Electric battery management encompasses cell monitoring, charging and discharging control, temperature control, fault analysis, and data acquisition to improve the performance of batteries in electric vehicles, ultimately achieving the automotive grade (AG).

Battery in EVs

Battery electric vehicles (BEVs) source energy from a lithium-ion (Li-ion) battery pack made of thousands of individual cells.

 An illustration of how battery cells are arranged into modules and then assembled into battery packs

Unlike lead-acid or nickel-cadmium-based batteries, Lithium-ion batteries come with maximum energy density and a high life cycle. This brings an incentive for manufacturers to save space with the provision of increased capacity.

Many factors influence the capacity of the battery packs and battery life including overcharge and discharge current, thermal runaway, over-voltage, or under-voltage. One important factor that contributes to decreased capacity is an imbalance in the cell voltage of these battery packs.

A battery management system (BMS) ensures the operation of the battery within its safe limits.

Battery Management System

• BMS monitors the state of charge (SOC) and state of health (SOH) of electric battery packs in real-time, serving as a vehicle fuel gauge assistant 
• It determines the SOC of an electric battery by using various algorithms. Since an electric battery is based on various Li-ion cells, it is the job of a battery management system to ensure that the cells will not be discharged completely, hence, ensuring the cell balancing. The safe limit of electric current retention is 3V
• SOH is another area where a BMS significantly contributes towards safe operations by measuring the expected age of the battery and helping in determining the mileage on each charge
• Processes such as charging control work simultaneously during real-time monitoring. An intelligent system determines the constant current and constant voltage of a battery for a seamless operation.

The following table provinces the key elements of battery management systems. 

Components	Description
Power Management	It comprises of protection circuit for power supply and voltage regulator to maintain a constant voltage even when there is  variation in supply power
HV Power Interface	It is a high-side driver used for automotives and contains MultiSense analog feedback
Interface between battery management and control unit	It is a serial peripheral interface (SPI) that serves as a communication link between devices in various voltage domains
Battery Management Unit	It is responsible for the protection as well as monitoring of each cell of the battery to ensure its reliability
Control Unit	It comprises of control logic, various registers (data, address, shift) and memory array
Wired Connectivity	It comprises of a bidirectional Can bus transceiver

Supporting Documentation

1. https://ieeexplore.ieee.org/document/8959965
2. https://www.nature.com/articles/d41586-021-02222-1
3. https://onlinelibrary.wiley.com/doi/full/10.1002/est2.203
4. https://www.einfochips.com/blog/understanding-the-role-of-bms-in-electric-vehicles/

Home charging for fleets can require a process to recoup costs for employees. From working with several councils, we’ve found that 60% of Council staff garage at home. Understanding the options for home charging, therefore, will be critical in the absence of a suitable public charging network. Typically, at home people can install a 3kW or 7kW charger; however, it is also possible to charge from a standard wall plug. 

It is generally a simple exercise which only becomes complex if switchboard upgrades, wall penetrations or civil works are required.

There are several key benefits of home charging:

1. Reducing the need for public charging
2. Taking advantage of the low household electricity costs at night
3. Ensuring that all electric vehicles are fully charged for the next day
4. Reducing the demand for fleet facility infrastructure investments

There are also several challenges with respect to home charging that must be considered:

1. Charging at night at home will not synchronise with daytime solar renewable energy provision unless there is a separate battery for the home or hydro/wind generation on the grid.
2. Policy decisions must be made in terms of who pays for the installation of the charger, and what happens when staff leave Council or move house.
3. It can create complexity in terms of the need to recoup costs.
4. The correct electricity rate must be applied to the energy consumed for proper reimbursement.  This may include varying time-of-use tariffs.

Reimbursements for infrastructure and electricity costs for home-based charging of fleet EVs can be considered as follows:

1. Infrastructure
   If the fleet decides to allow for home charging, then clear policy guidelines can ensure that home charging installation costs are fully reimbursed – including labour, electrical upgrades, charger installation and network service fees.
   
