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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Symposium on High Power, Ambient Temperature Lithium Batteries, 180th Meeting of the Electrochemical Society, Phoenix, AZ, Oct. 13-17, 1991, Proceedings

Papers presented in these proceedings are on the state of the art in high-power lithium batteries, a design analysis of high-power Li-TiS2 battery, the performance and safety features of spiral wound lithium/thionyl chloride cells, the feasibility of a superhigh energy density battery of the Li/BrF3 electrochemical system, and an enhanced redox process of disulfide compounds and their application in high energy storage. Attention is also given to the structure and charge-discharge characteristics of mesophase-pitch based carbons, a study of carbons and graphites as anodes for lithium rechargeable cells, Li metal-free rechargeable Li(1+x)Mn2O4/carbon cells, and rechargeable lithium batteries using V6O13/V5O5 as the positive electrode material. Other papers discuss the electrochemical stability of organic electrolytes in contact with solid inorganic cathode materials, the electrochemical behavior of methyl formate solutions, and the interface between a solid polymer electrolyte and lithium anode.

Clark, W. D. K.↗
NASA NTRS2003

Development of Highly-Conductive Polyelectrolytes for Lithium Batteries

Future NASA and Air Force missions require reliable and safe sources of energy with high specific energy and energy density that can provide thousands of charge-discharge cycles at more than 40% depth- of-discharge and that can operate at low temperatures. All solid-state batteries have substantial advantages with respect to stability, energy density, storage fife and cyclability. Among all solid-state batteries, those with flexible polymer electrolytes offer substantial advantages in cell dimensionality and commensurability, low temperature operation and thin film design. The above considerations suggest that lithium-polymer electrolyte systems are promising for high energy density batteries and should be the systems of choice for NASA and US Air Force applications. Polyelectrolytes (single ion conductors) are among most promising avenues for achieving a major breakthrough 'in the applicability of polymer- based electrolyte systems. Their major advantages include unit transference number for the cation, reduced cell polarization, minimal salt precipitation, and favorable electrolyte stability at interfaces. Our research is focused on synthesis, modeling and cell testing of single ion carriers, polyelectrolytes. During the first year of this project we attempted the synthesis of two polyelectrolytes. The synthesis of the first one, the poly(ethyleneoxide methoxy acrylateco-lithium 1,1,2-trifluorobutanesulfonate acrylate, was attempted few times and it was unsuccessful. We followed the synthetic route described by Cowie and Spence. The yield was extremely low and the final product could not be separated from the impurities. The synthesis of this polyelectrolyte is not described in this report. The second polyelectrolyte, comb polysiloxane polyelectrolyte containing oligoether and perfluoroether sidechains, was synthesized in sufficient quantity to study the range of properties such as thermal stability, Li- ion- conductivity and stability toward lithium metal. Also, the batteries containing this polyelectrolyte were assembled and tested. The results are detailed below. The synthesis of another polyelectrolyte similar to polysiloxane polyelectrolyte has been started, however, the synthesis was not completed due to termination of the project.

Shriver, D. F.↗
NASA NTRSDate not supplied

Molten Salt Electrolytes: Computational Analysis of Transport, Electrochemical Properties and Designing New Mixtures

Electric aircraft propulsion has gained a traction over the last decade due to possible high-energy density electrochemistries with reasonable cycle life and identification of non-flammable chemistries that can guarantee much better safety. Commercial Li-ion batteries cannot reach such high capacities because of weight limitations that arise from the widely used intercalation electrodes. Also, use of organic electrolytes make them highly susceptible to fire on exposure to air and humidity. Currently, use of Lithium metal anode along with conversion electrochemistries such as Li-O2 and Li-S are being pursued to achieve such high energy densities. Safer inorganic solid-state electrolytes, recently discovered Water-in-Salt electrolytes, molten salt electrolytes are some of the alternatives being pursued for a safer/non-flammable battery. Of these safer alternatives, molten-salt electrolytes offer some attractive properties: liquid at operating temperatures resulting in better electrode-wetting, stable interface with Li-metal anodes and good ionic conductivity; their only drawback being high operating temperatures. In this talk, we will discuss some of the computational studies, driven via atomistic simulations, of the properties of molten-salt electrolytes including transport mechanism and interface stability. We will also discuss predicting electrochemical properties of these high-temperature electrolytes. Further, we will discuss a thermodynamic approach to predicting new molten-salt eutectics with lower melting points.

