Any vehicle that has two or more sources for its driving power can be referred to as a ‘hybrid’, but carmakers are employing three general hybrid types. A mild hybrid is a vehicle driven by an internal combustion engine (ICE) that may turn itself off when the vehicle is coasting, braking or stopped in traffic, restarting as the accelerator is pressed, brake pedal is released, or the clutch is engaged. A parallel hybrid has both an ICE and one or more electric motors that work together to create wheel-turning power. A series hybrid also includes an ICE and electric motor(s), though in this case power is only delivered via the electric motor(s), with the ICE only running to charge the batteries as needed.
As the recent Frankfurt Motor Show demonstrates, virtually all major OEMs now offer (or plan to offer in the near future) models incorporating one or more of these systems, either in vehicles adapted to use hybrid systems, or in ‘dedicated’ vehicles designed from the ground up to use a hybrid propulsion solution. Cars adapted to use hybrid systems include BMW’s Mini and GM’s Malibu, while Honda’s Insight and the Toyota Prius are well-known examples of dedicated hybrids.
Turning an ICE off at idle is clearly going to save fuel, yet while the concept behind mild hybrid systems may appear simple, the working solution involves considerable complexity. A standard engine is started only once on any given journey; a mild hybrid vehicle has to be able to automatically restart its engine an unlimited number of times – this, with a minimum of intrusion and without detracting from the overall driving experience.
Since 2007, the Mini has employed BMW’s Efficient Dynamics Technologies (also offered on 1- and 5-Series models) as its mild hybrid solution. In addition to the startstop feature, it also includes brake energy regeneration and a switch point display system. Offered with all manual transmission versions, the start-stop is engaged when the car is put in neutral, the engine restarting when the clutch pedal is depressed. The so-called Intelligent Alternator Control (IAC) drives the regeneration system, channelling current developed on the overrun to the heavy-duty battery.
This is separate from the belt-driven alternator. The switch point display signals when the driver should change gear for optimum fuel economy.
Uprated parts added post-launch to second-generation Mini models with the stop-start feature include a new starter motor and alternator, which can disengage when not required, and a new, heavy-duty absorbent glass mat (AGM) battery by Varta, part of Johnson Controls. The sealed AGM battery uses glass mats saturated with boron silicate between the plates instead of a gelled or liquid electrolyte.
While the charging voltage is the same as a standard 12V car battery, the internal resistance of an AGM battery is extremely low, virtually eliminating heat build up in the battery when either under heavy charging or discharging – such as when regenerated current is delivered or when multiple engine starts are required.
Controlled Power Technologies’ Belt-driven Integrated Starter Generator (B-ISG) system also features an AGM battery. Mike Dowsett, Senior Manager, Micro Hybrids at CPT explains: “For our micro-hybrid stop-start system, the recommended battery upgrade is from a flooded lead acid battery to an AGM or valve-regulated lead acid model. They provide an energy supply that can withstand a deep discharge and rapid recharge.”
CPT’s B-ISG system has, according to Dowsett, been designed as a direct replacement for the alternator, and features very similar fittings. While the donor engine requires new calibration to reflect faster starting, including quicker crank sychronization and minor modifications to the air/fuel mix, these will result in both improved emissions and fuel economy.
“CPT SpeedStart is the highest-powered 12V B-ISG available,” claims Dowsett. “It provides 2.4kW of cranking power, which is more than most starter motors. It also provides 72Nm of torque, which when multiplied through a 3:1 belt ratio will deliver 216Nm at the crankshaft.” Dowsett goes on to say that the system can work with most larger European vehicles, even handling the compression ratio of a 2.0-litre common rail diesel. Systems that go above 12V have significantly higher hardware and integration costs, he reasons, with two voltages on a single vehicle requiring converters and other additional equipment.
GM has been offering its own belt alternator starter (BAS) system on models including the Chevrolet Malibu and Oldsmobile Aurora. While similar in concept to the CPT unit, the GM BAS replaces the conventional starter and alternator with a 36V system that controls a variety of engine functions.
