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Thursday, August 31, 2006

Why do we need a Nickel Metal Hydride Battery (NiMH) in a Hybrid Electric Vehicle (HEV)?

Nickel Metal Hydride Battery (NiMH)
the NiMH cylinder
Why do we need a Nickel Metal Hydride Battery (NiMH) in a Hybrid Electric Vehicle (HEV)?

By Lou Ann Hammond

Hybrid sales are phenomenal. Every vehicle that is a hybrid is selling out virtually before it hits the store lot. Lexus PR folks have said that there will be 24,000 Lexus RX 400hs produced this year and that 11,000 are already pre-sold.

It doesn’t make sense that with hybrids so hot that the Manufacturers would dole out hybrids so sparingly, not really letting the public see the full demand of the hybrid. Is there a demand for hybrids or is the hype for the 100,000 or so hybrids brought about because there are so few hybrids. We know the demand for vehicles was over 16,000,000 last year because there were over 16,000,0000 produced and over 16,000,0000 sold. In fact, production outweighed sales. Production of hybrids have never outweighed sales of hybrids. Why aren’t more hybrids being produced?

There are four major suppliers of automotive Nickel Metal Hydride (NiMH) batteries; Japan’s Panasonic and Sanyo, China’s GP Industries (Goldpeak), U.S. based Johnson Controls and Cobasys. Cobasys has a joint venture with Energy Conversion Devices (ECD) and Chevron Texaco on their NiMH batteries. Goldpeak supplies buses in Asia and Europe. Ford uses Sanyo’s batteries, Toyota uses Panasonics. Honda uses both. Johnson Controls is just starting a pilot operation at their Hanover, Germany facility

The one company that has been quoted as saying there is a shortage of batteries is Ford Motor Company. Ford uses Sanyo for their Ford Escape hybrid batteries. Ford is expected to build 20,000 Escape hybrids in 2005, but would like to build more, save for the lack of batteries. Ford is in talks with Sanyo to boost production. Ford cannot just go to another battery maker and buy these batteries off the shelf like one would do if they needed a lead acid battery.

The Nickel Metal Hydride battery powers everything from cellular phones to hybrid electric vehicles. According to Cobasys, the first use of a NiMH battery was in the form of a Nickel hydrogen battery used in aerospace applications. A NiMH is the configuration of a battery using metal hydride hydrogen storage materials as one of the battery electrodes. You see NiMH batteries in solid state format in the batteries you use today in cameras, blackberrys, PDAs and palm pilots and a slue of other gadgetry. Making a NiMH for automotive use requires cranking amps that are not needed in the gadgetry.

NiMH is a rechargeable battery technology that has approximately 30-50% more charge per pound than nickel cadmium (NiCD). Cadmium is a toxic heavy metal that can leach into the water supply if the case breaks and harm people and animals that ingest it. Introduced in the early 1990s, NiMH uses nickel and metal hydride plates with potassium hydroxide as the electrolyte. NiMH batteries do not suffer quite as much from the "memory effect" as do nickel cadmium batteries, but still require complete discharges in order to obtain the most efficiency and longest life. Nickel Metal Hydride batteries have pretty much eclipsed the nickel cadmium battery in solid state use and are not even considered for automotive use. NiMH and lithium-ion (Li-ion) and even newer lithium-polymer batteries, lithium-based formulations, pose less of a threat to the public than NiCd.

Johnson Controls is the latest company to start producing automotive NiMH batteries. The NiMH cell was developed using technologies from its Varta Battery Automotive Business in Europe. "HEVs represent

the NiMH prismatic
a small but rapidly growing part of the modern-day automotive market," said Lou Senunas, vice president of advanced battery and hybrid technology for Johnson Controls. "With our technological strengths, long-term experience, and manufacturing capacity, we are well-positioned to charge forward as a key supplier of battery technology and products to the emerging HEV segment."

A hybrid vehicle is a standard vehicle with electric power assist. A hybrid is different from an electric vehicle in that it doesn’t need to be plugged in for the battery to work. It has what we call regenerative braking. The hybrid can be a mild or full hybrid, but the definition of a hybrid is that it is able to run on its own for a short time. All hybrids still have lead acid batteries, but most - not all - hybrids have Nickel Metal hydridge batteries to assist in fuel savings and lower emissions.

Let’s start with a mild hybrid, such as a General Motors (GM) pickup. According to Joe LoGrasso, Engineering Manager of Electrical Power and Advanced Systems for GM Global Electrical Engineering Center, GM uses a mild hybrid system that employs three 12 volt batteries and a fly-wheel alternator starter for a twelve-fifteen percent savings in fuel. This doesn’t seem like much and could probably be achieved just as easily if you took some of the weight out of the vehicle. There are some very simple reasons that make a mild hybrid important.