2. Electricity
   When fleet vehicles are charged at home, there may be a need to  track and reimburse electrical expenditures. Electricity consumption from EV charging can be measured in a variety of ways:

a.   Odometer readings: a corporate cost per km could be established, which is seen as a fair reflection of the average cost per km. This would be the simplest way to manage the issue, given that employees may also charge at public charging stations.

b.   Telematics: Making use of fleet vehicle telematics enables the company to track energy consumption by vehicle rather than charger. Setting up charging reports by location guarantees that the amount of electricity consumed at home can be tracked.

c.   Smart or networking-based charging stations: Smart charging stations that are networked have the capacity to track electricity usage and provide reimbursement. Some networks enable for company accounts, allowing for use reports to be delivered directly to the company administrator. Additional capabilities such as access control and charge management may be available with networked stations.

d.   Monitoring through digital meters: Electricity meters are commonly used to assess energy consumption for invoicing and/or monitoring purposes. The meter must be dedicated to the EV charging circuit or integrated with a smart home monitoring system in order to track only the EV load. However, there are some restrictions to this approach. If the charger is ever used by non-fleet vehicles, or if the meter is not connected to a dedicated EV-only circuit, consumption data for the fleet vehicle will not be accurate.

Given the large number of home garaged vehicles, it’s important for organisations like utilities, local governments , logistics companies or corporates  to explore potential solutions to home charging including potential policy changes. There is also an opportunity to work closely with state and national government agencies and charging networks to create a network that assists Council’s fleet transition while giving networks greater financial certainty.

Just like with other types of vehicles, you can maximise the lifespan and operability of your EV, depending on how it is used and maintained.

What can affect EV efficiency?

The range is usually determined by the capacity of a fully charged battery and the power of the vehicle’s electric powertrain, but there are also other factors that can affect the range performance.

Source: American Automotive Association [1]

To maximise the driving efficiency of an EV, one can follow these five suggestions: [2]

1. Conserve momentum: Just like with conventional vehicles, conserving momentum is the best method for efficient driving as it reduces the additional need for accelerating and braking, and thus energy consumption.
2. Avoid harsh braking: One of the key features of EVs is regenerative braking, where some of the movement (kinetic energy) is converted back into electricity to recharge the batteries. Once a driver stops accelerating the motor creates a reverse torque – slowing down the car. Energy captured through regenerative braking is ~10% in normal driving and up  30% on descents. Regenerative braking differs from vehicle to vehicle.
3. Observe the speed limit: EVs tend to be more efficient at lower speeds – which is why they are great for city driving.[3]
4. Reconsider use of heating and air conditioning: the use of heating or air cooling in an EV has the most impact on energy efficiency when in extreme conditions.
5. Be aware of eco-features: Most EVs have eco-driving features that can increase the driving range up to 20%.

Note: Checking that tyres are correctly inflated, closing windows at higher speeds and removing unnecessary weight from the car can also improve driving efficiency- just like in internal combustion engine vehicles.

Maximising range in extreme weather conditions

Extreme weather conditions can have an impact on battery efficiency. However, understanding the effects of the weather, and the tips to counteract them, will allow for range optimisation.

The biggest drain on an electric vehicle battery is the use of the air-conditioning and heating systems.

In freezing conditions (-6°C), when the vehicles’ heating is being used, range can be reduced by around 40%. Similarly, driving in hot conditions (35°C +) with the use of air conditioning, range can be reduced by approximately 17%. [1] For this purpose, one can maximise driving range when driving in extreme weather conditions by: [4]

• Using the precondition mode: Most EVs have a precondition mode that allows you to heat or cool the cabin (and battery) remotely. This can be activated when the EV is still connected so it uses electricity directly from the grid (or the power source) instead of using the electricity stored in the battery.
• Using seat heaters: Most EVs use resistance heaters to heat the air in the cabin, which consumes a lot of power. Preheating the car while plugged in, and then switching to a seat heater, will extend the efficiency of your vehicle in cold weather. [5]
• Parking the car in a garage: This will protect the battery from extreme cold, particularly if there is insulation in the garage or parking facilities.
• Parking in the shade: When parking for long periods of time, it is wise to park in the shade to stop the vehicle and battery from getting warm in direct sun.

