Abstract: A battery control apparatus includes: a battery circuit in which a plurality of batteries are connected in series; a plurality of bypass circuits, each of which removes a corresponding battery from the battery circuit; a plurality of switches, each of which switches whether to connect a corresponding battery in series with the other batteries, or to connect the corresponding battery to a corresponding bypass circuit to remove the corresponding battery from the battery circuit; a deterioration detecting section that detects deterioration of each of the plurality of batteries; and a switch control section that controls the plurality of switches to remove, from the battery circuit, the batteries having greater deterioration and connects, in series, the batteries having smaller deterioration.

Abstract: The present invention is a control system for an assembled battery that controls an assembled battery comprising a plurality of cells, including: a bypass circuit connected in parallel to each cell of the cells, and comprising a switching element and a resistor connected in series; and a control circuit that controls a bypass current flowing in the bypass circuit by opening and closing the switching element, in order to discharge the cell; wherein the bypass circuit is set so that a current of a same magnitude as a self-discharge current in a predetermined overcharged states of the cell flow in the bypass circuit.

Abstract: Rechargeable battery systems and rechargeable battery system operational methods are described. According to one aspect, a rechargeable battery system includes a plurality of rechargeable battery cells coupled between a plurality of terminals and shunting circuitry configured to shunt charging electrical energy around respective ones of the rechargeable battery cells during charging of the rechargeable battery cells from substantially discharged states of charge of the rechargeable battery cells to substantially charged states of charge of the rechargeable battery cells.

Abstract: Without battery cell balancing, voltages of multiple series-connected battery cells may quickly become out of balance, which causes some cells of the battery to deteriorate faster than others, and reduces the life cycle of the battery. Embodiments of the present invention address this problem by providing a system for balanced charging of multiple series-connected battery cells. The system includes resistors that are selectably and electrically coupled in parallel with respective battery cells via activation and deactivation of respective switches. The system also includes a control unit that is configured to determine a battery cell having a lowest voltage among the battery cells, and to activate and deactivate the switches as a function of differences in voltages between the voltage of the lowest battery cell and voltages of each of the other battery cells, thus, providing balanced charging of the multiple series-connected battery cells.

Abstract: The present disclosure describes a power storage apparatus including a housing made of a durable material and defining an installation space of a plurality of secondary batteries; a plurality of secondary batteries accommodated in the housing and connected to each other in series or in parallel; a Battery Management System (BMS) for controlling charge and discharge of the plurality of secondary batteries and monitoring an electric characteristic value thereof; and a status setting switch for setting a status of the BMS. According to the present disclosure, a power storage system may be easily configured by means of a simple BMS setting. Also, if any one of the power storage apparatuses is not working properly, the power storage apparatus with a problem may be easily distinguished by the naked eyes of a manager, which facilitates easy maintenance and repair.

Abstract: A balancer circuit for a cell in a rechargeable battery, having connecting terminals for connection of the balancer circuit to the cell. A first resistor is electrically connected to one of the connecting terminals and a voltage switch is arranged in series with the first resistor and electrically connected to the other one of the connecting terminals. The voltage switch, e.g., an adjustable voltage reference circuit, is operable to shunt a balancing current through the first resistor when a load voltage sensed over the connecting terminals is higher than a threshold voltage.

Abstract: A power cell system such as a fuel cell system, with apparatus for detecting a discontinuity. A power cell system, e.g. a fuel cell system, includes a plurality of power cells, e.g. fuel cells and plurality of first resistances, the plurality of power cells and first resistances being connected in the form of a ladder circuit, and electronic filters each having a first connection to a first node between two of the first resistances, each electronic filter having a second resistance and a charge storage device connected to the second resistance.

Abstract: A mobile electric appliance is disclosed. The mobile electric appliance includes at least one battery bay for accommodating a battery with at least one voltage-generating cell and a battery-side charge status indicator, an electrical consumer, a power connector, as well as a charging device for charging the at least one battery. In addition, the mobile electric appliance includes means for detecting the charge status of the at least one battery and a device-side charge status indicator arranged on the mobile electric appliance. The battery may also include an interface, which is prepared to relay the charge status determined to an external processing unit.

