The starter motor and alternator as we know them could be on the way out, if the latest news from their suppliers and technology developers is anything to go by. Mark Wilkinson reviews some of the latest technical developments, company by company.
There are two main drivers behind technical change affecting the starter and alternator:
- Emissions – increasingly strict European CO2 emissions regulations are pushing manufacturers to find new ways to reduce their vehicle fleet emissions;
- Electrical power demand – new high tech equipment such as heated seats and electrical power steering is pushing car electrical systems to the limit. Already, power demand is so high in luxury vehicles that an intelligent battery management system is needed. This cuts power to non-safety equipment (heated seats, heated rear window etc) when necessary to ensure that the brakes, steering etc have sufficient power to operate safely.
2008 is the European deadline to bring average fleet CO2 emissions down to 140g/km, and 2012 is expected to bring along the 120g/km limit. The 2008 deadline can be dealt with by improvements to fuel systems, electronic control and friction-reducing measures. 2012, however, will need big investment in some very new technologies.
One solution to this is the belt-driven starter-alternator. Shaped like an alternator, this electronically controlled machine replaces the starter motor and alternator and provides an instant stop-start function for fuel savings up to 5%. Various refinements of this belt-driven device can boost economy further – such as brake energy regeneration and mild engine boost. The device can produce either 12 or 42-volts.
The other version of the machine is the crankshaft-mounted integrated device – a much more complex animal that is considerably more costly. It is also more complex to engineer, since it requires a complete under-bonnet re-think. 42-volts and above is the accepted norm for this device.
Suppliers of the crankshaft systems are agreed that their time will come – but most predict that we won’t see them this decade in Europe. The enormous cost of moving to 42-volts has meant a huge re-think on the part of the vehicle manufacturers, so instead of a wholesale switch, there will be a gradual evolution to dual-voltage systems and then full 42-volt concepts. But 12-volt systems are expected to survive for at least the next two decades.
Later this year a crankshaft-mounted unit (from Continental) will go into series production for a US truck and we will see belt-driven units in use in Europe from 2004. Ricardo predicts that starter-alternator hybrids will cover up to 10% of the global passenger vehicle market by 2012, from virtually nothing today – a staggering rate of growth. In the beginning, most units will be start-stop devices (3-5% fuel saving), but by 2012, the majority will also offer regenerative braking and mild boost capabilities (raising efficiency to 7-10% in total).
Here are the main players and what they are doing:
Bosch is less bullish about starter-alternators than it once was – the company is beginning to say that only the completely redesigned car will be able to take best advantage of its crankshaft-driven starter-alternator device. Bosch doesn’t have a battery capability – and the battery is one of the key requirements for such a fully capable system. Bosch does have a joint venture with a battery maker, however. The company has also spent a lot of time and effort getting its systems up to 42-volt readiness: the CAN-bus system, for a start. One of the most challenging things about the 42-volt network is maintaining the power source, keeping it useable. For Bosch, this means that the size of the battery is of key importance.
Bosch points out that the need for a 42-volt system will initially be only in top-end luxury cars – cars with engine-off air conditioning, electric seat heating and other items that are expected to function for the comfort of the driver and passengers. For this reason, they don’t see a need for their crankshaft-driven device until 2008 at the earliest – because the unit volumes are not economic. Other companies may choose to price their units to make a profit at lower production volumes and have invested in such. Continental is one such company. ZF-Sachs too, so Bosch believes.
However, besides providing the power for luxury accessories, Bosch says that 42-volts will become much more important by the time EU VI comes along in 2012. EU VI will place much more importance on weight issues – one way to reduce weight is by reducing the size/bulk of the wiring loom – 42-volts makes this possible.
Bosch spokesman Stephan Kraus says that to combine 42-volts and starter-alternator together would make a 100 percent benefit, whilst to implement either 42 volts or simple starter-alternator would offer much less benefit than the combination. He says that there may be other methods to improve the benefit, but Bosch is not working on those at present. In other words, Bosch is convinced that the starter-alternator has a future – but, speaking for itself, not within the next five-six years.
