EALABC paper outlines approach to 48V hybrid systems with advanced lead-carbon batteries

19 November 2014

The European Advanced Lead-Acid Battery Consortium (EALABC) is delivering a paper this week outlining the consortium’s approach to 48V hybridization at the 2^ndInternational Conference on Advanced Automotive 48V Power Supply Systems in Düsseldorf. The EALABC focus is on the environmental and cost benefits of current and future advanced lead-carbon batteries for 48V hybrid vehicles.

The state-of-charge (SoC) of current lead-carbon batteries is typically maintained at between 30 and 50%, with the voltage and amperage meeting VDA requirements by not exceeding 54V at 150A when recovering joules of energy from vehicle deceleration (kinetic energy recovery) and exhaust gas energy recuperation (thermal energy recovery), also dropping not less than 38V at 180A when discharging energy for engine starting and torque assist. Advanced lead-carbon batteries for vehicles currently under development will be capable of operating in the 30 to 70% SoC range at 12.5kW.

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Additionally, says Allan Cooper, European projects coordinator for ALABC, as with conventional starter-motor batteries, advanced lead-carbon batteries can be charged at minus 30 °C (-22°F), which is not possible with lithium-ion batteries.

Significant emissions reduction and major improvements in fuel efficiency can be achieved with advanced lead-carbon batteries using materials that can be fully recycled into new batteries. This electrochemical breakthrough provides the most cost effective solution for 48V hybrids, which have a unique requirement for a battery demanding a high rate partial state-of-charge (HRPSoC) capability.

Augmenting its existing LC Super Hybrid program (earlier post), which deploys a downsized gasoline-electric powertrain, ALABC is working on advanced diesel-electric applications in development programs being undertaken with car makers including Ford and Kia.

Developed by Kia’s European RD centre, its ‘future technology’ diesel hybrid system employs a 48 volt lead-carbon battery, which powers a small electric motor to increase the engine’s output and cut exhaust emissions. Kia’s mild hybrid system will enable a car to be driven in an electric-only mode at low speeds and when cruising, while the battery is recharged under deceleration at all speeds. The Valeo electric supercharger was developed in the UK by Controlled Power Technologies. Click to enlarge.

Other industry partners comprise AVL Schrick, Controlled Power Technologies, East Penn, Exide, Faurecia, Furukawa, InnovateUK (previously known as the UK Technology Strategy Board), Mubea, Provector, Ricardo, University of Nottingham, US Department of Energy, and Valeo.

The Consortium’s global initiative is supported by test and validation programmes carried out at high and low altitudes in Arizona, and at Millbrook proving ground in the UK.

Future battery developments will most likely combine advanced lead-carbon electrochemistry with other types of battery design, for example bi-polar technology, which will reduce the lead content by as much as 40 percent, substantially reducing the size of a 1 kWh battery required for mild electrification of the powertrain. Meanwhile, advanced lead-carbon batteries, with their high levels of carbon in the negative active mass, already represent an exciting development that is truly state of the art, resulting in much improved battery performance ideally suited to 48V hybrids.

The additional functionality of a 48V hybrid vehicle fitted with a Belt Integrated Starter Generator (BISG), compared with simple 12V stop-start systems, characteristically includes torque assist as well as kinetic energy recovery. This is achieved effectively using electronically controlled switched-reluctance motor-generators, which avoid the need for rare earth permanent magnets.

These compact electrical machines can be rated up to 12.5 kW in a package little larger than a conventional alternator. Connected to the powertrain belt system, they avoid the cost and complexity of directly driving the road wheels.

ALABC has employed commercially available Exide Orbital batteries as well as Furukawa and East Penn UltraBattery packs in its technology development programs. The Exide Orbital absorbent glass mat battery is of spiral wound construction enhanced with added carbon in the negative plate.

The UltraBattery is a hybrid energy storage device invented by Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). (Earlier post.) It combines ultra-capacitor technology with lead-carbon electrochemistry in a single cell with a common electrolyte. The result is an economical, fast-charging and discharging battery with high power and a long life, and can be made using existing manufacturing facilities. The technology has been licensed to East Penn, which is working on 14V modules as a building block for nominal 42V batteries required for 48V hybrid vehicles.

With further development of 48V powertrain technology, we anticipate being able to reduce CO₂ emissions by as much as 30 percent compared with today’s baseline. Moreover, the low additional cost of €50-60 [$63-75] for each 1 percent of CO₂ reduction achieved is as little as one-tenth the premium of high voltage (200-400V) hybrids and pure battery electric vehicles—which presently are deemed unaffordable by the average motorist.

The European Advanced Lead-Acid Battery Consortium (EALABC) is the London-based arm of its parent Advanced Lead-Acid Battery Consortium (ALABC) international research and development organisation based in North Carolina. Formed in 1992, the ALABC is dedicated to enhancing the capabilities and competitiveness of the advanced lead-carbon battery in various energy storage markets. These markets include telecommunications, remote area power supply (RAPS), 12V micro-hybrid stop-start systems, 48V mild hybrids with their torque assist and regeneration energy capabilities, as well as full hybrid vehicle applications.