Maximising the life of an electric vehicle battery

It is important to charge your battery correctly, to maximise its life span. Vehicle manufacturers, such as Nissan, believe that EV batteries will outlast the vehicles they are in by 10-12 years.[6]

To maximise the lifespan of a battery:

• Avoid charging to full when possible. Just like with other batteries, EV batteries degrade faster when they are frequently fully charged or completely drained. To maximise the battery’s life, keep it charged between 20% and 80% of the onscreen capacity. Many EV drivers only charge every few days to meet their driving requirements. [7]
• Use timers when charging. Allow the battery to have a cooling period in between charging and driving to minimise the use of the battery when the cells voltage is high. For this a simple clock timer used as a reminder to unplug your EV 30-60 minutes before the drive can be helpful. [8]
•  

Source: American Automotive Association [9]

Understand what powers an EV.

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References

1. https://www.aaa.com/AAA/common/AAR/files/AAA-Electric-Vehicle-Range-Testing-Report.pdf
2. https://www.energysavingtrust.org.uk/sites/default/files/reports/Efficient%20driving%20in%20electric%20and%20low%20emission%20vehicles.pdf
3. https://www.energy.gov/eere/electricvehicles/maximizing-electric-cars-range-extreme-temperatures
4. https://www.greencarreports.com/news/1081982_electric-cars-in-winter-six-steps-to-maximize-driving-range
5. https://www.greencarreports.com/news/1081982_electric-cars-in-winter-six-steps-to-maximize-driving-range
6. https://www.autonews.com/automakers-suppliers/nissan-looks-ways-use-long-lasting-ev-batteries
7. https://www.fleetnews.co.uk/electric-fleet/charging-and-infrastructure/make-your-electric-vehicle-battery-last-longer 
8. https://www.plugincars.com/eight-tips-extend-battery-life-your-electric-car-107938.html
9. https://exchange.aaa.com/automotive/automotive-testing/electric-vehicle-range/ 

During a fleet transition, ensuring the vehicles are operationally ‘fit for purpose’ should not be compromised when considering electric vehicles.

It is essential that fleet assets are suitable for their corporate and operational requirements and also meet occupational health safety and transport legislation obligations in the mobile workplace.

Understanding the main ‘fit for purpose’ criteria

Electric vehicles should:

• be operationally effective and have the range and performance needed to do the job
• have an Australasian New Car Assessment Program (ANCAP) or
  European New Car Assessment Programme (NCAP) equivalent five stars rating
• be available in the market as and when required
• have a demonstrated level of reliability and local service agents
• be supported by their manufacturers
• come with spare parts – commitment to parts inventory and expedient supply lines.

Are current electric vehicles ‘fit for purpose’?

Electric vehicles are designed with the same fit for purpose considerations as other vehicles. Whether they are fit for purpose for a specific organisation depends on the self-established criteria set by each organisation.

Each organisation will prioritise a variety of the above components differently and it is important to review these when considering an electric vehicle

The focus when organisations are first considering electric vehicles is often on whether they will have a driving range to perform a specific job function. Many of the newer electric vehicles will have sufficient range for the function, as the average daily driving distances for vehicles is generally far less than the typical range of new electric vehicle.

How to assess whether vehicles have sufficient range

Telemetry (vehicle data monitoring), and/or user interviews, average km readings from (odometer) or fuel card information can be used to determine the average kms a vehicle drives.

It is important to properly understand real range under conditions to do this assessment properly. In addition, when assessing range, it is important to understand “dwell-times” as this will indicate if the vehicles have sufficient time to charge between being used for tasks.

What to take into consideration when buying an EV

When considering electric vehicles, it is important to take into account that vehicle servicing needs are reduced, and the implications of this on staffing and support needs.

It is important to use a holistic approach when considering an electric vehicle.

You need to think about:

• model availability
• spare parts
• customer service
• quality of support for maintenance

These will all affect the decision to purchase a new fleet vehicle.

How EVs are supported

The more volume a product has in a market, the more likely it will be supported and have a ready supply of spare parts.