Molten Salt Electrolytes↗
NASA NTRS1993

Advanced Energy Storage for Space Applications

NASA is planning a number of space science and space exploration missions into the early 21st century. The JPL Advanced Battery Program, which has the goal of developing batteries for these missions, is described. Under program consideration are Li-SOCl(sub 2) cells, secondary lithium cells, advanced metal hydride cells, and high-temperature sodium-nickel chloride cells.

JPL Advanced Battery Program energy storage batter↗
NASA NTRS2006

The 2004 NASA Aerospace Battery Workshop

Topics covered include: Super NiCd(TradeMark) Energy Storage for Gravity Probe-B Relativity Mission; Hubble Space Telescope 2004 Battery Update; The Development of Hermetically Sealed Aerospace Nickel-Metal Hydride Cell; Serial Charging Test on High Capacity Li-Ion Cells for the Orbiter Advanced Hydraulic Power System; Cell Equalization of Lithium-Ion Cells; The Long-Term Performance of Small-Cell Batteries Without Cell-Balancing Electronics; Identification and Treatment of Lithium Battery Cell Imbalance under Flight Conditions; Battery Control Boards for Li-Ion Batteries on Mars Exploration Rovers; Cell Over Voltage Protection and Balancing Circuit of the Lithium-Ion Battery; Lithium-Ion Battery Electronics for Aerospace Applications; Lithium-Ion Cell Charge Control Unit; Lithium Ion Battery Cell Bypass Circuit Test Results at the U.S. Naval Research Laboratory; High Capacity Battery Cell By-Pass Switches: High Current Pulse Testing of Lithium-Ion; Battery By-Pass Switches to Verify Their Ability to Withstand Short-Circuits; Incorporation of Physics-Based, Spatially-Resolved Battery Models into System Simulations; A Monte Carlo Model for Li-Ion Battery Life Projections; Thermal Behavior of Large Lithium-Ion Cells; Thermal Imaging of Aerospace Battery Cells; High Rate Designed 50 Ah Li-Ion Cell for LEO Applications; Evaluation of Corrosion Behavior in Aerospace Lithium-Ion Cells; Performance of AEA 80 Ah Battery Under GEO Profile; LEO Li-Ion Battery Testing; A Review of the Feasibility Investigation of Commercial Laminated Lithium-Ion Polymer Cells for Space Applications; Lithium-Ion Verification Test Program; Panasonic Small Cell Testing for AHPS; Lithium-Ion Small Cell Battery Shorting Study; Low-Earth-Orbit and Geosynchronous-Earth-Orbit Testing of 80 Ah Batteries under Real-Time Profiles; Update on Development of Lithium-Ion Cells for Space Applications at JAXA; Foreign Comparative Technology: Launch Vehicle Battery Cell Testing; 20V, 40 Ah Lithium Ion Polymer Battery for the Spacesuit; Low Temperature Life-Cycle Testing of a Lithium-Ion Battery for Low-Earth-Orbiting Spacecraft; and Evaluation of the Effects of DoD and Charge Rate on a LEO Optimized 50 Ah Li-Ion Aerospace Cell.

Source record↗
NASA NTRS2014

Characterization of Commercial Li-ion Cells in Pouch Format

The li-ion pouch design cells exhibit similar behavior under off-nominal conditions as those in metal cans that do not have the internal safety devices. Safety should be well characterized before batteries are designed. Some of the li-ion pouch cell designs studied in this program reacted most violently to overcharge conditions at the medium rates but were tolerant to overcharge at very low rates. Some pouch cell designs have higher tolerance to vacuum exposures than some others. A comparison of the pouch material itself does not show a correlation between this tolerance and the number of layers or composition of the pouch indicating that this is a property of the electrode stack design inside the pouch. Reduced pressure (8 to 10 psi) test environments show that the extent of capacity degradation under reduced pressure environments is much less than that observed under vacuum conditions. Lithium-ion Pouch format cells are not necessarily true polymer cells.

