the following detailed description of the present subject matter refers to subject matter in the accompanying drawings which show , by way of illustration , specific aspects and embodiments in which the present subject matter may be practiced . these embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter . references to “ an ”, “ one ”, or “ various ” embodiments in this disclosure are not necessarily to the same embodiment , and such references contemplate more than one embodiment . the following detailed description is demonstrative and not to be taken in a limiting sense . the scope of the present subject matter is defined by the appended claims , along with the full scope of legal equivalents to which such claims are entitled . certain implantable devices have been developed to operate in remote portions of a patient . these remote devices include , for example , remote sensors , neurostimulation devices , and other devices . depending on the implant location , remote devices must be small enough to fit into various confined areas of the human body . the requirements for such devices are unique compared to other applications because their size must be small enough to be noninvasive . therefore , the size of these remote devices is typically considerably smaller than common devices , like cardiac rhythm management devices . the limited size of remote devices correspondingly limits the size of the components of the device , including its power source . while the power source is not as large , the power demands of these remote devices must still be satisfied . large batteries , with volumes on the order of 1 cubic centimeters or greater , are commonly used for devices such as cardiac pacemakers and defibrillators . remote devices benefit from batteries which are a fraction of that size . battery sizes smaller than 1 cubic centimeter are contemplated by the present subject matter . the present subject matter extends to thin film batteries . various thin film batteries are formed using vapor deposition of electrode and electrolyte materials onto a semiconductor substrate ( such as silicon ). however , achieving battery sizes small enough to meet the requirements of remote devices using thin film technology is problematic . either very thick layers of deposition are required , or a number of thin film batteries must be stacked and connected in parallel . in either case , rendering the thin film battery or batteries into a cylindrical shape , which is often a requirement of remote device power sources , can be difficult . an improved power source for remote sensing and neurostimulation is needed . this disclosure provides an efficient electrochemical power source for remote implantable medical devices . battery chemistry and technology from large battery applications are adapted to appropriately size power sources for remote implantable medical devices , while ensuring that power and capacity demands of the devices are satisfied . fig1 illustrates a block diagram of an electrochemical power source for use in a remote implantable medical device , according to various embodiments . the electrochemical power source 100 includes a housing 102 geometrically defined to reside within a remote implantable medical device . the power source 100 includes at least one anode 103 , at least one cathode 107 , and an electrolyte 105 within the housing . in various embodiments , the electrochemical power source has a displacement volume of below 0 . 024 cubic centimeters and is adapted to provide electrical current used to operate the device . according to some embodiments , the remote implantable medical device includes a remote implantable sensor . the remote implantable medical device includes a remote neurostimulation device , according to some embodiments . the electrochemical power source is rechargeable in some embodiments . some examples of methodologies for device battery layouts are provided in u . s . patent application ser . no . 11 / 264 , 966 , filed on nov . 2 , 2005 , entitled “ system and method for sealing battery separator ”, which is commonly assigned and herein incorporated by reference in its entirety . according to various embodiments , the power source has a cylindrical shape . non - cylindrical shapes ( or form factors ) additionally are covered by the present subject matter . in some embodiments , the remote implantable medical device sized for placement in a blood vessel . in some of these embodiments , measurements are taken so that flow at the implant site can be modeled . some embodiments use statistical models of the human body to model flow at the implant site . in various embodiments , the power source is sized to enable an implantable device which is shaped to provide the following benefits : reduced hydrodynamic drag , reduced turbulence , reduced stagnation and / or reduced fluid sheer stress . in various embodiments , the power source is small to enable such benefits . in some embodiments , the power source is shaped to conform to an interior of a device shaped to provide such benefits . various embodiments of the present subject matter include implantable medical devices . in various embodiments , implantable sensors are discussed . implantable sensors , in various embodiments , are self - powered measurement devices . in some embodiments , these devices provide a wireless signal to one or more receivers . receivers may be located in vivo or ex vivo . a transceiver relationship is additionally possible , in various embodiments . because