Support is of particular concern to fleet managers in remote locations where local dealer partners may not support the vehicles. Some vehicles have nationwide support offerings, however organisations should ensure that there is sufficient support for fleets from local dealerships and manufacturers when evaluating their purchasing decisions.

EV batteries

The lithium ion-battery is the most important component of an electric vehicle, as it is the energy source. The battery size is demonstrative of the vehicle’s driving range and charging capabilities. Battery size will also affect the cost of the vehicle.

It is important to consider how to manage your electric vehicle battery, as its condition can impact residual values and vehicle efficiency.

An electric vehicle battery

The most common type of electric vehicle battery is made of lithium-ion. This is due to their specific energy (Wh/kg), cycle life and high efficiency. The battery is made up of two electrodes in an electrolyte.

The electrolyte is where the exchange of ions takes place to produce electricity.  The lithium ions act as the charge carrier, allowing for the simultaneous exchange of positive and negative ions in the electrolyte. There are many options for the materials of the electrodes and electrolytes, hence there are different possible battery chemistries, each with their own advantages and disadvantages.

These include:

• Cobalt Oxide (LCO)
• Lithium Manganese Oxide (LMO)
• Lithium Iron Phosphate (LFP)
• Lithium Nickel Manganese Cobalt Oxide (NMC)
• Lithium Nickel Cobalt Aluminium Oxide (NCA)
• Lithium Titanate (LTO). [1]

Comparisons of different types of Li-ion batteries used in EVs from the following perspectives:

• specific energy (capacity)
• specific power, safety
• performance, lifespan and cost.

Source: Miao Y. et. al, Energies, 2019

Battery life

Electric Vehicle (EV) batteries do not need to be replaced as frequently as a battery in an ICEV.  Car manufacturers offer battery warranty to provide comfort for consumers, though it is not intended to be demonstrative of a battery’s life.

A BEV may need a battery replacement after 10-20 years, just like parts in an ICEV will need to be replaced over its lifetime. In an ICEV there are more moving parts, so there are more things to be replaced.

Battery charging

Electric vehicles now include Battery Management Systems (BMS) that limit charging capacity to prolong battery life. They control the temperature of the battery to reduce degradation and capacity loss. [2]

As electric vehicle batteries are lithium-ion it means that certain conditions degrade the battery over time. It is important to charge the battery according to the guidelines to get the most out of the technology.

Australian driving habits indicate an average drive distance of less than 50km per day, [3] so most drivers wouldn’t have to recharge daily given that the average BEV range for 2018/2019 Battery Electric Vehicles is 379km at 100% charge. [4]

There are different ways to charge an EV, all with different capacities and time frames to suit the situation. There are currently four levels of chargers. For more information, refer to the All about chargers article.

Battery conditions 

Heat can affect battery life, so automakers are continuously innovating and investing in thermal management systems which protect the battery in harsh conditions.

Battery Thermal Management Systems (BTMS) form part of the battery cells to protect EV batteries by warming them up or cooling them down as required.  A BTMS consists of systems that may be either active (external or internal sources of heating and/or cooling) or passive (natural convection). [5]

Climate has not shown to be a barrier to uptake in warm or cold regions. California, which has a similar climate to the highly populated areas of Australia, has reached EV market penetration of 9% EV uptake in June 2021. [6] India, with a comparative temperature to the northern regions of Australia, has committed to EV policies to build India ‘as a driver in electric vehicles. [7] Norway, with an average winter temperature of -6.8°C [8] has the highest global EV uptake and a 54.3% market share of BEVs as of December, 2020.

Battery technology: cost and range

Battery prices

Battery technology is constantly evolving, and as battery technology develops, the kWh cost of the battery drops. The price of a lithium battery has dropped significantly since 2010. In China the minimum reported price for batteries in e-buses is below $100/kWh. [9] On average, it is expected that the battery cost will reach $100/kWh by 2023.[10]

Source: Union of Concerned Scientists

Technological advancements are increasing Lithium-ion battery capacity, and innovation in the chemical make-up of lithium-ion batteries is driving the price of vehicles and end-of-EV-life replacement down. New developments include NCM 811 cells (available as early as 2019), [11] Lithium-sulfur, and lithium-solid state (2020-2030). [12, 13]

Battery sustainability

Read more about battery recycling and repurposing here.