There are two ways to go in the current race for greater power to feed all the new on-board devices:
Full 42-volt starter-alternator system – this will provide all the needed power (and a boost to the engine if needed) no problem – but the downside is the big investment required. To avoid the enormous cost of a 42-volt system, Bosch says that it is possible to uprate its alternators at little cost to improve their output. These higher energy 14-volt alternators can boost maximum output from 180A to 220 or 230A. These higher output alternators will run with intelligent energy management control that regulates all the devices in the car. Current systems might be capable of providing a 2.2kW power supply, but the sum total of all the on-board consumers might add up to 2.5kW – and if the vehicle is run in this state for any length of time, the result will be a flat battery. This is out of the question – particularly when some of the on-board consumers are safety-critical – ESP, brakes, active steering, ignition, engine management etc.
So Bosch’s energy management will temporarily turn down the seat heating for instance (notorious for its high current drain) to make sure that the car’s electrical systems run within capacity. It could switch off the heated rear window or reduce the output of the electrical heaters being used to compensate for the low heat generation of today’s super-efficient diesels. Even a reduction to 70, 60 or 50 percent will make a real energy saving – enough to allow the car to cope – but small enough for the occupants not to notice. Bosch already has this intelligent energy management running in the new Audi A8, the Mercedes E-class, and, to a lesser extent, in the new SL-class. BMW’s new 5-series has a similar energy management system – its revolutionary new active steering is electrically-motivated and is a much higher priority than seat heating, for instance!
Bosch says that when the number of energy consumers increases to the point where a 3-4kW power net is required – this will be the time for a re-think, the point at which 42-volt systems become essential.
Continental, one of the earliest champions of the integrated starter-alternator, is setting a precedent by launching its first true production model in 14-volt, rather than the widely expected 42-volt form.
During its years of ISAD (integrated starter-alternator damper) development, one of the most significant events has been the company’s take-up of the remaining shares in Temic, DaimlerChrysler’s electronics expertise division. The Temic acquisition has brought Continental ‘deep knowledge in electrical machines,’ says the company’s Dr Frank Kozlowski, who points out that Temic already mass produces powerful, wear-free, brushless motors at its Berlin facility for engine cooling fans.
On the subject of 42-volts, Dr Kozlowski says, “We see that the 42-volts revolution won’t happen so soon”.
Continental’s ISAD generates 14-volts instead of 42-volt s, but when in engine boost mode, it runs at higher voltages. When cold-starting engines, greater torque is required – so much so that the current becomes so high as to become unmanageable. Continental ISAD reduces the current by increasing the voltage – so the vehicle effectively becomes a twin-voltage machine – charging the battery at 14-volts and running the car’s systems on 14-volts whilst electric boosting and engine starting at higher voltages. As the ISAD is driven, the supply voltage floats between 20-45-volts. This energy comes from a ‘super-capacitor’, a device that can store and ‘dump’ large amounts of electrical energy in a very short time. This sets it apart from the conventional lead-acid battery, which has difficulties with such a task. The super-capacitor’s 100-200 Farad storage capacity means that it can hold an electrical charge some 100-200 million times that held by conventional capacitors found in domestic radios, for instance.
Continental’s ISAD also needs a DC/AC voltage inverter to produce the necessary AC current to drive the electric motor for boosting and engine starting. An intermediate circuit will be needed, too, complete with DC/DC converter, to charge the conventional 14-volt battery when the ISAD is in charge mode. Power electronics are also a very important part of the package. Continental goes into production later this year in the V8 gasoline (285PS) GM Chevrolet Silverado and MC Sierra pick-ups. The super-capacitor will be sourced from a partner and will provide currents up to 20 amps to power equipment that would normally need a separate generator to operate garden tools etc. The pick-up will carry two US domestic (115-volts AC power sockets) to achieve this. The vehicle itself will initially be marketed as a ‘contractor’s special’ – specially targeted at building contractors/handymen in the US.
The company itself will concentrate on its core competences: the electric machine, its ECU and advanced energy management.
On its own, Continental’s ISAD will produce the required 12-15% overall fuel economy and CO2 improvement. However, Dr Kozlowski says that an improvement of 20-30% is easily achievable if all the secondary benefits are added up – belt-driven ancillaries (HVAC, power steering etc) can be downsized and switched to electric, on-demand, devices, for instance. GM’s first application of ISAD will only produce an approximate 10% efficiency improvement because GM wants to gauge customer acceptance before going any further.
