Bosch's 48V mild hybrid system to debut this year

With so many innovative vehicle concepts testing the market we almost forget that most vehicles sold are still traditional gasoline vehicles. Such vehicles can be made more fuel-efficient by adding a mild hybrid system.

A new trend in the development of mild hybrid systems has been the use of 48 Volt lithium-ion batteries. These batteries replace lower voltage systems, often using 12V lead-acid batteries (or occasionally even nickel-metal hydride (NiMH) batteries). This has been made possible by advances and cost savings in li-ion technology. According to Just-Auto a 48V architecture provides about four times the energy recuperation from regenerative braking than is available on the traditional 12V system. Full hybrids use much higher voltages, for instance the Toyota Prius hybrid synergy drive uses a 220V battery.

Many automotive suppliers have jumped on the band-wagon, including Continental, Johnson Controls and Bosch.

Automotive news Europe interviewed Bosch executives about this subject recently. In 2013, GS Yuasa, Bosch and trading house Mitsubishi Corp. formed a joint venture to develop low-cost, high energy-density lithium ion batteries by 2020. A Bosch executive told Automotive news that they are "on a good path" toward their goal of developing a lithium ion battery that costs half as much as today's batteries but has twice the energy density.
Such advances will greatly popularize the use of hybrid and electric-only drive trains. Bosch expects such drive trains to account for 15 percent of the global automotive market by 2020. Mild hybrids are expected to break through with the introduction of 48V technology and could account for most of those vehicles.

Bosch also is rolling out a new 48 V mild-hybrid system this year that it says will improve fuel efficiency at minimal extra cost. Bosch has named its system "Boost Recuperation System" (BRS) which features an electric motor, with a 48V 0.25kWh lithium-ion battery and DC/DC converter. The system potentially reduces fuel consumption by 5 to 18%.
BRS offers four functions:
- coasting
- start-stop
- recuperation
- torque boost
When coasting and during start-stop the 48V battery keeps the car's electronics and climate control running. Recuperation enables the car to recover braking energy. The battery can provide the vehicle a torque boost of up to 10 kW. 
Bosch's system debuts this year in a nameplate for Europe offered by a European automaker, executives said. They declined to name the customer. Bosch aims to sell the mild hybrid system in other markets, including North America.

Aluminum batteries might find application in hybrids and FCVs

New publications about battery breakthroughs appear regularly in the media. In practice however not much has changed in the field of battery technology in the last few years. Recently Stanford University came up with a new story.

This time the story is about the aluminum-ion battery. Stanford has developed such a battery that they present as very promising. Of course they are looking for investors to help further develop this technology into actual products.

The main difference with the commonly used lithium-ion battery is the use of aluminum instead of lithium.

Advantages
Aluminum offers a number of advantages compared to lithium. Aluminum does not cause a fire hazard in case of incidents. Another important advantage is the shorter charge time: Stanford has succeeded in charging the battery in only a minute. Finally the battery has a much longer life time than lithium batteries. Standford's battery could withstand 7,500 cycles without capacity decay, where a typical lithium battery lasts about 1,000 cycles. Finally aluminum is also cheaper than lithium.

Disadvantage
The major disadvantage of the aluminum is the lower voltage, about half the voltage of a lithium battery. That also leads to lower battery energy density. In other words: more batteries are needed to store the same amount of energy. That is a key disadvantage which disqualifies this battery for most of the popular applications of lithium batteries, such as mobile devices and electric vehicles.

Applications
Still there are applications where the advantages of this aluminum battery seem more important than the disadvantage. Stanford suggests using this battery for storage of excess electricity from sustainable energy sources such as wind and solar. In such a stationary application the size of the battery stack is much less relevant and life time is more crucial.

Hybrid vehicles
Although aluminum seems unsuitable for electric vehicles and plug-in hybrids, I do see opportunities for vehicle applications. Hybrid vehicles without a plug such as the Toyota Prius have a relatively small battery which can be charged and uncharged multiple times during a single trip. And it is crucial that the battery can be charged quickly as this is needed to store breaking energy. The life time of lithium batteries in hybrid vehicles is a major bottleneck. In Toyota's hybrid synergy drive system the potential capacity of the batteries is only used for a small amount in order to extend battery life. In Honda's IMA (Integrated Motor Assist) system it is even worse. Battery failure is one of the main reasons why the IMA system is unsuccessful on the market. Aluminum batteries might offer new opportunities for such hybrid systems.

Fuel Cell Vehicles 
Another type of vehicles that might see use of this type of batteries is the Fuel Cell Vehicle. FCVs are in fact hybrid vehicles which use a lithium-ion battery to store energy which can be used to improve response to the gas pedal. The battery is charged from breaking energy or when you let go of the gas pedal because the fuel cell doesn't stop producing power immediately. Just like ordinary hybrid vehicles, FCVs have relatively small capacity batteries that are typically charged and uncharged multiple times during a single trip.