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Lead-Acid Battery Developers Targeting Hybrid Applications

30 May 2007

Although lead-acid batteries are ubiquitous in automotive starter-lighting-ignition (SLI) applications, they have, with a few exceptions, been bypassed in favor of NiMH for current hybrid applications and li-ion for applications to come. 

There are a long list of reasons for that decision: battery weight, limited cycle life in heavy use, loss of capacity from sulfation, corrosion of electrodes, degradation of active material, maintenance requirements, short life at high temperatures and a long charge time, among others. But developers of new lead-acid batteries argue that the problem is not with the fundamental chemistry, but with the battery design to date—a limitation they are trying to rectify.

Nickel
Nickel price over five years. Click to enlarge.

There arguments are also being supported by an external, non-technology factor—the rapid rise in the price of nickel. (See chart at right.)

At the recent Advanced Automotive Battery Conference 2007, a panel session discussed the requirements for lead-acid batteries in hybrid applications, and explored some of the emerging lead acid technologies. 

Eckhard Karden of Ford Research and Advanced Engineering Group in Aachen, Germany, noted that today’s absorptive glass-fiber mat (AGM) lead acid batteries already can meet the demands of micro-hybrid vehicles with limited regenerative braking capability. BMW’s use of AGM batteries to support its start-stop and regenerative braking systems in the 1- and 5-Series models and now in the MINI is a case in point.

Karden outlined the requirements for hybrid electric vehicle (HEV) applications, which involve a fundamental shift away from the traditional SLI requirements.

  • Robustness and reliability. HEV traction batteries are required to meet six-sigma (<12 ppm failures) over an operational life of 10 years or 240,000 km (150,000 miles). By contrast, current production SLI batteries not only do not perform to this standard, but are seen as a “wear-out” component to be replaced several times during vehicle life.

  • Shallow-cycle life. Cyclic wear has been a dominant cause of SLI battery failure in high-demand applications such as taxis. Hybridization increase cyclic battery use significantly, with quantitative throughput demands from micro- to full-hybrids varying by a factor of around 30, according to Karden.

  • Service life in partial state of charge operation. To support regenerative braking, HEV batteries operate at a partial state of charge (PSOC) to provide significant pulse-charge acceptance. Classical SLI batteries, however, are generally continuously charged at alternator output voltage, and are not optimized for PSOC operation. (BMW has developed a work-around for this with its battery management software that will be described below.)

    A significant fraction of [lead-acid] battery capacity might be lost early during service life due to sulfation, particularly in the lower part of the negative plates. At higher discharge and charge rates (high-rate partial state of charge—HRPSOC), as they would be typically applied to traction batteries in mild HEVs, lead-acid (AGM) batteries tend to show equally detrimental sulfation...

    Ensuring robust PSOC operation is, hence, a key challenge for the application of lead-acid batteries in advanced applications, and requires careful joint optimization of battery design and operating strategy of the battery system and vehicle.

  • Dynamic charge acceptance. HEV applications require good charge acceptance in a dynamic discharge/charge microcycling operation—dynamic charge acceptance (DCA). This is in contrast to the recovery form deep discharge in traditional SLI battery applications. In lead-acid batteries, DCA capability is extremely sensitive to the short-term previous charge/discharge exposure of the battery.

  • Battery management. Energy management and hybridization require precise monitoring and active control of the battery.

Karden also outlined the limitations of lead-acid electrochemistry:

  • The high molar mass of lead restricts the gravimetric energy and power density.

  • The electrode reaction is a true chemical conversion of lead and lead dioxide into lead sulphate and vice versa. The microscopic electrode structure is thus destroyed and rebuilt during each charge/discharge cycle, eventually leading to gradual disintegration of the porous electrode structure.

  • Water in the aqueous electrolyte and lead in the positive current collectors are thermodynamically unstable at the equilibrium cell voltage, leading to side reaction s such as water loss, hydrogen evolution and grid corrosion.