Continental is also working on a ‘killer application’ of the ISAD – by integrating it into dual-clutch automated manual gearbox. This will then smooth the gearshift as well as allowing all the battery charging, engine starting/boosting and brake energy recovery functions.
Delphi has been developing belt-driven starter-alternators for a number of years – and has also shown prototypes of a crankshaft-mounted version. However, packaging problems (it was too big, requiring too much under-bonnet re-design) led the company to drop the latter device and concentrate on belt drive models. Delphi then announced that it would wind down its starter motor and alternator business. Existing programmes will continue but not be replaced when they cone to the end of contract.
Delphi has taken a different line to its competitors – it will leave them to produce the starters and alternator systems, but Delphi will provide the necessary know-how and components to bring those units together into an intelligently functioning vehicle. In place of the starter motor and alternator activity, Delphi’s strategic decision has been to concentrate on electrical management, developing the types of electrical and electronic management that will be essential to tomorrow’s vehicles. These three areas are:
- Electrical storage systems – batteries – lead-acid, NiMH, lithium and others;
- Connection systems – the wiring harness, along with switches and relays and also the hardware necessary to make sure that one voltage network doesn’t interfere with another of a different voltage;
- Power electronics – this is not only the use of an inverter to step voltages up and down for various systems, but it also affects the distribution of the power and control of functions around the vehicle.
Pankaj Dhingra says that the company is working on electrical hardware to assist in the use of three different types of motive system:
- 12-volt Stop-start – simple switching on and off of the engine, using a combined starter-alternator device (not produced by Delphi!);
- 42-volt Mild hybrid – as stop-start, but with the additional features of energy recovery during braking, and, in some cases, electrical boost during driving;
- Strong hybrid – these systems will still combine an internal combustion engine with an electric motor, but the electric motor will be very substantial – because it needs to be able to power the vehicle during many driving situations. In this case, the 35-50kW electric motor (or motors) will only be joined by the conventional engine during cruise. Delphi cites the latest Toyota Prius and Honda Civic IMA as being examples of such ‘strong’ hybrids – where the voltages used are far in excess of 42-volts.
Most interestingly, the company says that we can expect to see examples of all three types of system on the market at the same time. What is not in question is that, without doubt, “in the end they (vehicles) will all have some form of electrification of the powertrain. Which path will be the most successful? “That depends on consumer acceptance of the different technologies,” says Dhingra.
Mild hybrids will still rely on lead-acid batteries – chiefly for reasons of cost.
Full hybrids will use alternative chemistries to store electrical energy – one of which is the NiMH battery. According to Delphi, lithium batteries are not yet in use in hybrid vehicles – again, chiefly for reasons of cost.
Delphi says that high voltage programmes are planned by a number of manufacturers – a number have already been announced for production starting 2005-2006. 12-volt hybrid systems have also been announced for production in the near future – and so have dual voltage system vehicles.
Delphi is actually working on all three types of system – not only for the US, but also for Europe – to satisfy what it says will be a wide range of packages from the vehicle manufacturers in the next ten years, each of which are targeted at specific markets and vehicle segments.
What are the motivations for these different types of system? Delphi says that each has its own attributes, but, broadly speaking, these are the main driving forces:
- Improved fuel economy and emissions – yes, even in the US!
- Image – a high-tech or a ‘green’ image is seen as a definite advantage by some vehicle manufacturers;
- Driveability – not to be overlooked, an intelligent electrical energy management package can certainly help to fill in the torque ‘holes’ in high-revving, highly tuned, multi-valve engines.
As for market timing, Delphi refuses to be drawn, only to say that all systems are ‘fairly well developed’, without going into the detail. But it does appear that even when such systems are launched, there will still be plenty of room for development in future – battery technology being a prime example. GM recently said that it would aim to have hybrid – both mild and strong – models on the market from around 2005. There’s not very long to go.