Facing limited popularity, the current BAS system is due to be phased out. But development of an improved system is already well advanced, according to Brian Corbett of GM’s Hybrid and Battery Division: “The new system will go into production in calendar year 2011. We are developing the technology in-house and Hitachi will provide the lithium-ion batteries. We have not announced the manufacturing location(s) for the vehicles that will use the next-generation mild hybrid system.” The second system is expected be approximately 24% smaller and 40% lighter than the previous version, delivering up to 120V (up from the original 36V).”
Corbett continues: “Compared to the current system, the next-gen technology will offer increased power and voltage, increased electric boost, increased regenerative braking, together with increased fuel efficiency. (The system) is a key part of GM’s environmental strategy; it’s our answer for a high-value, affordable hybrid system. It’s easy to integrate globally, offering potentially significant volume growth via broader engine and transmission application.”
Toyota’s Hybrid Synergy Drive is perhaps the most well known hybrid system. Available on a range of models, including the Prius and Lexus LX range of SUVs, the system offers familiar hybrid features, electric-only driving at low speed, regenerative braking, etc. Though while the Hybrid Synergy Drive combines petrol and electric power at the driven wheels, there are other ways to arrange a parallel hybrid.
With the upcoming launch of its HYbrid4 models, the first of which will be the Peugeot 3008, PSA Group will introduce its own parallel hybrid solution. This system is fundamentally different to other similar hybrid arrangements in that it is the first to use a diesel engine.
Further, instead of using combined petrol and electric power at the same driven wheels, the electric motor independently drives the rear wheels, effectively making this a hybrid fourwheel drive system.
Where as most other parallel hybrids locate the electric motor in close proximity to the engine, the PSA solution has the electric motor housed in the rear suspension linkage. As such, the system becomes a modular solution, meaning that a given vehicle platform does not have to be comprehensively altered in order to accommodate the new drive package, offering so-called ‘cross-range adaptation’.
According to PSA, this will allow hybrid technology to be applied to a range of vehicles, while cutting the overall cost.
In addition to claimed CO2 reductions of up to 35% over an equivalent diesel-only model, the PSA system means four-wheel drive with less complexity. The Lexus LX450h, for example, while having two separate electric motors (front and rear) has only the single petrol engine, meaning a driveshaft and transfer case is required to deliver the variable petrol-electric power to the rear axle. PSA further claims that relocating the electric motor from the engine bay to the rear axle has considerably improved vehicle weight distribution.
It is a hybrid solution that has minimal impact on production line setup, explains Eric Breton, Director of PSA Hybrid Technology Programmes: “HYbrid4 cars will be assembled on the same line as the conventional ICE versions at our Sochaux facility. To this end, some workstations will be adapted or added. The rear suspension will be provided completely assembled, with the electric motor and its wiring.
The power electronics and battery packs will be installed separately in their respective locations (under the floor of the trunk). This will allow for both maximum quality of assembly and very good cost effectiveness.”
While Peugeot is the first OEM to use a diesel engine in partnership with an electric motor, Hyundai is the first to use an LPG (liquid petroleum gas) and electric combination to create its hybrid application. The result of a $200m, 43-month development programme, this new model is also the first HEV (hybrid electric vehicle) to use lithiumion polymer (LiPoly) batteries supplied by LGChem, the company also providing the test battery packs for the GM Volt. The Elantra HEV (hybrid electric vehicle) went on sale in South Korea earlier this year, where LPG is a popular alternative to petrol. Hyundai says that it is investigating the possibility of exporting the model to other areas that have an LPG delivery infrastructure, including Australia.
Perhaps the most famous hybrid PHEV – or petrol/electric vehicle - is the Chevrolet Volt or Opel Ampera, as it is to be called in Europe. For all the talk about the Volt, GM’s Brian Corbett claims few - if any - have accurately described how the powertrain will work. “The Voltec propulsion technology used in the Volt isn’t always easily understood. It’s not a series hybrid, as these never run on electricity alone and the engine runs at a constant speed. The Volt can run on electric only and the engine does not run at a constant speed.
