BATTERYTECHNOLOGIESA N O V E R V I E W

Product Engineering 16.12

OVERVIEW OF BATTERY TECHNOLOGIESOVERVIEW OF BATTERIES USED IN AUTOMOTIVE APPLICATIONSDifferent vehicle types require batteries with different performance profiles and characteristics. For example, the ability to deliver a low temperature, short duration, high power burst is a key requirement for cranking the internal combustion engine (ICE) in conventional vehicles, but is not as important for batteries in electric vehicles. For these high voltage electric vehicle batteries, energy density and cycle life are the most important characteristics.

Currently, several battery technologies are installed in vehicles across the Asia Pacific car parc, from 12 volt batteries used for conventional internal combustion engine cranking and Idle Stop Start (ISS) systems (also known as Micro Hybrid systems), to high voltage traction batteries for hybrid (HEV), plug-in hybrid (PHEV) and Battery Electric Vehicles (BEV).

Where a single battery system cannot cope with all requirements at the same time, different combinations of several battery types are installed to operate at different voltage levels. For example, all hybrid, plug-in hybrid and electric vehicles are currently equipped with both a traction battery and an auxiliary 12 volt lead-based battery, which is used to power the vehicle's electrical system including the on-board electronics and safety features. The automotive batteries currently being used across the car parc are as follows:

1. Lead-based batteries

• For conventional and micro hybrid vehicles• As auxiliary 12V batteries in all hybrid and electric

vehicles

2. Nickel Metal Hydride (NiMH) batteries

• For the propulsion of mild hybrid vehicles only

3. Lithium-ion batteries

• For the propulsion of HEV’s, PHEV’s & BEV’s

Other large format battery technologies used in heavy commercial vehicles and public transport are not explored in this report.

2

LEAD-BASED BATTERY TECHNOLOGYLead-based batteries (i.e. lead-acid) are the most widely used battery chemistry in Asia Pacific and worldwide due to their proven safety, performance and low cost. All automotive SLI (starting the internal combustion engine, lighting, and ignition) batteries are currently lead-based.

Lead-based batteries are currently the only available mass-market technology for SLI applications in conventional vehicles, including those with basic micro hybrid systems, due to their cold cranking performance, reliability and low cost. 12 Volt SLI are standardised globally and the handling and behaviour of these batteries is well understood.

Advanced lead-based batteries like Absorbent Glass Mat (AGM) or Enhanced Flooded Batteries (EFB), support ISS functionality to improve fuel efficiency in all micro-hybrid vehicles. In ISS systems, the internal combustion engine is automatically shut down when the vehicle is stationary with the brakes applied, reducing fuel consumption. Some ISS systems also include regenerative braking, in which the vehicle’s kinetic energy is converted to electricity and stored in the lead-based battery.

All lead based batteries use the same basic chemistry; there are however, three different types of constructions currently used:

• SLI (Starter Lights & Ignition), also known as conventional, flooded or Calcium batteries

• EFB (Enhanced Flooded Battery)• AGM (Absorbent Glass Mat)

Conventional flooded lead based batteriesConventional flooded lead based batteries are used in the vast majority of conventional ICE vehicles to provide starter, lighting and ignition (SLI) functions due to their lower cost. Batteries are characterised by a vented design and an excess of free flowing electrolyte between and above the plate group in each battery cell. A plate group is where positive and negative plates are sandwiched together in layers with envelope separators between them. They are then inserted into the plastic automotive battery case and the lid attached.

Advanced lead based batteries: AGM AGM technologies have been introduced more recently for use in micro hybrid vehicles. AGM technology became popular in the early 1980s as a solution for military aircraft to reduce risk of acid damage to wiring looms and airframes and improve reliability. All of the sulfuric acid required for each cell is absorbed by a very fine fiberglass mat, making the battery spill-proof which enables shipment without hazardous material restrictions. AGM has very low internal resistance, is capable of delivering

high currents on demand, and offers a relatively long service life, even when cycled. AGM is a recombination battery, which means that it is maintenance free, and provides good electrical reliability. It is heavier however than an equivalent SLI battery. While regular lead acid SLI batteries require charging every four to six months to prevent the build-up of sulfation1, AGM batteries have a slower self-discharge rate due to their lower internal resistance, resulting in a longer period of time in storage before charging is necessary. This also means that AGMs are less prone to sulfation in storage when compared to a flooded SLI battery.