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References

1. https://www.mdpi.com/1996-1073/12/6/1074/pdf 
2. https://roskill.com/news/electric-vehicles-china-takes-steps-to-streamline-ev-battery-recycling/
3. http://www.abs.gov.au/ausstats/abs@.nsf/mf/9208.0/
4. https://myelectriccar.com.au/evs-soon-in-australia/ https://www.carsales.com.au/editorial/details/paris-motor-show-kia-e-niro-slated-for-australia-114925/ https://thedriven.io/2018/11/26/hyundai-launches-electric-vehicle-range-in-australia-first-ev-under-50000/ https://www.whichcar.com.au/car-advice/electric-vehicles-coming-to-australia-in-2019 https://reneweconomy.com.au/hyundai-lets-slip-pricing-for-new-ioniq-electric-vehicle-models-87892/
5. https://iopscience.iop.org/article/10.1088/1757-899X/912/4/042005/pdf#:~:text=The%20main%20aim%20of%20the,such%20as%20water%20or%20air.
6. https://www.energy.ca.gov/news/2021-06/report-shows-california-needs-12-million-electric-vehicle-chargers-2030 
7. https://www.thehindubusinessline.com/opinion/electrifying-mobility-why-post-covid-rebound-promises-an-ev-boom/article34176082.ece 
8. https://www.visitnorway.com/plan-your-trip/seasons-climate/winter/
9. https://about.bnef.com/blog/battery-pack-prices-cited-below-100-kwh-for-the-first-time-in-2020-while-market-average-sits-at-137-kwh/ 
10. https://www.bloomberg.com/opinion/articles/2019-04-12/electric-vehicle-battery-shrinks-and-so-does-the-total-cost
11. https://insideevs.com/lg-chem-ncm-811/
12. https://pubs.acs.org/doi/pdf/10.1021/acs.chemmater.0c02398 
13. https://energy.mit.edu/news/designing-better-batteries-for-electric-vehicles/ 

EV driving range

The driving range is the distance your EV can drive with the energy stored in its battery.

An EV’s driving range can depend on:

• the battery capacity
• how the vehicle is driven
• the external conditions (e.g. cold or warm weather)
• the weight of the vehicle.

Battery capacity

The average range for an electric vehicle depends on the battery size. New EV models have driving ranges between 270-600km on a single charge. [1]

How the vehicle is driven

The way in which EVs are driven can also have an impact on range.  As with an internal combustion engine, quick acceleration and fast driving can impact a vehicles’ fuel efficiency.

Extreme conditions (hot and cold weather)

Driving in extreme temperatures (from -6C up to 35C) can affect battery range.  The use of heating and air conditioning can have a significant impact on an electric vehicle’s range.

In weather conditions of -6°C, driving range can decrease up to ~40% while using heating, but it only decreases 12% when heating systems are not used.

Similarly in hot weather temperatures of 35°C+, with the use of air conditioning the driving range can decrease up to 17%, and without air cooling around 5%. [2]

Range Standards

Range standards are a key driver of the EV industry because vehicle manufacturers advertise driving range to market their electric vehicles. As such, standardised range testing provides consumers with a uniform approach to range measurement.

There are three main standards used to measure a vehicle’s range:

• The Worldwide Harmonised Light Vehicle Test Procedure (WLTP)
• The New European Driving Cycle (NEDC)
• The Environmental Protection Agency (EPA) testing standards.

The Worldwide Harmonised Light Vehicle Test Procedure (WLTP)

WLTP is the newest accepted test standard. It is a dynamic test cycle that aims to reflect a more representative picture of real driving conditions. All new-car registrations in Europe from September 2018 are required to use WLTP range estimates. [3]

The WLTP test includes: [4]

• More realistic driving behaviour;
• A greater range of driving situations (urban, suburban, main road, motorway);
• Longer test distances;
• More realistic ambient temperatures, closer to the European average;
• Higher average and maximum speeds;
• Higher average and maximum drive power;
• More dynamic and representative accelerations and decelerations;
• Shorter stops;
• Optional equipment: CO2 values and fuel consumption are provided for individual vehicles;
• Stricter car set-up and measurement conditions;

The WLTP will tend to show lower range and energy efficiency (fuel consumption) than NEDC values due to the more realistic conditions.