of their implanted nature , implantable sensors should be as compact as possible . device profile should be optimized for a minimally invasive implantation . as some embodiments are intended for endovascular use , several design parameters are important . for example , it is important to provide an implantable device which reduces hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation . an improper design in light of these phenomena can lead to the creation of an embolus , and can lead to occlusion of the vessel caused , in part , by the implanted device . the present subject matter provides an implantable medical device , in various embodiments , which features an improved profile for implanted use . in some embodiments , the profile provides improved performance for endovascular use . example shapes are found in u . s . provisional application “ method and apparatus for improved battery profile ,” ser . no . 60 / 750 , 517 , filed dec . 15 , 2005 , which is commonly assigned and is incorporated herein by reference in its entirety . according to various embodiments , an outer surface of the housing is coated with a biocompatible coating . some of these embodiments include drug eluting coatings . some of these coatings reduce various unwanted effects , such as stenosis . additionally , some eluting coatings deliver chemical therapy . examples of biocompatible coatings are provided in u . s . pat . no . 6 , 664 , 335 , entitled “ polyurethane elastomer article with ‘ shape memory ’ and medical devices therefrom ”, which is commonly assigned and incorporated herein by reference in its entirety . other types of coatings are contemplated by the present subject matter . various cathode configurations are contemplated by the present subject matter . the physical forms of cathode 107 used in various embodiments include , but are not limited it , compressed powder , dough and / or slurry . in various embodiments , the cathode can be formed by the processes including , but not limited to , disposing the cathode directly in the battery container , pressing the cathode into the battery container , and / or pressing the cathode onto an electrically conductive material . cathodes compositions contemplated by the present subject matter include , but are not limited to , one or more of the following : metal oxide , metal sulphide , metal selenide , metal halide , metal oxyhalide compound and / or their corresponding lithiated forms . the cathode may include manganese , vanadium , silver , molybdenum , tungsten , cobalt , nickel , or chromium . the cathode may also include a main group compound such as carbon monofluoride or iodine . other compositions of the cathode are within the scope of this disclosure . anodes of the present subject matter include , but are not limited to , carbon and / or metals . anode compositions include , but are not limited to , one or more of the following : metals such as lithium , sodium , potassium , rubidium , cesium , magnesium , calcium , strontium , barium , tin , zinc and / or silver , and other anode compositions not expressly recited herein . the electrochemical power source 100 is capable of supporting charging and discharging currents on the order of 10 ma to 1 pa , according to various embodiments . waveforms contemplated by the present subject matter include , but are not limited to , continuous , pulsed and other waveforms . additional levels of charging and discharging currents can be supported using the disclosed power source without departing from the scope of the disclosure . various electrochemical power sources of the present subject matter are designed and the components and chemistries selected to ensure a reduced level of self - discharge . some embodiments are constructed to encourage detectable state of charge or depth of discharge ( dod ) indicated when monitoring open - circuit cell voltage ( ocv ). various power sources of the present subject matter are designed to have a near - linear ocv vs . dod curve for the first 60 - 90 % of dod . fig2 illustrates a block diagram of an implantable medical device , according to one embodiment . the implantable medical device 201 includes electronics 208 . the implantable medical device 201 also includes at least one electrochemical power source 200 adapted to provide electrical current to the electronics . a power source 200 , in various embodiments , includes a battery . in additional embodiments , the power source 200 includes a capacitor . the power source 200 includes a housing 202 geometrically defined to reside with the remote implantable medical device . the power source also includes at least one anode 203 , at least one cathode 207 , and an electrolyte 205 within the housing . according to various embodiments , the power source has a displacement volume of below 0 . 