The fly wheel is a motor generator. It helps store energy in a 42 volt system. There is also the difference, according to Tom Dougherty, Director of Advanced Battery and Advanced Systems for Johnson Controls, in the cold start. The first is that it reduces cranking time. A regular internal combustion engine vehicle take 3/4 to 1.5 seconds of pumping gas to start. This passes gas through the engine, unused and causes the most amount of Nitrous Oxide (NOX) and hydrocarbons. These are called pollutants which are not good to breath. GMs mild hybrid cold start is 1/3 the time of just an ordinary internal combustion engine.

Another advantage is in the platform. The engine doesn’t have to be retooled to include the lead acid batteries (LAB). GM only had to find four inches more space to include the batteries and they did so. Retooling a platform and including advanced technology can be very expensive. Using the same design and adding three lead acid batteries will add some cost, but not the $4,000-$6,000 ticket that we are seeing on NiMH batteries. The Nickel Metal Hydride battery has a greater sensitivity to elevated temperatures which is why it is not under the hood like the LAB, but in the trunk or under a seat instead. There are Hybrid Electric Vehicles (HEV) that include a thermistor in the battery pack which monitors the battery temperature and cuts off charging if the temperature becomes too high.

The other advantage is in the lead acid batteries themselves. There may not be a shortage of NiMH batteries, but you won’t see the cost going down anytime soon. According to Dougherty that is because there is no low cost, Or cost effective, recycling available for NiMH batteries available. "Lead Acid batteries are 97.6% recyled. They are the highest recycled product in the world, far more than for any other consumer product including aluminum beverage cans (55 percent), newspapers (45 percent), glass bottles (26 percent), and tires (26 percent). Lead-acid batteries now have a closed-loop life cycle. In the United States, the typical new Johnson Controls battery can contain 70 to 80 percent recycled lead and

Sanyo's battery used by Ford
plastic. When a spent battery is collected, it is sent to a permitted recycler where, under strict environmental regulations, the lead and plastic are reclaimed and sent to a new-battery manufacturer. The recycling cycle goes on indefinitely, which means the battery materials in a given car, truck, boat or motorcycle have been recycled many times and will continue to be recycled."

There is no mass marketing to the general public planned of NiMH batteries to bring the cost down like there is in lead acid batteries. NiMH batteries are different from lead acid batteries in that they are an advanced chemistry that if left on the shelf too long degradation will occur. A lead acid battery will have to be recharged if left on the shelf for 6-8 months while a NiMH battery will have to be recharged every three months.

Right now there is no circle of life for the Nickel Metal Hydride battery. Recycler Toxco, a Canadian company, is in research and development phase of recycling NiMH batteries. According to Todd Coy, Vice President Battery Division Kinsbursky Corporation, the parent company of Toxco, "Kinsbursky is obtaining a larger melting unit that would get a cleaner more refined nickel." According to Coy, "It is our responsibility to be in a state of preparedness. The economics may not be there in the beginning, but in order to be the leader in recycling batteries you have to be on the forefront. We can partner with Manufacturers and recycle the batteries and return the raw product to producers."

This does not explain why General Motors is only producing 1,500-2,500 hybrid pickups when they sell 900,000. If GM were to build all 900,000 pickups as just mild hybrids the United States would save 80,000,000 gallons of gas.

But for maximum effect you want a full hybrid which uses a Nickel Metal Hydride battery. There are two types of NiMH batteries; cylindrical and prismatic. The chemistry is the same in both, the difference is preferential to the Manufacturers platform. NiMH batteries weigh about 30 percent less than a LAB. The NiMH battery is more "power specific" than a lead acid battery. Power Specific refers to the power by weight; it weighs less for the same amount of power. The NiMH energy throughput lasts 8-10 years whereas the lead acid battery is only warrantied for 2-3 years.

On the full hybrid the engine size is reduced because the motor generator supplies the extra horsepower not normally needed in the engine. For example, you don’t need all your horsepower to go 65 mph down a flat street that you do need if you want to go 65 mph up a hill. But upon ascent, the motor generator, powered by the NiMH battery, kicks in and provides the extra horsepower. The 2005 Lexus RX 400h internal combustion engine has a horsepower of 205. When you combine that with the three motor generators the combined horsepower is 268.

This does not explain why Toyota/Lexus is only producing 48,000 hybrid SUVs when they sell 300,000. If Toyota/Lexus were to build all 300,000 as hybrids the United States would save 30,000,000 gallons of gas. If they were to make all their Camrys (the most similar car to the Prius)hybrids it would save us 106,000,000 gallons of gas a year.

The Nickel Metal Hydride Battery (NiMH) is an integral part of a hybrid. The Lithium Ion battery has the potential of eclipsing the NiMH battery but it is not ready for primetime yet. The Lithium Ion hasn’t met the abuse tolerance test; it has to be able to overcharge in a vehicle without catastrophic incidence to the vehicle.

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