Finally! Ultra Cap / Lithium-Ion Battery Combination Testing Ultra capacitors are a better way to store, as electricity, the kinetic energy quickly recovered with regenerative braking / suspension systems. Their quick discharge ability then make them suitable for release of high current to boost acceleration. On the other hand, deep cycle batteries have greater capacity. Batteries cannot absorb all the power available from regenerative braking. The chemical reaction is much too slow; more than 50% of this energy is wasted. This blog previously wrote about energy storage that integrated batteries and super capacitors. Batteries also wear out more quickly from charging cycles than ultra capacitors. Integrating the energy storage technology not only could extend the range for electric vehicles, but also could mean greater durability. Green Car Congress reports that an Argonne National Laboratory team led by Dr. Don Hilebrand, director of the Center for Transportation Research, will assemble and evaluate an energy storage system that combines ultra capacitors and lithium-ion batteries. Maxwell Technologies, Inc. will supply the ultra capacitor cells and integration kits to the U.S. Department of Energy. No word as to which company previously supplied the Argonne team with the advanced lithium batteries and power electronics. The design challenge is an integrated energy system for hybrid-electric and plug-in hybrid vehicles. So, Maxwell has a lot to gain from collaboration with the Advanced Powertrain Research Facility (APRF) in Argonne Center for Transportation Research. A prime objective of the research project is HIL (Hardware-in-the-Loop) validation and benchmark testing of this combined technology and their supporting subsystems for advanced vehicles. Plans are that the test system will undergo HIL validation during the summer of 2007. Argonne and Maxwell have agreed on an active parallel system configuration that will combine a standard lithium-ion plug-in hybrid battery with a string of 112 of the Maxwell BOOSTCAP BCAP0650 P270 650-farad ultracapacitor cells, along with appropriate power electronics and cooling and safety-related features. The other design challenge, frequently mentioned when ultra capacitors are used in traction application (most recently in a Swiss context), is the cost of ultra capacitors. There has been conjecture about the price coming down with mass production and new development, but, so far, nothing to put on the asphalt. Nota Bene: When this blog applauds that finally there is testing underway of a combination of Maxwell ultra capacitors and advanced lithium batteries, it certainly could be subject to the criticism of missing prior art. A UK company, PML Flightlink, previously had installed and tested such a combination in a Mini Cooper S. The former testing was more “proof of concept”, whereas the upcoming testing should be more scientifically rigorous. Other Similar AG Posts Possibly Related Automatically Generated Nesscap Super Capacitors with Kokum Lithium-ion Batteries Battery / Capacitor Combined Energy Storage GM Still Trying to drum up interest in the Saturn VUE Green Line Nano Structure for Hybrid Energy Storage Abstract (from “Power enhancement of an actively controlled battery/ultracapacitor hybrid” Lijun Gao Dougal, R.A. Shengyi Liu IEEE Transactions on Power Electronics, 20(1), Jan. 2005): An actively controlled battery / ultracapacitor hybrid has broad applications in pulseoperated power systems. A converter is used to actively control the power flow from a battery, to couple the battery to an ultracapacitor for power enhancement, and to deliver the power to a load efficiently. The experimental and simulation results show that the hybrid can achieve much greater specific power while reducing battery current and its internal loss. A specific example of the hybrid built from two size 18650 lithium-ion cells and two 100-F ultracapacitors achieved a peak power of 132 W which is a three-times improvement in peak power compared to the passive hybrid power source (hybrid without a converter), and a seven times improvement as compared to the lithium-ion cells alone. The design presented here can be scaled
to larger or smaller power capacities for a variety of applications.