Denso already has a 42-volt belt-driven starter-alternator in production in Japan for a special version of the local market-only mild-hybrid Crown. The device offers stop-start functionality and is therefore able to take advantage of the government cash incentive aimed at car buyers. The Crown also has brake energy regeneration for maximum efficiency. The company introduced a belt-driven starter-alternator in 2001 in the hybrid Toyota Estima (known as the Previa MPV in other markets). That model also uses an integrated starter-alternator between the engine and gearbox housing to boost the vehicle’s IC engine when necessary.
Back in 2001 Siemens VDO was very bullish about the prospects for its ISG (Integrated starter-generator) device, with very low volume series production starting in 2002 for a European small car platform. Time has sadly shown this not to be the case. These days, Siemens says that its expectations for a fast take-off of ISAD are very much diminished. Whilst the company admits that low volume applications will appear, it goes on to say that it does not expect these applications to reach profitable volumes this decade. The cost of switching to 42-volts is huge – everything needs to change – the wiring loom and the architecture of all power-consuming units in the car. First we can expect split voltage systems to appear – sometime around 2008. The 42v/12v car will have certain high power systems operating on 42-volts – such as the air conditioning unit (especially), high power electric steering, electromagnetic valve actuation etc – whilst the majority of the car’s consumers will remain on 12-volts.
Siemens believes that “one day there will be a market” for the systems – but obviously nowhere near as early as the company had originally thought only two years ago. Siemens goes on to say that its ‘market’ won’t be for electrical machines, but for electronics, which are the company’s core competence. The company will however retain its ISAD design for the time being as a way to keep up with developments in such technology.
Unlike some of the other suppliers, Valeo is testing three different ‘hybrid-enabling’ technologies based around the alternator and starter motor
- Micro hybrid – 14-volt stop start (regenerative braking is optional)
- Mild hybrid – 42-volt – stop start, torque boost, regenerative braking 80% motive force provide by ICE
- Full hybrid – 100s of volts – full electric power for distances of a few miles
One of the first Valeo systems to appear on the market will be its start-stop model, with production ramp-up beginning mid-2004. This will be for a B/C-sized gasoline car produced by an important European OEM. A second application is expected to start with another manufacturer in 2005. StArs will produce up to 2.5kW at 14-volts in charging mode. The vehicle will use a lead-acid battery that is no bigger but is slightly more technical than conventional designs – and an advanced battery management system will be utilised to deal with the strains of stop-start operation etc. In addition to start-stop and emissions benefits, the design of the alternator means that it runs at 5-10% higher efficiency than a conventional unit. Valeo’s stop-start unit is a brushless design for long life.
Valeo says that the system works well with diesel engines – despite their higher compression ratios – but stresses that temperatures below -30C, can cause cold starting difficulties.
On the market for such stop-start devices, Valeo says that it is receiving a lot of interest in Japan and North America as well as in Europe – and that the focus is on reducing emissions and improving gasoline consumption. This makes sense, because, as Valeo says, diesel engines have a smaller problem with fuel consumption or CO2 emissions. But the company also has a couple of diesel applications in development at present.
Whilst the marketing of the device is really up to the OEMs, a number of benefits jump out; mainly being comfort and fuel efficiency. One customer is seeking to promote just the ‘comfort’ aspect of the device when the vehicle is stopped – silence, faster engine starting etc, with no mention whatsoever of improved fuel efficiency. Another is seeking to promote benefits of faster engine starting. However, fuel economy benefits are also available – along with the ‘green’ image that such a vehicle could carry.
In Japan there is high interest in Valeo’s device, because the company’s key rival in that market is going along a different path. There, a major Japanese Tier 1 company (working mainly with Toyota – thought to be Denso) is seeking to offer a stop-start system based around a conventional starter motor. For Valeo, this introduces a number of downsides, not only with noisy starting of the engine, but also the issue of long-term reliability: starter motors use brushes – and can thus suffer from wear and shorter life-time than brushless motors. The Japanese government offers a €400 incentive to buyers of simple stop-start cars, so there is a great market opportunity in Japan for companies like Valeo.
Valeo’s mild hybrid (MArs)
Valeo’s next system will be the MArs (Motor-alternator reversible system), or mild hybrid solution, expected to be installed from late 2006 or early 2007. This provides 42-volt generation capability and an electrical torque boost for the engine, as well as brake energy regeneration and stop-start functions. This, says Valeo, is on a completely different level to the 14-volt start-stop micro-hybrid system, because it represents a much higher investment in terms of engineering and the additional components required. In addition to the belt-driven starter-alternator, MArs needs power electronics, a 42-volt battery, a DC/DC voltage converter and ultra-capacitors.
