The heart of the matter
Altelium’s Alex Johns on how you can advise electric car owners to keep their battery in good health
Published: 01 December, 2021
The most valuable component part by far of an electric vehicle is its battery. Yet it is the one component that regular mechanics are not supposed to touch and due to lack of advice, it appears that few owners know how to keep the battery heart of their cars in good health.
Drivers tend to be primarily focused on short term-data that they can expect from their battery such as range or charge. EV manufacturers tend to give surprisingly little information about how to keep an EV battery in good shape on a day-to-day basis. What advice can be given to EV owners to help them look after their batteries for the long term?
Advice
If we look closer at the EV, the Li-ion battery and electric motor combination do the work of not just the engine, but also the gearbox and fuel tank you would find in an internal combustion engine (ICE) vehicle. With an ICE vehicle, mechanics and engineers at a car dealer or garage would be able to give tips and advice on how to maintain these parts in good working order. Few, however, know how best to look after an electric battery. In fact, EV owners are much more likely to be given advice and help in finding charging points or battery range, which is useful, but perhaps not as valuable long-term. By offering EV owners good advice on battery health, you are offering them a long-term benefit - and in turn, building a good reputation amongst that growing EV community.
Most of us are used to keeping an eye on the state of charge on our smart phones, making sure it is always charged as needed. You may even have discussed whether it is better to let it run down and then charge it overnight in one big charge or perhaps think it’s best to keep it topped up through the day and charge it little and often.
This is a great comparison to use when explaining battery health to customers. In practice, the same principal applies to the electric battery in your vehicle but obviously with vastly more energy involved. For example, one Tesla car battery can contain over 7,000 individual cells, whereas your phone might only have one small cell.
It was recently suggested by Tomas Ingenlath, Chief Executive of Polestar, the electric vehicle sister brand to Volvo, that people are “starting to feel a bit more relaxed about the EV question” – but what is the EV question?
Is it how far your car will go when charged and if you’ll reach your destination? Is it how much it will cost to charge your EV? Is it whether the battery can be recycled at the end of its life in a car? Or is it how to keep your battery healthy and make sure it lasts as long as possible? We think this is the key question for EV owners.
In some ways understanding battery State of Health (SoH) answers all these questions. Battery state of health is described as the current capacity of your battery as a percentage of its original capacity.
When I oversaw the trial of five Tesla electric taxis stationed at Gatwick Airport in 2019, before I joined Altelium, each vehicle had 300,000 miles on the clock when the trial concluded after three years, but the batteries were still at 82% state of health (SoH). They were still working really well with many years life left in them. There is no question over the quality of the batteries, but we were given clear guidelines on how to use them and charge them.
Battery health
How can this help to advice EVs drivers on how to best maintain battery heart health in their cars? First, fast charging on DC chargers should be no more than 30% of all charging. Charging has a large impact on battery health so try to charge at home wherever possible, using a household plug or A/C slow-medium rate charger.
Secondly, it is important to try not to let a battery run completely flat. It is best to keep it in the middle range as much as possible where the chemicals in the battery are held at optimal conditions. A car battery computer will be set to do this as far as possible, but drivers can certainly help by not running it down completely.
Additionally, if someone finds they are running a battery all the time, for example in a taxi role or delivery operation, then let it rest – not charging or driving – once a week at a moderate state of charge (30-50%). This allows the battery cells to rest. Although this is not the place to explain in full, information is available online from electro-chemists about what this allows a battery to do internally - and you could certainly suggest that as something EV drivers might want to read up on.
Another good tip is to keep electric cars in the shade on sunny days. The optimal temperature for a battery is at 21-21.5⁰C and extreme heat or cold will really impact the range of that electric car battery. While extreme cold will reduce battery performance, the effect of heat is more important from a health and longevity point of view. For more information, visit: www.altelium.com
- technologies of electric and hybrid vehicles
In the previous two issues, we looked at the way batteries store energy. We could in fact compare a battery to a conventional fuel tank because the battery and the tank both store energy; but one big difference between a fuel tank and a battery is the process of storing the energy. Petrol and diesel fuel are pumped into the tank in liquid/chemical form and then stored in the same form. Meanwhile, a battery is charged using electrical energy that then has to be converted (within the battery) into a chemical form so that the energy can be stored.