EnerDel/Argonne Advanced High-Power Battery for Hybrid Electric Vehicles The EnerDel/Argonne lithium-ion battery is a highly reliable and extremely safe device that is lighter in weight, more compact, more powerful and longerlasting than the nickel-metal hydride (Ni-MH) batteries in today's hybrid electric vehicles (HEVs). The battery is expected to meet the U.S. Advanced Battery Consortium's $500 manufacturing price criterion for a 25-kilowatt battery, which is almost a sixth of the cost to make comparable Ni-MH batteries intended for use in The EnerDel Lithium-Ion Battery HEVs. It is also less expensive to make than comparable Li-ion batteries. That cost reduction is expected to help make HEVs more competitive in the marketplace and enable consumers to receive an immediate payback in gas-cost savings rather than having to wait seven years for the savings to surpass the premium placed on HEVs. Additionally, the EnerDel/Argonne battery does not use graphite as the anode material, which been the cause for concerns about the safety other Li-ion battery brands. Instead, Argonne developed an innovative, more stable new form of nano-phase lithium titanate (LTO) to replace the graphite. It also developed a new way of making nano-phased LTO that will allow for easier industrial processing, as well as provide a high packing density that can increase the battery's energy density and provide the power needed for vehicle acceleration and regenerative charging of HEVs. The battery's principal developers are Khalil Amine, senior scientist and group leader; materials scientist Illias Belharouak; Zonghai Chen, assistant chemist; Taison Tan, EnerDel's research and development manager; Hiroyuki Yumoto, EnerDel's director of research and development; and Naoki Ota, EnerDel president and chief operating officer. The DOE Office of Energy Efficiency and Renewable Energy's (EERE) FreedomCAR and Vehicle Technologies program provides funding for Argonne battery research. email : ttrdc@anl.gov
An active parallel configuration controls the ultracapacitor energy flows via an energy management strategy with a power electronics converter to minimize battery cycling. Green Car Congress reports that Maxwell Technologies, Inc. now has formed an alliance with Tianjin Lishen Battery Joint-Stock Co., Ltd., Lishen, China. The leading producer of rechargeable lithium-ion batteries in China plans to manufacture and market novel hybrid energy storage system (HESS) products. The companies have identified a number of initial target applications for the combination of their respective ultracapacitor and li-ion battery technologies, ranging from quick-charge cordless tools to electric vehicles. Production and delivery of initial product samples is anticipated in early 2008. After Green Car Congress reported that Maxwell Technologies, Inc. and Tianjin Lishen Battery Joint-Stock Co., Ltd. planned to manufacture and market novel hybrid energy storage system (HESS) products, combining ultra capacitors with lithium ion batteries, an interesting discussion ensued in the EV forum between Danny M, Morgan La Moore and “Kaido Kert”. La Moore began the discussion in a reply to Steven Ciciora about hybrid battery packs. He suggests stiffening a flooded lead-acid pack, a.k.a., “floodies”, with A123’s cells, which don’t have the voltage drop problem that ultra-caps do. The biggest design problem is matching the nominal and max voltages of the A123 and flooded packs. (Also, the stiffening would only work really well in the middle 80% of the A123’s SOC.) During a subsequent exchange, La Moore makes the following suggestion: To prevent the floodies from over-charging the A123’s, put a contactor between the floodies and the A123’s. When the A123 voltage drops below 2.7 volts per cell, the contactor closes, and because the floodies are about 10-20V higher than the A123’s, they start charging the A123’s at a rate determined by their internal resistance. When the A123 voltage rises above 3.5 volts per cell, the contactor opens, and the A123’s handle all the load until they drop below 2.7V again. The circuit required isn’t very complicated, and the only expensive component is the contactor. Depending on the internal resistance of the batteries, it wouldn’t have to handle too much current, either. The more A123’s you use in parallel, the better they’ll handle the current. I think you’d want at least enough to double the stiffness of your pack. (In the low quantities we’re talking about here, the A123’s aren’t really all that stiff. You can control how stiff they are by changing the amount you use.) If you have a 120V