Jeevarajan, Judith↗
NASA NTRS1993

Cathodes for molten-salt batteries

Viewgraphs of the discussion on cathodes for molten-salt batteries are presented. For the cathode reactions in molten-salt cells, chlorine-based and sulfur-based cathodes reactants have relatively high exchange current densities. Sulfur-based cathodes, metal sulfides, and disulfides have been extensively investigated. Primary thermal batteries of the Li-alloy/FeS2 variety have been available for a number of years. Chlorine based rechargable cathodes were investigated for the pulse power application. A brief introduction is followed by the experimental aspects of research, and the results obtained. Performance projections to the battery system level are discussed and the presentation is summarized with conclusions.

Argade, Shyam D.↗
NASA NTRS2021

Local Ultrasonic Resonance Spectroscopy of Lithium Metal Batteries for Aerospace Applications

As next-generation aircraft and vehicles continue to develop, so do their associated energy demands. Lithium metal batteries are a leading candidate to fulfill this energy requirement, but these batteries are prone to internal dendrite defects that can lead to catastrophic thermal runaway events. Current battery management systems are capable of mitigating such risks, but are unable to detect such defects until thermal runaway has already begun. Various nondestructive evaluation (NDE) techniques, particularly ultrasonic NDE, can directly monitor internal battery parameters giving them the potential to detect critical defects prior to catastrophic failure. However, most of the current battery NDE research has focused on improved battery state-of-charge (SOC) and stateof- health (SOH) monitoring with little emphasis on critical defect detection. Thus, a measurement technique sensitive to subtle battery defects is needed. In addition, the complex mechanics of ultrasound in porous, thin, multilayered batteries prompt the use of physics-based simulation to guide inspections. In this work, an ultrasonic NDE technique has been developed utilizing frequency domain analysis of local battery resonances to detect the presence of battery defects. This technique is a practical extension of local ultrasonic resonance spectroscopy (LURS) – which previously required non-contact laser ultrasonics – to measurements with piezoelectric contact and immersion scan transducers. To extend the technique to work with piezoelectric transducers, ultrasonic battery measurements were compared to a sans-battery calibration measurement. Then, a linear systems deconvolution was used to eliminate the transfer functions of extraneous factors such as the transducer and electronics, leaving only the frequency-dependent battery reflection coefficient. The LURS technique was first validated on stainless steel and aluminum plates, producing reflection coefficients in line with analytical and numerical finite element modeling (FEM) results. Functioning Li-metal pouch cells were then seeded with lithium chip defects prior to LURS measurements. The presence of these defects is shown to cause a measurable shift in the battery’s through-thickness local resonances. 2D, frequency-domain poroelastic models of ultrasonic propagation in a single-cell lithium metal pouch battery were created and corroborated these findings. Thus, this work has both extended and proven the feasibility of the LURS technique in the detection of local battery defects.

Ultrasound↗
NASA NTRS2019

Transparent Conducting Oxides as Cathodes in Li-O2 Batteries: A First Principles Computational Investigation

Li-O2 batteries have traditionally used carbon based electrodes (graphite, buckypaper) as the cathode of choice due toits good electrical conductivity, stability against non-aqueous electrolytes like dimethoxyethane (DME) and ease ofhandling. But, the carbon cathode also leads to formation of carbonate by-products that increase overpotentials duringcharging leading to degradation of the cathode and reduction of cyclability. Recent investigations have focused on using metal-oxides like SnO2, TiO2 as viable cathodes-alternatives in Li-O2 systems. In this paper, we investigate transparent conducting oxides (TCOs) as cathodes with focus on the interface between the TCO surfaces and the discharge product, Li2O2, in the Li-O2 battery using first principles computations.

transparent conducting oxides↗
NASA NTRS2014

Investigation of Metal Oxide/Carbon Nano Material as Anode for High Capacity Lithium-ion Cells

NASA is developing high specific energy and high specific capacity lithium-ion battery (LIB) technology for future NASA missions. Current state-of-art LIBs have issues in terms of safety and thermal stability, and are reaching limits in specific energy capability based on the electrochemical materials selected. For example, the graphite anode has a limited capability to store Li since the theoretical capacity of graphite is 372 mAh/g. To achieve higher specific capacity and energy density, and to improve safety for current LIBs, alternative advanced anode, cathode, and electrolyte materials are pursued under the NASA Advanced Space Power System Project. In this study, the nanostructed metal oxide, such as Fe2O3 on carbon nanotubes (CNT) composite as an LIB anode has been investigated.