“After the Volt’s electric-only propulsion is depleted, the engine will start, but only to generate electric energy to drive the wheels, not charge the battery. The engine comes on to make enough electric energy to turn the wheels, because the wheels are always turning electrically. With the electric generator about half the size of the motor, you might expect there to be performance problems but that’s where the battery comes back into play, because the customer depletion point is not full depletion; by design, there’s still energy available. In peak situations, such as climbing a hill or merging into traffic, the system takes some more energy out of the battery, meaning that the system may actually come down a little below the customer depletion level.”
Corbett goes on to explain that the depleted battery charge can then be replaced through regenerative technology, or alternatively, energy not used to turn the wheels can replenish the charge. But the key, Corbett says, is what the system does not do: “We don’t recharge the battery. In fact, the customer won’t recognize any of this is taking place, as their electric range indicator will remain at zero. At that point we are actually using the battery as a peak buffer, trying to recapture energy as the opportunities allow.”
General Motors has confirmed that it plans to invest $43m in its GM Subsystem Manufacturing facility, in Brownstown, Michigan, for production of the 200kg, T-shaped battery packs used in the Volt, the first case of a lithium-ion battery production centre being controlled by an OEM company.
To support this and other vehicle battery technologies, the carmaker has also opened a new $25m Global Battery Systems Lab, part of the GM Tech Center in Warren, Michigan.
As Volt production plans remain uncertain, there is time for a little last-minute lobbying. On a recent tour of GM’s Warren Technical Center, South Australia Premier Mike Rann announced that he would like to see GM’s Voletc technology appear in a version of the Holden Cruze, production of which is due to start at the GM subsidiary’s Elizabeth, Adelaide plant in 2010.
Yet there in lies the fundamental problem with the Volt. Unlike Peugeot’s HYbrid4 system, which can be adapted for use in a wide range of vehicles, the Volt is a powertrainspecific model. Although the Cruze and Volt share a similar platform and versions of the Cruze were used to test the Voltec system, those cars were highly adapted in order to accommodate the electric motor and batteries. That said, GM are considering a Holden Volt version, as part of a move to increase the choice of fuel-efficient models that use E85 biofuel and have stop-start systems.
While some OEM carmakers, battery manufacturers and even national and local governments have announced supply deals, production joint ventures and new factory builds aimed at producing lithium-ion batteries, the fact is that most hybrid vehicles use NiMH (nickel metal hydride) batteries. With Toyota (and Lexus) already having built more than two million hybrids using this battery type, PSA Group is taking the tried and tested route in using the same technology to deliver its HYbrid4 models.
All NiMH batteries use nickel as their primary material.
Another essential constituent are so-called rare earth metals (REMs), with the term ‘rare earth’ coming from the ‘uncommon oxide’ minerals first found in combination with the REM base elements. A battery pack for the Toyota Prius uses between 10 and 15kg of the REM lanthanum, together with smaller quantities of the REMs neodymium and praseodymium. In addition, the high-power magnets in the electric motor used in a hybrid vehicle require approximately 1kg of neodymium, together with small quantities of terbium and dysprosium, added to preserve magnetic characteristics at high temperatures.
Yet doubts remain over the sourcing of rare earth metals.
While India, Brazil and South Africa have previously operated REM mines, virtually all global operations have closed in the face of Chinese competition.
Estimates put Chinese production of REMs at 95% of global output, and with the Chinese government considering imposing REM export quotas, the situation could have a serious impact on hybrid vehicle production outside China. With the Toyota Prius said to be the largest single product using rare earth metals, the company is reportedly investigating alternative sources in Canada and Vietnam, while a former mine in California (Mountain Pass) is scheduled to reopen in 2012.