  • The electrolyte is not inert, but is consumed in the discharge reaction. This leads to a variety of issues such as transport limitation and acid concentration gradients that in turn lead to an inhomogeneous current distribution. That in turn can lead to localized overcharge or undercharge—the latter being one of the causes for sulfation during shallow cycling at partial SOC.

So far, in most HEV applications, lead-acid batteries could not meet the performance and life requirements. Instead, mostly advanced battery technologies have been chosen, namely nickel-cadmium, nickel metal hydride, lithium-ion or supercapacitors. Nevertheless, there are multiple efforts, both at established battery manufacturers and at technology-driven start-up companies to develop lead-acid based battery systems that meet the requirements of at least certain types of hybrid electric vehicles.

—Eckhard Karden

BMW and AGM for micro-hybrid functions.. Earlier this ear, BMW launched two micro-hybrid functions applied in the 1- and 5-Series, and now in the MINI: Brake Energy Regeneration and Auto Start Stop Function. (Earlier post.) Both are based on today’s 14-volt vehicle electrical system and current series components.

BMW is using valve-regulated AGM batteries to support both functions. AGM batteries use absorptive glass-fiber mats soaked with electrolyte to fill the distance between plates in a lead acid battery. AGM batteries slow down structural disintegration and cyclic wear; reduce the build-up of vertical electrolyte stratification that, in conjunction with a poor charge balance, can lead to sulfation; and can inhibit acid spillage in case of mechanical battery destruction.

BMW’s battery operates at a partial state of charge to be able to accept the recuperated energy from brake regen. The battery management system  monitors the state of charge of the battery at all times, and maintains a minimum state of charge to preserve cranking ability.  As soon as the SOC falls below a threshold value, a switch-on request is triggered, restarting the engine (absent any constraints preventing restart). There is a switch-off prevention level, below which the start stop will not function. The amount of charge reserved for cranking varies with temperature—e.g., in cold weather, the battery reserves more charge for cranking.

Using the valve-regulated AGM battery increases the “ability of cyclisation by about three times in comparison to a conventional lead acid battery,” according to Christian Diegelmann, Development Engineer, Department Electrical Energy Storage Systems, BMW Group.

Effpower
Effpower’s design. Click to enlarge.

Effpower bipolar lead acid batteries. Effpower, founded in 1999 by Volvo and Gylling Optima Batteries AB, is commercializing ceramic bipolar lead-acid batteries. Bi-polar designs have advantages for high-power batteries, including homogeneous current distribution; low resistance; and high current throughput.

Earlier attempts to commercialize bipolar lead-acid batteries failed primarily due to corrosion and electrolyte leakage. Lead is not inert enough to form a stable substrate for a bipolar plate. Other problems included the sealing between the cells; poor adhesion in the interface between the positive active mass (PAM) and the bipolar plate; shedding of PAM; and gas venting due to high internal gas pressure during operation.

In Effpower’s bipolar design the partitioning walls are made out of porous, lead-infiltrated ceramic (LIC) plates. The Effpower bipolar plates have shown high corrosion resistance, and the lead surface on the bipolar plate enables good contact to the active material in the same way as common lead acid technology.

A limiting factor in the use of the battery for hybrid applications had been charge acceptance, according to Bengt Wahlqvist, Chief Technical Officer for Effpower. The company had used graphite additives in the negative mass, however, with significant improvement in recharge.

Effpower Insight Fuel Consumption Test
Parameter Effpower
PbA modules
NiMH
OEM
CO (g/km) 0.7 0.5
HC (g/km) 0.12 0.10
NOx 0.08 0.09
CO2 (g/km) 89.9 95.2
FcUDC—City
(l/100km)
5.29 5.69
FcEUDC—Highway
(l/100km)
3.03 3.14
FcComb—Combined
(l/100km)
3.87 4.07

Effpower has installed an Effpower battery pack in a Honda Insight for 15,000 km if testing in real traffic. The vehicle underwent four different drive cycles in Göteborg: city driving in rush hour traffic; combined highway and city; a city bus cycle; and an Effpower designed acceleration/braking test cycle. 