battery performance↗
NASA NTRS2008

Method of Making Fine Lithium Iron Phosphate/Carbon-Based Powders with an Olivine Type Structure

Processes for producing fine LiFePO.sub.4/C and nanostructured LiFe.sub.xM.sub.1-xPO.sub.4/C composite powders, where 1.ltoreq.x.ltoreq.0.1 and M is a metal cation. Electrodes made of either nanostructured LiFe.sub.xM.sub.1-xPO.sub.4 powders or nanostructured LiFe.sub.xM.sub.1-xPO.sub.4/C composite powders exhibit excellent electrochemical properties. That will provide high power density, low cost and environmentally friendly rechargeable Li-ion batteries.

Singhal, Amit↗
NASA NTRSDate not supplied

Ultrahigh Areal Capacity Holey Graphene Air Cathodes for Li-O2 and Li-CO2 Batteries

Advanced lithium (Li) batteries using gaseous cathode reactants such as oxygen (O2) and carbon dioxide (CO2)are attractive energy storage platforms because the gases are obtained externally and thus not accounted for in the total battery weight when fully charged.The discharge products at the cathode, typically Li2O2 for Li-O2 batteries and Li2CO3 for Li-CO2 batteries, are insoluble in the electrolyte.Therefore, in order for such batteries to function properly, an “air cathode”,which is a conductive scaffold within the battery cell,is required as a physical location for cathode electrochemical reactions to occur. Prior research has identified many carbon nanomaterials such as carbon nanotubes and graphene as viable choices for air cathode scaffold, while various metallic and metal-free catalytic systems integrated onto carbon-based air cathodes have been developed to improve the sluggish discharge and charge reactions. For future practical applications, the air cathode must exhibit a usable capacity per unit electrode area, or areal capacity, a critical parameter that has been largely overlooked so far in this field. In order to achieve high areal capacity, the air cathode must exhibit a sufficient amount of accessible void volume per unit electrode area while maintaining the conductive scaffold integrity during the entire electrochemical process. Here we present an ultrathick,holey graphene-based air cathode platform fabricated from a facile dry compression process that exhibits remarkable areal capacity values. Holey graphene is a carbon nanomaterial derived from graphene, but with nanometer sized holes through the nanosheet thickness.The presence of these holes enhances mass transport through electrode thickness and also enables the unique dry-press fabrication process that is not achievable using other carbon scaffold materials.The dry-pressed holey graphene air cathode platform is not only compatible with catalyst incorporation to improve battery reaction kinetics, but also allows for novel engineering of electrode architectures that is not achievable using conventional electrode fabrication approaches.The applications of such highly versatile, ultrahigh areal capacity air cathode platforms to both Li-O2 and Li-CO2 battery chemistries will be discussed.

Li-O2 batteries, Li-CO2 batteries, holey graphene,↗
NASA NTRS1989

The electrochemical generation of useful chemical species from lunar materials

The current status of work on an electrochemical technology for the simultaneous generation of oxygen and lithium from a Li2O containing molten salt (Li2O-LiCl-LiF) is discussed. The electrochemical cell utilizes an oxygen vacancy conducting solid electrolyte, yttria-stabilized zirconia, to effect separation between the oxygen evolving and lithium reduction half-cell reactions. The cell, which operates at 700 to 800 C, possesses rapid electrode kinetics at the lithium-alloy electrode with exchange current density values being greater than 60 mA/sq cm, showing high reversibility for this reaction. When used in the electrolytic mode, lithium produced at the negative electrode would be continuously removed from the cell for later use (under lunar conditions) as an easily storable reducting agent (compared to H2) for the chemical refining of lunar ores via the general reaction: 2Li + MO yields Li2O + M where MO represents a lunar ore. Emphasis to this time has been on the simulated lunar ore ilmenite (FeTiO3), which we have found becomes chemically reduced by Li at 432 C. Furthermore, both Fe2O3 and TiO2 have been reduced by Li to give the corresponding metal. This electrochemical approach provides a convenient route for producing metals under lunar conditions and oxygen for the continuous maintenance of human habitats on the Moon's surface. Because of the high reversibility of this electrochemical system, it has also formed the basis for the lithium-oxygen secondary battery. This secondary lithium-oxygen battery system posses the highest theoretical energy density yet investigated.

