Energy management of blood pump controllers

Systems and related methods for supplying power to a medical device employ self-charging serially-connectable portable batteries. A system includes a base module and external battery modules. The base module is operatively coupled with the medical device and includes a base module input connector. Each of the external battery modules includes one or more battery cells, an output connector, an input connector, and a controller. The output connector is configured to output electrical power from the external battery module. The input connector is configured to receive electrical power from another of the plurality of external battery modules. The controller is operatively coupled with the one or more battery cells, the output connector, and the input connector. The controller is configured to control distribution of electrical power received via the input connector to charge the one or more battery cells and/or to be output via the output connector.

BACKGROUND

Ventricular assist devices, known as VADs, often include an implantable blood pump and are used for both short-term (i.e., days, months) and long-term applications (i.e., years or a lifetime) when a patient's heart is incapable of providing adequate circulation, commonly referred to as heart failure or congestive heart failure. According to the American Heart Association, more than five million Americans are living with heart failure, with about 670,000 new cases diagnosed every year. People with heart failure often have shortness of breath and fatigue. Years of living with blocked arteries and/or high blood pressure can leave a heart too weak to pump enough blood to the body. As symptoms worsen, advanced heart failure develops.

A patient suffering from heart failure may use a VAD while awaiting a heart transplant or as a long term destination therapy. A patient may also use a VAD while recovering from heart surgery. Thus, a VAD can supplement a weak heart (i.e., partial support) or can effectively replace the natural heart's function.

All ventricular assist systems (VAS) require several watts of power to provide cardiac support. Thus, patients using a ventricular assist system and their supporting caregivers or providers (hereinafter “users”) can use non-implanted replenishable and/or replaceable power supplies to maintain mobility. Such non-implanted power supplies typically include battery packs and AC wall power converters. The power from these sources may be conveyed to the VAD via a VAS controller using cables.

Existing products, however, use several power cables or a single large enclosure containing both a power source and a VAS controller. The use of several power cables requires users to manage multiple cables. A single large enclosure is cumbersome to wear on the body owing to the relatively large size of batteries and other energy storage devices realizable using present-day technology.

Additionally, while using existing portable, wearable energy sources, users have limited options for expanding the amount of wearable energy storage with present commercial products. Instead, many existing products employ a single energy storage configuration, typically a battery of fixed capacity. Some existing devices allow for optional larger capacity battery packs to be used in lieu of a standard battery pack.

Finally, for all existing products, depleted energy sources must be disconnected before new energy sources can be connected. If a failure occurs with an energy storage system, rendering it inoperable, a user must disconnect the failed energy source before connecting another one. During this time, the medical device may not have been functional or functioning at a reduced capacity. Accordingly, improved portable energy supply systems and related methods that do not have at least some of the above-discussed disadvantages would provide benefits to users of wearable or implanted medical devices.

BRIEF SUMMARY

Embodiments of the invention described herein include energy supply systems for wearable or implantable medical devices, and related methods, that provide increase flexibility with regard to carried battery capacity and recharging of the carried battery capacity without having to disconnect batteries for recharging. In many embodiments, each of a plurality of external battery modules includes an input connector to receive electrical power and an output connector from which to output electrical power. The wearable or implantable medical device or a controller for the medical device can include an input connector that is connectable with the output connector of a first of the external battery modules. In many embodiments, the output connector of a second of the external battery modules is connectable with the input connector of the first of the external battery modules. The input connector of the second of the external battery modules can be connected with the output connector of a third of the external battery modules, and so on in a similar fashion so as to serially connect any desired suitable number of the external battery modules. In some embodiments, the number of the external battery modules that can be serially connected may be limited by software algorithms in the wearable or implantable medical device or the control unit of the medical device. At least where the wearable or implantable medical device or the controller of the medical device includes internal energy storage, the minimum number of connected external battery modules can be zero. In many embodiments, each of the external battery modules includes an integrated charger configured to recharge battery cell(s) of the external battery module. Each of the external battery modules can include a controller configured to monitor and communicate state of charge of the external battery module and/or to control recharging of the external battery module. Each of the external battery modules can communicate with the wearable or implantable medical device or a controller of the medical device so as to receive parameters used to control charging and discharging of the external battery module. Accordingly, users can add and remove external carried battery capacity in a flexible manner and the battery modules can be recharged without having to disconnect the battery modules.