One of the big problems for many potential owners of pure electric vehicles is the relatively slow process of
re-charging the batteries compared to the short time that it takes to re-fill a petrol or diesel fuel tank. If the battery is getting low on energy, the driver then has to find somewhere to re-charge the batteries, and this leads to what is now being termed ‘range anxiety’ for drivers.
Whilst some vehicle owners might only travel short distances and then have the facility to re-charge batteries at home, not all drivers have convenient driveways and charging facilities. Therefore, batteries will have to be re-charged at remote charging points such as at fuel stations or motorway services; and this is especially true on longer journeys. The obvious solution is a hybrid vehicle where a petrol or diesel engine drives a generator to charge the batteries and power the electric motor, and for most hybrids the engine can also directly propel the vehicle. However, much of the driving will then still rely on using the internal combustion engine that uses fossil fuels and produces unwanted emissions. The pure electric vehicle therefore remains one long term solution for significantly reducing the use of fossil fuels and unwanted emission, but this then requires achieving more acceptable battery re-charging times.
Charging process and fast charging
Compared with just a few years ago, charging times have reduced considerably, but there are still some situations where fully re-charging a completely discharged electric vehicle battery pack can in take as long as 20 hours. It is still not uncommon for re-charging using home based chargers or some remote chargers to take up to 10 hours or more.
Although there are a few problems that slow down charging times, one critical problem is the heat that is created during charging, which is a problem more associated with the lithium type batteries used in nearly all modern pure electric vehicles (as well as in laptops, mobile phones and some modern aircraft). If too much electricity (too much current) is fed into the batteries too quickly during charging, it can cause the battery cells to overheat and even start fires. Although cooling systems (often liquid cooling systems) are used to help prevent overheating, it is essential to carefully control the charging current (or charging rate) using sophisticated charging control systems that form part of the vehicle’s ‘power electronics systems.’
Importantly, the overheating problem does in fact become more critical as battery gets closer to being fully charged, so it is in fact possible to provide a relatively high current-fast charge in the earlier stages of charging; but this fast charging must then be slowed down quite considerably when the battery charge reaches around 70% or 80% of full charge. You will therefore see charging times quoted by vehicle manufacturers that typically indicate the time to charge to 80% rather than the time to fully charge. In fact, with careful charging control, many modern battery packs can achieve an 80% charge within 30 minutes or less; but to charge the remaining 20% can then take another 30 minutes or even longer.
Battery modules
Many EV battery packs are constructed using a number of individual batteries that are referred to as battery modules because they actually contain their own individual electronic control systems. Each battery module can then typically contain in the region of four to 12 individual cells. One example is the first generation Nissan Leaf battery pack that contained 48 battery modules that each contained four cells, thus totalling 192 cells; although at the other extreme, the Tesla Model S used a different arrangement where more the 7,000 individual small cells (roughly the size of AA batteries) where used to form a complete battery pack.
The charging control systems can use what is effectively a master controller to provide overall charging control. In many cases the electronics contained in each battery module then provides additional localised control. The localised control systems can make use of temperature sensors that monitor the temperature of the cells contained in each battery module. This then allows the localised controller to restrict the charging rate to the individual cells to prevent overheating. Additionally, the localised controller can also regulate the charging so that the voltages of all the cells in a battery module are the same or balanced.
One other problem that affect battery charging times is the fact that a battery supplies and has to be charged with direct current (DC) whereas most charging stations (such as home based chargers and many of the remote charging stations) provide an alternating current (AC). Therefore the vehicle’s power electronics system contains a AC to DC converter that handles all of the charging current. However, passing high currents through the AC to DC converter also creates a lot of heat, and therefore liquid cooling systems are again used to reduce temperatures of the power electronics. Even with efficient cooling systems, rapid charging using very high charging currents would require more costly AC to DC converters; therefore, the on-board AC to DC converter can in fact be the limiting factor in how quickly a battery pack can be re-charged. Some models of electric vehicle are actually offered with options of charging control systems: a standard charging control system which provides relatively slow charging or an alternative higher cost system that can handle higher currents and provide more rapid charging.