Abstract: Methods, systems, and apparatus for determining whether an accessory includes particular circuitry. A host device may measure a first voltage and a second voltage received from an accessory, where the voltages are provide through the accessory from a power source. Before measuring the second voltage, the host device may send an instruction to the accessory instructing the accessory to alter an impedance of the power path between the power source and the host device, and the host device may draw at least a threshold amount of current from the power source via the accessory. The host device may then determine whether the accessory includes particular circuitry based on the relationship between the first voltage and the second voltage.

Abstract: An apparatus is provided, which monitors an operation state of a battery composed of a plurality of cells mutually connected in series. In this apparatus, a cell voltage of each of the plurality of cells is detected as information indicating an operation state of the battery. Based on the detected cell voltages, an operation state is monitored for a cell having a highest cell voltage and a cell having a lowest cell voltage among the plurality of cells.

Abstract: A battery voltage monitoring circuit includes a first power supply terminal to be connected to the positive terminal of a battery pack having rechargeable cells connected in series; a first supply voltage sensing terminal to be connected to the positive terminal of the battery pack; a first resistor connected between the first power supply terminal and the first supply voltage sensing terminal; a second supply voltage sensing terminal to be connected to the negative terminal of a first rechargeable cell of the rechargeable cells, the first rechargeable cell being on the positive terminal side of the battery pack and connected to the positive terminal of the battery pack; a second resistor connected between the second supply voltage sensing terminal and the first power supply terminal; and a first comparator configured to compare a voltage at the first power supply terminal and a voltage at the first supply voltage sensing terminal.

Abstract: Embodiments of the invention provided circuits and methods for balancing battery cells. According to a first embodiment, a cell balancing circuit includes an auxiliary current path for controlling a conductance status of a shunt path. According to a second embodiment, a cell balancing circuit utilizes a total voltage of multiple neighboring cells in a battery pack to generate a current. Based on the current, a voltage drop is generated to conduct a shunt path corresponding to one cell of the neighboring cells. According to a third embodiment, a cell balancing circuit utilizes a total voltage of multiple neighboring cells in a battery pack to generate a current. Based on the current, a voltage drop is generated to conduct a shunt path corresponding to one cell of the neighboring cells. The cell balancing circuit can turn on multiple internal switches at the same time to balance multiple neighboring cells simultaneously.

Abstract: The present invention discloses a charging management system and a charger with such charging management system. The charging management system includes a first signal-output port, a second signal-output port, a third signal-output port and a controller electrically connected with the first, second and third signal-output ports. The first and second signal-output ports are adapted for outputting first and second control signals representing first and second charging currents, respectively, to a charging circuit. The third signal-output port is adapted for outputting a third control signal representing a variable third charging current to the charging circuit. The controller controls the charging management system to operate under at least one of two modes. In the first mode, the controller alternately controls the first and second signal-output ports to output the first and second control signals. In the second mode, the controller only controls the third signal-output port to output the third control signal.

Abstract: A method for operating a battery system having multiple battery packs. The method includes decoupling the output of a discharged battery pack from the vehicle load, reducing the voltage between an output of a charged battery pack and the vehicle load prior to coupling the output of the charged battery pack to the vehicle load.

Abstract: A rechargeable battery is used with a plurality of battery cells restrained by a restraint member. After the rechargeable battery has the restraint member removed therefrom and is thus disassembled when the rechargeable battery is subsequently re-restrained by the restraint member and thus reused an internal resistance measurement unit measures the rechargeable battery's internal resistance based on battery data detected after the rechargeable battery is re-restrained. At least for the internal voltage, from a value thereof as measured after the battery is re-restrained an evaluation unit evaluates a value of the rechargeable battery that is reused.

Abstract: A rechargeable battery assembly provides load balancing for individual battery cells making up a battery assembly. The battery assembly includes a plurality of series-connected battery cell assemblies. Each battery cell assembly includes a battery cell and a charge bypass load connected in parallel with the battery cell. A cell supervisory circuits (CSCs) and battery interface unit (BUI) interface between the battery cell assembly and a battery charge/discharge circuit to provide load balancing by comparing the voltages monitored with respect to each battery cell assembly to an end of charge voltage (EOCV) threshold and in response to the monitored voltage equaling the EOCV threshold issues a charge bypass command to the CSC to activate the charge bypass load.

Abstract: A battery management system and a driving method thereof, to set a discharge completion voltage using the cell voltages of cells of a battery, and to balance the cell voltages according to the set discharge completion voltage.