Thus, in one aspect, a system is provided for supplying power to a medical device worn by a user or implanted in the user. The system includes a base module and a plurality of external battery modules. The base module is configured to be operatively coupled with the medical device to supply electrical power to the medical device. The base module includes a base module input connector. Each of the external battery modules includes one or more battery cells, an output connector, an input connector, and a controller. The one or more battery cells are configured to store electrical power. The output connector is configured to output electrical power from the external battery module. The input connector is configured to receive electrical power from another of the plurality of external battery modules. The controller is configured to control distribution of electrical power received via the input connector to charge the one or more battery cells and/or to be output via the output connector.

In many embodiments of the system, the base module includes one or more base module battery cells and base module controller. The base module battery cells are configured to store electrical power. The base module controller can be configured to control distribution of electrical power received via the base module input connector to charge the one or more base module battery cells and/or to be output to supply electrical power to the medical device.

In many embodiments, the system is configured to detect the configuration of connected external battery modules and control charging of the medical device, a controller of the medical device, and/or the connected external battery modules in accordance with the detected configuration of connected external battery modules. For example, each of: (1) the base module input connector, (2) the output connector of each of the plurality of external battery modules, and (3) the input connector of each of the plurality of external battery modules can include a data connection for transferring a connection signal to the base module controller and/or to the controller of another of the plurality of external battery modules indicating connection of one or more of the plurality of external battery modules. The base module controller can be configured to control the controller of each of the plurality of external battery modules via the data connection to control the distribution of electrical power received via the input connector of the external battery module to charge the one or more battery cells of the external battery module and/or to be output via the output connector of the external battery module. In many embodiments of the system, the plurality of external battery modules can be connected to the base module in a connection sequence order. The base module controller and the controller of each of the plurality of external battery modules can be configured to implement a charging sequence in which the base module is charged first and at least one of the plurality of external battery modules is charged in the connection sequence order. In many embodiments of the system, the data connection includes a fiber optic connector for connecting fiber optic data lines. A fiber optic data connection eliminates many electromagnetic interference considerations present in existing system.

In many embodiments of the system, the state of charge of the system is monitored and communicated. For example, the base module controller can be configured to monitor a base module charge level of the one or more base module battery cells. The base module controller can be configured to indicate the base module charge level to the user or a person other than the user. The base module can include a wireless transmitter to wirelessly transmit the base module charge level to an electronic device, such as a cellular/smart phone, tablet, computer, watch, etc., for communication to the user or a person other than the user (e.g., physician, family member, etc.). The controller of each of the plurality of external battery modules can be configured to monitor a charge level of the one or more battery cells of the external battery module and communicate the charge level to the base module controller. The base module controller can be configured to communicate the charge level of at least one of the plurality of external battery modules to the user or a person other than the user. The base module can include a wireless transmitter to wirelessly transmit the base module charge level and the charge level of each of at least one of the plurality of external battery modules to an electronic device for communication to the user or a person other than the user. Each of the plurality of external battery modules can include one or more indicators controlled by the respective controller to indicate the charge level of the one or more battery cells of the external battery module. In many embodiments of the system, the one or more indicators include visual indicators, such as one or more light emitting diodes (LEDs), audio indicators, or haptic indicators.

In many embodiments of the system, the input and the output connectors are configured to prevent orientation based misconnection. For example, each of the input connector and the output connector of each of the plurality of external battery modules and the base module input connector can include two ground line connectors and two power line connectors arranged in a linear array symmetrically on opposite sides of the data connection to accommodate connection of the input and output connectors in opposite orientations.

Connection of an external battery module can be detected via a voltage potential output from the external battery module. For example, each of the base module controller and the controller of each of the plurality of external battery modules can be configured to detect the connection of one or more of the plurality of external battery modules via a voltage potential applied to the base module input connector or the input connector of the external battery module, respectively.

In many embodiments, the system includes one or more electronic switches to control charging of the base module and/or the external battery modules. For example, the base module controller can include one or more electronic switches connected between the base module input connector and the one or more base module battery cells to control charging of the one or more base module battery cells via electrical power received via the base module input connector. The controller of each of the plurality of external battery modules can include one or more electronic switches connected between the input connector and the one or more battery cells of the external battery module to control charging of the one or more battery cells via electrical power received via the input connector.