truck with 20 6V, 4 mOhm batteries, then those batteries have a combined internal resistance of 80 mOhms. A 34s4p pack of A123’s would have 85 mOhms internal resistance, so the combination of both in parallel (when accelerating) would double the stiffness of your pack. (The voltage sag of the A123’s would trip the contactor, which would put both in parallel, making it much more stiff.) The problem is that this would require 136 A123’s, which would cost $1190 plus shipping at E-bay prices. The A123’s would have a capacity of about 1 kWh. If I under-estimated the internal resistance of the floodies, though, it wouldn’t take as much A123 to double the stiffness of your pack. If you’re interested, I’m willing to draw up the circuit, post it here for others to look at, and build it for you if the other EE’s on the list don’t notice big problems with it. Danny M. replied and the following is a subsequent exchange between La Moore and DM On Nov 21, 2007 12:39 AM, wrote: “Unless there’s something different about A123’s charge procedures, I think you’re oversimplifying the charge procedure and it may
quickly damage the cells.” LM: I’m operating entirely in the middle of the range, where the procedure is “dump current in, don’t dump too much”. However, you’d have to be careful and choose trip voltages such that you don’t fail the “don’t dump too much” part. Yes, charging a Li-Ion requires more care at the end of charge, but I cut off the capacitor before then. A123’s are much, much less picky than most Li-Ion, and I’m using that to my advantage. DM: Shorting on the batt pack 10V-20V could create very high currents that could be bad for both batts. Aren’t A123’s rated for 30C at best? LM: Yeah, the A123’s are rated at 30C continuous, 52C peak. That equates to 70A max continuous, 120A max peak. With a 120V floodie pack at a topped-off charge of 132V and ESR of 80 mOhm and a 34s4p A123 pack with a cutoff of 2.7*34=91.8V and ESR of 85 mOhm, you have a worst-case charging current of 243A. Split 4 ways, this is 60.8A, less than the 70A rating per cell of the A123’s. It’s probably not good for the cells to charge so quickly, though. If you change the lower cutoff to 3.0V, the max charging current is 182A (with topped-off floodies); this is probably a better value. In that case, it would be a good idea to add temperature compensation so that you still operate in the middle of the range in low temperatures, though. DM: I doubt the A123’s going to pull it down to its normal charging voltage. I suspect that like putting 300A charging current on a battery at 11V open-circuit (partial SOC) could bring it up to 14.6V instantly without regard to its charge state, this will make the A123’s terminal voltage rise above the set point even though its SOC wouldn’t be up there yet. LM: No, that won’t trip the upper set point. Say you have a 34s pack of A123 and a 120V “floodie” pack. The lower cutoff is 3*34=102V and the upper cutoff is 3.5*34=119V. You just charged up and your “floodies” are sitting at 132V. You’re driving along, and your A123’s discharge below 102V. The contactor closes; now, ignoring the load, you get (132-102)V/(.165 Ohm)=182A charging the A123 pack. The voltage between the internal resistances (what you’re measuring) is 102+30*(85/165)=117V. This is a worst-case voltage, and any load from the motor or a “floodie” SOC below 100% will make that initial voltage even lower. DM: There’s also balance issues. Charging a long string of Li-ion is sort of a mess. I suppose if you never try to reach full charge and use it as a buffer then the risk of overcharging a cell is minimized at least. LM: Yeah, a BMS for the A123’s is definitely a good idea. The way I’d like to do it: use a proper buck converter in current-mode control, with the output current equal to the moving average of the last 30 seconds of controller current. This would require a microcontroller, current shunt, and DC-DC converter, though. The nice thing is that the DC-DC can be sized to the average load instead of peak load, and it would have a voltage ratio of 3:4 at the worst and almost 1:1 at the best, which is a good thing. A happy medium would be to do amp-hour counting on the A123’s and control the contactor based on that. Then “Kaido Kert” adds: If you substitute the contactor to a MOSFET/IGBT in this idea, and put some cheap micro in charge of it providing the intelligence and PWM, this would work. Could probably work out cheaper than contactor and save the batteries. But one would have to do the programming of course. Bill Dube’, developer of the KillaCycle, then comments on a related thread: Just to add a little twist to all of this. A123 Systems are building, in prototype, cells with twice the specific power. (Half the internal resistance.) Also, by heating the cells to about 70 C, we manage to get 175 amps per cell from the present M1 cells. This is an internal impedance of 0.010 Ohms. David Schramm, Maxwell’s president and chief executive officer, who would seem to be sticking to The Business Plan of Great Failure, said that the companies see a large market opportunity for their products. We believe that the products we envision will give end-users
