Power packs

According to research, over 70 billion batteries worth more than e30bn (£20bn) are produced annually, and the race to produce more powerful and longer-lasting batteries is being hotly contested by manufacturers worldwide.

BCC Research (Norwalk, CT) also found that the relatively new portable electronic device market alone is worth hundreds of billions, and it depends almost entirely on the latest battery technology in tandem with evolving recharger technology.

But besides the phenomenal growth of relatively new battery materials, such as lithium metal hydride, and a size and weight reduction of about 40 per cent, the higher power areas continue to be served by established lead-acid batteries.

Electric hybrid vehicles have demonstrated the ability to get 30–40km per litre using a combination of batteries and small combustion engines. In the US, this market has been growing at an annual rate of 80 per cent, and in Asia over a million are on the road.

Several new classes of advanced batteries have been commercialised during the past 10 years, including nickel-metal hydride, secondary lithium, and zinc-air. Meanwhile, improved microelectronic battery charger controller technology is allowing the commercialisation of new types of batteries and improving the marketability of existing battery systems.

In the UK, battery manufacturer Yuasa has two plants, Ebbw Vale, south Wales, and Birmingham. Its parent, Japan’s GS-Yuasa, was formed in April 2004 when the country’s two largest secondary (rechargeable) battery manufacturers merged. The group recently announced that it had signed a deal with the Japanese government to develop and produce rechargeable lithium batteries suitable for hybrid vehicles.

Chief technologist Peter Stevenson said: ‘The GS-Yuasa Group manufactures every type of secondary battery, and the UK operations are responsible for all our secondary sales in Europe.’

The group’s range includes: NiMH for electric vehicles, lead-acid (Pb-acid), nickel-cadmium (NiCad), silver-zinc (AgZn) for military applications, and the ‘niche’ alloy NiZn.

But in the UK, Yuasa makes only lead-acid models (Ebbw Vale) and SLI — starting, lighting and ignition — car batteries (Birmingham). However, competition from Asia means the Birmingham plant is due to close in the middle of next year, marking the end of UK car battery manufacture. Many European-based manufacturers are also going the same way.

Stevenson said: ‘Our Ebbw Vale production is focused on valve-regulated lead-acid batteries which are not sealed, but have a valve to release the pressure, which also prevents oxygen from entering the cell and causing self-discharge. Our aim is to recombine at least 99.9 per cent of the cell gases, mainly hydrogen and oxygen, to minimise the need for topping up.’

Besides electric vehicles, Yuasa’s products are used widely in security alarms, computer back-up systems and in hospital buildings as alternative power supplies. This latter applications is typically a combination of parallel and serially-linked batteries that can deliver several 100MWh, providing power up to 400–500V.

Often improving battery lifetime is linked to factors such the discharge rate. The telecoms industry is always looking for longer lifetimes, at higher temperatures, so Yuasa has been looking at developments in lead alloys that can support active materials. In some cases the average lifetime can be doubled, at higher temperatures.

Another important area is the uninterruptible power supply market, where customers want shorter and shorter times, at higher powers, to restore optimal conditions or make situations safe more quickly.

Users want to get maximum energy out of the battery in perhaps five to 10 minutes until other power systems kick in. At the same time, of course, they want as low-cost a battery as is possible.

The amount of energy delivered depends on how it is discharged. For example, usually when you discharge a 100 amps/hour battery over 10 hours you will get a current of 10 amps. But if you try to discharge it over one hour you are not likely to get 100 amps for more than 60 or 70 per cent of the theoretical hour, due to reciprocity failure.

Yuasa is working to achieve the full capacity for the full time, to improve on the typical 70 per cent of high current performance.

As far as lead-acid batteries go, there is no replacement in prospect, and to some extent it is the same for nickel-cadmium. However there’s a lot of research being done on lithium. Research investment is probably 100:1 in favour of lithium against lead, said Stevenson.

New technologies are usually developed for new markets such as the general improvements in lithium batteries for mobile phones and computers — but for these applications there was no alternative.

‘When it comes to today’s car batteries nobody would really be prepared to pay 10 times more for a lithium-based battery, so lead-acid looks like it’s here to stay,’ said Stevenson.

A couple of companies are working on lead-acid batteries’ relative lack of efficiency and improving the electrical storage capabilities of the lead. Perhaps only 40 per cent of the lead oxide is converted, so it would be a dramatic improvement to raise this — even to 60 or 70 per cent conversion.

Another wasteful aspect of lead-acid batteries is in the lead support used inside the battery, which often accounts for half the battery weight. So there is research into using conductive ceramics as an alternative, and TNO of Holland is believed to be working on a carbon-based support.

If these projects are successful we could see a doubling of the potential output of a given lead-acid battery.

About five years ago, many in the industry thought that NiMH would be the next big thing. Stevenson believes that, although there are still cost and safety issues to resolve, it will be displaced by lithium ion technology as the major type of mini consumer battery.

Bolton battery manufacturer CMP produces about 1.5 million cells a year and its Trafford-based charger manufacturing plant turns out around 50,000 units annually. product support manager Nigel Harris believes the firm is the world’s biggest manufacturer of motive power battery chargers.

Harris said: ‘Over the past few years the company has been developing charging technologies. One of the difficulties we face is that batteries give off either hydrogen or oxygen, which reduces the water content of the electrolyte. So we decided to use less antimony to remove the need for over-charging the battery.’

CMP has three main types: the taper charger, based around the saturation of a transformer; the regulated charger, which Harris refers to as the company’s ‘bread and butter’ charger and probably offers the optimal charge profile for motive power batteries; and the high-frequency charger, which presents a better profile, delivers higher power, is more efficient and weighs less.

Overall, said Harris, the company has been concentrating more on chargers than advancing lead-acid technology.

He said that CMP does not want to be just a battery supplier, but to be involved in service and support. The markets it is mainly supplying are forklift trucks; materials handling systems; pallet trucks and airport vehicles. Emergency power supplies are handled by its Stevenage-based industrial energy division, and it has an R&D and test centre — also based in Bolton — employing 650 staff.

‘Currently, the big issue in charging is high-frequency charging and power modelling,’ said Harris. ‘We have just gone through a big redesign of our power modules — which alone accounts for about 80 per cent of the cost of the charger.’

As well as looking at how to improve batteries and chargers, CMP is seeking ways to cut its maintenance costs. ‘Our Liberator Gold & Air system will run for 200 days without needing a top-up — compared with 7–10 days for standard batteries,’ claimed Harris.