In many embodiments, the system is configured to control charging rate(s) for patient safety, such as to prevent charging induced temperature rises above a threshold level suitable for a patient. For example, the base module can include a base module temperature sensor configured to output a base module temperature signal to the base module controller indicative of a temperature of the base module. The base module controller can be configured to control charging of the one or more base module battery cells based on the base module temperature signal feedback. Each of the plurality of external battery modules can include a temperature sensor configured to output a temperature signal to the controller of the external battery module indicative of a temperature of the external battery module. The controller of each of the plurality of battery modules can be configured to control charging of the one or more battery cells of the external battery module based on the temperature signal feedback. Charging can also be limited based on the amount of power available from the external power source(s).

In another aspect, a method is provided for supplying power to a medical device worn by a user or implanted in the user. The method includes supplying electrical power to the medical device via a base module that includes a base module input connector. Electrical power is supplied to the base module from a first external battery module via the base module input connector. The first external battery module includes one or more first battery cells, a first output connector, a first controller, and a first input connector. The one or more first battery cells are configured to store electrical power. The first output connector is operatively connected with the base module input connector to transfer electrical power to the base module. Electrical power is supplied to the first external battery module from a second external battery module via the first input connector. The second external battery module includes one or more second battery cells, a second output connector, a second controller, and a second input connector. The one or more second battery cells are configured to store electrical power. The second output connector is operatively connected with the first input connector to transfer electrical power to the first external battery module. Distribution of electrical power received by the first input connector from the second output connector is controlled, via the first controller, to charge the one or more first battery cells and/or to be output from the first output connector to the base module.

In many embodiments of the method, the base module includes one or more base module battery cells configured to store power and a base module controller. Distribution of electrical power received by the base module input connector from the first output connector can be controlled, via the base module controller, to charge the one or more base module battery cells and/or to be output to the medical device.

In many embodiments of the method, one or more signals are transferred to communicate connection of one or more of the external battery modules. For example, the method can include transferring a first signal from the second external battery module to the first external battery module indicating connection of the second external battery module to the first external battery module. The method can include transferring a second signal from the first external battery module to the base module indicating connection of the first external battery module to the base module and connection of the second external battery module to the first external battery module. The method can include controlling, by the base module controller, the distribution of electrical power received via the input connector of at least one of the plurality of external battery modules to charge the one or more battery cells of the respective external battery module and/or to be output via the output connector of the respective external battery module. The method can include implementing a charging sequence in which the base module is charged first and the first external battery module is charged after the base module is charged.

In many embodiments of the method, charging is controlled for patient safety, such as to prevent charging induced temperature rises above a threshold level suitable for a patient. For example, the method can include generating a base module temperature signal indicative of a temperature of the base module. Charging of the one or more base module battery cells can be controlled, via the base module controller, based on the base module temperature signal feedback to prevent a charging induced exceedance of a predetermined base module temperature. The method can include generating a first external battery module temperature signal indicative of a temperature of the first external battery module. Charging of the one or more first battery cells can be controlled, via the first controller, based on the first external battery temperature signal feedback to prevent a charging induced exceedance of a predetermined first external battery module temperature.

In many embodiments of the method, charge level of the base module and/or the external battery modules are monitored and communicated via the base module controller. For example, the method can include monitoring a base module charge level of the one or more base module battery cells. The base module charge level can be communicated to the user or a person other than the user. The base module charge level can be communicated to the user or a person other than the user by wirelessly transmitting the base module charge level to an electronic device, such as a cellular phone, for communication to the user or the person other than the user. The method can include monitoring, via the first controller, a first charge level of the one or more first battery cells. The first charge level can be communicated to the base module controller. The method can include monitoring, via the second controller, a second charge level of the one or more second battery cells. The second charge level can be communicated to the base module controller. The first and second charge levels can be communicated, via the base module controller, to the user or the person other than the user. Communicating the first and second charge levels to the user or the person other than the user can include wireless transmitting the first and second charge levels to an electronic device for communication to the user or the person other than the user.