Abstract: A two-stage charge equalization apparatus for a series-connected battery string having a two-stage DC-DC converter including a first DC-DC converter; and a second DC-DC converter which is inputted. A battery string is divided into one or more battery modules having a plurality of battery cells connected in series, and a current conversion switch module forms a path of the charge current between the battery module and the second DC-DC converter to allow the charge current to be applied to the particular battery cell composing the battery module and controls an application direction of the charge current. A microprocessor determines a battery cell to be charged of a low-charged battery cell and controls the current conversion switch module to allow the charge current to be applied to the battery cell to be charged.

Abstract: An apparatus for balancing charge capacity of battery cell includes a voltage sensing/discharging circuit having a battery with cell group, a switching unit for selectively connecting both terminals of each battery cell to conductive lines, capacitor connected to the conductive lines, a voltage amplifying unit connected to both terminals of capacitor via a first switch, and a discharge resistance connected to both terminals of capacitor via a second switch; and a voltage balancing unit for controlling the switching unit in ON state of first switch to connect both terminals of each battery cell to the conductive lines and then sense voltage of each battery cell through the voltage amplifying unit, and controlling the switching unit in OFF state of first switch to charge voltage of balancing-requiring cell to the capacitor and then turning on the second switch to discharge charged voltage of capacitor through the discharge resistance.

Abstract: There is disclosed a battery monitoring device including a voltage equalization circuit that equalizes cell voltages of a plurality of battery cells being connected in series and forming a battery pack, and a microcomputer that outputs an instruction signal to instruct the voltage equalization circuit to start an voltage equalizing operation for the battery cells. The microcomputer includes a first timer section that stops the voltage equalizing operation a first predetermined set time after the start of the voltage equalizing operation, and the voltage equalization circuit includes a second timer section that stops the voltage equalizing operation a second predetermined set time after the start of the voltage equalizing operation. This can enhance reliability during the voltage equalizing operation.

Abstract: A battery unit balancing system comprises a discharging circuit and means for connecting the discharging circuit to a battery unit. The discharging circuit is configured such that it is automatically activated, when a voltage of the battery unit exceeds a predetermined threshold, to draw a constant discharging current from the battery unit until the voltage of the battery unit falls below the predetermined threshold.

Abstract: An electronic system has a capacitor that smoothes voltage of a direct current source, a resistance circuit that discharges charge of the capacitor, and an inverter circuit that converts the smoothed voltage into a three-phase ac voltage and applies this ac voltage to a motor. The resistance circuit has resistors and patterned wires disposed on a substrate such that the wires serially connect the resistors to discharge charge of the capacitor. The resistors are aligned in a straight line. The resistors located at positions different from ends of the series of resistors have resistance values lower than resistance values of the resistors located at respective ends of the series of resistors. More preferably, as the position of one resistor approaches the center of the series of resistors, the resistor is set at a lower the resistance value.

Abstract: A battery pack and a method of sensing a voltage of the battery pack are disclosed. The battery pack has more battery cells than an individual cell voltage sensing unit can sense the voltages of. The additional battery cells are sensed using a multi-cell voltage sensing unit and digital processing.

Abstract: Systems and methods for management of a backup power system are described herein. At least one illustrative embodiment includes a backup power system configured to couple to a power source including a plurality of batteries, each comprising one or more cells, used to provide power if the power source fails, and processing logic coupled to the batteries and configured to monitor the state of each of the plurality of batteries and control the charging and discharging of each of the plurality of batteries. If the power source has not failed, the processing logic repeatedly and sequentially causes each battery to discharge while at least one of the remaining batteries remains fully charged, and monitors the power provided by the discharging battery. The processing logic determines the available energy stored in each fully charged battery based upon the power provided by the discharging battery during the time it takes to discharge.

Abstract: Disclosed is a battery balancing circuit for balancing the voltages of a reference battery module and a detachable battery apparatus, which has a load channel, a charging-discharging channel, a MCU and a charging-discharging control circuit. The reference battery module and detachable battery apparatus are connected in parallel. The load channel is connected to the reference battery module. The charging-discharging channel is disconnected from the reference battery module. The load and charging-discharging channels are connected to the detachable battery apparatus respectively through a first and a second switches. When the voltage of the detachable battery apparatus is higher or lower than a threshold value, the MCU controls the first and second switches, such that the detachable battery apparatus is connected to the charging-discharging control circuit through the charging-discharging channel and disconnected from the load channel.