Tsai, Kan J.↗
NASA NTRS2015

Metallography of Battery Resistance Spot Welds

Li-ion cells provide an energy dense solution for systems that require rechargeable electrical power. However, these cells can undergo thermal runaway, the point at which the cell becomes thermally unstable and results in hot gas, flame, electrolyte leakage, and in some cases explosion. The heat and fire associated with this type of event is generally violent and can subsequently cause damage to the surrounding system or present a dangerous risk to the personnel nearby. The space flight environment is especially sensitive to risks particularly when it involves potential for fire within the habitable volume of the International Space Station (ISS). In larger battery packs such as Robonaut 2 (R2), numerous Li-ion cells are placed in parallel-series configurations to obtain the required stack voltage and desired run-time or to meet specific power requirements. This raises a second and less obvious concern for batteries that undergo certification for space flight use: the joining quality at the resistance spot weld of battery cells to component wires/leads and battery tabs, bus bars or other electronic components and assemblies. Resistance spot welds undergo materials evaluation, visual inspection, conductivity (resistivity) testing, destructive peel testing, and metallurgical examination in accordance with applicable NASA Process Specifications. Welded components are cross-sectioned to ensure they are free of cracks or voids open to any exterior surface. Pore and voids contained within the weld zone but not open to an exterior surface, and are not determined to have sharp notch like characteristics, shall be acceptable. Depending on requirements, some battery cells are constructed of aluminum canisters while others are constructed of steel. Process specific weld schedules must be developed and certified for each possible joining combination. The aluminum canisters' positive terminals were particularly difficult to weld due to a bi-metal strip that comes ultrasonically pre-welded by the manufacturer. This was further complicated as the maximum electrode force was limited to low-electrode force to prevent deflection of the aluminum can during welding. Other Li-ion cells are comprised of smaller diameter cylindrical steel canisters which are inherently capable of handling greater force from the electrodes. Allowing higher-electrode forces aids greatly in insuring a consistent resistance network for the weld. Overall lessons learned: developing good jigs is critical to insure the parts and electrodes are planer to one another and the location of the weld sites remains accurate and repeatable; maintaining strict control over materials is critical--materials must be of a specific hardness and chemical composition to insure that a weld schedule is repeatable; accuracy of the die used to stamp the projections is critical and worth the investment; and proper seasoning of the electrodes is critical to producing consistent welds--once the electrodes have been properly seasoned, cleaning/dressing should be avoided until it is absolutely necessary.

Martinez, J. E.↗
NASA NTRSDate not supplied

Fabrication of Solid-State Li-S Battery Components for Electric Aviation

The development of high-energy, high-safety, and high-power batteries beyond electric automobile requirements is vital for future electric aviation applications. The transition to non-volatile solid-state electrolytes (SSE) promises many advantages over traditional flammable liquid electrolytes, and may also be an enabling technology for next generation chemistries. However, significant manufacturing challenges must be overcome before the adoption of such technology. Electrolytes developed in this study were produced as sulfide-polymer composites with densified thicknesses between 20-30 microns using several processing techniques [1]. Ionic conductivity and lithium metal compatibility for the composites were compared and shown to retain reasonable ionic conductivity with improved flexibility and scalability which identifies a critical path for the production of practical solid-state batteries. Films were produced 10-15 times thinner than comparable bulk cold pressed powder electrolytes and achieved thicknesses comparable to commercial polyolefin separators (25 micron) used in commercial liquid containing lithium-ion cells. Composite conductivities were maintained above 0.2mS/cm, which holds promise for future electric aviation applications. Processing techniques are investigated to further improve electrochemical performance.

