21 Jun 2024
The voice of the independent garage sector

Li-Ion batteries: Size does not matter

Imagine if today we had only ever known electric cars, which were the dominant powertrain of choice in the late 1800s. Consider someone coming along and suggesting the use of a powerplant which consumed a highly flammable liquid derived from oil? The headlines could be ‘oil is for lighting, not vehicles’, and ‘the dangers of explosions’.

Of course, the very reason internal combustion engines won the battle with pure electric vehicles was because of better range, faster speeds and the ability to get the fuel source refilled in a matter of minutes rather than days. Everything about the late 1800s electric car made sense apart from the battery. It has only taken about 120 years so far to produce a better battery pack, along with infinitely better traction motors and power control. Speedy, no?

From around 2010 the push to add electric drive or only have electric drive really got underway. This was also after the vehicle manufacturer lobby argued that the real intermediate solution to reduce tail pipe emissions – yes, that’s what this has been about all along – was to enhance the internal combustion engine. Only then did the EU Commission and collective MEPs seemed to relent.
Meanwhile, politicians such as Lord Deben (formerly John Selwyn Gummer) chaired the Climate Change Committee (CCC) which gave the primary advice that led to the 2017 Climate Change Bill. The EU Commission had similar devices. This led to the pivot. Just as vehicle manufacturers rolled out mild-hybrid (MHEV), hybrid (HEV) and plug-in-hybrid (PHEV) as well as pure electric (BEV) models for 2019, the UK and EU stormed off into an electric-only future.  Suddenly national leaders and city mayors competed with each other to make the most unfeasible deadline to stop selling any new vehicle with an internal combustion engine.

Why did this happen? The UK CCC’s research for example suggested that pure electric cars would cost £11,000, and that the electricity to recharge them was going to cost “very little.” When challenged on these assumptions, the committee said the projected cost was not about battery size, but vehicle size – but did not define that. Yes, it was based on the quadracycle known as G-Wiz.
The politicians bought the whole flawed proposal, which is why vehicle manufacturers are running to keep up with the pivot to BEV-only, and there is an ever-increasing mountain of electrification technology, which seems to be sidelined as rapidly as it appears. This is why we see in some model ranges the electrical architecture for HEV, PHEV and BEV have stark differences.

It is worth remembering that there are no common solutions and no agreed standards for the way motors, power controllers or traction batteries are built. We do know if the traction battery is recharged at a slower pace, and the vehicle driven without trying to spin the wheels most of the time, the whole powertrain should have a service life of at least eight to 10 years. We also know the garage trade will end up looking after every single variation of every form of electrified powertrain built from 1997 onwards (Toyota Prius I, for example) even though the volumes really only started to climb to significant numbers from 2019 onwards. For those in areas with a higher demand for HEV, PHEV or BEV none of this is a surprise – the news is it is now going nationwide. How did the electric car re-appear after such a long break?

Enter the lithium-ion (Li-Ion) battery
Of all the competing battery constructions, it is the Lithium Ion (Li-Ion) chemistry that has been at the centre of power density as well as discharge/charge rate improvements. There are many, many combinations of Li-Ion chemistry on the market, along with multiple formats ranging from cylindrical to pouch cells. Not only has the battery a store of electric energy, it also has combustible materials. As long as the vehicle does not develop a serious electrical issue or the battery is severely damaged, as many Li-Ion HEV, PHEV and BEV owners already know, the only thing to happen is a slight reduction in charge capacity as the battery gets older.
In 2011 NHTSA performed a side impact test with a pole on a first-generation Chevrolet Volt, and the test result was good. The wreck was carefully stored, just in case further analysis was required. Some three and a half weeks later, the battery ignited – and did so again, and again with more repeats than a television series on Dave. It was a forewarning.

GM admitted that in their private testing the battery pack was discharged yet in the public test it had been subject to impact while charged. When the test agency asked GM about the equipment, and if it would be available to support the newly delivered Volts the answer was… no. Subsequently, the special discharge tool did see the light of day, and very few Chevrolet Volts suffered from a fire caused by the battery.

More to the point, in the real world, a Li-Ion battery will not have the electrical energy discharged during impact or even some time after impact. Safe isolation – the default in the event of severe impact – is not the same as zero stored energy. This applies to everything from e-scooters through hybrids to full electric vehicles.

The event
What happens if the battery damage is enough to initiate thermal runaway? The story starts at point of impact, where the cooling system – especially if it uses a combination of coolant and refrigerant typically used to manage heat rejection of larger battery packs – could be damaged. In effect the battery may not have the ability to regulate internal heat rejection. If the battery is internally damaged and if internal shorting takes place it will draw on the remaining stored energy, which then may result in chemical reactions taking place. From then on, a major thermal event will occur. Each cell in thermal runaway will initiate the failure of adjacent cells:

  •  Thermal run away generates…
  •  Gases and heat which…
  •  Vent – the cloud will contains toxic heavy metal particles, and…
  •  A highly flammable white vapour cloud which can explode or burn, leading to…
  •  A fire burning at 1000 C or more.

If a battery does catch fire, it takes less than a minute to start and will burn for days. Water is not required to put it out, but to cool the battery core, so reducing the chemical reaction process. Given the internal chemicals are chosen for their performance, it may come as no surprise they are hazardous. The fumes that come off the burning Li-Ion batteries are highly toxic, and in enclosed spaces, dangerous. Worse, this mechanism applies to Li-Ion batteries fitted to MHEV, HEV, PHEV and BEV vehicles – as well as e-scooters.

So how does everyone remain safe from point of impact to completion of repair? Everyone who handles the vehicle with a Li-Ion battery needs to recognise the potential risks, and prepare for the worst. An approach would be: Ensure all staff who come into contact with the vehicle have a level of high voltage system training, and those who don’t are kept away. Place the vehicle in a dedicated zone whilst in storage. When the vehicle is undergoing repair and if the battery pack is removed, place the pack into a dedicated storage zone. In any event, research the repair documentation for the specific vehicle under repair – no research or use of general instructions could cause financial loss or even worse, damage colleagues.

Magic numbers
The amount of space recommended by vehicle manufacturers varies from five metres to as much as 10 metres from surrounding vehicles and buildings. There are not too many businesses that can devote that much space to the storage of a single vehicle, let alone a small fleet.This is a rapidly evolving situation, even as sales of vehicles equipped with larger Li-Ion batteries continue to grow steadily.
How will this mess be solved? Well, the good news is the battery technology is also evolving quickly, and the hope is to find less toxic chemicals to use in such batteries. Make no mistake, the ‘old’ chemistries are in use now and have been for years, so the issue outlined above will be with us for years to come.

Keep gathering information
The first action is to seek information – what vehicles are you likely to want to repair, and what is the status of the training in the team? Not everyone needs to be trained, but everyone who is likely to come into contact with such a vehicle needs to know enough to get the right people working on it – in effect, a minimum level for nearly all colleagues, and a few specialists. Return on investment is a primary concern.

The next action is to plan. Assuming the business is already or wants to repair vehicles with high voltage systems, think about how the workshop can be protected in the event of fire, and extend that thinking to the external storage area. Then, think again about return on investment – can the business make a living with fewer vehicles in the shop – are there ways to speed up the work flow and so improve rate of throughput? As always, think about the next steps before shelling out any cash.