The Honda Insight with the Effpower lead-acid battery pack outperformed the OEM NiMH pack in terms of fuel consumption. (See chart at right.)

Effpower currently has formed a partnership with Banner Batterien in Austria for the manufacturing of Effpower batteries. High volume serial production is planned for mid-2008. Effpower also has been testing the Advanced lead Acid Battery Consortium’s work with negative graphite paste with promising results.

Advanced Lead-Acid Battery Consortium. The Advanced Lead-Acid Battery Consortium (ALABC) is focused on two primary design modifications to enable the application of lead-acid batteries in HEVs: the provision of a grid design that allows the battery plates to accept the high charge rates required; and the incorporation of elevated concentrations of carbon in the negative active mass to alleviate sulfation.

Ultra
Configuration of the Ultra Battery.

Patrick Moseley of the ALABC also noted work being done on the “Ultra Battery”: the combination of a supercapacitor in parallel with a lead-acid battery to cope with the high rate partial SOC cycling.

In the Ultra battery, a carbon capacitor plate is attached to the negative plate and enclosed within a single battery casing. Prototype batteries of this design meet or exceed the FreedomCAR targets for power, available energy, cold cranking and self-discharge, for both minimum and maximum power assist systems, according to Moseley. The battery is now in road test.

Firefly Energy and graphite foam plates. The Firefly battery replaces the conventional lead plates in a lead-acid battery with a lightweight carbon or graphite foam to which the chemically active material—in the form of a paste or slurry—has been applied. Firefly contends it can deliver lead-acid battery performance comparable to NiMH, but at about one-fifth the cost, and with greatly reduced weight compared to traditional lead-acid batteries. (Earlier post.)

According to Kurt Kelley, Firefly Energy’s CTO, the micro-cellular structure of the foam enables much greater utilization of the chemistry. The Firefly 3D battery features higher power, fast recharge capability, 15-20% increased capacity at slow discharge, better deep discharge recovery than competitive lead-acid batteries, and better capacity retention at high discharge rates.

Firefly is currently developing a newer, lighter-weight, higher-rate battery technology.

May 30, 2007 in Batteries, Hybrids | Permalink | Comments (25) | TrackBack (0)

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Comments

Could be interesting for domestic power storage - if you had solar cells or a windmill on the roof.
Even if they turned out to be too heavy for cars, this would not be a problem in a domestic situation.
How would it compare to LiOn ?
If it is 1/5 the cost of NiMh, it could make for quite a nice hybrid application, even if it did not have the bragging rights of a LiOn battery powered one.
I wonder if they have tried it in a Prius ?

Yes the cost of nickel, and also the cost, and availability, of lithium will affect the introduction of many BEV and PHEV vehicles. The Zaps and Teslas of the automotive community are probably realizing the shortages and price fluctuations. And pricing them accordingly. Not a bad thing, but just unavailable to the masses to make the kind of impacts we need to start making.

Perhaps the big automakers pursuing EV's, like the GM's, BMW's, Toyotas's, Mitsubishis, etc. have done their homework in researching current and short term future battery offerings, and are being cautious and realistic.

Everyone is aware and hoping for the next big battery breakthrough. Perhaps it will be with a "cheaply produced hydrogen" fuel cell, which in essense is a sort of "battery", or energy supply device. There are many great minds working on the next "breakthrough". I am confident in our future.

For all the ballyhoo about Li-ion, the good old lead-acid battery isn't about to go away anytime soon. Design refinements such as those described above will keep lead-acid competitive, especially for the micro-hybrid applications that will likely become standard issue in many cars in the next 10 years.

Remember, a 5% gain on 50% of all new cars makes twice the dent in fleet average fuel economy that a 25% gain on 5% of new cars does. Full hybrids account for barely 2% of US LDV sales right now and deliver just 15-20% more MPG than comparable conventional models.

