The LC Super Hybrid program was conceived by Controlled Power Technologies (CPT) and the Advanced Lead-Acid Battery Consortium (ALABC) to show that significant CO2 reduction can be achieved through electric hybridisation at low voltages (12-48 volts) using new chemistry lead-carbon batteries.
In the modified vehicle, a Passat 1.4, the existing integrated starter generator (ISG) was replaced with the CPT SpeedStart ISG for quicker response during start/stop events.
The existing 68Ah VRLA battery was replaced with a 100Ah battery (two Exide 50Ah Orbital High Carbon batteries in parallel) located under the boot floor. These batteries use a spiral wound absorbent glass mat design with added carbon in the negative active material. They have been laboratory tested to 220,000km of simulated car use.
The electrical connection to front of vehicle is via a laminated aluminium bus bar. The battery not only provides the ‘hotel loads’ (i.e. non-propulsion energy), but also captures the recovered or “regen” energy from the ISG to power a CPT electric supercharger. The electric supercharger, fitted in conjunction with the standard turbo, acts to prevent turbo lag and lack of power at low engine revolutions. The peak current consumption of the electric supercharger (sampled at 1000Hz) is 477 amps.
Other international companies involved are powertrain developer and systems integrator AVL Schrick based in Austria and Germany, drive belt specialist Mubea also from Germany, and Provector, a leading expert in battery management systems, based in the UK.
The range of technology offers at 12 volts the potential of a mass market, petrol-powered, large family car with good drivability, good performance and 5.6 litres/100km fuel economy achieved at substantially lower cost than an equivalent diesel or high voltage full hybrid model.
The relatively low cost, low voltage technology enables down-sizing and down-speeding of existing engine families – rather than the need to develop brand new drivetrains.
The initial 12V demonstrator vehicle uses low voltage switched reluctance motor-generators, which are not yet currently employed by the automotive industry in mass production. The motors are of simple robust construction using steel, aluminium and copper and by avoiding the use of permanent magnets, are claimed to provide an innovative cost-effective solution to the growing problem of insufficient and ever more expensive rare earth materials.
With global CO2 emission targets rapidly converging, the auto industry has less than a decade to achieve almost another 30 per cent reduction by 2020 putting pressure on automakers to come up with innovative and affordable technical solutions.
“Energy recuperation is the key to ground-breaking solutions that the motorist can afford and this has caused the industry to re-visit the previously mooted higher than 12 volts, but less than 60 volts, electrical architecture,” says Pascoe. “Mild electrification deploying a proposed nominal 48 volt standard will be a major factor for enabling the required motor-generator efficiency and power levels.”
Pascoe says the industry has reckoned the additional cost to the motorist to achieve the required 30 per cent reduction in CO2 emissions is estimated at less than £1,000 for an equivalent performance family sized saloon. This is significantly less than the £5,000 UK government subsidy for electric vehicles; an on cost that would seem to remain unavoidable unless there is a significant breakthrough to reduce the cost of the high energy density batteries required for full hybrid and electric vehicle traction motors.
This table compares the LC Super Hybrid with the original donor Passat 1.4 TSI, the Passat 1.8 TSI and the Volvo S40.
The project developers suggest that the achievements to date are these:
· Demonstrated the feasibility of a cost-effective advanced lead-acid solution which is fully recyclable.
· Demonstrated the attractiveness and simplicity of the evolutionary micro-hybrid concept.
· Has attracted strong OEM interest in the concept from all parts of the World.
CPT and ALABC will have a 48 volt version of the LC Super Hybrid running in 2013 able to provide torque assist to the engine for launch and acceleration, optimise fuelling during cruise conditions, and harvest kinetic energy during braking.