Abstract: A circuit arrangement for transferring electrical charge between accumulators of an accumulator arrangement includes a number of first series circuits, each connecting in parallel to one of the accumulators, and each comprising a switching element and an inductive storage element connected in series to the load path of the switching element. The circuit arrangement also includes a further series circuit connected in parallel to the accumulator arrangement and comprising a further switching element having a load path and a control terminal, and a further inductive element connected in series to the load path, the further inductive element being inductively coupled to the inductive elements of the first series circuits. The circuit arrangement also includes a control circuit comprising a number of first control outputs connected to the control terminals of the switching elements of the first series circuits, and a further control output connected to the control terminal of the further switching element.

Abstract: A power supplying apparatus for supplying power to a plurality of loads has been needed. Therefore, a power supplying apparatus for supplying power to a plurality of loads, including: a rectifying circuit connected to each of the plurality of loads; an AC circuit to sequentially connect between the rectifying circuits; and an AC generating circuit to apply AC voltage to the AC circuit, in which the AC circuit includes a capacitor and an inductor connected in series is provided.

Abstract: A method and system for managing a plurality of batteries and useable by way of example with a partially or completely electrically powered vehicle (EV) includes a plurality of monitor modules each coupled to at least one of the plurality of batteries and configured to monitor the voltage and temperature thereof, a master controller, and a non-conductive fiber optic network coupling the plurality of monitor modules to one another and to the master controller. The master controller commands the transmission of battery voltage and temperature information from the plurality of monitor modules over the network, receives battery voltage and temperature information from the monitor modules over the network, and perform calculations based on the received information to determine if any of the plurality of batteries require balancing measures, and based thereon, commands the corresponding monitor modules to implement balancing measures over the network.

Abstract: The invention provides in various embodiments methods and systems relating to controlling energy storage units in flowing electrolyte batteries.

Abstract: A power pack system for charging a set of isolated batteries is provided. In an illustrative embodiment of the invention, a single fuel cell, a single DC-DC converter and a single system controller device comprises the power-generation side of the power pack. A set of switches is used to connect the power-generation side of the Power pack to one of the isolated batteries in the power pack, thereby recharging that particular battery in the battery power pack set. A battery protection and powerpath control device communicates with the system controller to determine which switches are to be closed depending upon which battery requires recharging. During normal operation the switches will follow the direction from the system controller. If a fault is detected by the battery protection circuit, the protection circuit will take priority and turn off the appropriate switch(es).

Abstract: A battery pack which includes a battery pack electronic control circuit adapted to control an attached power tool and/or an attached charger. The battery pack includes additional protection circuits, methodologies and devices to protect against fault conditions within the pack, as the pack is operatively attached to and providing power to the power tool, and/or as the pack is operatively attached to and being charged by the charger.

Abstract: A battery module system includes a battery module and a control member. The battery module comprises battery units are connected in series. Each of the battery units comprises a unit cell having a voltage variation rate A (mV/% SOC) at a full charge voltage VH1 (V) is larger than 20 (mV/% SOC), which is a value obtained when the unit cell is charged at a current of 1 C at 25° C. The control member controls current to a current I1 until a maximum value Vmax (V) among the voltage of each unit cell reaches the full charge voltage VH1 (V) and then controls a voltage of the battery module to a voltage V2 (V) given by the following equation (1): V2=VH2×n??(1).

Abstract: A large battery array, particularly for use in an electric vehicle, is formed of multiple modules, each containing plural battery cells and module management electronics. Each battery module has a nominal output voltage in the range of about 5 volts to about 17 volts. A controller communicates with individual battery modules in the array and controls switching to connect the modules in drive and charging configurations. The module management electronics monitor conditions of each battery module, including the cells it contains, and communicates these conditions to the controller. The module management electronics may place the modules in protective modes based upon the performance of each module in comparison to known or configurable specifications. The modules may be pluggable devices so that each module may be replaced if the module is in a permanent shutdown protective mode or if a non-optimal serviceable fault is detected.

Abstract: An assembled battery voltage detecting apparatus includes a sampling switch section which samples a voltage of each of single batteries, capacitors charged with voltages of single batteries, a transfer switch section to transfer a charge voltage charged in each of the capacitors, a ground potential setting switch section which, in the case of reading the voltage charged in the capacitor, connects a reference electric potential of the capacitor to a grounding terminal of a voltage detecting apparatus, and a voltage detecting circuit which controls a switching timing of each of the above switches, and then reads a voltage of each capacitor.