For the moment at least, a sustained policy of reducing export quotas has effectively created a Chinese rare earth metal monopoly.
Although the country has the capacity to supply global demand, which is rising at 10% per year, its 2009 export allocation was 38,000 tonnes – less than the total amount used by Japan in a year.
The success of the recently-released third-generation Prius has had the knock-on effect of causing a hybrid battery shortfall. While batteries for the Prius had been supplied by a joint venture between Toyota and Panasonic EV Energy, the carmaker has been forced to arrange additional battery deliveries from Sanyo Electric in order to maintain current production numbers.
The battery shortage has caused bottlenecks in production, with Prius customers waiting up to eight months for delivery. Further complicating matters, the Lexus HS250h, the premium manufacturer’s first dedicated hybrid model, has placed added demands on hybrid battery supplies.
Anticipating sales of 500 units per month, Lexus received 10,000 orders in the models’ first month of availability.
Reports suggest Toyota will start using li-ion batteries for its hybrid models in 2011, though this has yet to be confirmed. Panasonic, though, is waiting for regulatory approval to take control of Sanyo – coincidentally the world’s largest producer of rechargeable li-ion batteries.
Valence Technologies is a leader in the field of lithium iron (magnesium phosphate LiFeMgPO4) energy storage solutions. In terms of full-electric and hybrid vehicle powertrains, Valance batteries can be found in a range of private and commercial vehicles, including commercial delivery vehicles and mass transit buses.
Incorporated in 1989, the company is at the forefront of energy storage design and development, from cathode materials to complete cells and custom tray design. Headquartered in Austin, Texas, company has recently opened two lithium iron magnesium phosphate battery production facilities in Suzhou, China. Mark Donaghy, Global Marketing Manager for Valence, talks to Julian Buckley about the design, development and production of the company’s products.
AMS: Can you briefly outline the structure of VET’s lithium phosphate batteries? Mark Donaghy: Our core batteries are essentially similar to other batteries, in that they are made up of cathode, anode, separator and electrolyte. Our core IP is wrapped up with the cathode material, lithium iron magnesium phosphate.
Valence markets a variety of large format batteries under the U-Charge brand, offering a range of voltages and capacities. We have two strengths; our cathode material and our command and control logic. Valence manufactures lithium iron magnesium phosphate using a unique carbon thermal reduction process. We have international patent protection on both of these. Valence also has developed Epoch technology, our command and control logic which allows customers to manage energy requirements within their application.
AMS: How did you develop the new phosphate batteries? Is there a scientifically-based process that led to the phosphate solution, or is it simply a case of experimenting with potential materials to discover which performs the best
MD: Valence has been developing phosphate materials since 1989, so we have 20 years experience of developing scientific solutions both in materials and processes. We are constantly working on improvements that will enhance specific energy density and cycling capabilities. Our current generation of cathode materials and processes, Saphion Technology, focuses on lithium iron magnesium phosphate. We are currently developing our next-generation materials, lithium vanadium phosphate and lithium vanadium fl ourophosphate. Valence has a sizeable R&D department focusing on material testing and development.
AMS: What makes these batteries the best solution for hybrid automotive applications
MD: Our batteries will work across many applications, but they work best in heavy use hybrid applications and fully electric vehicles. Our chemistry is delivered though energy cells, which give excellent energy density along with cycling capability coupled with intrinsic safety. Some of the lithium metal oxide batteries display tendencies to overheat, potentially causing thermal events.
AMS: Are there cooling issues with lithium phosphate batteries, as with li-ion products
MD: All batteries should be cooled to enhance performance and longevity. If you mean are there any issues where batteries can overheat and cause a thermal runaway event, overheating some metal oxide-based lithium batteries can lead to serious runaway events. This can be caused by a short, or the battery getting punctured or crushed. The phosphate chemistry is inherently safe due to the strong phosphate oxygen bonds that are formed. These bonds are strong up to 800oC, whereas some metal oxide bonds will break at just over 100oC
AMS: What user benefits do Valence li-phosphate batteries offer over other battery manufacturer, supplier products
MD: Our batteries offer the combination of inherent safety, energy density, deep cycling capability for thousands of cycles. We also offer an entire energy storage solution, i.e. the ability to integrate our batteries into modular and scalable solutions that include battery management systems, cooling, and charging, as well as populating them into custom or standard trays and pods.