In many embodiments of the method, the charge level of each of the external battery modules is monitored and communicated via the respective external battery module. For example, the method can include monitoring, via the first controller, a charge level of the one or more first battery cells. The charge level of the one or more first battery cells can be indicated via an indicator included in the first external battery module. The method can include monitoring, via the second controller, a charge level of the one or more second battery cells. The charge level of the one or more second battery cells can be indicated via an indicator included in the second external battery module.

The method can include supplying electrical power via one or more additional external battery modules. For example, the method can include supplying electrical power to the second external battery module from a third external battery module via the second input connector. The third external battery module can include one or more third battery cells, a third output connector, a third controller, and a third input connector. The one or more third battery cells are configured to store electrical power. The third output connector can be operatively connected with the second input connector to transfer electrical power to the second external battery module. The method can include controlling, via the second controller, distribution of electrical power received by the second input connector from the third output connector to charge the one or more second battery cells and/or to be output from the second output connector to the first external battery module.

For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings.

DETAILED DESCRIPTION

Referring now to the drawings, in which like reference numerals represent like parts throughout the several views,FIG. 1shows a system10, in accordance with many embodiments, for supplying power to a medical device worn by a user or implanted in the user. The system10includes a wearable or implantable medical device12, a base module14, a plurality of external battery modules16, and a non-worn energy source18. The external battery modules16are configured for selective serial connection to enable the connection of any suitable number of the external battery modules16to the base module14to vary the total battery capacity worn by the user. The non-worn energy source18can be any suitable energy source, for example, a wall power unit configured to convert utility power (e.g., 110 volt AC power) to direct current having a voltage level compatible with the external battery modules16and the base module14. The non-worn energy source18can be selectively and intermittently connected to the most distal external battery module16to supply electrical power used to recharge the external battery modules16, recharge the base module14, and/or be output to the medical device12via a connection line20.

The base module14is configured to supply operating electrical power to the medical device12via the connection line20. The base module14includes one or more base module battery cells22, a base module controller24, and a base module input connector26. The base module controller24is configured to supply power to the medical device12output by the one or more base module battery cells22and/or received via the base module input connector26. In many embodiments, the base module controller24includes an integrated charger for recharging the one or more base module battery cells22via electrical power received via the base module input connector26. In many embodiments, the base module controller24is configured to detect when at least one external battery module16or the non-worn energy source18is connected to the base module input connector26. For example, the base module input connector26can include a data connection to receive a signal when at least one external battery module16or the non-worn energy source18is connected to the base module input connector26. Alternatively, the base module controller24can be configured to detect when a suitable voltage potential is applied to the base module input connector26indicative of at least one external battery module16or the non-worn energy source18being connected to the base module input connector26. When the connection of at least one of the external battery modules16or the non-worn energy source18to the base module input connector26is detected, the base module controller24can supply electrical power to the medical device solely via electrical power received via the base module input connector26and can simultaneously recharge the one or more base module battery cells22via electrical power received via the base module input connector26if the one or more base module battery cells22are not already fully charged. When the base module controller24does not detect the connection of any power source to the base module input connector24, the base module controller24is configured to supply electrical power to the medical device12via electrical power from the one or more base module battery cells22.

In the illustrated embodiment, each of the external battery modules16includes an output cable28, an output connector30, one or more external battery cells32, an external battery controller34, and an input connector36. The external battery controller34is configured to supply power via the output connector30output by the one or more external battery cells32and/or received via the input connector36. In many embodiments, the external battery controller34includes an integrated charger for recharging the one or more external battery cells32via electrical power received via the input connector36. In many embodiments, the external battery controller34is configured to detect when at least one external battery module16or the non-worn energy source18is connected to the input connector36. For example, the input connector36can include a data connection to receive a signal when at least one external battery module16or the non-worn energy source18is connected to the input connector26. Alternatively, the external battery controller34can be configured to detect when a suitable voltage potential is applied to the input connector36indicative of at least one external battery module16or the non-worn energy source18being connected to the input connector36. When the connection of at least one of the external battery modules16or the non-worn energy source18to the input connector36is detected, the external battery controller34can supply electrical power via the output connector30via electrical power received via the input connector36and can simultaneously recharge the one or more external battery cells32via electrical power received via the input connector36if the one or more external battery cells32are not already fully charged. When the external battery controller34does not detect the connection of any power source to the input connector34, the external battery controller34is configured to output electrical power via the output connector30via electrical power from the one or more external battery cells32.