Abstract: A plurality of discharge resistors Rd1 to Rdn having different resistance values is provided. A CPU 72 selects one from a plurality of unit cells B1 to B16 as a connection cell and selects one resistance value according to a voltage across the connection cell from the plurality of resistance values. The CPU 72 turns on/off a cell selecting switch group 2, a polarity reversing switch group 3 and a discharge resistor selecting switch group 5 and connects the connection cell to the discharge resistor having the selected resistance value to discharge stored electric charge of the connection cell, thereby equalizing the respective voltages across the unit cells.

Abstract: A voltage controller having an input distribution network with imbedded input switches, a number of charge storage elements such as capacitors, an output distribution network with imbedded output switches, and a switch actuator which controls the input switches and output switches to provide for the controlled charging and discharging of the charge storage elements.

Abstract: A battery management system for controlling a secondary battery module which includes a plurality of unit batteries includes a sensor, a comparator and a controller. The sensor sequentially measures respective voltages of the unit batteries. The comparator compares the respective voltages of the unit batteries to a cut-off voltage range and a recovery voltage range to determine if the voltages are within the cut-off voltage range and the recovery voltage range. The controller receives comparison results from the comparator, cuts off the secondary battery module from an external device when there is at least one unit battery within the cutoff voltage range, and couples the secondary battery module to the external device when all of the unit batteries are within the recovery voltage range.

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 batteries (12). Each battery has an associated plurality of control circuits (32, 36) which monitor and control the charging of individual battery. These units are controlled by a central microcontroller (14) which shunts current around the battery if fully charged and stops discharge if a battery is fully discharged in order to prevent damage to the batteries.

Abstract: Disclosed are system and method for adjusting a voltage balancing of cell in a lithium ion multicell battery pack, the system comprising; a multicell battery pack including a master module and a slave module, a CPU located in the system controller and outputting a synchronization signal for each of the cells in the master module and the slave module, a first vertical interface transmitting the synchronization signal outputted from the CPU to the master module, and a second vertical interface transmitting the synchronization signal to the slave module through the first vertical interface.

Abstract: A battery pack for a power tool of self-contained over-charge protection is proposed. The battery pack includes a battery stack composed of a plurality of series connected secondary cells, and a charge terminal connected through a charge current path to the battery stack for flowing a charge current from a charger. The battery pack includes an interrupter inserted in the charge current path, and an over-charge detector which detects a cell voltage across each of the secondary cells and actuates the interrupter to open the charge current path when any one of the cell voltages becomes higher than a predetermined threshold (VTH3). Thus, even if the charger fails to limit the charge current, the battery pack can itself protect the secondary cells from being over-charged.

Abstract: A method to supply power to one or more battery-backup assemblies, wherein the method supplies a first controller, a second controller, a first battery-backup assembly, and a second battery-backup assembly. The method further supplies a power bus interconnected to the first controller, the second controller, the first battery-backup assembly, and the second battery-backup assembly, and a first power supply and a second power supply interconnected with the power bus. The method provides power to the first controller and to the second controller and to the first battery-backup assembly over a first period of time, and provides power to the first controller and to the second controller and to the second battery-backup assembly over a second period of time, where the first period of time differs from the second period of time.

Abstract: To maximize the life of a rechargeable battery and the life of cells forming the rechargeable battery, the rechargeable battery is so constructed that each of the cells forming the rechargeable battery can be charged independently of the other cells. To charge this rechargeable battery, a cell to be charged is selected, and the selected cell is charged.

Abstract: Disclosed is a system for adjusting a voltage balancing of cells in a lithium ion multicell battery pack. The system comprises a vertical interface outputting inputs of a reading balance signal defining a voltage reading period and a balance period and a reading hold signal holding a cell voltage when reading a voltage; an interface outputting an address clock for designating an address of a cell to be controlled and an input of a balance hold signal for independently reading a cell voltage within a voltage balance period; and a control section of a cell balancing adjusting circuit connected to the vertical interface and the interface and receiving signal outputs therefrom to adjust a balancing of cells.