The battery-UC combo cells sound particularly promising. Of course, the starter and alternator functions also need to be optimized for efficiency to maximize the benefit. Only if and when battery cost per kW and Ah comes down and, regulators demand further reductions in fleet average fuel consumption/CO2 emissions, will the industry bite the bullet and switch to a higher voltage grid, e.g. 42VDC.

funny enough , the price of lead has also gone through the
roof since the beginning of the year !

Lead production is limited - if we start trying to make millions of 1.5 kWh PbA batteries, we will rapidly run into lead supply constraints - yes production can be expanded but it is a toxic, unpleasant metal to mass produce.

Zinc Air is the ONLY feasible mass market EV/HEV battery technology. Zinc is the metal already used in global production of alkaline and Zinc carbon batteries. Current metal prices: Nickel - $45,000 /tonne, Zinc - $3,500 / tonne. Cheap, abundant, high production and highest specific energy of any EV battery, including LiIon.

Emph: Interesting, do you have some links to manufacturers for us?

Don't forget that the lead availability problem is significantly lowered by the firefly bat. which only uses a fraction of the lead.

LiFePO4 should have no particular problem with resources.

Emphyrio, have you read up on nickel-zinc batteries? So far the best sourceof information I have on them is on the company website for PowerGenix.
http://www.powergenix.com/service.htm

The claim is that the batteries are easiily recyclable with a power output similar to NiCd. Battery technology, in fact energy storage as a whole, has several technologies in the works. It will be interesting to see which combination works best or the OEM's pick. It might even be one of these new PbA cells.

Perhaps the answer to battery usage is to start with the lighter, limited firefly batteries because they can be manufactured in mass currently. Then as the others are developed and ramped up into production, replace the fireflies. But, for God's sake somebody do something instead of just talking!

It's shaping up to be a struggle between continuing the use of inefficient, and expensive diesel ICEs or BEVs/PHEVs, with the oil companies and large auto manufactures on the the diesel side of the line in order to recoup their investments. The only bright side is they can burn bio diesel; however, the facts are ICEs are still 25 to 35% efficient at the rear wheels at best and most of the energy is wasted.

In my mind diesels are not green cars because no matter what the fuel, the emissions are still the product of gas explosions and at the tailpipe they all produce some form of health-harming chemistry.

Lad: I think things are actually happening. But for those of us on the without big budgets and large volumes it seems terribly slow. I've been trying to upgrade my limited speed motorcycle/scooter for almost a year now and it's only recently that we've had any success finding a supplier of LiFePO4 batteries. I'm hoping that once EVs catch on things will accelerate as the economics swing in our favour.

I think the GM EV1 had some kind of special lead-acid batteries in which the acid solution was gelatinized.

If the actual lead-acid batteries are not subjected to deep discharge cycles, sometiemes they can last long.
My last battery lasted 6-1/2 years.

So, when will we see the Firefly foam+lead plates combined with a cheap, light ultracapacitor?

Speaking of cheap ultra capacitors, anybody heard any recent rumors about eestor's ceramic powder ultracapacitors?

What does Lithium cost per ton? What does Lead cost?

There is no way I would ever buy any vehicle that runs using Lead based batteries. I want to get rid of the 12v one in my present car. The electronics industry as spent Billions to rid active & passive components of lead so that it does not go to the dump and now someone thinks we are going to use lead in mass quantities in cars.
Doubt it!
Too heavy, to much fuel to push it up hills, don't want to be in a car wreck with it. Time for society to stop thinking about using lead.
The cost of Lithium will come down radically before too long as the big players go head to head to supply the feed stock. I'll wait, by next year Toyota, Nissan and many others will be offering Li-ion for HEVs and PHEVs. The other guys are working hard to play catch up.

David R,,

Recycling is no panacea, but when you replace a battery the auto-parts store will usually refuse to sell the battery to you unless you put down a deposit ("core charge"). You get the deposit back when you bring old battery (and your receipt) back for recycling. This is true for many parts (alternators, brake pads, etc), but, like junkyards and scrapyards, nobody talks about this kind of recycling much because it's the status quo and because it makes money for the supply-chain either way...

I like lightweight components as much as the next guy, but my reflex is to put the emphasis on maintaining my current vehicle so that another one doesn't need to be manufactured...

