Jelen, Dov

Kalman, Andrew

Wright, David

DigitalCommons@USU

Slide 1David J. Wright & Andrew E. KalmanPumpkin, Inc. Development of a Smart High-power Battery forCubeSatsSlide 2Desirable Features• Better estimate of battery capacity, to include aging effects• P = V x I; higher power requires either higher battery voltages and/or higher battery currents• Local intelligence may be required to recover from various types of faults• Smart inhibits offer interesting possibilitiesPanasonic 18650B discharge curvesSlide 3How Can We Improve?• Safety – not a laughing matter• Power – it’s never enough• Lifetime – it’s never enough• Capacity – it’s never enough• Reliability – no excuses for failure• Obsolescence – we want our design to last• Telemetry – provide fully formatted data or go home• Linkage to EPS design – 2S batteries force 6-8.4V buses• Charging – as fast as possible, limited by many factors• Special features – At-a-glance status, clean POR• Interface – Connectors, harnesses, etc.Slide 4Prismatic vs Cylindrical Lithium Cells• Prismatic  Plastic pouch construction Rectangular (L x W x T) or form-fitting Can be combined into packs External protection circuitry Theoretically higher current Flat form factor more conducive to heater design Requires physical constraint for best power & to avoid bulging No built-in pressure relief valve• Cylindrical  Steel can construction Cylindrical (dia x L) Can be combined into packs External or internal protection circuitry Built-in pressure relief valve Inherently “tight” layers Mechanically very tough A standard, mass-produced cell Extra mass of steel case Interstitial spaces better thermally?Slide 5The Ubiquitous 18650 Cell• 18mm dia x 65(.0)mm long• Panasonic, LG Chem, Samsung, A123,                        and many other top-tier manufacturers• Multiple chemistries available: Lithium-Ion LiPeFO4 (Lithium Iron Phosphate): non-explosive, long life Other, more esoteric chemistries• Cells are combined in series (S) and parallel (P) combinations into batteries. For Li-Ion, Each cell has a capacity (in mAh), a measure of stored energy Every ‘S’ adds +3.7V (nominal) in battery voltage Every ‘P’ delivers additional current (in A)  The resultant series-parallel pack can deliver power based on its voltage (S) and current (P) ratingSlide 6What If …• … we could pick from various 18650 cell models? Can offer different battery capacities (in Wh), to satisfy safety requirements • … we could support multiple ‘S’ configurations? Can support EPSes that operate at 7.4V (2S), 11.1V (3S), 14.8 (4S) and maybe 29.6 (8S) battery voltages• … we could support multiple ‘P’ configurations? Can greatly increase available power (via more Amps) Can potentially reduce battery charge time• … we could support multiple battery chemistries? Can use Li-Ion for higher energy density Can use Lithium Phosphate for higher power and more safety• … we could have insight into battery condition, over lifetime? Can predict real-time performance, e.g. “How long can I pull 17.6A? 139 minutes.” Can accurately report on battery condition over time, e.g. “Fully charged, now at 87% of maximum.”Slide 7Approach Taken• Let’s face it, batteries for space is a tiny market• Let’s look at a small market that is uses more batteries than space, but has similar requirements: Tesla• Tesla Model S w/85kWh battery has 7,104 18650 Li-Ion cells from Panasonic (x2E5 cars)• What problems has Tesla solved? Choice of battery cell & chemistry Mechanical packaging & electrical interconnects Battery management (via electronics) Thermal control (in Tesla’s case, cooling)• Lifetime, power, energy, capacity, telemetry, charging are all directly related to Tesla’s component and design decisions above• An even bigger market is power tools, but not as sexy for this discussion …. but it also standardized on 18650 cellsSlide 8But How Do We Get There?• In 2014, 9.8GWh of battery capacity solely for electric vehicles (1 Billion 18650-cell equivalent)• Battery protection circuits are per-cell or per-pack• Smart battery controllers appear in more technologically advanced products (like electric vehicles)• Consumer requirements are small in scope: Gas gauge Don’t start a fire Provide some means of clearing a (rare) fault• More advanced requirements for space use Full telemetry from the batteries Automatic identification and clearing of faults Seamless integration with EPSSlide 9The BM 2 SolutionSlide 10The BM 2 Solution• By choosing a smart battery controller chip and the 18650 cell form factor: 2S, 3S and 4S configurations are possible (and maybe 8S in the future) – accommodate different EPS topologies Can support a wide range of cells  Can support a wide range of chemistries• The battery controller chip’s intelligence enables: Tracking the electrons moving in and out of the batteries Battery aging and other environmental effects are taken into account when reporting on battery SoC• By adding a SupMCU: Local intelligence permits autonomous clearing faults Easy reprogramming of battery parameter limits on-orbit Additional functionality (e.g., heat batteries to 60C on purpose) Extreme attention to system power managementSlide 11The BM 2 SolutionSlide 12BM 2 Features• Can support any 18650 cell+chemistry in 2S4P, 3S2P and 4S2P configurations• 1st- and 2nd-level safeties independent of SupMCU• Independent charge & discharge paths & limits• Intelligent gas gauge with over 100 telemetry point that take temperature, cycles etc. into account when reporting SoC• Active cell balancing on charge and discharge• Integrated heaters in robust thermal design• VBATT of 6-8.4Vdc, 9-12.6Vdc or 12-16.8Vdc• 10A in/out baseline config• 72-100Wh using typical cells• 84-168W using typical cells• 70A MOSFETs – currents are connector/harness-limited• Rapid charging, too!• Very low (<5μA) sleep mode guarantees battery health –integrated storage ca. 2yrs• Intelligent Charge Override (ICO) to top off after integrationSlide 13Q&A SessionSlide 14Appendix• Acknowledgements Dr. Eric Swenson and his team at the Air Force Institute of Technology (AFIT), for the partnership in developing, analyzing and testing SUPERNOVA.• Speaker information David Wright is a systems engineer at Pumpkin, and is responsible for much of the BM 2’s electronics, analog design and firmware. Contact David at david@pumpkininc.com. Dr. Kalman is Pumpkin's president and chief technology architect. He entered the embedded programming world in the mid-1980's. After co-founding Euphonix, Inc – the pioneering Silicon Valley high-tech pro-audio company – he founded Pumpkin, Inc. to explore the feasibility of applying high-level programming paradigms to severely memory-constrained embedded architectures. He is the creator of the Salvo RTOS, the CubeSat Kit and the SUPERNOVA architecture. He holds several United States patents. He is a consulting professor in the Department of Aeronautics & Astronautics at Stanford University and directs the department’s Space Systems Development Laboratory (SSDL). Contact Andrew at aek@pumpkininc.com.• CubeSat Kit information More information on Pumpkin’s products can be found at http://www.pumpkinspace.com/. Patented and Patents pending.• Copyright© 2000-2017 Pumpkin, Inc. All rights reserved. Pumpkin and the Pumpkin logo, Salvo and the Salvo logo, The RTOS that runs in tiny places, CubeSat Kit and the CubeSat Kit logo, CubeSat Kit Bus, nanoLab Kit and thenanoLab Kit logo, MISC and SUPERNOVA are all trademarks of Pumpkin, Inc. Don’t leave Earth without it is a service mark of Pumpkin, Inc. All other trademarks and logos are the property of their respective owners. No endorsements of or by third parties listed are implied. All specifications subject to change without notice. Unless stated otherwise, all photographs, images and illustrations are the property of Pumpkin, Inc. and may not be used without permission.

Development of a Smart High-Power Battery for CubeSats

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?filename=0&article=3793&context=smallsat&type=additional

Development of a Smart High-Power Battery for CubeSats

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