Abstract: Method for managing a battery system including a number of serially coupled batteries in a flexible, reliable, and cost effective way and that can be used in a wide variety of applications, such as tools, for example, hand tools, cars, boats, back-up systems, buses, trucks, golf carts, wheel chairs, electric cars and fork-lift trucks. The method includes the steps of detecting the battery voltage over each individual battery of the battery system; and utilizing a voltage imbalance between different batteries of the system during operation of the battery system. Furthermore, the method controls the voltage distribution of the batteries to create a voltage imbalance between different batteries of the battery system.

Abstract: A charging method for charging a battery module. The battery module receives a different charge voltage according to the voltage or current status of the battery module. The charge voltage is decreased to increase battery power when any battery voltage level is greater than a preset voltage. A charging system thereof is also disclosed.

Abstract: A system for managing energy stored in a plurality of series connected energy storage units has a plurality of energy storage unit controllers, each controller being associated with one of the plurality of energy storage units, a balancing circuit between two of the energy storage units, the balancing circuit being controlled by at least one of the energy storage unit controllers, a serial electrical interface between the energy storage unit controllers for providing voltage isolated bi-directional communication, and a central controller in electrical communication with the energy storage unit controllers.

Abstract: This present invention provides a bridge battery voltage equalizer to equalize the voltages of the serially connected battery strings, comprising at least one battery crossing over an energy-transferring circuit. A plurality of the energy-transferring circuits are interconnected in a bridge architecture. Each energy-transferring circuit having four nodes comprises a first semiconductor switch, a first diode, a second semiconductor switch, a second diode, and an inductor. One end of the first element switch is connected to a negative pole of the first diode thereto. A positive pole of the second diode is connected to one end of the second element switch thereto. The inductor is an energy storing element that crosses over between the negative pole of the first diode and the positive pole of the second diode.

Abstract: A battery pack having a plurality of electrically connected unit cells and configured so that the cells degrade at similar rates is provided. The battery pack may comprise a first unit cell and a second unit cell, wherein a temperature of the second unit cell is lower than the first unit cell. A condition of the first cell, such as states of charge or an open circuit voltage is set so that the condition of the first unit cell is less than a corresponding condition of the second unit cell. The unit cells may be thin battery cells stacked in a thickness direction of the thin battery cells, and the first unit cell may be located on an inner side of the second unit cell as viewed in a stacked direction. A temperature detecting unit may detect a temperature of each of the first and second unit cells and a charge control unit may be configured to control charging of the plurality of unit cells according to the temperatures of the first and second unit cells.

Abstract: A methodology for balancing batteries for use in an electric vehicle. The methodology includes initializing a target balance voltage value to a predetermined voltage. Sampling a first voltage of the batteries at a predetermined interval. Sending the lowest voltage value to all of the batteries. Replacing the target value voltage with the lowest voltage if the lowest voltage is lower than the target balance voltage and bleeding the batteries if a sampled voltage is higher than the target balance voltage.

Abstract: In a high power system, plural batteries provide back-up power when primary power is unavailable. Each battery has an associated discharge controller which is controlled by a local bus control amplifier which regulates the power bus voltage set-point lower than the main bus voltage set-point. A single main bus control amplifier tightly regulates the power bus to a main bus voltage set-point and controls charging and discharging of all batteries to prevent charging of one battery at the expense (discharge) of another battery. There is one master battery discharge controller, with the remaining controllers being slave units. A local bus voltage set-point of each slave unit varies under the control of a slave unit current sharing amplifier which compares its own discharge current to the average discharge current, and an error signal modifies the reference voltage in the local bus control amplifier to allow equal discharge current from all batteries.

Abstract: A method and apparatus for the management of rechargeable series-connected cells (C1, C2, C3) by means of individual measurements, by monitoring each cell during the course of its charging, storage or discharging cycle for measuring the cell properties and for adjusting the properties of inconsistent cells by manipulating the same for mitigating inter-cellular discrepancies.

Abstract: When a control section (39) turns on a switch (31, 33, 35), a capacitor (37) is connected to a secondary battery (B1) in parallel. Accordingly, voltage between both ends of each capacitor (37, 38) reaches voltage between both polarities of each secondary battery (B1, B2). Thereafter, when the control section (39) turns off the switch (31, 33, 35) and turns on a switch (32, 34, 36), each capacitor (37, 38) is connected to the secondary battery (B2, B3) in parallel. The capacitor (37, 38) is charged/discharged to balance voltage between both polarities of the secondary battery (B1 to B3).