Home & Away
One factor to consider with home based chargers is that a low cost charger could connect directly to the household 13-amp circuit, which would provide relatively slow charging of maybe 10 hours for a battery pack. However, higher power chargers are also available that connect to the 30-amp household circuits (in the same way as some cookers and some other appliances); and assuming that the vehicle’s AC to DC converter will allow higher currents, then the charging time could be reduced to maybe 4 hours operate (but note that all the quoted times will vary with different chargers and different vehicles).
Finally, there are high powered chargers (often referred to as super-chargers) that are usually located at motorway services or other locations. These super-chargers all provide much higher charging currents to provide fast-charging (as long as the vehicle electronics and battery pack accept the high currents); but in a lot of cases, these super-chargers contain their own AC to DC converter, which allows direct current to be supplied to the vehicle charging port. In effect, the vehicle’s on-board AC to DC charger is by-passed during charging thus eliminating the overheating problem and the high current DC is then fed directly to the battery via the charging control system.
In reality, the potential for re-charging a battery pack to 80% of its full charge in 30 minutes or less usually relies on using one of the super-chargers, but battery technology and charging systems are improving constantly, so we
will without doubt see improving charges times for
newer vehicles.
- Electric Dreams
The inaugural World EV (Electric Vehicle) Day, held in September, was the first of its kind. Designed to take place as an annual event, the day aimed to encourage the acceleration towards pure-electric motoring. World EV Day was a great opportunity to celebrate how EVs are the cornerstone of the world’s transition to a sustainable energy circular economy – and the movement towards battery power in cars is certainly gathering momentum.
At the heart of the EV industry is the battery. Lithium ion batteries have finally given us a power source which can be used thousands of times in their first lives, then thousands more in their second lives, before being recycled to do it over and over again. Although there are still emissions from mineral extraction and manufacturing, there are no operational emissions. This means that EVs are helping us to breathe cleaner air in our cities and are helping us to live longer and healthier lives.
It’s estimated there are around 1.2 billion vehicles on the road in the world, and in the UK alone there are 38.4 million licensed vehicles on the road. The sooner we switch to electric vehicles and take traditional diesel or petrol cars out of use the better for the health of people and the planet.
Environmental implications
While celebrating the merits of the EV we must also continue to think about how we enable the rest of the new circular economy to ensure we get the most out of both the environmental and economic opportunities created by these new technologies.
The key ingredients in an EV battery, including lithium and cobalt, are hard to mine, and come via a challenging supply chain. Happily, they are not consumed when either storing or releasing energy unlike fossil fuels. However, their performance is slowly degraded, so we must seek to understand this process and maximise performance and utility in their first and second lives, before recycling them for a further generation of uses at peak performance. This creates a circular economy which is about to get dramatically larger and more exciting.
Built on data
Data is fundamental to achieving this. Altelium is working with diverse stakeholders to ensure that data flows to where it is needed to unlock the potential of this new economy, while respecting and protecting the commercial interests of each link in the supply chain. While each stage in the lifecycle helps the planet, it also creates value. Data is the glue that holds it together.
Altelium collects this data and uses its expertise to turn it into the useful information. This underpins Altelium’s warranty and insurance products which facilitate the finance, confidence and value of all the products and businesses in each part of this circular economy.
In order to use the batteries from EVs in second life application, it is essential to know its state of health (SOH) and the performance history of the individual battery cell. Armed with accurate data from the cells we are able to identify the healthiest ones and use them in new products such as stationary storage.
Data will also ensure that any cells not fit for second life uses can be processed as part of an efficient recycling system. These systems are being developed by many interested parties worldwide, targeting at least a 95% recovery and reuse of materials. Sharing data will help the motor industry prosper as we develop the energy circular economy.
Service and repair industry
The garage industry is centred around service and repairs, and the main challenge here is based on the availability of technicians who have the necessary skills and qualifications to work on high voltage systems. The systems found in EVs are very high voltage; as such, it’s a very specialised area of work and there is a shortage of engineers and technicians already.