The leading advantages of AGM are a higher charge acceptance (up to five times higher than a flooded SLI), and superior cyclic durability due to the sandwich type construction. AGM batteries are often used in micro hybrid vehicles as the flooded SLI battery design is simply not robust enough and repeated cycling2 will cause premature failure.

Advantages

• Spill-proof through acid suspension in matting technology• High specific power, low internal resistance, responsive to load• Up to 5 times higher charge acceptance than SLI

Excellent cycle life compared to SLI (3x) and EFB (1.5x)• Water retention (oxygen and hydrogen combine to

produce water)• Vibration resistance due to sandwich construction• Extended shelf life• Can tolerate deeper discharge cycle compared to SLI

Limitations

• Higher manufacturing cost than flooded• Capacity has gradual decline• Must be stored in charged condition (less critical than flooded)• Unable to shed heat as efficiently as flooded designs

Advanced lead based batteries: EFBEFB technology was developed to provide automotive manufacturers with a more cost effective battery solution for micro hybrids with ISS technology. EFB’s can be manufactured using the same equipment used for conventional flooded SLI batteries which makes manufacturing easier and also cheaper than AGMs. As the name suggests, EFB’s are an enhanced version of the flooded conventional battery. Enhancements include thicker plates, improved active material formulation and a high strength polyester scrim which is wrapped around the plate to help retain the active material. Their improved durability, cycle life and performance allow them to fit in between the conventional flooded and AGM designs.

Advantages

• Superior starting performance compared to conventional flooded

• Improved cycle life compared to conventional flooded (2x)• Longer service life compared to conventional flooded• Supports ISS functionality• Maintenance-free• Lower cost than AGM batteries• Higher charge acceptance compared to AGM

1 Sulfation is the growth of lead sulphate crystals in Lead-Acid batteries which inhibits current flow. Sulphation is caused by storage at low state of charge2 A charge cycle is the process of charging a battery and discharging it as required into a load. The term is typically used to specify a battery's expected life, as the number of charge

cycles affects life more than the mere passage of time 3

3 The ability of the battery to store energy

Battery architecture SLI battery vs AGM battery

4

Grid plate

Grid plate

Absorbent Glass Mat

(AGM)

Acid is captured with

glass mat

Envelope separator Positive plate

Negative plate

Negative plate

1 cell

6 cells

Bath of acid

Battery housing

Positive plate

Limitations

• Lower cycle life and durability compared to AGM• Flooded design means battery is not spill proof

ISS applicationsAGM and EFB technology is built to serve vehicles with ISS functionality to keep electrical devices running when the engine is off. Start-stop vehicle technology automatically shuts off the engine when the vehicle stops, such as at traffic lights or in stop-and-go traffic, and restarts it quickly

and quietly when the clutch is engaged or the brake pedal is released. When the engine is off, the battery is the sole source of power to all the car’s electrical devices, such as air conditioning, the radio and the navigation system.

In order to power electrical loads during ‘engine-off’ periods and to support a high number of starts per trip, these vehicles need technology like an AGM or EFB with superior cycling capability, charge acceptance3 and the ability to operate at a partial state of charge.

ChemistryFirst of all, a battery does not store electricity; it is an electrochemical device which is used to accumulate and store chemical energy which can be released as electrical energy upon demand. Lead-based batteries all use the same basic chemistry. The active material of the positive plate mainly consists of lead dioxide (PbO2) and the active material of the negative plate is finely dispersed metallic lead. These active materials react with the sulphuric acid electrolyte to form lead sulfate on discharge and the reactions are reversed on recharge.

A fully charged lead acid battery is made up of three main elements. The active material on the positive plates is lead dioxide (PbO2), and the negative plate active material is called sponge lead (Pb). The electrolyte is a diluted solution of sulfuric acid (H2SO4 and H2O).

As a battery discharges, the electron flow allows the oxygen (O2

4-) molecules to be released from the lead dioxide at the positive plates. Oxygen has a higher attraction to hydrogen (H+) than the sulfate molecule, so hydrogen breaks its bond with the sulfate and combines with oxygen to create water (H2O). The now free sulfate molecules (SO4

2-) combine with the available lead molecules (Pb2+) at both plates creating lead sulfate (PbSO4).

Basically, when a battery is being discharged, the sulfuric acid in the electrolyte is being depleted so that the electrolyte more closely resembles water.