the best of both worlds in terms of the long cycle life, rapid charge/discharge characteristics and low temperature performance of ultracapacitors and the large energy storage capacity of lithium-ion batteries,” Schramm said. “We also plan to move some of our BOOSTCAP product assembly to Lishen in order to leverage our joint process engineering capabilities, and Lishen will conduct development and qualification testing on battery electrode material produced through Maxwell’s proprietary dry process, so we see this as a deep and strategically important alliance for both companies. Energy Blog commentator bigTom observes: This would seem to be a step forward for portable electric storage systems. The ultracap can efficiently absord or put out significant short lived energy spikes, while the battery allows significant long-term storage capacity. I would presume that the ratio of capacitor energy storage to battery energy storage would be fairly low, 1 to ten or possibly 1 to 100. Quick charging the capacitor in order to leisurely charge the battery would not be effective in this case. Ultra-Caps are really amazing in their capabilities, but I’ve never seen any information on cost. Presumably it is quite high per KJoule? And, Energy Blog commentator Chan retorts: Maxwell ultra caps will cost $0.02/Farad. That is $54 for a 2600F Ucap @ 2.7V, which equates to $20/Wh. The USABC (United States Advanced Battery Consortium) wants $0.15/Wh (a factor of 100 less) in PHEV (Plug-in Hybrid Electric Vehicle) battery, does it not?
Nesscap Super Capacitors Lithium-ion Batteries
with
Kokum
Subtitle: That’s Kokum, Not Hokum, Lutz Baiters As previously noted, Maxwell Technologies and Argonne National Laboratory have been investigating combinations of batteries and ultra capacitors. Green Car Congress now reports that General Motors is “actively exploring” the concept, which is especially suited for the EREVs (Extended Range Electric Vehicles) “because of the combined requirement for high energy and high power.” General Motors had indicated previously that their concept vehicle, the Volt, would an EREV. During a recent presentation at an AABC (Advanced Automotive Battery Conference) in Tampa, Florida, Dr. Mark Verbrugge, Director, Material and Process Labs at GM’s Tech Center, said that GM is testing a proof of concept system consisting of 6 100F Nesscap supercapacitors and two Kokum high-energy lithium-ion batteries.
Initial results from General Motors tests show improved power delivery from a combination of 6 100F Nesscap super capacitors and two Kokum high-energy lithium-ion batteries compared to two conventional Li-ion battery systems (Supercap-Li-ion combo is the green line). (Note: Although contraindicated, no DC/DC converter was used in order to keep complexity down.) The tests were conducted at lower battery surface temperatures and testers noted a slight sacrifice in energy density. AG readers may recall that researchers at the Electric Vehicle Institute at Bowling Green State University developed and patented a supplemental, electric drive that uses ultra capacitors to complement an existing propulsion system. Nesscap super capacitors were in the proof of concept transit bus developed for NASA. More recently, implemented there have begun pilot projects with Maxwell ultra capacitors helping to power transit buses. However, this has been with super capacitors alone rather than a combination. Super capacitors alone have also been proved on the race car track. On the other hand, AG readers may recall that PML Flightlink has tested a combined system in a passenger car. And, more recently, AFS Trinity Power Systems of Bellvue, Washington, has tested a converted Saturn Vue. Not only was the AFS test vehicle a flex-fuel, plug-in, the energy storage system was a combination of ultra capacitors and standard, deep-cycle batteries. Other Similar AG Posts Possibly Related Automatically Generated Battery / Capacitor Combined Energy Storage Finally! Ultra Cap / Lithium-Ion Battery Combination Testing Hybrid Booster Drive Nano