024 cubic centimeters . according to various embodiments , the at least one power source includes multiple power sources electrically connected in series , connected in parallel , or connected in a combination of series and parallel , to provide the necessary electrical current to power the remote implantable medical device . the electronics 208 includes sensor circuitry , stimulation circuitry , and combinations thereof , according to various embodiments of the present subject matter . according to various embodiments , the electronics 208 includes sensor circuitry adapted to provide diagnostic functions . some of these embodiments include a pressure transducer . embodiments within the present subject matter additionally include , but are not limited to , ultrasonic transducers , inductive transducers , and / or other transducers . the electronics 208 may also include stimulation circuitry adapted to provide a therapeutic function , such as neurostimulation circuitry adapted to provide neurostimulation therapy . electronics 208 , in various embodiments , include various components . some embodiments include components adapted to communicate other devices . in some embodiments , communications are conducted wirelessly . communications with devices external to the implantable medical device 201 are contemplated by the present subject matter . additionally , wireless communications with receivers located in vivo are contemplated . some embodiments include a processor interconnected to other components to assist components in communicating with each other . this list of components is not an exhaustive or exclusive list covering the present subject matter , and additional components not expressly listed herein additionally are contemplated . the implantable device 201 can be symmetrical along three , two , or no axes , in various embodiments . in various embodiments , the device includes a device housing 202 . in some of these embodiments , the device housing 202 is hermetically sealed . in some embodiments , the device housing 202 is partially defined by a case which houses electrodes for the power source 200 . embodiments of the present subject matter include a housing which has a shape which is modeled to achieve a fluid flow objective , in various embodiments . in some of these embodiments , a power source has a shape which is compatible with said device housing shape . in various embodiments , the device housing includes a profile which improves fluid flow . in some embodiments , the housing profile reduces hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation . in some embodiments , the housing is elongate . some of these embodiments include a housing which is elongate , and which includes portions which have a circular cross section . an elongate housing is useful for implantation in a blood vessel in a manner which reduces hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation . various embodiments include applications which have a profile adapted for implantation in a vein or in an artery . various embodiments use an elongate housing in which the power source 200 and electronics 208 are stacked in a column along the interior of the elongate housing . in various embodiments , hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation are determined using computational fluid dynamics . in some embodiments , measurements are taken of a target implant site . in some of these embodiments , the measurements are used to determine the shape of an implantable medical device which reduces hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation . some embodiments do not base modeling for reduced hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation on the measurement of an individual implant site . in some embodiments , the shape of the housing is determined based on reduced hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation in a statistically significant hypothetical model . for example , in some embodiments , a patient population is measured , and a model having blood - flow characteristics which typify the population is created . this model is used in the creation of a housing which reduces hydrodynamic drag , turbulence , fluid sheer stress , and / or stagnation , in various embodiments . in some of these embodiments , a power source 200 is created to fill a portion of the interior of the implantable medical device in a manner which limits the amount of unused space . in some of these embodiments , the power source 200 is made from a stack of substantially planar power source 200 electrodes . some embodiments use a stack of substantially planar power source 200 electrodes having different layers perimeters . such a stack can have contours which are adapted to efficiently adhere to all or a portion of the interior space of the implantable medical device . additional embodiments use wound electrodes . battery embodiments having shapes which are determined as a function of improved fluid flow also fall within the scope of the present scope , including , but not limited to , battery embodiments having a prismatic shape , a generally cylindrical shape , and other shapes fall within the present scope . in various embodiments , the implantable medical device 201 is adapted for reduced invasion during surgery . for example , in some embodiments , a profile is used which delivers reduced tissue damage . various embodiments include a profile having reduced tissue damage includes an elongate device having a length of from about 5 millimeters to about 10 millimeters . devices up to 5 millimeters are possible , in various embodiments . additional embodiments use devices of over 10 millimeters . additionally , various embodiments include a profile which has an average width of from about 1 millimeter to about 3 millimeters . some embodiments are sized up to 1 millimeter . additional embodiments are sized over 3 millimeters . various embodiments are cylindrical , and are from about 5 to 10 millimeters long , and about 1 to 3 millimeters in diameter . some embodiments are around 2 . 