The New European Driving Cycle (NEDC)

NEDC is the previously accepted standard of testing. It was designed in the 1980s but has become outdated due to technological advances and changes in driving conditions. [5]

The NEDC cycle is a cold-start driving cycle and it is divided into two parts, the first part simulates the driving conditions in an urban area, while the  second part simulates the driving conditions in extra-urban areas (or highways) [6].

The NEDC has been found to have large differences (around 38%) between tested performance and real world performance. In Europe NEDC results on carbon emissions were on average 123 grams per kilometer (g/km), significantly less than the 170g/km evidenced on real world driving conditions [7]. Discrepancies are attributed to unrealistic low testing parameters and the narrow temperature range of NEDC testing [8]. The NEDC tests determined values based on a theoretical driving profile, which are considered to not match current driving profiles [9].

The Environmental Protection Agency (EPA)

EPA’s testing standards are from the United States. They were established in 1978 and last updated in 2009, and they produce fuel economy estimates for the country’s fuel economy-related programmes.

The EPA requires car manufacturers to change and update their fuel economy values on fuel economy labels (the stickers visible in cars). The EPA tests for city, highway, high speed, with the use of A/C and in cold conditions. The EPA fuel economy ( energy efficiency and range for EVs) tend to show lower values than WLTP.

EPA fuel economy test parameters

The table below shows the test cycles and its attributes.

Source: EPA [11]

Comparing EV range across testing standards

BEV	WLTP	NEDC	EPA
Nissan Leaf 2018 [7]	270km	378km	242km
BMW i3 2018-19 [8]	310km	359km	246km
Hyundai IONIQ 2019	294km [9]	378km [10]	218km [11]

Measuring range

The range displayed on an EV’s digital display is not 100% of the actual capacity of the battery. While manufacturers tend to advertise the rated capacity (the full capacity the battery can provide), some of this total capacity is also used for other purposes.

For example: battery management systems save a reserve of approximately 5% for emergencies and prevent damage to the battery. [12]

If an EV displays 0% charged, it has emergency reserves (just like in an ICEV) however, it is not recommended to drive a battery down below 0%, because completely draining the battery can affect the health of the battery cells.

Optimum state of charge

An EV is typically between 20%-90% of its total capacity under most operating conditions. When discussing EV battery states of charge, common expressions such as “empty” or “fully charged” refer only to the portion of a battery’s capacity that is available for normal use, not its entire energy potential.

As the battery degrades, the battery management system will continue to show the virtual 100% of range until capacity reserves are fully used (see figure below) [13]. Once the battery gets to about 70% of its original usable capacity, then the battery is no longer usable for EV driving.

Source: CleanTechnica [12]

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References

1. miles-by-2022-400-miles-by-2028-new-research-part-1/
2. https://www.aaa.com/AAA/common/AAR/files/AAA-Electric-Vehicle-Range-Testing-Report.pdf
3. https://insideevs.com/features/343231/heres-how-to-calculate-conflicting-ev-range-test-cycles-epa-wltp-nedc/
4. https://wltpfacts.eu/wltp-benefits/
5. https://wltpfacts.eu/fuel-consumption-increase-wltp/
6. http://www.unece.org/fileadmin/DAM/trans/doc/2010/wp29grpe/WLTP-DHC-04-03e.pdf
7. https://theicct.org/sites/default/files/publications/ICCT_EU-CO2-stds_2020-30_brief_nov2016.pdf
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5304423/
9. http://caremissionstestingfacts.eu/nedc-how-do-lab-tests-work/
10. https://wltpfacts.eu/fuel-consumption-increase-wltp/
11. https://www.fueleconomy.gov/feg/fe_test_schedules.shtml
12. https://cleantechnica.com/2018/08/26/the-secret-life-of-an-ev-battery/ 
13. https://www.geotab.com/blog/ev-battery-health/