David R. seems not to have understood the article. These new batteries, (Firefly), are lighter, smaller, and use LESS lead than traditional lead batteries. They also last longer and are recyclable. Other than that.....

If you talk EV battery these days and not mention NANOSAFE from AltairNano(Alti)...you are not really talking EV battery.

Another set of questions for David R.

Where will Toyota, Nissan etc get the supply of lithium for their battery offerings? How will they go head to head "to supply the feed stock", bringing lithiums cost radically down? Have Toyota and Nissan discovered some vast lithium field somewhere? Or perhaps they found out a way to make it out of thin air. Interesting, since neither is in the direct battery making business......

But back on topic, lithium, sodium, lead or even a combination of all of the above may be a start to what we need. Perhaps a combination to derive the best benefits of each. And recycling will become, if it already hasnt, the order of the day, whether its lead, gold, lithium or plastic. Someday perhaps, we will be required to turn in an equal amounts of plastic, lead, glass, and metal, in order to receive the benefit of buying a new car with these same amounts of materials, into some sort of waste stand off purchase. But I am just dreaming......

"Interesting, since neither is in the direct battery making business......"

Toyota owns Panasonic EV, which manufactures the old-skool NiMH hybrid battery packs, and has come up with and will manufacture the new lithium-ion packs for the next Prius.

By doing this the costs can be kept low. Incidentally, the cost of lithium is only a very small percentage of the cost of a typical lithium-ion battery. There are dozens of areas where costs could be cut dramatically with economies of scale (a fact Toyota are well aware of).

Mark: You don't have to get Lithium out of thin air, it's currently extracted from brines. The ocean is of course more dilute than the brines currently being used, but in total it contains a staggeringly large amount of lithium. Of course recycling it is still the best.

Zinc-air batteries are not electrically rechargeable so they can't replace Li-ion, NiH, and Pb batteries.

Zinc-air or metal-air batteries (zinc is just one possible fuel, others include magnesium aluminum, iron, etc) are not batteries but fuel cells that use metal instead of hydrogen. The advantage over a hydrogen fuel cell system is the metals are much MUCH safer and easier to store (as an electrolyte paste, or pellets or in plated cassettes). The disadvantage is the spent metal oxides must be recycled either at a refueling station or at a recycling plant. For some reason people go on and on about hydrogen as the fuel of the future, but metal-air fuel cells have already solved the problems of storage and fuel cell price that hydrogen is still struggling with.

Luke & John,

Recycling current Lead-Acid automobile batties is no panacea. They contain a great deal of recyclable material per unit volume. This is not the case with the new Lead batteries mentioned in the article.
The incentive to reclycle these batteries will not really be there due to the low material content.
This means that you will have to pay to have these batteries recycled as opposed other batteries which have more material cost. People for the most part will not do this (pay) which means they will be dump somewhere.

Mark A

Both Toyota and Nissan are heavily invested in Li-ion batteries - do your research.
As others have mentioned Lithium is available everywhere - again do your research.
Just about anything can happen in the future with battery technology - but for now ALL auto manufactures and looking to Li-ion - search this site for the last two years for articles on Li-ion activity.

Just out - unfortunately Toyota is delaying its introduction of Li-ion for the Prius:
http://www.autobloggreen.com/2007/05/30/toyota-to-delay-introduction-of-lithium-ion-batteries-in-the-pri/

Aquiring a company that makes batteries, in my mind, does not make you a battery manufacturer. Just an invester, with a vested interest in using what your investment is producing.

As far as the lithium supply, I heard reports about there either being "severe shortages", to "barely able to meet demands". Heres one such link:

http://www.theinquirer.net/default.aspx?article=37311

Obviously I am no battery expert, or lithium expert, and have not kept on top of it sufficiently. I only gather what info I can, when I can. Thats why I also frequent this site, to learn. After doing a little more digging, lithium production is not as dire as some of my earlier beliefs. But lithium production, storage, transportation, and use, does have its drawbacks and concerns, and is not the final answer.