Abstract: In a battery pack manager that manages series-connected rechargeable unit cells, a cell equalizer equalizes the cell voltages by individually discharging the unit cells according to deviations from reference voltages. An overcharge/overdischarge detector detects an overcharge and an overdischarge state of each unit cell. An inhibit circuit prevents the cell equalizer from discharging the unit cells when the overcharge/overdischarge detector is activated to reduce the cell voltage variability, which would otherwise occur as a result of interference from the overcharge/overdischarge detector, so that the overcharge/overdischarge states of all unit cells can be determined with precision. Connecting lines of the unit cells are monitored to detect a line-cut.

Abstract: An electronic battery tester for testing a storage battery includes test circuitry configured to provide an output based upon a selected test criteria. Additionally, circuitry is provided to assist in balancing batteries used in a string of multiple batteries.

Abstract: In a chargeable-and-dischargeable power supply system, a plurality of battery cell sections are connected in series with one another, a plurality of cell state detecting sections are installed for the respective battery cell sections and configured to detect a charge state in the respectively corresponding battery cell sections, a power control section is configured to carry out a power supply control for the battery cell sections, a first electrical isolation section is installed in a first signal route from the power control section to one of the cell state detecting sections which is for a highest potential positioned battery cell section, and a second electrical isolation section is installed in a second signal route from one of the cell state detecting sections which is for a lowest potential positioned battery cell section to the power control section.

Abstract: A battery charger includes a master charge manager, and a slave charge manager coupled to the master charge manager. The master charge manager is coupled to a power source and one battery and is configured to charge the one battery with a first continuously decreasing portion of the available current after a voltage across the one battery exceeds a first predetermined maximum voltage threshold. The slave charge manager is coupled to the power source and another battery and is configured such that, while the master charge manager charges the one battery with the continuously decreasing portion of the available current, the slave charge manager charges the other battery with a continuously increasing portion of the available current. The total of the decreasing portion and the increasing portion are substantially equal to the current available from the power source.

Abstract: Battery charge management systems for charging a battery bank including a plurality of batteries connected in series are disclosed that include: a power source having a charging port, the power source capable of providing power to each battery in the battery bank; a multiplexer connected to the battery bank, the multiplexer capable of connecting the charging port to a single battery at a time and capable of switching the connection of the charging port to each battery in the battery bank; and a microcontroller connected to the multiplexer and operatively coupled to each battery in the battery bank, the microcontroller capable of receiving discharge data and charge data for each battery in the battery bank, the microcontroller capable of instructing the multiplexer to switch the connection of the charging port with each battery in dependence upon the discharge data and the charge data for that battery.

Abstract: A method and system for charging multi-cell lithium-based batteries. In some aspects, a battery charger includes a housing, at least one terminal to electrically connect to a battery pack supported by the housing, and a controller operable to provide a charging current to the battery pack through the at least one terminal. The battery pack includes a plurality of lithium-based battery cells, with each battery cell of the plurality of battery cells having an individual state of charge. The controller is operable to control the charging current being supplied to the battery pack at least in part based on the individual state of charge of at least one battery cell.

Abstract: Apparatus for a modular battery management system with interchangeable slave modules connected to each cell and including a master module controlling and managing the battery system. All the modules receive power through a transfer switch that selectively switches between an external source, an auxiliary source, and the battery. The modules are configured to connect to a cell of the battery for charging and monitoring the cell individually. Each module is electrically isolated from the other modules. The modules are autonomous and shut down the battery and disconnect the module when a critical parameter of the cell is reached. When the battery is in service and a cell parameter approaches the critical level, the master controller instructs the corresponding slave module to charge the cell using battery power. The master module initializes the slave modules to uniquely identify the modules.

Abstract: An electronic device, which captures and accumulates varying levels of electrical energy in suitable short-term storage means until the energy is of such a level that it can be efficiently transferred to at least one long-term storage device means, such as electro-chemical batteries. The invention further permits simultaneous transfer to a variety of electro-chemical batteries, which can possess different storage chemistries.