Structure for Hybrid Energy Storage Writing for the Canadian Financial Post, Nicolas Van Praet reports on a recent assertion by Masaaki Kato, who is president of Honda Motor Co.’s research unit, that Lithium-ion powered cars would fail to satisfy most consumers, because they are costly and such batteries still hold less than half the energy of gasoline by weight. Those reasons — high cost and less energy — are correct for now. The snapshot of consumer behavior taken by Kato is more accurate than inaccurate since it certainly will require a significant shift by consumers to adapt to electric drive. Honda Motor Company, which is world renown for building exceptionally quality automobiles, has done considerable research on electric drive vehicles, so this is other than someone’s uninformed opinion. On the other hand, it seemingly ignores how electric drive addresses the combined threats of Peak Oil and Climate Devastation. (Editor’s jibe:
Kato is no doubt a member of the Society of Automotive Engineers (Otto motive means propulsion from internal combustion operating on an Otto cycle) and probably a honorary member of the Most Esteemed Makers of Buggy Whips.) It also ignores the leap frog effort by Chinese car makers, which is expected because of lower cost to take a bigger bite of future market share than the “Shebby Bolt“. And, while HMC is to introduce a dedicated gasoline-electric hybrid car next year to compete with Toyota’s Prius, Kato’s snapshot would seem to ignore the obvious success of the Toyota Prius, which offers an electric only at low speed mode. It also sidetracks from the decided advantage of kinetic energy reclamation. Lastly, the Kato observation would seem oblivious to the global gearing up by battery manufacturers. He certainly is correct that battery technology needs to advance further. Nonetheless, his decision that battery-powered vehicles have yet to become widespread and popular in the market to warrant manufacturing by Honda does seem ill-advised. (Editor’s exhoration: AG readers demand a plug (No plug, No deal!), you have nothing to lose but your GHG! Also, tell the plug-in hybrid makers that you want a medium speed electric only mode while they are at it.) The author interviewed Jerry Chenkin, executive vice-president of Honda Canada Inc., who opined, “The key is in the end we need to conserve the world’s energy resources and protect the environment for future generations.” Toward such a goal, Honda “is pushing zero-emission hydrogen fuel cell technology. This summer, it leased a new hydrogen-powered sedan called the FCX Clarity to a limited number of U.S. clients for $600 a month.” Mike Millikin relays a report that “China, already a global center for lithium-ion battery component production and battery manufacturing, is ramping up its research and development efforts in the field, both within the private sector and with government support.” At the 1st International Conference on Advanced Lithium Batteries for Automobile Applications, organized by Argonne National Laboratory, Dr. Jiqiang Wang of the Tianjin Institute of Power Sources (TIPS) provided an overview of the government-supported R&D projects for lithium-ion batteries for transportation, which are now focusing on two primary cathode materials: manganese spinel (LiMn2O4) and iron phosphate (LiFePO4). Dr. Wang began by observing that the Beijing Olympics had served as a large-scale field test for some of the domestically-developed lithium-ion technology: there were 55 electric passenger buses and 20 fuel cell hybrid vehicles equipped with lithium-ion batteries that accumulated about 200,000 km (124,000 miles) of service during the Games. Fifty of the buses used lithium-ion systems with 137 kWh capacity, comprising 7 smaller packs of 10 kWh each and three larger packs with about 20 kWh each. These packs used 90 Ah prismatic cells from Beijing Citic Guoan Mengguli (MGL), with LiMn2O4 cathodes. The other five buses used 10 large packs with a total of 205 kWh capacity. The fuel cell hybrid vehicles used 350V packs comprising 8Ah prismatic high-power cells from Suzhou Phylion Battery Co., Ltd., again with LiMn2O4 cathodes. The packs delivered maximum pulse power of 50 kW. According to an overview of lithium-ion developments in China published by Argonne earlier this year, MGL ranks as China’s largest manufacturer of LiCoO 2 cathode material, and is the first to market the new materials LiMn2O4 and LiCoO0.2Ni0.8O2. Besides cathode materials, MGL also produces lithium-ion secondary batteries of high energy density and high capacity for power and energy storage. Suzhou Phylion Battery Co., Ltd., is a battery technology corporation set up by Legend Capital Co., Ltd.; the Institute of Physics of the Chinese Academy of Sciences; and