AMS: Does Valence currently have/plan to set up purchasing arrangements with material suppliers to maintain raw material prices?
MD: VET has OEM agreements in place for key components which defines longer term pricing. VET also works closely with these vendors to recommend process enhancements which will allow vendors to improve their capacities and yields, and to pass along the associated savings to VET.
AMS: In your opinion, is hybrid technology a ‘stepping stone’ or a permanent solution that stands further technology investment
MD: Yes we believe that it is a stepping stone. As battery technology improves and becomes cheaper, we see the demise of the weak hybrid (eg Prius) and the growth of fully-electric applications for urban use and the growth of the plug-in hybrid for longer commuter / weekend journeys. After all it is a simpler, and potentially cheaper solution to have one drive system rather than two.
AMS: What can be done to improve the recharging time of batteries used in pure EVs?
MD: There are alternatives, like battery swapping, as being marketed by organisations such as Better Place. There are also “superfast charging stations”. However the latter requires batteries to have the ability to take large amounts of current very quickly and this depends on the battery chemistry.
AMS: What is your take on the Chevy Volt, in that the gasoline engine starts to recharge the batteries with a 30% charge remaining? According to GM, this is the most effi cient way to preserve batteries over their lifetime in the charge/discharge cycle? Do you agree and could your product offer a better solution?
MD: The Chevy Volt is an example of a plug-in hybrid and is an area we see developing in the market. With all lithium batteries, reducing the depth of discharge increases the cycle count. The advantage of our phosphate materials is that even at 100% depth of discharge the cycle life is exceptional. This would provide an optimal solution for a PHEV.
AMS: Nissan has announced plans to construct battery-making facilities in Portugal and the UK, with backing from the respective national governments, in order to supply its future EVs. How do decisions such as this impact Valence.
MD: We are looking closely at opportunities to work with OEMS and Tier 1s in the US and Europe. There is a lot of federal funding available right now with the aim of reducing carbon emissions. Obviously battery manufacturers are in a position right now to benefit from government backed initiatives through improved R&D. One of the major goals is reducing battery costs while improving efficiencies.
AMS: In supplying OEM carmakers with batteries for EV and hybrid vehicles, does Valence play a role in designing the on-board system architecture – does system architecture impact overall battery efficiency?
MD: We have considerable experience working with a number of OEMs and integrators, so we have a lot of experience that we can share with customers in helping them implement a solution. We believe that this is a real added value in that a lot of battery manufacturers simply ship batteries to a customer and let the customer figure out their solution. The system architecture and contained ‘knowhow’ help ensure that batteries operate at optimal levels hence increasing the longevity and performance of the battery.
AMS: Can li-phosphate batteries suffer from ‘memory effect’ due to deep discharge or overcharging?
MD: No – no memory effect at all
AMS: Is production based on a production line system MD: Yes we are using semi- and fully-automated production lines our two 50,000 sq ft facilities in VET in Suzhou, China. These manufacture our cathode materials and our packs.
AMS: What types of automation feature in the production process?
MD: VET has developed multiple automated processes unique to the battery manufacturing industry. These include processes related to cellblock fabrication (laser welding, resistance welding, cell inspection) as well as those associated with battery assembly.
All Valence’s processes feature real time data capture and reporting. This provides everyone involved in the assembly process with clear visibility to the state of the production lines as well as excellent traceability which is a big plus for our customers.
AMS: Can you briefl y outline a step-by-step battery production
MD: Valence’s battery manufacturing begins with the production of our unique lithium iron phosphate magnesium cathode material. Not only is this one of the safest cathodes available today, it also displays excellent energy density and cycling capabilities.
