Some so-called battery events don’t even give them a platform but this wasn’t the case this week when tireless lead-acid old stager Allan Cooper delivered a cracking account of how advanced lead-acid batteries will bring serious environmental and cost benefits to the car industry.
Speaking at IQPC Automotive’s Second International Conference on Automotive 48V Power Supply Systems, Cooper said the low additional cost of introducing 48V mild hybrid powertrains is proving a major attraction to carmakers, because it will help them comply with stringent CO2 regulations being introduced in 2020 with even tougher rules following in 2025.
Cooper, European projects coordinator for ALABC, has been making the case for lead-acid for more than 20 years.
“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,” he said. “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.”
The state-of-charge (SoC) of current lead-carbon batteries is typically maintained at 30-50%, 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 per cent SoC range at 12.5kW.
“Additionally, as with conventional starter-motor batteries, advanced lead-carbon batteries can be charged at minus 30°C (-22°F), which is simply not possible with lithium-ion batteries,” said Cooper. “This is an essential requirement for vehicles used in the snow-belt areas of the northern United States and Europe. And unlike lithium-ion, they require no active cooling and no expensive battery management system.”
Looking to the future, Copper believes battery developments will most likely combine advanced lead-carbon electrochemistry with other types of battery design such as bi-polar technology, which will reduce the lead content by as much as 40%, substantially reducing the size of a 1kWh 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 12.5kW 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.
“With further development of 48V powertrain technology, we anticipate being able to reduce CO2 emissions by as much as 30% says Cooper. “Moreover, the low additional cost of €50-60 for each 1% 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.”