Abstract: The invention relates to a battery comprising a plurality of modules arranged in series, characterised in that a module comprises a cell and a cell switch arranged in series with the cell, and in that a circuit for controlling the cell switch is electrically fed directly by at least one cell of a module of the battery.

Abstract: The present invention generally relates to a device and method for stabilizing a battery pack, wherein the battery pack stabilization device has a by-pass circuit to prevent individual cell overcharge. In one embodiment, the present invention relates to an efficient balancing and monitoring system for use in an electric vehicle that utilizes nickel-zinc-based batteries. In another embodiment, the present invention relates to a device that permits over-voltage protection as well as the ability to monitor cell voltage. In still another embodiment, the present invention provides a method to coordinate multiple packs of cells within a vehicle so a driver could be aware of possible distance and time parameters, as well as a monitoring or alert system to inform the driver of reduced power, thus preventing damage to the cells.

Abstract: A cell management system and method for balancing energy across a plurality of cells coupled to a circuit bus. The system can include a transformer, two transformer switches, and for each cell, a first switch pair allowing transfer of energy between the transformer and the cell, and a second switch pair allowing removal or inclusion of the cell in the serial connection of cells. The system can include an energy storage device, a switch pair allowing transfer of energy between the transformer and the storage device, and for each cell, a third switch pair allowing transfer of energy between the storage device and the cell. The system can include cell, bus and storage device sensors and state estimators. The system can include a controller that controls the transformer switches, cell switches, and storage device switches based on the sensor readings and states.

Abstract: A battery management system can be provided which can include a plurality of battery management units connected in series and a host controller. Each battery management unit can include a battery cell, an isolation element, and at least one bypass element. The isolation element is connected with the battery cell in series, and the battery cell is isolated by turning off the isolation element. The bypass elements can be in parallel connection with the battery cell and isolation element, and the battery cell is bypassed by turning on the bypass element. A battery management method can include: activating the battery cell of the battery management unit by turning on the isolation element and turning off the bypass elements of the battery management unit; and deactivating the battery cell of the battery management unit by turning off the isolation element and turning on the bypass elements of the battery management unit.

Abstract: A method for charging an electric storage battery in a plug-in electric vehicle through a power supply circuit includes coupling a charger to the circuit, providing the charger with a signal representing a current capacity of the circuit, using the signal to determine a maximum charge rate corresponds to the current capacity of the circuit represented by the signal, and charging the battery through the circuit and charger at the maximum charge rate.

Abstract: Effective scheduling of battery charge and discharge activities, by making the most of battery characteristics, can extend the battery pack's operation-time and lifetime. A system and method for scheduling battery activities is disclosed. This framework dynamically adapts battery activities to load demands and to the condition of individual battery cells, thereby extending the battery pack's operation-time and making them robust to anomalous voltage imbalances. The scheduling framework includes two components. An adaptive filter estimates the upcoming load demand. Based on the estimated load demand, a scheduler can determine the number of parallel-connected battery cells to be discharged. The scheduler also effectively partitions the battery cells in a pack, allowing the battery cells to be simultaneously charged and discharged in coordination with a reconfigurable battery circuit.

Abstract: A circuit includes multiple battery modules and protection circuits respectively coupled to the battery modules. Each protection circuit includes a controller and a shunt circuit. The controller is coupled to one of the battery modules and detects a fault associated with the battery module. The shunt circuit is coupled to the battery module and the controller, and shunts a current around the battery module if the fault associated with the battery module is detected by the controller.

Abstract: The disclosure describes a battery system having a large number of battery cells which are connected in series. At least one battery cell of the large number of battery cells is connected in parallel with an electrical component. The resistance of the electrical component is reduced when a voltage, which is applied to the electrical component and to the battery cell, exceeds a predetermined voltage threshold value. The disclosure also describes a method for charging a large number of battery cells which are connected in series. The method can be executed using the battery system according to the disclosure.

