From the
Page 60
Page 61
If you've noticed an error in this article please click here to report it so we can fix it.
(q1 /f))( M.
by Graham Montgomer
World vehicle growth has given a real boa to the battery world. And field trials on a new type of battery have been showing encouraging results
"BETTER BATTERIES are a commercial reality and are just the tip of the iceberg", said Ross Stubbs, director-general of the zinc/cadmium and lead/acid development association, in his opening address to a battery seminar organised by ERA Technology.
Although primarily aimed at the non-automotive market, the seminar did provide some useful information in the use of nickelcadmium batteries in dual-mode buses.
Mr Stubbs said that the world vehicle growth had given a real boost to the battery world although he sounded dubious when he estimated that 60 per cent of the "free world" battery production was in the hands of 16 companies.
The battery industry is the biggest growth area in the use of lead, according to Mr Stubbs, who said that the industry had used 1.5m tons of lead in 1980 compared with the 1.1m tons in 1960.
One of the main advantages of the nickel cadmium battery mentioned earlier is its resistance to misuse, according to John Atkin of SAFT (UK) Ltd. Describing some of the advanced nickel-cadmium systems for the future, Mr Atkin claimed that electricity is the most economical form of energy for passenger transport, but that its distribution by overhead wire for trolley buses tends to counteract this, which has led to the concept of dual and triplemode hybrid systems.
The former uses the overhead wire to supply traction power and to charge the on-board batteries, which are then used to permit running of the bus in the suburbs where the cost of installing the overhead wiring could not be justified.
Mr Atkin said that a new kind of battery has been proposed, a nickel-cadmium of the high performance sintered plate type, which has a long life where frequent short discharges are called for. He described the field trials which started some 12 months ago and have been showing encouraging results.
The vehicle in question is at articulated trolley-bus using a Berliet chassis. The experimel is being conducted in Lyons, where the buses are built, for reasons of convenience. A number of buses will take par the field trials and they have a gross weight capacity of 27.6 tons compared with the kerb Weight of 171/2 tons.
The maximum cruising spe of the 145 passenger vehicle i claimed to be 50km/h (31mplwhen running on the batterie; and 60km/h (37mph) when linked to the overhead line.
Mr Atkin mentioned that all of people had gone for lead-al batteries for this type of application, but he claimed th the nickel-cadmium type was ss prone to damage through isuse. "The nickel-cadmium rn be ill-treated and still come ) again", he said, "whereas in any cases the lead-acid is fished if it is discharged too r."
One of the problems .sociated with electric vehicles storage space for the aeries. This is less of a oblem with the nickel
dmium type but a lot of space still taken up by the electrical ,ntrols which are bigger than e batteries and the motors. )ace is also required to
ssipate the heat generated. The battery itself consists of .8 Ni-Cd cells with thin sintered ates, said Mr Atkin, and has a ted capacity of 160Ah and a Led voltage of 420V. It weighs 38 tonnes (2 tons 13cwt). According to Mr Atkin, the rttery has a life of more than ,000 cycles to 20 per cent ipth of discharge (DOD) and a using range of 5km (three iles) to this 20 per cent figure. The long life of the battery was limed by Mr Atkin to be due to high charge current of 350A lich allowed the available ergy to be stored in a few iflutes. This resulted in the ilisation of only about 20 per nt of the total battery capacity normal operating conditions. It was suggested that this type operation is possible because three particular features of the Sign: (iii) the battery is connected to an electronic amperehour meter which ensures high energy efficiency and lower water consumption.
Mr Atkin claimed that if the electrolyte level gets too low the nickel-cadmium type is not prone to the corrosion problems associated with the lead-acid type, another example of its resistance to abuse.
The triple mode mentioned earlier was described by Mr Atkin as using a relatively lowpowered diesel engine as the third energy source. This would run "off-wire" at a constant load corresponding to the engine's point of maximum efficiency and would drive a generator which would be of sufficient size to propel the bus on the level but not to accelerate it. Mr Atkin said that the generator would top up the battery when the vehicle is at a standstill or braking, with the battery augmenting the , generator output for acceleration or hill climbing.
In the case of the pure traction battery — where it is the sole source of power in an electric car — the nickel-iron battery is being developed along similar lines, said Mr Atkin.
Not previously available in high-performance form, the NiFe battery has an extremely long life on deep discharge cycle claimed Mr Atkin, who went on to say that the present development programme shows a cycle life of 50Wh/kg with projections of 60 and 70Wh/kg in five and 10 years' time respectively.
As far as Mr Atkin was concerned, applications of the Ni-Cd battery in the immediate future will benefit from the use of modern techniques in plate manufacture, seals and the materials for the separator and membrane.
When used in a heavy lorry as part of the electrical system, the Ni-Cd is claimed to be superior for cold starting. "Cold" is, of course, relative, but in this particular case Mr Atkin suggested that the Ni-Cd battery could cope down to around —30 to —40°C (-22 to —40°F) compared with the —15°C (-5°F) where the conventional lead-acid can have a comparatively short life.