When a lead acid battery is fully charged, there is an excess of electrons on the negative plates (electrons are negatively charged). The positive plates do not have any electrons, which creates a high potential difference (i.e. voltage) between the positive and negative plates.

When an electrical device is connected, electrons begin to flow (i.e. current flow) from the negative side along the conductor and through the device to the positive side. As more electrons flow to the positive plate, the voltage is reduced and the battery discharges. This movement of electrons through the device is what makes it operate (e.g. creates movement, heat, light etc.).

ChargingCharging is a process that reverses the electrochemical reaction in a battery. When there is a movement of electrons, the battery undergoes a chemical change which enables the battery to store energy. It converts the electrical energy of the charger into chemical energy which is stored in the battery. The charger creates an excess of electrons at the negative plates which allows the lead molecules to release the sulfate molecules and combine with the positive hydrogen molecules which are strongly attracted to them creating sulfuric acid. The oxygen in the electrolyte reacts with the lead sulfate on the positive plates to turn them once again into lead dioxide.

The level of charge current that can be applied without overheating the battery or breaking down the electrolyte into hydrogen and oxygen is known as the battery's "natural absorption rate." When charge current is in excess of this natural absorption rate, overcharging occurs. The battery may overheat, and the electrolyte will bubble as hydrogen and oxygen are released.

Reasons for lead-based battery failure1. Extended periods of discharge. Each time the battery

is deeply discharged, corrosion occurs and active material drops off of the plates and falls to the bottom of the battery case. Naturally, this reduces the amount of active material available to conduct the chemical reaction. If enough of this material accumulates in the bottom of the case, it'll begin to short the plates together and kill the battery.

2. Overcharging. If a charger charges at a higher rate than the battery's natural absorption rate at full charge, the electrolyte will begin to break down and boil away. Overcharging will also cause the plates to buckle and twist, releasing active material and reducing battery capacity.

3. Sulfation. As a lead acid battery discharges it begins to sulfate. If a battery is allowed to sit in a discharged state for an extended time the sulfate crystals grow larger and block the pores of the active material. Sulfate is an insulator so this reduces the surface area of active material available for chemical reaction, increasing the internal resistance of the battery and reducing battery capacity.

NICKEL-BASED BATTERY TECHNOLOGYNickel Metal Hydride batteriesThe NiMH battery has been commercially available since the late 1980’s. Unlike Nickel Cadmium (NiCd) batteries, which they effectively replaced, NiMH batteries do not suffer from ‘memory effect’ and do not contain any highly toxic substances like cadmium. They are also more cost effective to recycle than NiCd’s and deliver a higher energy density.

In automotive applications, NiMH batteries have been primarily used in mild hybrid and full hybrid vehicles where their durability, stability and cost have made them a more attractive choice over lithium based batteries.

NiMH was the technology of choice in the HEV market over the last decade due to their design flexibility, good energy density, high power performance and better environmental profile. This was the technology selected by Toyota when the Prius HEV was introduced in 1997. 5

H2OWater

H2OWater

H2OWater

H2SO4Sulphuric Acid

H2SO4Sulphuric Acid

H2OWater

LITHIUM-BASED

BATTERY TECHNOLOGYLithium ion is the battery technology of choice for plug-in hybrid-electric vehicles (PHEVs) and full electric vehicles (BEVs). Lithium ion batteries are used in these vehicles due to their high energy density, extended cycle life, high charge acceptance and relatively light weight. The main barrier to use in mass market 12 volt applications is cost.

ChemistryA lithium-ion battery is a rechargeable battery in which lithium ions move between the anode and cathode, creating electricity flow useful for electronic applications. In the discharge cycle, lithium in the anode (carbon material) is ionized and emitted to the electrolyte. Lithium ions move through a porous plastic separator and insert into atomic-sized holes in the cathode (lithium metal oxide). At the same time, electrons are released from the anode. This becomes electric current traveling to an outside electric circuit. When charging, lithium ions go from the cathode to the anode through the separator. Since this is a reversible chemical reaction, the battery can be recharged.

A lithium-ion battery cell contains four main components: cathode, anode, electrolyte and separator. The table below shows the main components’ functions and material compositions. Lithium ion battery cells are sold in “battery packs”, which include battery management systems. A detailed description of each component is provided in the table below.

12V lithium-ion batteries are not expected to become a viable mass market substitute for lead-based starter batteries in the next decade due to their higher cost (with no significant trade off benefit).