5 millimeters in diameter . some embodiments are greater than 3 millimeters in diameter . additionally , some embodiments are longer than 10 millimeters . in some embodiments , the implantable medical device is elongate , with a proximal portion and a distal portion . in various embodiments , during implantation , the device is grasped at the proximal portion , and the distal portion is led through vasculature . in some of these embodiments , the distal portion has one or more edges . edges , in various embodiments , are rounded to reduce tissue damage during implantation . profiles which reduce tissue damage may also be included . for example , implantable medical devices having a parabolic distal portion fall within the present scope . some of these embodiments are bullet shaped . other profiles not expressly listed herein are additionally encompassed by the present scope . in one process of the present subject matter , a profile of the implantable medical device 201 is determined as a function of power and size requirements . power requirements , in various embodiments , are determined by the number of energy use events which occur during implantation . in some embodiments around 33 milliamp - hours are consumed per month , for example . it is understood that other devices using other power and size requirements are contemplated to be within the scope of this invention . in some embodiments , power requirements are further defined by battery efficiency . battery efficiency , in various embodiments , is a function of self - leakage . power requirements are further determined by battery type . for example , some embodiments use primary batteries . some embodiments use secondary batteries . secondary batteries enable recharging . recharging , in various embodiments , is depending on patient compliance . recharging frequency should be reduced to increase patient satisfaction . in an additional process of the present subject matter , a power requirement is determined and a power source 200 profile is selected to satisfy the power requirement and to satisfy a size requirement which reduces invasiveness . in some of these embodiments , a power management algorithm is developed to comply with these constraints . in some of these embodiments , a secondary power source 200 is used . in some of these embodiments , a power source 200 charging algorithm is used to improve power source 200 profile and the reduce requirements to a patient to visit a clinic to recharge the power source 200 . in various embodiments , an iterative process of selecting a profile , and selecting a power management algorithm is used to determine the final profile of power source 200 which meets predetermined therapeutic requirements . fig3 illustrates a block diagram of an implantable medical device having sensing and stimulating capabilities , according to one embodiment . the implantable medical device 301 includes sensor circuitry 340 adapted to provide a diagnostic function , such as sensing pressure , blood flow , or other measurable medical parameter . the implantable medical device 301 also includes stimulator circuitry 335 adapted to provide a therapeutic function . an example of stimulator circuitry 335 includes neurostimulation circuitry adapted to provide neurostimulation therapy , while other types of stimulator circuitry are within the scope of this disclosure . the implantable medical device 301 further includes at least one electrochemical power source 300 adapted to provide electrical current to the stimulator and sensor circuitry . the power source 300 includes a housing 302 geometrically defined to reside with the remote implantable medical device . the power source also includes at least one anode 303 , at least one cathode 307 , and an electrolyte 305 within the housing . according to various embodiments , the power source has a displacement volume of below 0 . 024 cubic centimeters . fig4 illustrates a block diagram of a system with a device having an electrochemical power source such as illustrated in fig1 , according to one embodiment . the system includes a device 401 , an electrical lead 420 coupled to the n device 401 , and at least one electrode 425 . the device includes a controller circuit 405 , a memory circuit 410 , a telemetry circuit 415 , and a neural stimulation circuit 435 . the device also includes a battery 400 having a housing geometrically defined to reside with a remote implantable medical device . the battery 400 also includes at least one anode , at least one cathode , and an electrolyte within the housing . the battery 400 has a displacement volume of below 0 . 024 cubic centimeters . the battery is adapted to provide sufficient electrical power to operate the device . the battery may be rechargeable , according to an embodiment . the controller circuit 405 is operable on instructions stored in the memory circuit to deliver an electrical neural stimulation therapy . therapy is delivered by the neural stimulation circuit 435 through the lead 420 and the electrode ( s ) 425 . the telemetry circuit 415 allows communication with an external programmer 430 . the programmer 430 can be used to adjust the programmed therapy provided by the device 401 , and the device can report device data ( such as battery and lead resistance ) and therapy data ( such as sense and stimulation data ) to the programmer using radio telemetry , for example . according to various embodiments , the device 401 senses one or more physiological parameters and delivers neural stimulation therapy . the illustrated system also includes sensor circuitry 440 that is coupled to at least one sensor 445 . the controller circuit 405 processes