Brake energy regeneration rewards the effort with an overall 2-5% improvement in fuel economy, depending on the test cycle and vehicle.
Valeo’s MArs will provide up to 8kW of mechanical boost and can produce up to 10kW (at 42-volts) when in battery charging mode.
Citroen cancelled its own integrated crankshaft starter-generator system in 2002, so it seems that the in-line integrated starter-alternator systems have temporarily run out of steam – in Europe at least. Even more surprising to hear is that Valeo doubts whether we will see a European integrated system (crankshaft-mounted) this decade. The problem, Valeo explains, is that the integrated system is too intrusive – it requires almost a completely re-designed front end, which would be completely un-economic at low volume production volumes. The belt-driven system requires only a minor front-end re-design and is easily adapted to many different vehicles. So the integrated solution does not make sense for today – not this decade, anyway.
Valeo’s strategy is to focus completely on its own alternator products when it comes to micro and mild-hybrid designs – for other components, the company has a wide range of working partnerships – with battery specialists, ultra-capacitor manufacturers etc. Valeo’s Electrical Energy domain provides a number of different electrical energy management architectures. DC/DC voltage converters etc., but the company says that battery technology is a very important part of hybrid strategy. Valeo has 50-60 hybrid vehicles of all types out on the roads with vehicle manufacturers around the world – including diesel versions and even models with automatic gearboxes (which requires a reprogramming of the automatic’s software).
When it comes to forecasting a likely launch scenario for its technology, Valeo stresses that it is important to forget about conventional vehicle segments. Mild-hybrid technology can cover all segments – regardless of vehicle cost. Valeo says that all the ingredients are already there – the manufacturers only have to decide whether to offer the system, and what level of service they wish to offer. Mild-hybrid technology can be marketed on many different levels – whether for pure economy or for driveability (torque boost) or a combination of both. It can equally be applied to a downsized turbocharged engine to provide a sporty, economical vehicle that does not suffer from turbo lag, or it could be marketed as an environmental ‘green’ technology.
On the subject of 42-volts – Valeo suggests that mild-hybrid technology is driving the charge towards the new voltage level. It also says that if the vehicle is already 42-volt-capable, then the implementation of mild hybrid kit is much easier. But, says Valeo, the vehicle manufacturers are saying that they are prepared to install 42-volt architecture in order to be able to use mild hybrid technology.
On the US market, Valeo says that things are quite different – there are already a number of Japanese full hybrid vehicles on sale there – and growing environmental pressure from states like California leaves the Big Three with no choice but to offer full hybrids. Valeo is currently working with all three on full hybrid technologies.
Visteon has been working on both belt and crankshaft-driven devices for a number of years and says that good progress is being made. The company’s belt-driven devices can generate up to 8kW and the crankshaft unit (brushless motor) will generate up to 20kW at voltages of up to 300-volts. Johnson Controls has worked with the company to supply the necessary battery technology. We can expect some news from the company in coming months.
ZF-Sachs has been developing a crankshaft-mounted starter-alternator (also known as integrated starter generator, or ISG) for a number of years – and it recently went into limited volume pilot production for various vehicle test fleets around the world. In addition to vehicle applications, the company has found strong interest in the field of industrial diesel engines – in fact, the company says that it will introduce a similar device for industrial diesels in the near future.
At present, says ZF-Sachs, the motor industry is not in a position to make the decision to use ISGs purely for fuel economy reasons. The company points out that two years ago there was a strong desire to develop a 42-volt power-net for the vehicle – that was a big driver for the ISG. But, for many reasons, the momentum of the 42-volt power-net brigade has been reduced – at least for the short term – “everyone is reluctant and cautious – this major driving force has no role at present”, says Martin Sattler of the Dynastart development team.