Any suitable serial combination of the external battery modules16can be used. For example, zero, one, two, three, four, or greater of the external battery modules16can be serially connected to the base module14to supply power to the base module14for supply to the medical device12. Additionally, in many embodiments, the non-worn power source18can be connected directly to the base module14to supply electrical power that can be used by the base module14to supply electrical power to the medical device12and to recharge the one or more base module battery cells22if the one or more base module battery cells22are not already fully charged. While the external battery modules16are configured to be serially connected physically, the external battery modules16are configured so as to be connected in parallel electrically so as to not vary the voltage supplied to the base module14.

FIG. 2shows a connector arrangement38that can be used in the base module input connector26, the output connector30, and the input connector36. The connector arrangement38includes two first power connectors40, two second power connectors42, and a data connector44. The first and the second connectors40,42are used to transfer power. For example, each of the first connectors40can be electrically connected to a power lead and each of the second connectors42can be electrically connected to a ground lead, and vice-versa. The data connector44is used to connect data lines to transmit data between the base module controller24and the one or more external battery controllers34and/or between any of the one or more external battery controllers34. In optional embodiments, the data connector44can be omitted, for example, in embodiments where connection of an external battery module16to either the base module input connector26or to the input connector36of another external battery module16is detected via detection of voltage potential applied via the first and second connectors40,42. The symmetrical arrangement of the connectors40,42,44accommodates connection of the connector arrangement38in opposite orientations, thereby accommodating proper connection in either of the two possible orientations between connectors.

The system10can be employed in any suitable medical system (e.g., a worn or at least partially implanted medical system). For example,FIG. 3illustrates a mechanical circulatory support system100that employs the system10. The mechanical circulatory support system100includes an implantable blood pump assembly (i.e., medical device12) implanted in a patient102, a ventricular cuff104, an outflow cannula106, and an external system controller (base module14). In the illustrated configuration, two of the external battery modules16are shown serially connected to the external system controller14. As described herein, however, any suitable number of the external battery modules16and/or the non-worn energy source18(e.g., that can be powered via being plugged into an outlet107) can be coupled with the external system controller14to supply power to the external system controller14for supply to the blood pump assembly12. The blood pump assembly12can include a VAD that is attached to an apex of the left ventricle, as illustrated, or the right ventricle, or both ventricles of the patient's heart108. The VAD can include a centrifugal pump (as shown) that is capable of pumping the entire output delivered to the left ventricle from the pulmonary circulation (i.e., up to 10 liters per minute). Related blood pumps applicable to the present invention are described in greater detail below and in U.S. Pat. Nos. 5,695,471, 6,071,093, 6,116,862, 6,186,665, 6,234,772, 6,264,635, 6,688,861, 7,699,586, 7,976,271, 7,997,854, 8,007,254, 8,152,493, 8,652,024, and 8,668,473 and U.S. Patent Publication Nos. 2007/0078293, 2008/0021394, 2009/0203957, 2012/0046514, 2012/0095281, 2013/0096364, 2013/0170970, 2013/0121821, and 2013/0225909, all of which are incorporated herein by reference for all purposes in their entirety. The blood pump assembly12can be attached to the heart108via the ventricular cuff104, which can be sewn to the heart108and coupled to the blood pump12. The other end of the blood pump12connects to the ascending aorta via the outflow cannula106so that the VAD effectively diverts blood from the weakened ventricle and propels it to the aorta for circulation through the rest of the patient's vascular system.

FIG. 3illustrates the mechanical circulatory support system100during battery powered operation by the system10via the two connected external battery modules16. A driveline (connection line20) that exits through the patient's abdomen110connects the implanted blood pump assembly12to the external system controller14, which monitors system100operation. Related controller systems applicable to the present invention are described in greater detail below and in U.S. Pat. Nos. 5,888,242, 6,991,595, 8,323,174, 8,449,444, 8,506,471, 8,597,350, and 8,657,733, EP 1812094, and U.S. Patent Publication Nos. 2005/0071001 and 2013/0314047, all of which are incorporated herein by reference for all purposes in their entirety. As described herein the power system10used to power the system100can include any suitable combination (zero, one, two, three, four, or more) of the external battery modules16and/or the non-worn power source18.