At the moment, most owners of high value EVs – and most of them are high value at the moment – will return to dealerships for servicing and repairs rather than independent garage or repair shops. Generally speaking, these are likely the only locations in which drivers will find the correctly qualified technicians to handle EV work, certainly in the first ownership of the car and battery; around five years.
The downside to running EV cars with limited service and repair options is the time drivers can spend waiting for appointments with their original dealership – currently this can be 3-5 weeks in many cases.
Another crucial point for garages to understand is that the drivetrain in a diesel or petrol vehicle uses thousands of moving parts, whereas the drivetrain in an EV has dramatically fewer, wiping out most of the common reasons drivers visit service and repair centres.
If we look at something that all cars need regardless of power source, such as tyre changes, you might be forgiven for thinking that this is an area in which smaller local garages will keep pace, despite the major EV shifts predicted. But again, even the amount of tyres from EVs will be less. EV drivetrains tend to be so smooth that despite high torque – which usually shreds tyres - EV tyres remain in good condition for longer. EVs are all automatic, but tyre usage is even less than ICE automatic vehicles. It’s not uncommon for an EV with a good set of tyres to last 30% longer than normally expected which will – across all the cars in the UK – further reducing garage bookings. In addition, EVs will also have self-diagnostic systems running which communicate problems as or before they arise. This will further reduce breakdowns and recoveries.
Other developments
Another development currently only running in China is battery exchange systems for EVs, as an alternative to charging. Cars would drive to an automated battery swap centre, knowing from an app that it’s time to change the battery and there’s one available, and a whole new one would be installed in just a few minutes. It will be the ‘EV pit stop’ – but one that requires no human input.
Overall the mechanical systems within EVs are dramatically reduced so what can service and repair centres do now, to survive in five or ten years’ time?
It seems to me that if you’re an owner of a garage and really wanted to see some return on investment for the future, you would start training your staff in high voltage. Already some of the older EV cars are coming to the end of their warranties, with second or third owners buying at lower prices and wanting the extra value of independent garage servicing, and the numbers will only increase. This is especially true of hybrid cars which need both combustion engines and electrical systems servicing.
It might also be worth looking at specialisms, such as battery reconditioning. Another option might be recycling processes for damaged batteries from collisions and crashes that can’t be used but can be recycled – will your garage be a first point for EV battery recycling?
Fundamentally, high voltage training and investment
will almost certainly be needed in garage settings, and a long-term plan put in place – there’s no doubt about it. Now is the time to stop and consider the future of traditional vehicle service centres – and look to future-proof service and repair businesses as we move into the age of the EV.
- Part Seven: Electric and hybrid vehicles
Over the past few months, we have looked at battery and electric motor technologies of electric and hybrid vehicles,
as well as looking at the advantages and disadvantages of batter power compared to fossil fuel power.
Irrespective of whether a vehicle is powered solely by batteries and an electric motor or whether the vehicle is a hybrid that has the addition of a petrol engine for propulsion and
re-charging the batteries, the vehicle will require a sophisticated electronic system to manage and modify the electrical energy. In effect, the vehicles have an electrical management system that is often referred to as the ‘power electronics’.
Controlling electric motor speed and power
The obvious task of the power electronics system is to control the speed and power of the electric motor so that the vehicle can be driven at the required speed and achieve the required acceleration. As mentioned in a previous article, with Alternating Current (AC) motors the motor speed is regulated by altering the frequency of the 3-phases of alternating current. For light load cruise driving, the current flow provided by the battery pack to the electric motor might only be in the region of a 70 or 80 amps or less, but when the vehicle is being driven under high load conditions, the current requirement will be much higher. Therefore the power electronics can allow higher current flows to be delivered to the electric motor, with some reports quoting as high as 1,800 amps for brief periods on some Tesla vehicles during hard acceleration. However, the power electronics system will monitor currents and temperatures of the electronics, the batteries and the electric motor to ensure that overheating and damage do not occur. As an additional function, the power electronics systems will also control the cooling system (often a liquid cooling system) for the electronics, the batteries and the motor to help maintain acceptable temperatures.
Because most modern electric motors fitted to electric and hybrid vehicles are alternating current motors, the power electronics system must convert the direct current supplied by the battery into alternating current. The power electronics system therefore contains a DC to AC inverter.