However, the issue of fuel economy could become the major ISG-promoter in the near future because of the European/German decision to self-regulate CO2 emissions down to a fleet average of just 140g/km by 2008. This self-regulation will see a number of new technologies competing for pole position. ISG remains a key technology that not only improves emissions and fuel economy but also has the potential to enhance driveability. The vehicle manufacturers have not yet decided which system they wish to use:
Other competing technologies include:
- Electrically driven turbo or superchargers (plus the conventional exhaust gas-or crankshaft driven units)
- Variable compression ratio
- Hydraulic launch assist
The crunch time for a decision will be 2004, which will then give the vehicle manufacturers three to four years to ready their systems for the 2008 deadline. Already, says ZF-Sachs, some vehicle makers have decided not to use the belt-driven starter-alternator, some have even avoided the whole idea of hybrid technology – preferring to use other technologies to achieve their goals.
ZF-Sachs’ has already delivered (and is still doing so) its devices to the OEMs for evaluation but it doesn’t expect to announce a series production contract before 2004. The system could also appear in commercial vehicles – but although the timescale for market launch and production contract is the same as for cars, ZF-Sachs says that it will be easier to get a positive decision (because fuel economy is much more crucial in the commercial sector). The company is also examining the area of industrial engines, where the decision will be even easier than for trucks – the evaluation and decision process is much shorter. ZF-Sachs says that it already has companies interested in using its device to assist diesel engines of up to 40 litres in capacity.
A key question for ZF-Sachs is whether the current ‘boom’ in interest in hybrids in the US is just a passing phase or is it the beginning of a major change in thinking? Sattler is not convinced that we will see hybrids in large production numbers within the next four-five years but he does say that the integrated starter-generator certainly forms part of his company’s long-term strategy. He also points out that the big US car manufacturers are also still not convinced. However, there is widespread interest in small volumes of hybrid vehicles for niche applications – US companies are looking at small test fleets of delivery vans equipped with ZF-Sachs’ Dynastart – and he is convinced that we will see series production for niche applications from 2005.
Sattler goes on to say that the current method of starting engines is completely old-fashioned – where the driver only ceases to start the motor based on what his ears tell him. In future he sees completely automatic starting of engines – he is convinced that the automatic start-stop function will come onto the market in large volumes.
Sattler believes that whilst start-stop is a noble cause, it is rather a lot of engineering effort simply to obtain a start-stop function. In the future he says that we will see 42-volt systems in cars – but that the 12-volt car network will remain for maybe another two decades. The 42-volt loads (1-3kW each) will be catered for with a special high-efficiency power source:
For all their advantages, Sattler says that belt drive machines are rather limited in comparison with integrated crankshaft (or other direct drive) systems.
Sattler goes on to say that the extra space needed by a direct drive starter-alternator device really depends on how it is integrated. For instance, it could be combined with a dual mass flywheel or a torque converter (TC), in which case it would take no additional length in the powertrain. However, he concedes that in some applications, a little extra space would be needed to accommodate the device.
Sattler says that the US – where different processes and a concerned public are at work – could play a leading role in the development in the hybrid market (much faster than in Europe), but no-one is really sure yet. In Japan, start-stop will enjoy a faster growth than in the US – encouraged by the government’s grant to consumers.
In the US, Ricardo says that hybrid technology is more likely to be used in SUVs and MPVs – these large, heavy and thirsty vehicles are somewhat of an embarrassment to the US government and the manufacturers, particularly when someone like Toyota brings in its own effective hybrid vehicles. The Big 3 all have hybrid development projects underway, mostly for large vehicles, but also for smaller models too. US manufacturers will start by offering smaller numbers of larger, more sophisticated machines. These will be marketed in a more visible way – and the cost of the technology will be easier to disguise in these more expensive vehicles. Neville Jackson (Ricardo technology director) suggests that this higher visibility will help to pave the way for the technology’s eventual acceptance by US car buyers. Cost of such systems is always going to be a significant issue for consideration says Jackson.
In Europe and Japan, stop-start systems will be at the forefront from the beginning, because, says Ricardo’s technology director, Neville Jackson, “there is a lot of mileage in stop-start systems”. Also “evolution is the key here, because the industry cannot afford the cost of technology revolution – the manufacturers don’t want anything too expensive”. The dilemma for the manufacturers is how to deal with the high cost of 42-volts – will the customer be willing to pay?