But back on topic, battery powered EV's are our future for personal transport, even if it is to use lead. Any and all power storage breakthroughs are achievements that should be applauded, as well as incorporated. Even if that means combining old and new battery technologies, if necessary. Lead acid is proven, and recyclable. Hydrogen powered fuel cells are close. Lets use what we can, to move forward. I am optimistic of our future!

good information about the car battery

Lithium is a poison.
Lead is a poison.
Copper is a poison.
Iron is even a poison.
Cadmium is declared a poison, but some sea life needs it.
The natural potassium in a person or its foods is and always has been radioactive.
In the wrong quantity or form, every element in the human body can kill it as well. Pounds of phosphorus compounds are processed by the body every day, but a small amount of the element will kill it.
Far more people are killed by cars than are killed by lead.

Everyone should fear a car much more than lead.

It is impossible to remove all of the dangers of life by declaring them dangerous and banning them.

The concrete safety barricades with multiple slopes that allowed tire contact without car body contact have been abandoned in favor of easier to build and maintain "walls" that will cost more lives and damage than lead batteries ever will.

Before lead is banned any more, all products that kill more people per year should be eliminated.

There are batteries available for long distance electric cars, but they cost too much as do lithium batteries. Plug in hybrid cars are the answer to the long distance problem. Light engines are being made that could be used for long distance travel in hybrid cars. A 13 hp engine is said to weigh 13 pounds(OPOC). With a plug in hybrid the engine can be used at maximum available efficiency or at maximum power depending on the immediate needs or wants, and the electric system helps fill in the gaps.

The UPS hydraulic hybrid could be a model for an inexpensive plug in hybrid cars. Very high power can be had for brief periods of time from compressed air tanks coupled with hydraulic motors. High power electric motors and their required transistorized contollers are now too expensive. Batteries and small engines can be coupled with the hydraulic system.

One Un-interruptable power system has combined tanks of compressed air, heat storage, fast air turbines and small cheaper flywheels to substitute for batteries. Compressed air hybrid cars could be an alternative to battery power in hybrids at lower cost. No crank diesel powered hydraulic pumps have been tested by some including NOAX.

For their horse power, steam locomotives had the best starting torque at a far lower price than diesel-electric locomotives. It is possible and economic to build coal fired steam locomotives that are cleaner burning and have much lower maintenance and operating costs than diesel locomotives. They can now even be built with more than half energy efficiency of diesels The raw price of the energy in crude oil is thirteen times the raw price of energy in coal delivered to the buyer. The cost of energy from diesel is about twice that of crude oil.

Diesel fueled small steam locomotives have been built recently that have similar fuel consumption per mile and much better starting performance and lower pollution than the diesel engines that they replaced. Better insulation and heat loss prevention were some reasons for this result. Also no fuel needs to be burnt on down hill grades with short up hill segments. A steam locomotive could be built easily that put heat back into the boiler on down hill runs. A small generator could be fitted to every wheel on the train, and while these generators were feeding the heaters in the boiler they would be braking the train without wear. There are actually more efficient ways of doing this as well. During times of coal shortages in Switzerland, some steam locomotives were fitted with electric heating elements in their boilers.

With modern materials and processes it would now be easy to build a coal-fired, steam semi-trailer-tractor-truck. It might have to be 100% percent bigger. It would have electric motors to run it in reverse, but would have a steam turbine directly coupled to the drive wheels for forward travel. The condenser for the steam would take up most of the extra space needed, but the boiler would also be extra large for long bursts of peak power for starts and hills. Gear shifting might be entirely eliminated. Steam turbine locomotives were used very successfully in some coutries for more than ten years, but modern materials might be brought to steam piston engines for higher performance possibly. There would be far less carbon particles, smoke or smell than a regular diesel. Clean coal slurry would be the fuel, but it could burn diesel or any other liquid fuel as well. No fuel at all would be burnt on long down hill grades except as preparation for a long up-hill, and as mentioned there are ways to return the hill energy to the boiler..HG...

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