Abstract: The present invention relates to a hybrid battery module, which comprises: a first cell set; a first programmable fuse; a first discharging switch; a first charging switch; a first analog front end circuit; a first thermister; a second cell set; a second programmable fuse; a second discharging switch; a second charging switch; a second analog front end circuit; a second thermister; and a controller; whereby the voltage of the first cell set and the second cell set can reach a balance status when the hybrid battery module is disposed into a jig; When the voltage of the first cell set and the second cell set are balanced, then the battery pack can parallel charging/discharging the first cell set and the second cell set simultaneously. Furthermore, the present invention also provides a method for manufacturing the hybrid battery module and its charging and discharging method.

Abstract: Providing a charge condition adjusting apparatus, which can shorten a time for equalization of each charge in unit cells, a low-voltage CPU selects each smallest unit cell in the each cell block, which has each smallest voltage between the both electrodes, from among plural unit cells structuring the cell blocks. The low-voltage CPU controls ON/OFF of a block-discharging switch to connect the both electrodes of each cell block and each block-discharging resistor for discharging the each cell block until the each voltage between the both electrodes of the selected smallest unit cell reaches the target voltage. Successively, the low-voltage CPU controls ON/OFF of a selecting switches and a cell-discharging switch to connect the both electrodes of each unit cell and each cell-discharging resistor to discharge the each unit cell until the each voltage between the both electrodes of the unit cells reaches the target voltage.

Abstract: In a combined battery pack of a plurality of battery cells, a comparison circuit compares a voltage appearing at a common connection point between two adjacent battery cells with a reference voltage. Based on a result of the comparison, an electric discharging operation of an electric discharging circuit connected between both terminals of each of the battery cells is carried out. The comparison circuit is driven to operate with a power supply voltage appearing between a positive-side terminal of a battery cell provided on a higher-potential side of a common connection point and the negative-side terminal of the battery cell provided on a lower-potential side of the common connection point.

Abstract: A battery structure and a charging device adapted for the battery structure are provided. The battery structure comprises N battery cells, (N?1) movable connectors, and a protection device, wherein N is a positive integer greater than one. The charging device comprises an open circuit device and a power supply. The N battery cells are arranged next to each other, and each battery cell has two junctions. When the battery structure is discharging, each movable connector electrically connects the two adjacent junctions of the every two adjacent battery cells, with all the battery cells cascaded. When the battery structure is charged by the charging device, the open circuit device will enable the movable connector to disconnect the two adjacent junctions of the two adjacent battery cells so that there would be open circuits between every two adjacent battery cells. Then, the 2N charging junctions of the power supply charge the junctions of each battery cell individually.

Abstract: A selector circuit configured to select among a DC power source and a plurality of batteries for an electronic device. The selector circuit includes a first comparator configured to compare a first input signal representative of a voltage level of the DC power source with a first threshold level and provide a first output signal representative of a difference between the first input signal and the first threshold level, and a selector output circuit. The selector output circuit is configured to provide selector output signals that control selection among the DC power source and the plurality of batteries. The selector output circuit providing said selector output signals to select the DC source and deselect the plurality of batteries if the first output signal is representative of the voltage level of said DC power source being greater than the first threshold level.

Abstract: The present invention relates to a microprocessor controlled battery management system that optimizes the total electrical capacity of that battery. It uses localized cell power sources that correct the capacity of the individual connected cells to achieve the maximum capacity of the battery as it acts in a synergistic series connection of cells. The microprocessor retrieves data of battery load current, cell voltage, cell temperature, and battery charger current in timed increments. Through the application of the microprocessor's algorithms, after an initial cell profiling of individual cell capacities has been performed, individual cell DC/DC converters are enabled to correct the condition of the individual cells. In this manner the battery capacity is not affected by the capacity of the weakest cell.

Abstract: A battery ECU controls a main battery composed of a plurality of battery cells connected to each other in series. The battery cells are grouped into cell blocks each having a cell-block monitor circuit. A control unit controls charging/discharging processes on the basis of signals output by the cell-block monitor circuit. A signal output by a cell-block monitor circuit on a high-voltage side turns on a transistor for propagating a signal to a cell-block monitor circuit on a middle-voltage side. In the cell-block monitor circuit on a middle-voltage side, the propagated signal turns on another transistor for further propagating a signal to a cell-block monitor circuit on a low-voltage side. In the cell-block monitor circuit on a low-voltage side, the propagated signal turns on a further transistor for outputting a signal to a control unit.