Component Functions Materials

Cathode- Emit Lithium-ion to anode during charging- Receive lithium-ion during discharging

Lithium metal oxide powder

Anode- Receive lithium-ion from cathode during charging- Emit lithium-ion during discharging

Graphite powder

Electrolyte - Pass lithium ions between cathode and anode Lithium salts and organic solvents

Separator- Prevent short circuit between cathode and anode- Pass lithium ions through pores in separator

Micro-porous membranes

6

NiMH batteries are still significantly more expensive than lead-based batteries and have not been considered for use in SLI functions because of their inferior cold-cranking performance.

For plug-in HEVs and EVs, NiMH batteries were an important technology while lithium-ion batteries reached sufficient scale and maturity. Their heavier weight, lower energy density and lower deep cycling capability mean they are not able to compete with lithium-ion batteries for the current generation of plug-in HEVs and full EVs, however. This is apparent in Toyota’s decision to change over to lithium-ion batteries for their current plug-in hybrid Prius model.

ChemistryNiMH batteries are comprised of nickel hydroxide and hydrogen-absorbing alloys as the components of the positive and negative active materials. These alloys operate in a concentrated alkaline electrolyte, usually with potassium hydroxide as the main ingredient. Under charging, the hydrogen storing alloy (M) in the negative electrode absorbs hydrogen from the electrolyte, thus forming a metal hydride (MH).

CURRENT MARKET SITUATIONThe selection of automotive battery depends on the application requirements regarding performance, life, safety and cost. The table below groups technologies by application and corresponding battery performance characteristics:

Class 1

Vehicle type:• Conventional vehicles• ISS vehicles• Micro-hybrid vehiclesPrimary battery:• Lead based battery (12V)Requirements: primary battery• Cranking performance• Capacity to bridge periods of engine shut down;

power safety and comfort systems• 12V compatibility

Class 2

Vehicle type:• Mild hybrid vehicles (HEVs)• Full hybrid vehicles (HEVs)Primary battery:• Lithium-ion or Nickel Metal Hydride battery (48-400V)Requirements: primary battery• Discharge power• Recharge power • High energy throughputAuxiliary battery• Lead based battery (12V)Requirements: secondary battery• Cranking performance• Capacity to bridge key off periods; power safety and

comfort systems• 12V compatibility

Class 3

Vehicle type:• Plug-in hybrid vehicles (PHEVs)• Full electric vehicles (BEVs)Primary battery:• Lithium-ion batteryRequirements: primary battery• Energy density• Recharge power (external)• Discharge power• High energy throughputAuxiliary battery• Lead based battery (12V)Requirements: secondary battery• Cranking performance• Capacity to bridge key off periods; power safety and

comfort systems• 12V compatibility

7

Class 1: Conventional vehicles(including start-stop and micro-hybrid vehicles)

Snapshot

This vehicle class requires 12V automotive batteries to crank the engine of conventional ICE vehicles and to supply the 12V electrical system in all vehicle types (SLI functionality). These batteries can also be expected to provide ISS functionality and entry-level braking recuperation.

Automotive SLI batteries are required to power a vehicle’s starter motor, lights and ignition system, as well as providing power to the vehicle’s on-board electronics. In start-stop and micro-hybrid vehicles the installed battery must also provide ISS functionality and entry-level braking recuperation. This demands a higher durability battery as micro-hybrids operate at a partial state of charge (approx. 80% SOC) to ensure they are always able to accept charge during recuperation. The battery in a micro-hybrid is also required to deliver up to 10 times more cranking events and provide a continued electricity supply during the stop phase.

Lead-based batteries are currently the only available mass-market technology for these applications.

There are several essential requirements that automotive SLI batteries are required to fulfil:

• Cranking performance. The battery must be able to effectively start an engine at low temperature (down to -30°C). The vehicle’s electric starter motor requires high currents to convert electrical energy into sufficient mechanical energy. The battery’s ability to provide high currents with stable voltage decreases with low temperatures, so battery manufacturers and OEM’s specify batteries using Cold Cranking Amps (CCA), measured at -18°C. In order to recharge the battery, charge acceptance at very low temperatures is also required.

• Calendar life. The elapsed time before a battery becomes unusable, whether it is in active use or inactive. Current SLI batteries can be expected to have a calendar life of 3-7 years depending on usage and temperature conditions.

• Safety. At present, SLI batteries are often placed in the engine compartment and may operate at high temperatures. Lead-based batteries are regarded as intrinsically safe systems, both in production and operation, and can be operated within a wide temperature range.