battery↗
NASA NTRS2012

NASA Tech Briefs, June 2012

Topics covered include: iGlobe Interactive Visualization and Analysis of Spatial Data; Broad-Bandwidth FPGA-Based Digital Polyphase Spectrometer; Small Aircraft Data Distribution System; Earth Science Datacasting v2.0; Algorithm for Compressing Time-Series Data; Onboard Science and Applications Algorithm for Hyperspectral Data Reduction; Sampling Technique for Robust Odorant Detection Based on MIT RealNose Data; Security Data Warehouse Application; Integrated Laser Characterization, Data Acquisition, and Command and Control Test System; Radiation-Hard SpaceWire/Gigabit Ethernet-Compatible Transponder; Hardware Implementation of Lossless Adaptive Compression of Data From a Hyperspectral Imager; High-Voltage, Low-Power BNC Feedthrough Terminator; SpaceCube Mini; Dichroic Filter for Separating W-Band and Ka-Band; Active Mirror Predictive and Requirement Verification Software (AMP-ReVS); Navigation/Prop Software Suite; Personal Computer Transport Analysis Program; Pressure Ratio to Thermal Environments; Probabilistic Fatigue Damage Program (FATIG); ASCENT Program; JPL Genesis and Rapid Intensification Processes (GRIP) Portal; Data::Downloader; Fault Tolerance Middleware for a Multi-Core System; DspaceOgreTerrain 3D Terrain Visualization Tool; Trick Simulation Environment 07; Geometric Reasoning for Automated Planning; Water Detection Based on Color Variation; Single-Layer, All-Metal Patch Antenna Element with Wide Bandwidth; Scanning Laser Infrared Molecular Spectrometer (SLIMS); Next-Generation Microshutter Arrays for Large-Format Imaging and Spectroscopy; Detection of Carbon Monoxide Using Polymer-Composite Films with a Porphyrin-Functionalized Polypyrrole; Enhanced-Adhesion Multiwalled Carbon Nanotubes on Titanium Substrates for Stray Light Control; Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries 23 Ultra-Lightweight; and Ultra-Lightweight Nanocomposite Foams and Sandwich Structures for Space Structure Applications.

Source record↗
NASA NTRS2018

Li-ion 18650 Thermal Runaway Particulate Analysis

Three types of atmospheres were tested for their effects on the particulates generated in a lithium ion (Li-ion) battery thermal runaway. Normal laboratory air (Ambient), a mixture of 23.5% O2/76.5% N2 meant to simulate the atmosphere on the International Space Station (ISS), and Vacuum environments were tested. Samsung 26F 18650 cells were driven to thermal runaway using heater tape, and the resultant particulates were collected analyzed using SEM/EDX, FTIR, GCMS, as well as conductivity and magnetic probes. All three conditions generated dense black particulate films composed of very fine carbon and metal particles. These films, however, were not very conductive, though individual particulates would be, and the particles demonstrated weak paramagnetism. FTIR and GCMS identified a substantial amount of volatile components in the particulate films, both organic partial combustion products, but also electrolyte salt products.

Nemanick, E. Joseph↗
NASA NTRS2006

Improved Control of Charging Voltage for Li-Ion Battery

The protocol for charging a lithium-ion battery would be modified, according to a proposal, to compensate for the internal voltage drop (charging current internal resistance of the battery). The essence of the modification is to provide for measurement of the internal voltage drop and to increase the terminal-voltage setting by the amount of the internal voltage drop. Ordinarily, a lithium-ion battery is charged at constant current until its terminal voltage attains a set value equal to the nominal full-charge potential. The set value is chosen carefully so as not to exceed the lithium-plating potential, because plated lithium in metallic form constitutes a hazard. When the battery is charged at low temperature, the internal voltage drop is considerable because the electrical conductivity of the battery electrolyte is low at low temperature. Charging the battery at high current at any temperature also gives rise to a high internal voltage drop. In some cases, the internal voltage drop can be as high as 1 volt per cell. Because the voltage available for charging is less than the terminal voltage by the amount of the internal voltage drop, the battery is not fully charged (see figure), even when the terminal voltage reaches the set value. In the modified protocol, the charging current would be periodically interrupted so that the zero-current battery-terminal voltage indicative of the state of charge could be measured. The terminal voltage would also be measured at full charging current. The difference between the full-current and zero-current voltages would equal the internal voltage drop. The set value of terminal voltage would then be increased beyond the nominal full-charge potential by the amount of the internal voltage drop. This adjustment would be performed repeatedly, in real time, so that the voltage setting would track variations in the internal voltage drop to afford full charge without risk of lithium plating. If the charging current and voltage settings were controlled by a computer, then this method of charge control could readily be implemented in software.

Timmerman, Paul↗