FIG. 4is a simplified schematic diagram illustrating components of an embodiment of the system10. In the illustrated configuration, the base module14is operatively coupled with the medical device12and a combination of two external battery modules16and the non-worn power source18are connected to the base module14to supply power to the base module14. Description of aspects of the system10already described above are not repeated here. Additional aspects of the base module14and the external battery modules16are described below.

In the embodiment shown inFIG. 4, the system10is configured to monitor and display the charge level of the one or more base module battery cells22and/or the one or more external battery cells32in each of the external battery modules16. In the illustrated embodiment, the base module14includes a display112and an input device114and each of the external battery modules16include one or more indicator lights (e.g., LED(s)116). The base module controller24can be configured to monitor the charge level of the one or more base module battery cells22and output the charge level of the one or more base module battery cells22via the display112. Each of the battery controllers34can be configured to monitor the charge level of the one or more external battery cells32and transmit the charge level to the base module14and/or output an indication of the charge level via operation of the LED(s)116. For example, the external battery module16having the lowest state of charge of the one or more external battery cells32(typically the most distal of the serially connected chain of external battery modules16) can operate the LED(s)116to indicate the state of charge (e.g., flashing either red or green based on the charge level). One or more indicators can be displayed on the display112suitable to communicate the charge state of the one or more base module battery cells22an/or the charge state of the one or more external battery cells32in each of the external battery modules16. For example, a bell shaped indicator can be displayed to output a lower priority notification regarding power level of the batteries. One or more battery shaped indicators can be used to display the charge level of the one or more base module battery cells22and/or the state of charge of any suitable number of the connected external battery modules16. For example, the display112can be configured to display the charge level of the one or more base module battery cells22via a first battery shaped indicator and display the lowest charge level of the connected external battery modules16via a second battery shaped indicator. In the illustrated embodiment, the base module14includes a wireless communication unit119configured to wirelessly transmit the charge level of the base module14and/or the charge level of any suitable combination of the external battery modules16to an electronic device, such as a cellular/smart phone, tablet, computer, watch, etc., for communication to the user or a person other than the user (e.g., physician, family member, etc.).

Additionally, in the embodiment shown inFIG. 4, the system10is configured to control charging to avoid charging induced excessive temperature of the base module14and the external battery modules16. The base module14includes a temperature sensor118that outputs a temperature signal to the base module controller24indicative of a temperature of the base module14. The base module controller24is configured to control the rate at which the one or more base module battery cells22are charged based on the temperature signal from the temperature sensor118to prevent having the temperature sensed by the temperature sensor118exceed a suitable limit with regard to patient contact with the base module14. Similarly, each of the external battery modules16includes a temperature sensor120that outputs a temperature signal to the external battery module controller34indicative of a temperature of the external battery module16. The external battery module controller34is configured to control the rate at which the one or more external battery cells32are charged based on the temperature signal from the temperature sensor120to prevent having the temperature sensed by the temperature sensor120exceed a suitable limit with regard to patient contact with the external battery module16.

While the external battery modules16are serially-connected physically, the external battery modules16are electrically coupled in parallel. In many embodiments, the base module controller24and the external battery module controllers34include electronically controlled switches (e.g., metal-oxide-semiconductor field-effect transistors (MOSFETs)) that are used to control distribution of electrical power received via the respective input connector to be output via the respective output connector and used to charge the respective one or more battery cells if not already fully charged.

FIG. 5is a simplified block diagram of acts of a method200, in accordance with many embodiments, for supplying power to a medical device worn by a user or implanted in the user. Any suitable external battery system can be used to practice the method200, including the systems described herein. The method200can include any suitable combination of a set of subset of the following: (1) outputting electrical power from a first external battery module to a medical device or a medical device controller of a medical device (act202); (2) outputting electrical power from a second external battery module to the first external battery module (act204); (3) outputting electrical power from an energy source to the second external battery module (act206); (4) Sequentially charging the medical device or the medical device controller first, the first external battery module second, and then the second external battery module third (act208); (5) monitoring state of charge of the medical device or the medical device controller, the first external battery module, and/or the second external battery module (act210); and (6) communicating the state of charge of the medical device or the medical device controller, the first external battery module, and/or the second external battery module (act212).