• On-board electronic (board-net) voltage. In all cases, a vehicle’s on-board electronics operate at a nominal 12V. This includes the lighting for the vehicle as well as control electronics, entertainment, navigation, and safety devices such as airbags or door lock systems. The operating voltage of electrical components have been globally standardised at this level and installed batteries must be compatible with these 12V systems. A solution without a 12V battery would require either the use of DC/DC converter (with significant additional costs) or the redesign of the Battery Management Systems (BMS), which is not expected on a global level in the near future.

• Cost. SLI batteries are a mass market technology essential in all ICE powered vehicles currently on the global market. Cost efficiency is a primary driver for OEMs and price-sensitive consumers and lead-acid is still the most cost effective electricity delivery medium.

• Manufacturing base and resource availability. Automotive batteries are required in all vehicles of this class globally. 12V batteries are also currently required in all HEVs, PHEVs and BEVs. A well established and strong battery manufacturing base is required to meet this ongoing demand and lead is the most recycled metal of all those commonly used.

Class 2: Hybrid vehicles(mild-hybrid and full-hybrid vehicles)

Snapshot

Vehicles with a level of hybridisation require industrial traction batteries ranging from 48V to 400V. These batteries provide several advanced functions to improve fuel efficiency in hybrid vehicles. The energy stored from braking is used to boost the vehicle’s acceleration and in full hybrid vehicles, it is additionally employed for a range of electric driving.

In hybrid vehicles, extra requirements are placed on the battery system. In a mild-hybrid, electrical energy stored from braking is used to boost the vehicle’s acceleration, while in full hybrid vehicles it is able to propel the vehicle independently of the ICE.

Mild Hybrid vehicle batteries are only required to store a small amount of energy, as they are recharged frequently during deceleration. They operate at a partial state of charge to ensure they are always able to absorb energy during braking. Due to the large number of micro-cycles they must complete, hybrid batteries are much smaller in capacity when compared to BEV batteries.

The full hybrid functions, as described above, require a battery technology with low internal resistance and high power performance. Its energy storage capability is also important, allowing the vehicle to operate independently of the internal combustion engine.

In contrast, batteries for mild hybrid vehicles are characterised by lower demands for power performance. High energy efficiency and charge acceptance is still essential, although the required energy storage capacity is smaller.

8

The typical requirements for these types of batteries are as follows:

Lead based Nickel Metal Hydride Lithium-ion

Voltage range Limited to 12 volts due to size and weight limitations

NiMH cells (1.2V) can be connected in series to reach high voltages. Usually cells are connected to sub modules that serve as the basic element of larger battery systems. The voltage and temperature of these modules are controlled by electronic devices.

As a result of their higher cell voltage (~3.3V), it’s possible to build high voltage lithium-ion batteries with a lower number of cells compared with other technologies. As long as normal safety measures are taken there is no maximum voltage limitation.

Discharge power

Lead acid batteries are able to power vehicle hotel loads⁴ when the engine is stopped. It would be rare for a lead acid battery to see more than 50A continuous discharge.

The availability of thin electrodes gives Nickel Metal Hydride (NiMH) batteries a high continuous power performance.

Hybrid vehicle applications require high discharge performance and low internal resistance. Lithium ion batteries can provide continuous discharge rates of up to 30C. (aka 30 times capacity).

Recharge power

A battery’s recharge power reflects its ability to reabsorb energy from braking and deceleration. Lead-based batteries are limited in their recharge power capability. Operating them at a partial state of charge increases their charge acceptance however for mild and full hybrid the energy is directed to the high voltage traction battery.

Due to its excellent charge absorption, the NiMH technology also provides superior recharge performance. The only limitation is the battery’s upper voltage, state-of-charge and temperature.

Recharge power depends on the temperature of the battery system. Charging at low temperatures may lead to lithium plating, which causes a degradation of the battery.

Cold cranking

Similar to SLI battery requirements, a certain power performance is needed to crank the internal combustion engine, even at very low temperatures. Depending on the engine, 1kW to 2kW pulses of approximately 5 seconds duration are prescribed by vehicle manufacturers

Continuous discharge capability decreases for NiMH batteries at lower temperatures. Locating the battery inside the trunk can help manage cell temperature. Cells naturally generate heat when being used which can help low temperature operation.

Lithium batteries are generally not employed for cranking duties in HEV’s however they are capable of delivering cranking power if required.

