Showing papers on "State of charge published in 1983"

Battery state of charge evaluator

Abstract: A combined battery state of charge evaluator and motor control system for an electric vehicle comprises a traction battery 10, a motor controller 14, a traction motor 11, a micro computer 16 and an interface circuit 15. The micro computer 16 receives signals representing battery temperature, total battery voltage, and battery current and calculates the charge withdrawn from the battery by integrating battery current and also calculates the remaining charge in the battery as a function of battery voltage. By summing the remaining charge and the charge withdrawn, the present charge storage capacity value of the battery is calculated. The micro computer 16 compares the present charge storage capacity value with a value representing 85% of the nominal charge storage capacity of the battery when new and selects the lower of these two values. The state of charge is then calculated as a function of the charge withdrawn and this lower value and displayed on a meter 34. When the remaining charge in the battery calculated by subtracting the charge withdrawn from this lower value falls below 6% of the battery capacity, the current supply to the motor 11 is limited to a predetermined percentage of the current demanded by the driver. This predetermined percentage is progressively reduced as the remaining charge falls toward zero.

Battery state of charge gauge

Abstract: A method of computing the state of charge for a battery including the steps of sensing the battery voltage and current, and computing the used battery capacity, C u , and the average battery current, I. The total battery capacity, C t is calculated from average current using the Peukert equation. The state of charge is calculated as a function of C u /C t to account for temperature and aging effects, recuperation effects, regeneration effects, and current variation effects.

Battery monitoring systems

Abstract: A microprocessor based electric vehicle traction battery monitoring system evaluates the state of charge, interfaces with a traction motor control system, and controls recharging. The state of charge is evaluated during the first part of discharge by integrating the current after compensating it for rate of discharge and during the last part of discharge by dividing the battery into sub-packs and evaluating the state of charge from the lowest sub-pack voltage compensated for polarization voltage. The charge storage capacity is also calculated from the lowest sub-pack voltage. The maximum traction motor current is progressively limited during the last part of discharge. During charging, the charge withdrawn is replaced while progressively reducing the charging current and the battery is then charged at a constant current until the rate of rise of the lowest sub-pack voltage falls below a fixed level.

Automatic load shed control for spacecraft power system

Abstract: An automatic load shed control for a spacecraft power system employs a selectable one of a plurality of charging gains to approximate a state of charge in a secondary battery system. An ampere hour meter is initialized when the battery system is known to be fully charged and the inefficiencies of the charging system are lumped into a charging gain parameter. An output of the ampere hour meter is compared with a load shed threshold to determine the time for load shedding. The charging gain can be remotely changed as required to a value which causes the output of the ampere hour meter to track the true state of charge of the battery system closely enough for system satisfactory operation of load shedding. The charging gain may be a constant or may be a variable in dependence on the state of charge of the battery system. Charge which is delivered at a rate below a predetermined threshold is ignored by the ampere hour meter.

The prediction of the state-of-charge of some commercial primary cells

Abstract: Research carried out at Loughborough during the last five years on the impedance of Leclanche, alkaline Zn-MnO2, alkaline Zn-HgO, Li-CuO, Li-SO2, Li-SOCl2 primary cells is briefly reviewed. The use of alternating current methods for the estimation of the state of charge of the cells is discussed. A search was made for properties of the impedance of each cell system which change in a marked and reliable manner when a prescribed amount of charge is withdrawn from the cell. It is concluded that simple tests based upon an assessment of these properties are adequate for the estimation of the state of charge of some of the systems studied. However, other systems are not so ‘well-behaved’. The impedance of each cell changed significantly during discharge and, although making measurements of these changes would enable the state of charge to be estimated, the test techniques required would not necessarily be simple. Using the results obtained on the impedance of the cells, test sets have been constructed which provide a digital presentation of the open-circuit voltage and the state of charge of Leclanche cells (Ever Ready type SP11), mercury cells (Mallory, type RM502R) and lithium cells (Mallory, type L032S and SAFT, type LC01). The electronic techniques employed in these test sets are described in outline with reference in block-schematic diagrams. A proposal is made for the construction of a general-purpose tester for primary cells which would incorporate microprocessors and provide an indication of state of charge based upon data relating to impedance, temperature and discharge history. The tester might also be made self-calibrating for field use.

Traction motor current control battery monitoring system

Abstract: A microprocessor based electric vehicle traction battery monitoring system evaluates the state of charge, interfaces with a traction motor control system, and controls recharging. The state of charge is evaluated during the first part of discharge by integrating the current after compensating it for rate of discharge and during the last part of discharge by dividing the battery into sub-packs and evaluating the state of charge from the lowest sub-pack voltage compensated for polarization voltage. The charge storage capacity is also calculated from the lowest sub-pack voltage. The maximum traction motor current is progressively limited during the last part of discharge. During charging, the charge withdrawn is replaced while progressively reducing the charging current and the battery is then charged at a constant current until the rate of rise of the lowest sub-pack voltage falls below a fixed level.

Battery state of charge evaluation

Abstract: A microprocessor based state of charge evaluator for the traction battery 10 of an electric vehicle evaluates the state of charge and displays it on a dashboard mounted meter 64. The battery is divided into nine 24V sub-packs. During both discharge and recharge, the battery current is integrated to obtain a value representing the charge withdrawn. During discharge, the current is adjusted to compensate for the rate of discharge. During the first part of each discharge, the state of charge is calculated from the charge withdrawn value and from a value representing the charge storage capacity of the battery 10. During the last part of discharge, the state of charge is evaluated from the voltage of the sub-pack having the lowest voltage after compensating for polarization voltage. Polarization voltage is calculated as a function of time and of battery current. The state of charge value obtained from the lowest sub-pack voltage is also used to up-date the charge storage capacity value.

Theoretical Prediction of Electric Vehicle Energy Consumption and Battery State-of-Charge during Arbitrary Driving Cycles

Abstract: The actual performance of an electric vehicle depends on the capability olthe batte­ ry to meet the power requirements of the drive train_ In order to predict the vehicle operating range an accurate battery model is required. The behaviour of a battery depends on its state of charge. In the definition of the state of charge the characte­ ristic relationship between available capacity and current must be accounted for. A voltage-current relationship is derived based on the polarization behaviour of a Teall lici

Testing charge state of vehicle battery - by connecting briefly to electronic tester during transition between charge and discharge states

Abstract: The problem of monitoring the state of charge of a vehicle battery, which is complicated by the continuous fluctuation during use between charging and discharging, is resolved by testing the battery while it is briefly disconnected from the circuit in the transition between both states. When the motor is stationary or ticking over, the battery supplies lights or signalling units and is then discharging. The battery (5) is disconnected briefly from the vehicle's electrical circuit and connected to a resistance (12) during the transition between discharging and charging, i.e. whenever the current flow is zero. The test arrangement (4) for the state of charge is an electronic unit containing an ammeter and switch, which work in conjunction with the resistance.

Circuit arrangements for the rapid charging of a battery of a vehicle electrical system

Abstract: A storage battery 5 is pulse- charged by connecting it via a voltage regulator 4 to a generator 1 which is driven by the vehicle engine 6 and which is operated in a fully excited state so that it has a non-regulated output voltage which increases with increase in its driver speed. The pulse-charging duty ratio can be charged when a high discharge current is measured. The duty ratio can also be varied in response to a timer or to the state of charge of the battery 5. A constant voltage is supplied by regulator 4 to a buffer battery 2 and loads 3. When the generator 1 is idling or not operating, battery 5 is connected to battery 2 by a voltage - or speed - dependent switch 7.