sensor data from the sensor circuitry and delivers a therapy responsive to the sensor data . fig5 illustrates a block diagram of a programmer such as illustrated in the system of fig4 or other external device to communicate with the device ( s ), according to one embodiment . an example of another external device includes personal digital assistants ( pdas ) or personal laptop and desktop computers in a wireless patient monitoring network . the illustrated device 522 includes controller circuitry 545 and a memory 546 . the controller circuitry 545 is capable of being implemented using hardware , software , and combinations of hardware and software . for example , according to various embodiments , the controller circuitry 545 includes a processor to perform instructions embedded in the memory 546 to perform a number of functions , including communicating data and / or programming instructions to the implantable devices . the illustrated device 522 further includes a transceiver 547 and associated circuitry for use to communicate with an implantable device . various embodiments have wireless communication capabilities . for example , various embodiments of the transceiver 547 and associated circuitry include a telemetry coil for use to wirelessly communicate with an implantable device . the illustrated device 522 further includes a display 548 , input / output ( i / o ) devices 549 such as a keyboard or mouse / pointer , and a communications interface 550 for use to communicate with other devices , such as over a communication network . fig6 illustrates a flow diagram of a method for manufacturing an electrochemical power source for use in an implantable medical device , according to one embodiment . according to various embodiments , the method 600 includes providing a housing geometrically defined to reside with an implantable medical device , at 605 . the method also includes providing at least one anode , at least one cathode , and an electrolyte within the housing , at 610 . according to various embodiments , the power source has a displacement volume of below 0 . 024 cubic centimeters and is adapted to provide electrical current used to operate the device . according to various embodiments , providing the cathode includes providing a cathode including compressed powder , dough and / or slurry . the cathode can be formed directly in the battery container or pressed or coated onto an electrically conductive material . in various embodiments , the cathode includes at least one metal oxide , metal sulphide , metal selenide , metal halide or metal oxyhalide compound or their corresponding lithiated forms . the cathode may include manganese , vanadium , silver , molybdenum , tungsten , cobalt , nickel , or chromium . the cathode may also include a main group compound such as carbon monofluoride or iodine . other compositions of the cathode are within the scope of this disclosure . in this method , providing the anode includes providing an anode including carbon or a metal , according to various embodiments . the anode may include metals such as lithium , sodium , potassium , rubidium , cesium , magnesium , calcium , strontium , barium , tin , zinc or silver . other compositions of the anode are within the scope of this disclosure . one of ordinary skill in the art will understand that , the modules and other circuitry shown and described herein can be implemented using software , hardware , and combinations of software and hardware . as such , the illustrated modules and circuitry are intended to encompass software implementations , hardware implementations , and software and hardware implementations . the methods illustrated in this disclosure are not intended to be exclusive of other methods within the scope of the present subject matter . those of ordinary skill in the art will understand , upon reading and comprehending this disclosure , other methods within the scope of the present subject matter . fig7 shows a cross section of a bobbin battery , according to one embodiment of the present subject matter . bobbin batteries benefit from having fewer inactive components and / or less of an inactive component . for example , some bobbin battery embodiments have less separator . additionally , some bobbin battery embodiments have less current collector . while bobbin batteries can provide a reduced discharge rate over other battery configurations for a given size , they provide improved performance in applications which are less sensitive to discharge rate . the improved performance is due , in part , to the reduction in inactive materials , which can lead to reduced size . a bobbin configuration includes a casing 706 . in various embodiments , the bobbin configuration includes an anode 708 . in various embodiments , the anode 708 is electrically interconnected with the casing 706 . in various embodiments , the bobbin configuration includes a cathode 710 . the cathode 710 , in various embodiments , is connected to a terminal 716 using a current collector 712 . separator 714 is disposed between the anode 708 and the cathode 710 . the polarity of components discussed herein is selected to assist in explanation , and can be reversed without departing from the present scope of embodiments . various embodiments require sealing the internal components of the bobbin configuration . in some of these embodiments , a seal 702 is disposed between the terminal 716 and the casing 706 . in various embodiments , the seal 702 resists electrical conductivity . in various