Capacity and cycle life

Even at low depth-of-discharge, lead-based batteries have a modest cycle life, which is unable to meet the requirements of full HEVs.

The cycle life of a NiMH is approx. double that of a lead acid battery. Reducing DoD to less than 5% as required by most hybrid vehicles means typically 15000 cycles is achievable.

Under typical HEV conditions with smaller micro cycles at low DoD, lithium-ion batteries have an excellent cycle life. Calendar life at normal ambient temperatures is expected to exceed 10 years and may reach 20 years.

Safety

Lead acid batteries (excluding AGM) are considered dangerous goods because of their corrosive electrolyte. They are however very stable under normal operating making them a safe technology.

The aqueous electrolyte and modest energy content make NiMH a safe system. There are no rare earth metals or toxins used in NiMH batteries.

Due to the organic electrolyte and high energy content, lithium-ion presents more safety challenges. Individual cell voltages must be carefully controlled; overcharging may cause a critical thermal event.

In ICE vehicles with higher degrees of electrification, including intensive recuperation of kinetic energy during deceleration/braking and other advanced micro-hybrid features, the battery is required to undertake a more active role. This is especially true for mild and full hybrid vehicles, where the stored energy is also used for vehicle propulsion.

Nickel-metal hydride and lithium-ion batteries cope best with this additional load due to their excellent performance characteristics in terms of fast recharging, discharging performance, and lifetime endurance. Such batteries will operate at elevated voltages which require special safety precautions such as battery management systems. Lead-based batteries are limited by their lower recharge/discharge power and insufficient capacity turnover.

94 Hotel load: the electrical load caused by all systems on a vehicle other than propulsion.

Class 3: Plug-in hybrid vehicles and electric vehicles

Snapshot

In plug-in hybrid vehicles, high voltage battery systems of at least 15kWh are installed to provide significant levels of electric propulsion, either for daily trips in plug-in hybrid vehicles, or as the only energy source in full electric vehicles. In plug-in hybrid vehicles, the battery must also perform hybrid functions, like regenerative braking, when its capability for electric drive is depleted.

Plug-in hybrid (PHEV’s) and full electric vehicles (BEV’s) require high voltage battery systems to act as the propulsion energy source. The battery must also support regenerative braking functionality. As a consequence of these requirements, batteries must provide high performance for both charge and discharge.

Although batteries for plug-in hybrid (PHEV) and electric vehicles (BEVs) have differences, they have been grouped together because they must both respond to higher demands for energy content compared to those for HEV batteries in order to provide sufficient levels of electric propulsion.

Therefore, the battery’s energy density is a primary focus in this class. Fast recharge capability is also required to limit the period of time needed for recharge with quick recharge to 80% important to extend the range of the vehicle. Batteries for both types of vehicle must also be highly efficient with low internal electrical resistance and sufficient calendar life.

Requirements for plug-in hybrid vehicle and electric vehicle batteries:

• Voltage range. The voltage range for these vehicles ranges from 200V to more than 500V for full electric vehicles. Lithium ion cells can be easily assembled into a high voltage battery system which is managed with a battery management system supervising the voltage of each of the cells contained in the system.

• Energy density. The energy density needs to be high to provide sufficient energy for extended driving on electric power. Compared to other batteries, lithium-ion batteries have superior energy density. This sets them apart from other technologies for plug-in hybrid and electric vehicles.

• Discharge power. BEVs and PHEVs require power performance of up to 100kW for a mid-size vehicle. Lithium ion batteries are designed for high energy applications in electric vehicles.

• Recharge power. Capability depends on the individual vehicle requirement to absorb energy from braking and deceleration. The charge must be managed by an electronic control system and is normally supported by an active cooling system.

• Cycle and calendar life. Batteries for plug-in hybrids and electric vehicles experience higher capacity turnover than other applications because of their direct involvement in the electric drive train system of the vehicle. Normally the DoD is relatively high. In addition to cycle life endurance, calendar life is important with a service life of 10 years expected from these batteries.

10

FUTURE TRENDS IN BATTERY TECHNOLOGYDue to the increasingly stringent environmental restrictions on vehicles, the use by OEM’s of start-stop and micro-hybrid technology is expected to increase to a point where every conventional ICE vehicle design will employ this technology. This, in turn, will drive an increased demand for advanced lead-based batteries. Greater demand will also develop for HEV’s, PHEV’s and BEV’s with power demand likely to increase for all applications.