Abstract: A cell controller capable of ensuring high safety even when a short occurs among voltage detecting lines without causing increased costs is provided. The cell controller 10 includes a unit cell voltage detecting section 7 to detect a voltage of each unit cell 1 constituting a battery group through each voltage detecting line and a SOC adjusting circuit for adjusting a SOC of each unit cell 1 having resistors 2 for SOC adjustment, switching elements 6, and a bypass control section 8 to exercise on/off control on the switching elements 6. Each resistor 2 is connected in series to each voltage detecting line and the unit cell voltage detecting section 7 to detect a voltage of each unit cell 1 through each of the resistors 2.

Abstract: A charge balancing circuit implemented within a charge storage device (cell) in a series connected charge storage unit (battery) made up of a plurality of cells. The charge balancing circuit may utilize a controller to sense the voltage in the cell it is implemented therein and the cells adjacent thereto. If the voltage of the current cell exceeds a threshold voltage and is greater than at least one adjacent cell the current cell can transfer charge to the adjacent cell having the lowest voltage. The transfer of the charge is done with a switching network that extracts current from the current cell and then transfers the current to the adjacent cell having the lowest voltage. The switching network may utilize switches and a current storage device (inductor) to transfer the charge. The controller may activate different switches based on which adjacent cell has the lowest voltage.

Abstract: A cell balancing circuit comprises a first cell having a first voltage, a second cell in series with the first cell and having a second voltage that is greater than the first voltage, and a bypass path in parallel with the second cell for enabling a bypass current for the second cell if a difference between the first voltage and the second voltage is greater than a predetermined threshold. The bypass current is enabled for a balancing time period that is proportional to the difference between the first voltage and the second voltage.

Abstract: An charging device includes: capacitors connected in series; a charging unit that charges the capacitors; bypass units, each respectively connects in parallel to each capacitors, wherein each bypass unit causes, when a charged voltage of any capacitor has reached a set voltage, a charging current to bypass the capacitor whose charged voltage has reached the set voltage; and a control unit that controls the charging unit to charge the capacitors in such a manner that, when a charging voltage of the any capacitor has reached the set voltage, the control unit causes the charging unit to reduce the charging current, and if a predetermined period has elapsed since the charging voltage has reached the set voltage, and if a charging voltage of any of the other capacitors has not reached the set voltage after the predetermined period, the control unit causes the charging unit to increase the charging current.

Abstract: A manager that lessens a difference in state of charge of a battery pack. The battery pack is constituted of a plurality of blocks. A slave unit is provided for each of the blocks, to thus detect a terminal voltage of the block and supply the detected terminal voltage to a master unit. A difference arises in state of charge among the blocks for reasons of a difference in current consumption of the respective slave units. The master unit makes up an operation clock signal for each of the slave units from a high frequency signal and a low frequency signal. A difference in state of charge among the blocks is lessened by controlling an appearance ratio of the high frequency signal to the low frequency signal for each of the slave units.

Abstract: A dynamically reconfigurable battery framework for management of a large-scale battery system systems is provided. The framework monitors, reconfigures, and controls large-scale battery systems online. The framework is built upon a topology-based bypassing mechanism that provides a set of rules for changing the battery-pack configuration, and a semantic bypassing mechanism by which the battery-cell connectivity is reconfigured to recover from a battery-cell failure. More specifically, the semantic bypassing mechanism implements a constant-voltage-keeping policy and a dynamic-voltage-allowing policy. The former policy is effective in preventing unavoidable voltage drops during the battery lifetime, while the latter policy is effective in supplying different amounts of power to meet a wide-range of application requirements.

Abstract: A battery system manages a plurality of battery cells of an assembled battery. The battery system includes at least a plurality of battery cell management units which is connected to the battery cells and manages the connected battery cells. The battery cell management units are connected to each other. Each of the battery cell management units comprises at least an operation mode switching unit, a parameter-related data generating unit, a parameter data transmitting unit, a parameter data receiving unit, a minimum value specifying unit, a switching command data transmitting unit, and a switching command data receiving unit.

Abstract: A system and method for equalizing a battery pack during a battery pack charging process in accordance with an exemplary embodiment is provided. The method includes receiving total capacity estimates for all battery cells in the battery pack, and receiving state-of-charge estimates for all battery cells in the battery pack. The method further includes computing an equalization metric for all battery cells in the battery pack. The method further includes determining an equalization action for all battery cells in the battery pack, and initiating that equalization action. The method further includes executing a battery pack charging step.