embodiments , the seal 702 additional provides mechanical structure to the bobbin configuration , orienting the terminal 716 with respect to the casing 706 . various embodiments include a space 704 which is empty . additional embodiments do not include space 704 . some embodiments dispose a sealant in the space 704 . additional embodiments dispose electrolyte in the space 704 . various embodiments incorporate battery chemistries compatible with bobbin style configurations . embodiments within the present scope include , but are not limited to , at least one of a metal oxide , a metal sulfide , a metal selenide , a metal halide , a metal oxyhalide compound , and corresponding lithiated forms . some of these embodiments include at least one of manganese , vanadium , silver , molybdenum , tungsten , cobalt , nickel , chromium , and main group compounds such as carbon monofluoride and iodine . additionally , some embodiments include at least one of carbon , lithium , sodium , potassium , rubidium , cesium , magnesium , calcium , strontium , barium , tin , zinc or silver . primary battery chemistry embodiments fall within the present scope . additionally , secondary battery chemistry embodiments fall within the present scope . in some embodiments a power source of an implantable medical device includes a plurality of batteries connected in series , parallel or a combination of series and parallel . various electrode constructions fall within the present scope . embodiments compatible with bobbin construction are included , including monolithic electrodes , pelleted electrodes , and other electrodes which have a solid shape . pelleted electrodes , in various embodiments , include pellets formed from compressed powder , dough or slurry . some electrode embodiments are formed from a tightly wound ribbon which is wound unto itself without an insulator to separate progressive wraps from one another . additionally , some embodiment include an electrode onto which is pressed or coated an electronically conductive material . other electrode configuration embodiments compatible with bobbin batteries additionally fall within the present scope . additionally , various battery profiles using these electrodes fall within the present scope . embodiments with the present scope include , but are not limited to , batteries having a cylindrical shape , batteries having a prismatic shape , batteries having a button shape , and batteries having other shapes . in some examples , batteries have shape which is determined as a function of the shape &# 39 ; s impact on reducing blood flow . in some examples , batteries have shape which is determined as a function of the shape &# 39 ; s impact on reducing tissue damage during implantation . as such , various embodiments include an annular anode . some embodiments include an annular cathode . embodiments discussed herein demonstrate an annular cathode concentric with an annular anode . fig8 shows a cross section of a bobbin battery , according to one embodiment of the present subject matter . in various embodiments , a bobbin configuration includes a casing 806 . in various embodiments , the bobbin configuration includes an anode 808 . in various embodiments , the anode 808 is interconnected with the casing 806 . in various embodiments , the bobbin configuration includes a cathode 810 . the cathode 810 , in various embodiments , is connected to a terminal 816 using a current collector 812 . in various embodiments , a separator 814 is disposed between the anode 808 and the cathode 810 . additionally , in various embodiments , a separator 818 is disposed between the cathode 810 and the casing 806 . the polarity of components discussed herein is selected to assist in explanation , and can be reversed without departing from the present scope of embodiments . various embodiments require sealing the internal components of the bobbin configuration . in some of these embodiments , a seal 802 is disposed between the terminal 816 and the casing 806 . in various embodiments , the seal 802 resists electrical conductivity . in various embodiments , the seal 802 additional provides mechanical structure to the bobbin configuration , orienting the terminal 816 with respect to the casing 806 . various embodiments include a space 804 which is empty . additional embodiments do not include a space 804 . some embodiments dispose a sealant in the space 804 . additional embodiments dispose electrolyte in the space 804 . this application is intended to cover adaptations or variations of the present subject matter . it is to be understood that the above description is intended to be illustrative , and not restrictive . the scope of the present subject matter should be determined with reference to the appended claims , along with the full scope of equivalents to which such claims are entitled .
one example includes a battery that includes a stack of at least one substantially planar anode and at least one substantially planar cathode , wherein the stack defines a contoured exterior , and a battery housing enclosing the stack , the battery housing defining a battery housing exterior , wherein the contoured exterior of the stack is shaped to conform to a contoured interior of the battery housing that approximately conforms to the battery housing exterior , the battery produced by the process of modeling , using fluid dynamics , an exterior of a biocompatible housing and shaping the battery housing to conform to at least some of the exterior of the biocompatible housing .