Abstract: A battery charging system uses power line carrier communications, for communicating battery state information associated with charging batteries, between a battery charger and a battery management system (BMS) located on the battery or battery pack. The power line carrier includes transmitters and receivers transmitting and receiving battery state information, such as current, voltage and temperature, as digital signals on existing cable conductors located between the battery/battery pack and the battery charger. The battery management system (BMS), which is physically located on the battery pack, receives the information from the power line carrier, in order to measure a variety of parameters relating to charging the battery, which may be a motor vehicle battery or a battery for operating machinery, such as fork lifts, bulldozers and other earth moving and product transportation vehicles.

Abstract: A battery pack control module for balancing a plurality of lithium secondary cells or groups of lithium secondary cells connected in series and method of use.

Abstract: The present invention relates to a hybrid battery module with voltage balancing unit, which comprises: a first cell set; a first programmable fuse; a first discharging switch; a first charging switch; a first analog front end circuit; a first thermister; a second cell set; a second programmable fuse; a second discharging switch; a second charging switch; a second analog front end circuit; a second thermister; a controller; and a voltage balancing unit; whereby the voltage of the first cell set and the second cell set can reach a balance state by the voltage balancing unit; and during the charging process, the first charging switch and the second charging switch will simultaneously be turned off when it meets a safety event; and during the discharging process, the first programmable fuse and the second programmable fuse will simultaneously be burned off when it meets a critical safety event so as to prevent cell from being burned; Furthermore, the present invention also provides a method for charging and disch

Abstract: A battery charging apparatus having a plurality of charging units connected in series. A charging unit has a series switch connected in series with a rechargeable battery, and a parallel switch connected in parallel with the series connected rechargeable battery and series switch. A charging control section controls charging of a rechargeable battery by switching the series switch and parallel switch ON and OFF. The charging control section changes the duty factor for switching series switches and parallel switches ON and OFF, switches a charging unit between a charging mode and a cut-off mode at a prescribed duty factor, and controls rechargeable battery charging currents to charge a plurality of batteries.

Abstract: A systematic method and system for testing the charging and starting systems of a vehicle, which requires each individual test to pass before proceeding is provided. In addition, the invention incorporates an improved alternator test that determines whether the alternator belt is slipping using data read using a vehicle data port. Further, the invention provides a battery bank test that correlates the voltage before and after a load is applied to the battery bank to the batteries' conditions. When testing the starter, the oil temperature is read via the vehicle data port, allowing for a determination of whether the current draw is abnormally high.

Abstract: A method and an arrangement for charging capacitors of a direct-voltage intermediate circuit of a frequency converter. The arrangement comprises a charging circuit (CCA) comprising a first diode (D1) and a second diode (D2) connected in series with the first diode (D1) and a current-limiting component (AA) connected in parallel with the series connection of the diodes (D1, D2), whereby said capacitors may be charged through a main switch (K1b, K2b, . . . , Knb) of the capacitor, the first diode (D1) and the current-limiting component (AA).

Abstract: A charge redistribution circuit (2) for an energy storage unit (1) with several storage elements (4) which are connected in series comprises several charge redistribution control units (5) for monitoring and redistributing the load, each of which is assigned an energy storage sub-group (3) of storage elements (4). The charge redistribution control units (5) take the energy used for their own supply in each case from the sub-group (3) assigned to them, and are thus supplied with a voltage which is higher than the voltage of the individual storage element (4) and lower than the voltage of the energy storage unit (1). The charge redistribution circuit (2) is established in such a manner that a monitoring and—when necessary a charge redistribution is achieved for each individual storage element (4).

Abstract: A serial battery charger including a number of serially connected battery charging sections in which the battery charging section is characterized by a first and second parallelly connected branches. The first branch includes terminals for connecting to the battery to be charged and a current blocking device and the second branch includes a by-passing switch which shunts across the terminals of the first branch when activated. The blocking device in the first branch prevents adverse reverse current flow from the battery to the charger when there is no power supply and also functions as a current block to prevent adverse flow of current from the battery into the shunting by-passing switch when the power supply to the charging section is in operation. This invention provides a simple solution to fulfil the conflicting requirements of an intelligent serial battery charger.