Abstract: A management unit and method for managing electric energy stored in a battery composed of a number of series-connected cells, the management unit having: a main equalizing circuit, which forms the primary of an electric transformer and has a constant alternating-current generator powered by the battery and which feeds alternating current of constant intensity through the main equalizing circuit; and, for each cell of the battery, a secondary equalizing circuit, which forms the secondary of the electric transformer, is connected parallel to the cell, has a one-way electronic device which imposes electric current flow to the cell in one direction only, and is connected to a drive device that can be activated to zero the voltage applied to the cell by the secondary equalizing circuit.

Abstract: A battery management system and method, the method including balancing cells and measuring the cell voltages of cells that are not directly adjacent to the cells being balanced.

Abstract: An electrochemical battery system in one embodiment includes a first electrochemical cell, a second electrochemical cell, a memory in which command instructions are stored, and a processor configured to execute the command instructions to (i) selectively charge or discharge the first electrochemical cell based upon an evaluation of first criteria associated with the first electrochemical cell, and (ii) selectively charge or discharge the second electrochemical cell based upon an evaluation of second criteria associated with the first electrochemical cell.

Abstract: An electrochemical battery system in one embodiment includes a plurality of first electrochemical cells, a memory in which command instructions are stored, and a processor configured to execute the command instructions to (i) evaluate each of the plurality of first electrochemical cells, and (ii) selectively connect a first of the plurality of first electrochemical cells to a power provider based upon the evaluation while selectively isolating a second of the plurality of first electrochemical cells from the power provider based upon the evaluation.

Abstract: A method and apparatus are disclosed for a Battery Management System (BMS) for the controlling of the charging and discharging of a plurality of battery cell (12). Each battery cell has an associated plurality of control circuits (32, 36) which monitor and control the charging of individual battery cells. These units are controlled by a central microcontroller (14) which shunts current around the battery cell if fully charged and stops discharge if a battery cell is fully discharged in order to prevent damage to the other cells.

Abstract: A balancing method for a battery pack includes balancing battery cells near an end of discharge. A deep discharge of the battery cells can be prevented without using an overdischarge control unit. One battery cell balancing method includes: a balancing check condition determination step for determining whether or not a maximum voltage out of voltages of the battery cells is smaller than a reference voltage; a balancing start condition determination step for determining whether or not a residual capacity difference or voltage difference between the individual battery cells exceeds a reference value; a balancing time calculation step for calculating a balancing time for discharging the battery cell that exceeds the reference value; and a balancing operation step for discharging the selected battery cell when the battery cells are under charge or are at rest or when a discharge current of the battery cells is smaller than a reference current.

Abstract: A dynamically reconfigurable battery framework for management of a large-scale battery system systems is provided. The framework monitors, reconfigures, and controls large-scale battery systems online. The framework is built upon a topology-based bypassing mechanism that provides a set of rules for changing the battery-pack configuration, and a semantic bypassing mechanism by which the battery-cell connectivity is reconfigured to recover from a battery-cell failure. More specifically, the semantic bypassing mechanism implements a constant-voltage-keeping policy and a dynamic-voltage-allowing policy. The former policy is effective in preventing unavoidable voltage drops during the battery lifetime, while the latter policy is effective in supplying different amounts of power to meet a wide-range of application requirements.

Abstract: A dynamically reconfigurable framework is provided for a large-scale battery system. The framework is comprised of a plurality of battery circuits arranged adjacent to each other to form a battery-cell array that is coupled to an application load. A given battery circuit includes: a battery cell with an input terminal and an output terminal; a first switch connected between the load and an input terminal of the battery cell; a second switch is connected between an input terminal of the battery cell and an output terminal of a battery cell in an immediately adjacent battery circuit; and a third switch connected between the output terminal of the battery cell and the output terminal of the battery cell in the adjacent battery circuit. The battery-cell array also includes a local controller that selectively controls the switches in the plurality of battery circuits.

Abstract: A modular and scalable power source can be used to supplement and/or replace existing sources of power. In some embodiments, a DC source can be used to charge a battery in a host system, provide power as a back-up system, or be a primary source of power. The power source includes a set of battery units and one or more circuits that provide an alternative signal path around the battery units if the battery units are at a particular charge level. Temperature sensors are used to turn off or otherwise adjust the alternative signal paths if the temperatures of the alternative signal paths become too high.