Battery system
In a battery system that connects a plurality of types of batteries through a switch SW, when the switch SW is switched at a voltage (charge rate), it has been possible to increase a stored charge during charging, depending on the DC resistance of the battery. An object of the present invention is to provide switch SW switching control so that the stored charge can further be increased. A first feature of the present invention is to provide a battery system in which a first battery and a second battery are connected in parallel through the switch SW, including an estimator which estimates the charging current by measuring the resistance and OCV of each battery. The battery system can further increase the stored charge by switching to a switch SW combination that can increase the stored charge.
1. A battery system that connects a first battery and a second battery in parallel through a switch, the battery system comprising:
an estimator which estimates a charging current of the first battery at least from an internal resistance of the first battery; and
an estimator which estimates a charging current of the second battery at least from an internal resistance of the second battery,
wherein the switch is switched between the first battery and the second battery based on the charging current of the first battery and the charging current of the second battery such that a sum of a stored charge in the first battery and a stored charge in the second battery increases,
wherein the procedure switches the switch once during a regenerative charging,
wherein, in a case that a regeneration time is T, a charging time of the second battery is τ, and a first charging time is T−τ, where T is greater than τ, the second battery first is charged, and the switch is switched to the first battery at the timing τ at which a charge amount of the first battery and a charge amount of the second battery are maximum, and
wherein τ is a time t from a start of charge and the switch is switched so as to select the first battery after the time t has elapsed from the start of charge.
2. The battery system according to claim 1 ,
wherein when the regenerative charging time T is unknown, a time t is obtained at which the current time series of the first battery is equal to the current convergence value of the second battery, and defines the time t as the τ.
3. A battery system that connects a first battery and a second battery in parallel through a switch, the battery system comprising:
an estimator which estimates a charging current of the first battery at least from an internal resistance of the first battery; and
an estimator which estimates a charging current of the second battery at least from an internal resistance of the second battery,
wherein the switch is switched between the first battery and the second battery based on the charging current of the first battery and the charging current of the second battery by a procedure in which a sum of a stored charge in the first battery and a stored charge in the second battery increases,
wherein the switch is switched between the first battery and the second battery two or more times during a regenerative charging, and
wherein an estimated charging current of the first battery is compared with an estimated current of the second battery, and the switch is switched so that the battery is selected with the larger of the two estimated currents.
4. The battery system according to claim 3 ,
wherein the switch is switched at regular intervals and each battery is charged until the individual charging of either the first battery or the second battery attains to a constant voltage charge.
5. The battery system according to claim 4 ,
wherein a time rate of the switch of the first battery is initially set to 1 when the first battery is charged with a constant current, and the time rate of the switch of the first battery is changed to (voltage in constant voltage charging of alternator−open circuit voltage of first voltage)/(current of alternator during constant current charging×polarization resistance) after the first battery is in a constant current charge completion state.
6. The battery system according to claim 4 ,
wherein the load is an alternator, and
wherein the time rate of the switch of the first battery is controlled so that the following equation is true when the first battery is charged with a constant current: Current in constant current charging of alternator=Polarization voltage of second battery/(polarization resistance of second battery*(1+polarization capacity of second battery/capacity of second battery))+Polarization voltage of first battery vp(t)/Polarization resistance of first battery.
7. A battery system that connects a first battery and a second battery in parallel through a switch, the battery system comprising:
an estimator which estimates a charging current of the first battery at least from an internal resistance of the first battery; and
an estimator which estimates a charging current of the second battery at least from an internal resistance of the second battery,
wherein the switch is switched between the first battery and the second battery based on the charging current of the first battery and the charging current of the second battery by a procedure in which a sum of a stored charge in the first battery and a stored charge in the second battery increases,
wherein the procedure switches the switch two or more times during a regenerative charging,
wherein when the switch is switched two or more times while a simultaneous connection is permitted during a charging, the charging current of the first battery and the charging current of the second battery for three following cases are estimated: an individual charging of the first battery; an individual charging of the second battery; and connection to both of the first and second batteries, and when the first battery or the second battery discharges, the switch is switched so that the battery with the larger of the two charging currents between the first and second batteries is connected, and otherwise, when a constant voltage charging takes place with the battery alone, both the first and second batteries are connected, and further otherwise, the rate of the switch ON time of the first battery alone, the rate of the switch ON time of the second battery alone, and the rate of the switch time for connecting both batteries are controlled, in order to perform a constant current charging.
8. A battery system that connects a first battery and a second battery in parallel through a switch, the battery system comprising:
an estimator which estimates a charging current of the first battery at least from an internal resistance of the first battery;
an estimator which estimates a charging current of the second battery at least from an internal resistance of the second battery;
wherein the switch is switched between the first battery and the second battery based on the charging current of the first battery and the charging current of the second battery by a procedure in which a sum of a stored charge in the first battery and a stored charge in the second battery increases; and
a measurement device that measures a voltage and current of the first battery, a voltage and current of the second battery, and a voltage of the alternator and auxiliary equipment,
wherein the DC resistance of the first battery, the resistance of the switch, the polarization capacity, the polarization resistance, the polarization voltage, the open circuit voltage, and the capacity of the second battery are measured; and
wherein the parameters are estimated as Polarization voltage=−Polarization voltage before measurement time×(1−measurement time step size/(polarization resistance×polarization capacity))+Measurement current×Measurement time step size/Polarization capacity.