Battery charging from a home charger or remote charging point
For pure electric vehicles the batteries are re-charged from home based chargers or remote charging points (and this is also true for many later generations of hybrid vehicles). The battery charging must be carefully controlled to prevent overheating and damage, therefore the power electronics system contains a charging control system to regulate the charging rate (voltage and current). Most charging devices provide alternating current, therefore an AC to DC converter forms part of the power electronics system to enable the batteries to receive direct current.
Note that for rapid charging (especially with lithium based batteries), the power electronics system can regulate the charging rate so that the batteries re-charge up to about 80% capacity relatively quickly (perhaps within 20 to 30 minutes with fast chargers), but to prevent overheating and damage, the charging rate is then significantly reduced for the remaining 20%
of charge.
Battery charging from an engine driven generator
Most mass produced hybrid vehicles use an internal combustion engine that can propel the vehicle, but the engine also drives a generator that can re-charge the main high voltage batteries. While the engine is running, the power electronics system again controls the charging rate; and again, the output from the generator passes through the AC to DC converter. Note that the power electronics system will be linked to or integrated with the engine management system, which will allow the power electronics to cause the engine to start and generate electricity if the batteries are low on stored electrical energy.
Because the electric motors fitted to electric and hybrid vehicles can usually function also as generators, when the vehicle is decelerating or braking (or coasting), the electric motor can therefore be used to help re-charge the batteries. The electrical output from the motor/generator will vary with speed; therefore the power electronics system must control the charging rate to the batteries. As with home/remote charging and charging with an engine driven generator, because the motor/generator produces an AC current, the generator output must pass through the AC to DC converter.
12-Volt battery charging
A 12-Volt electrical system is still used for electric vehicles, but because there is no engine driven alternator, the 12-volt battery is charged using power from the high voltage system. The power electronics system contains a DC to DC converter that converts the high voltage of the main battery pack down to the required voltage for the 12-volt battery. The charging rate for the 12-volt battery is also controlled by the power electronics system.
Additional functions of the power electronics system
As mentioned previously, modern electric vehicles (and hybrid vehicles) will be fitted with cooling systems to maintain the temperatures of the batteries, the electronics and the electric motor. Pure electric vehicles are more likely to be fitted with liquid cooling systems due to the higher currents required for the electric motor that is the only source of propulsion, whereas with hybrid vehicles that also use an internal combustion engine to propel the vehicle generally have less powerful electric motors and therefore often make use of air cooling. However, whichever system is used for cooling, the cooling system can be controlled by the power electronics system to regulate the amount of cooling being applied; note that with liquid cooling systems, the control can also apply to the electric cooling pumps that force the coolant to flow around the cooling system.
Another cooling or heating related function of the power electronics system is to ensure that the battery temperature is at the optimum temperature for charging (and for discharging when the battery is providing electrical power). Batteries charge much more efficiently and faster if they are at the optimum temperature of typically between 10 and 30ºC (or slightly higher for some lithium batteries); but the charging rate should be lowered for lower temperatures; and for many consumer type lithium based batteries, charging is not possible below 0ºC.
Because vehicles are equipped with a cooling/heating systems (for driver/passenger comfort as well as for controlling vehicle system temperatures), the power electronics system can switch on an electrical heater (that would form part of the cooling/heating system) when the batteries are being charged. Therefore, if the vehicle is being charged from a domestic based charger or remote charging station and the ambient temperature is low or below freezing, the battery cooling/heating system can raise the battery temperature to ensure charging take place at the fastest possible rate.
- Plug-in car sales soar, but overall demand remains muted
Plug-in cars made up 28.1% of the total sold during November according to the latest figures from the SMMT, which saw overall registrations up 1.7% on the same month in 2020, which also brought four months of continuously falling sales to an end.
- Plug-in charging points not keeping up with surging vehicle sales study finds
The ratio of vehicle chargepoints to plug-in cars dropped by 31% during 2020, according to a new study from the SMMT, and the organisation is calling for charging infrastructure targets to match the growth in the sales of these vehicles, which now account for one in six new cars sold.