FIG. 6is a simplified schematic diagram of a charging sequence214and a discharging sequence216that can be employed in the medical device system10, in accordance with many embodiments. In the illustrated configuration in which a charger18is connected, the power supplied by the charger18can be used to charge the base module14first. When the base module14is fully charged, the power supplied by the charger18can be used to charge the first external battery module16. When the first external battery module16is fully charged, the power supplied by the charger18can be used to charge the second external battery module16. And finally, when the second external battery module is fully charged, the power supplied by the charger can be used to charge the third external battery module16. When the charger18is disconnected, the medical device12can be run first via power supplied by the third external battery module16, thereby discharging the third external battery module16first. When the third external battery module16is effectively discharged, the medical device can be run second via power supplied by the second battery module16, thereby discharging the second external battery module16second. When the second external battery module16is effectively discharged, the medical device can be run third via power supplied by the first battery module16, thereby discharging the first external battery module16third. When the first external battery module16is effectively discharged, the medical device can be run last via power supplied by the base module14, thereby discharging the base module14last.

A combination of the charging sequence214and the discharging sequence216can be used at the same time when the charger18is not connected. For example, power supplied by the third external battery module16, in addition to being used to power the medical device12, can first be used to charge the base module14when the base module14is not already fully charged, and can then be used to charge the first external battery module16when the first external battery module16is not already fully charged, and can then be used to charge the second external battery module16when the second external battery module16is not already fully charged. A similar combination of the charging sequence214and the discharging sequence216can be used when only the first and second external battery modules16are connected to the base module14and when only the first external battery module16is connected to the base module14.

The utility of the systems and methods disclosed herein can be understood through example embodiments. Consider a VAS controller with only two daisy-chained external battery modules connected. In one method of operation, the most distal external battery module discharges first so that it can be removed when depleted without disconnecting the other external battery module from the VAS controller. Once the most distal external battery module is disconnected, the user is then carrying less weight and bulk. In another method of operation, both of the external battery modules discharge evenly. In some embodiments, a preferred method of discharge behavior can be selected and the selection stored as a parameter in the VAS controller and passed to the connected battery modules. In some embodiments, a preferred method of charge behavior can be selected and the selection stored as a parameter in the VAS controller and passed to the connected battery modules.

In addition to the approaches described above, any suitable method can be used for charging the battery modules. For example, one method is for the external battery modules to disable recharging unless an AC power source is connected at the distal end of the daisy-chained battery modules. Another method is for the distal most battery module or modules to recharge the innermost battery module in addition to providing power to the VAS. A combination of these first two methods is to sequentially charge the innermost battery module when AC power is present or allow some set of the battery modules in the daisy-chain to charge simultaneously. As described herein, charging rate can be limited to avoid temperature exceedance(s) with respect to regulatory requirements for the surface temperature of devices in proximity to humans. Overall charging levels may also be limited by the size of the power cables used. Charging rate can also be controlled to prevent temperature exceedance(s) via logic embodied within each battery that knows a priori how much heat is generated for a given charge current at a given state of charge. The logic can further modulate the charge current based on temperature sensors placed near the surface of the external battery module. The logic can communicate the charge current level to the VAS controller. The VAS controller, knowing the charge level commanded by all daisy-chained battery packs, can scale or otherwise change individual charge currents based on system level considerations or user preferences.

To further illustrate, consider three external battery modules daisy-chained to a VAS controller. Based on a user preference to keep the innermost battery module fully charged at all times, the VAS controller can send a message to the innermost battery module to begin charging. The VAS controller can also send messages to the outer battery modules to not charge and for the outermost battery module to preferentially discharge first. The outermost battery module then discharges fully. When the outermost battery module is depleted of energy, the penultimate pack begins discharging—providing power to the medical device and, if still necessary, to continue charging the innermost battery module. During this time, if the temperature sensor(s) inside the innermost battery module measure a surface temperature nearing its maximum allowable limit, the innermost battery module can reduce the charge current per a local control feedback algorithm and communicates this condition to the VAS controller.

Other variations are within the spirit of the present invention. For example, the medical device12and the base module14can be combined in a single unit such as, for example, in the case of a wearable medical device. Thus, while the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims.