Keywords: electric car, hybrid car, traction battery, charger, power factor corrector, battery balancing device, charge and discharge controller.