From now until 2025 a significant development for the global battery industry will be the ongoing mass market rollout of start-stop and micro-hybrid vehicles. Already in 2014 a major portion of new vehicles being placed into the Asia Pacific market by OEMs contain start-stop systems powered by advanced lead-acid batteries. Start-stop and micro-hybrid vehicles are an important bridge between conventional ICE vehicles and higher priced hybrid and electric vehicles. This allows OEMs to improve fuel efficiency in line with EU targets, without significant extra cost being imposed on consumers. The growth of these segments will create an increased demand for advanced lead acid batteries (EFB and AGM designs) as the only feasible commercialised option for use in start-stop and basic micro-hybrid systems.

The market penetration of HEV’s, PHEV’s and BEV’s is expected to steadily increase through 2025. While forecasts for the development vary widely, with anywhere between 0.5 and 5 million electric vehicles to be sold globally by 2020, under all scenarios PHEVs and EVs will still only comprise a relatively minor share of the total global vehicle market.

Avicenne’s 2020 projections for market development of automotive applications and their corresponding battery technologies (2014) are highlighted in the table below:

11

The projections provided by Avicenne Energy clearly highlight the dominance of lead-acid battery technology well into 2020. McKinsey and Company’s 2010 ‘A portfolio of powertrains: a fact-based analysis’ projected that electric vehicles and plug-in hybrid electric vehicles will only be cost competitive with ICEs in relevant segments by 2030. At this point, their three credible scenarios still predict a 65-80% market share for ICE-powered vehicles in the Asia Pacific and Europe vehicle mix.

Expected developments of battery technologiesResearch and development is ongoing to increase the performance of lead based batteries, while lowering the quantities of lead used in their manufacture.

Lead-based battery manufacturers have identified several priority areas for increasing the competitiveness of their products in micro-hybrid applications:

• Higher cycle life• Higher power density• Better charge acceptance• Lower battery weight

To reach these targets, several improvements are being made in the chemistry and design of lead-based batteries. Battery manufacturers are currently working to implement the following general improvements (source: Eurobatt):

• Carbon nanotechnologies. Developing new types of additives to improve the conductivity of active materials.

• High surface area doping materials. Increasing charge acceptance while avoiding hydrogen evolution (gassing).

• Low-cost catalyst. Recombining hydrogen and oxygen produced at regenerative braking events.

• Light weighting solutions. Developing new designs and materials to improve overall weight.

Eurobatt suggests that by 2025, these developments will enable lead-based batteries in micro-hybrid vehicles to provide several additional functions to improve fuel efficiency, including:

• ISS with voltage stabilisation system, potentially including lead-based AGM battery with supercapacitors.

• Stop-in-motion. Engine off at higher speeds when acceleration is not required.

Where increased electrical functionality is required, lead-carbon designs have been introduced to inhibit the negative plate sulphation frequently observed in the battery’s partial state-of-charge operation.

Various lead-carbon batteries have been introduced to the market in recent years including the PbC battery and Ultrabattery, as well as those with carbon blended into the negative active material. Through these developments, lead-based batteries can provide higher performance both in terms of charge recoverability and by their capability to operate at partial states-of-charge. These improvements will increase their competitiveness in micro-hybrid and mild-hybrid vehicles.

Dual battery systemsDual battery systems have been on the market for the last ten to fifteen years. Several luxury vehicles use two 12V lead-based batteries to secure cranking capability under stress operational conditions. Furthermore, several vehicles with ISS functionality use a second lead-based battery to stabilise the system voltage when the engine automatically restarts for comfort and security reasons.

The way ahead: Nickel-based batteriesAlthough nickel metal hydride batteries have been an important technical resource in the rise of hybrid and electric vehicles, their potential for further market penetration is reduced as a consequence of the increased performance and reducing cost of lithium-ion batteries. They have also reached a relatively high degree of technological maturity with only limited scope for performance and cost improvements.

The way ahead: Lithium-ionThe global battery industry is focused on improving the performance, cost, systems integration, production process, safety and recyclability of lithium-ion batteries. All of these areas need further development to improve their market competitive integration into electric vehicles.

With the recycling industry for lithium-ion batteries still in its infancy, businesses are also looking at how to optimise the separation of lithium-ion battery components at the end of a battery’s life. This is unlikely to occur however, until sufficient scale in exhausted lithium-ion batteries is achieved.