This cathode material is then packaged into discrete cells, ranging from industry standard cylindrical cells to the newer, higher-capacity pouch cells. Cells are then assembled into cellblocks using Valence’s proprietary Cellblock Assembly Process.
These processes (laser welding, resistance welding, cell OCV) have been finely tuned to maximize production capacity and yields, and at the same time guaranteeing repeatable and scalable production of a premium, reliable product. Cellblocks are then combined with Valence’s battery control logic to create the final product.
Following each stage of assembly, product is subjected to an automated test gate specifically designed to guarantee the product will meet or exceed all performance criteria.
We have attained the ISO9001:2002 certification for quality and are working towards the TS16949 accreditation for automotive standards.
AMS: What were the reasons that convinced Valence to select China as the location for its new production facility? MD: One of the main drivers was reducing overheads and cost. China represented a way to move our production to a lower cost base. Obviously we had to maintain high standards which we have done through our ISO accreditation
AMS: Your promotional material refers to ‘furnaces, welding stations, wet ball mills and spray dryers’.
Can you outline how each these is used in the production process
MD: There are several steps involved in our production processes, a lot of which is proprietary.
In terms of our cathode material production the individual raw materials are initially measured and packaged in preparation of mixing. The ingredients are added in a control sequence to a milling machine. Solutions are added and then mixed until there is a homogeneous blend of all ingredients. We then heat and remove the moisture, leaving a course powder product. After inspection the material is mulled to improve its density and then compressed. The material is then fed into the automated fl owing furnace and heated in a controlled environment. The compressed powder is then ground down into a consistent powder substance. Several more qualifying and screening tests are carried out to assure the product meets specifi cations. The powder is dried and packaged in air tight containers and tested to verify product conformance.
AMS: It’s referred to as ‘intelligent pack’ manufacturing. Can you offer more details as to what this means in terms of the fi nal products?
MD: Valence offers complete electrical and communication connectivity. Valence high-capacity modules are constructed using individual cells, which are connected together into blocks. Connectors, sensors, wires and electronics are all added before the sub-assembly is sealed inside a robust outer case. Our packs are designed to integrate with our battery management systems (BMS), our command and control technology, which monitors and protects all modules within a system. A single BMS can monitor up to 128 modules and acts as the interface between the modules and the vehicle management unit through CANbus communication, maximising the performance of the whole battery system.
AMS: Are li-phosphate batteries susceptible to cold weather and if so, what can be done about this
MD: Most batteries have limitations with extreme weather, be it hot or cold.
In terms of low temperatures Valence batteries will operate effectively to -10C and can be stored to -40C.
AMS: What can be done to reduce the price per kW of battery storage, reducing the retail cost of EVs
MD: There are many market factors that will reduce price. As demand for EVs rise, the economies of scale will enable volume production and so price reductions. Certainly the price of lithium will fall if demand improves and mining techniques and so yield. In addition constant cell development which Valence is involved in, particularly the move to large format and the improvement in formulation.
AMS: Can you outline some of your key supplier contracts, who they’re with and why Valence was selected over other battery suppliers.
MD: We have supply agreements with many global companies including Smith Electric Vehicles (EV vans and trucks), Brammo (motorcycles), Oxygen (Scooters). We are also working with companies like Wrightbus and IC Corporation (part of Navistar). There are two main reasons why customers want to work with us. The main one is safety. Our lithium phosphate displays intrinsic safety that other lithium chemistries do not.
There have been many news stories about incidents with lithium-ion batteries that have exploded or caused fires. These tend to be caused by lithium metal oxide batteries (manganese or cobalt). The second reason is the cycling qualities of lithium phosphate. Our batteries cycle (100% charge and discharge) to almost 3,000 cycles and still display 80% of initial capacity. That’s double or nearly treble the cycling ability of other lithium chemistries and five times that of lead acid.
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