Chengdu Diao Group. The company specializes in manufacturing and selling lithium-ion cells with high capacity and current, and has been selling into the portable devices, battery-powered tools and e-bike markets. The batteries deployed in the vehicles for the Olympics adhered to a new, more stringent national safety standard. The performance of cells and modules needed to be confirmed in one of two national testing centers, in Beijing and Tianjin. Looking ahead for the next two or three years, said Dr. Wang, the government-supported 863 project will continue to support R&D on LiMn2O4, but will also start to support R&D on LiFePO4. The government has set development targets for iron phosphate and manganese spinel cathodes for HEV and EV applications: Specifications for Li-ion batteries Capacity (Ah)
8, 20
50
100
≥1,800
≥700
≥500
Specific Energy (Wh/kg) LiFePO4
≥65
≥110
≥110
Specific energy (Wh/kg) LiMn2O4
≥70
≥120
≥120
Max. discharge rate
30C (20s)
6C (30s)
5C (30s)
Max. charge rate
10C (10s)
4C (60s)
4C (60s)
≤3.0
≤2.5
Specific power (W/kg)
Cell internal resistance (m&Ohm;)
≤2.0
Cell-to-cell voltage deviation (V)
≤0.02
Cell-to-cell capacity deviation (%)
≤2
Operating temp. range (°C)
-25 to +60
Storage temp. range (°C)
-40 to +80
Charge retention (28 days at ambient temp.) (%)
≥90
SOC estimation error (%)
≤5
Safety
Pass industry or specified standard. 4
15 (LiFePO4); 10 (LiMn2O4)
Whole battery running life (10 km Reliability Cell-level cost at mass prod. (Yuan/Wh; US$/Wh)
Operate normally under environment humidity of 100%; meet relative requirements during whole vehicle running mode test of 30,000 km ≤3/ ≤0.44
≤2/ ≤0.29
Lishen and BAK are each leading an R&D group for lithium iron phosphate development for EV and HEV applications; MGL and Phylion are each leading an R&D group for manganese spinel development for EV and HEV applications. Research is also looking into new anode materials, such as hard carbon. Besides the government-sponsored research programs, Dr. Wang noted, there are several large lithium-ion battery manufacturers who are also doing R&D on lithium-ion batteries for EV and HEV applications, such as BYD. The Edgerton Center Summer Engineering Workshop — a group of students from MIT and their friends from some area high schools — have started an electric kart project.
≤2/ ≤0.29
“The [electric] kart is capable of going about 35 miles per hour and has a max output of 300 amps.” Weighing in at 350 lbs. with 36 volts of lead-acid batteries on board, the coolest piece of the e-kart puzzle is the ultracapacitor “boost” mode. That capacitor is also called upon to store extra energy from braking that would otherwise be lost. The students designed and built their own motor controller in lieu of purchasing one off-the-shelf. A separately excited motor allows for a bit of “gearing” despite the single speed transmission.
Battery / Capacitor Combined Energy Storage
At the recent British Motor Show, PML Flightlink and its partner Synergy Innovations showed a MINI QED — an in-wheel, plug-in, series hybrid conversion of a MINI, which many would agree is a fun car to drive even before these developers achieved an ability to accelerate from 0-60 in 4.5 seconds. Speaking of incorporating ultra caps into the electric drive, I recently learned from Mike Millikin that PML Flightlink put 350V worth of 11 Farad ultra capacitors into its Mini QED prototype. The ultra capacitors accept power
from regen braking and discharge when high current is required for acceleration.
For now a combination of ultra capacitors and advanced lithium batteries is possible only in a “proof-of-concept” prototype. As one GCC commentator observed, “I’d hate to see the bill.” My ignorance of power electronics still prevents me from puzzling out how exactly the bank of ultra capacitors and the lithium battery pack interact. The GCC article focused more on the engineering of anti-skid and traction control afforded by in-wheel motors than on combining power from ultra capacitors and advanced lithium batteries. In the commentary, there was considerable discussion regarding pros and cons of in-wheel motors, plus evidence that such performance is only possible with a high power / high energy system. Other Similar AG Posts Possibly Related Automatically Generated Finally! Ultra Cap / Lithium-Ion Battery Combination Testing Nesscap Super Capacitors with Kokum Lithium-ion Batteries Nano Structure for Hybrid Energy Storage Modified Urban Delivery Model