The way ahead: High voltage architectureAutomotive manufacturers in Europe have collaborated to agree on a 48 volt vehicle electrical architecture. A 48V system will deliver a number of benefits over 12 volts. Wiring looms and components can be downsized, reducing weight, cost and size. High voltage devices are also more efficient, reducing loads on the vehicle's power systems.

48V architecture will deliver a new generation of high efficiency systems like electric supercharging and active suspension. Lithium based battery technology is being used for the 48V battery as the higher cell voltage and energy density enable a compact and efficient battery when compared to lead acid. 48V also has the potential to further improve efficiency of mild hybrid vehicles.

First generation vehicles will use a dual voltage architecture. In this set-up, the 12V network continues to support traditional SLI loads (lighting, ignition, entertainment, etc.), while the 48V system supports new higher efficiency systems (electric supercharging, active suspension, AC compressor etc.).

12

CONCLUSIONSBattery technologies have specific performance profiles that serve a well-defined purpose in automotive applications and because of this it is not possible to replace one technology with another technology without impacting overall performance and vehicle cost.

• 12V lead-based batteries are the only battery technology tested for the mass market that satisfies the energy supply requirements for conventional ICE vehicles (including basic micro-hybrid systems). For the foreseeable future, as long as any residual risks to human health and the environment are properly managed, their cost-efficiency, durability and cold-cranking ability will set them apart from other technologies in this high volume segment.

• The performance profile of high voltage lithium-ion battery systems makes them the technology of choice for plug-in hybrid and electric cars. These batteries are set apart by their high energy density, low weight, good recharge capability and energy efficiency.

• In between, several combinations of battery technologies can be used for different levels of hybridised powertrain (from 48V mild-hybrid vehicles to 400V full hybrid vehicles), with nickel-metal hydride and lithium-ion batteries coping best as requirements increase.

Lead acid battery technology for automotive applications will continue to play an important role in conventional vehicles, HEVs, and EVs for the foreseeable future. Their low cost, ability to start in cold temperatures and recyclability sets them apart from other battery technologies. The table below shows the predicted mix of battery technologies in the marketplace through to 2020, clearly illustrating the dominance of lead-acid technology:

While Club Assist continues to keep abreast of new battery and automotive technologies due to be introduced to the APAC car parc, lead-acid batteries will continue to be the dominant battery product in the range for the next 10-15 years.

Club Assist is the brand under which our Product Engineering specialists collaborate with motoring professionals across the globe with expertise and assistance to provide complex mobile automotive service solutions for their customers. To maintain our momentum, Club Assist continues to invest in new product development and services while expanding the business through new partnerships, alliances and organic growth.

Learn more about Club Assist's range of products and services at www.clubassist.com.au

Club Assist - our business is to grow yours. 13

APPENDIXExamples of hybrid vehicles by type:

Mild Hybrid

• Honda Jazz hybrid• Honda Civic hybrid• Honda Insight• Honda CR-Z• Toyota Camry Hybrid• Toyota Corolla Hybrid

Full Hybrid

• Toyota Prius• Toyota Prius C• Toyota Prius V• Lexus C7200h, IS300h, ES300h, ES450h, ES600h, RX450h• BMW Active Hybrid 3, 5, 7• Porsche Cayenne Hybrid• Infiniti M35h, Q50• Mercedes-Benz E300 Blue Tec Hybrid

Plug-in Hybrid

• Mitsubishi Outlander PHEV• Porsche Panamera S E-hybrid• Porsche Cayenne S E-Hybrid• BMW i8• Holden Volt

Battery Electric Vehicle (BEV)

• Nissan LEAF• Tesla Model S• BMW i3• Mitsubishi i-MiEV

ICE ISS HEV HEV PHEV BEVHybrid Type Micro Mild Full Plug-in ElectricICE DriveElectric BoostElectric Drive12V system? Yes Yes Yes Yes Yes YesHigh Voltage system >200v >400V >400V >400VEnergy Recuperation? Some Yes Yes Yes Yes YesUsed for? 12V 12V Propulsion

Vehicle type characteristics:

Acronyms:

ISS – Idle Stop StartICE – Internal Combustion EngineBEV – Battery Electric VehicleHEV – Hybrid Electric VehiclePHEV – Plug-in Hybrid Electric VehicleSLI – Starter, Lights & IgnitionAGM – Absorbent Glass MatEFB – Enhanced Flooded BatterySOC – State of Charge

14

Product Engineering 16.12