“Stringent Criteria for Repairing Electric Car Batteries Disclosed – Latest Update”

From the beginning, potential customers have had one big concern with electric cars, namely the cost of repairing a malfunctioning traction battery or a battery at the end of its useful life, when the car will no longer provide sufficient range. These concerns are indirectly supported by the policy of the Tesla car company, which tends to replace batteries as a whole even in the case of a minor defect.

Replacing the entire battery is an extremely expensive operation due to the price of the battery itself. And that’s why many other car manufacturers have decided to design batteries in such a way that they can be repaired. The Volkswagen concern, which offers a number of Audi, VW, Škoda and Cupra cars on the MEB platform, is one of them and showed us what it means to work on a traction battery on a car with this platform.

Both mechanical damage and electrical faults can be repaired on the battery, in such a way that the technician – at least on paper – is looking for a really defective part, not a whole set of parts. The batteries are designed to be serviceable and basically the only thing that cannot be replaced separately is the battery cell inside the module.

This is because the modules cannot be disassembled so that they can be reassembled; it is not possible to disassemble them into individual cells without damage. In the case of a defective module, whether the defect is a reduced capacity compared to other modules, or e.g. it leaks electrolyte, the entire module is changed.

This is made possible by the design of the battery, the basis of which is the frame. Individual modules with cells are attached to it. The technician gets to it by first removing the battery from under the car and then removing its top cover. Subsequently, he already has individual modules in front of him.

However, not just any technician can do it. There are three levels of staff qualification in the authorized service centers of Volkswagen Group brands that repair electric cars – there are currently 15 of them in the Czech Republic, where they can handle complete work on the battery -: electrically trained person (EPO), high-voltage technician (VNT) and high-voltage expert ( OUTSIDE).

In short, all service personnel who work on electric cars must be electrically trained persons. This is so that they know, for example, that they have to avoid a dismantled electric car in a larger arc, if they are carrying a bucket of water, for example – to put it simply. However, this also includes mechanics who work on the high-voltage system after it has been disconnected.

That disconnection is done by a high voltage technician. He must already be qualified according to “fifty” – Decree No. 50/1978 Coll. on professional competence in electrical engineering, or from July 2022 Act No. 250/2021 on occupational safety in connection with the operation of reserved technical equipment. He will write a record about disconnecting the battery from the car after it has been carried out and, of course, is responsible for it.

A high-voltage expert is a person who is allowed to work with batteries under voltage, can repair them – for example, replace defective modules – and can also disconnect, dismantle or pack so-called critical batteries. These are those that are damaged to such an extent that they present some danger to the surroundings.

How does the battery work? It starts by creating a so-called no-voltage state, the principle of which is similar to turning off a circuit breaker when a person wants to change a switch or socket at home. This is the disconnection that a high-voltage technician is allowed to make, and it is primarily done by the so-called maintenance connector under the hood of the car.

This is followed by security so that it cannot be connected unintentionally, and checking whether the car is really in a de-energized state. Then the technician makes a log that is archived and marks the car with a high-voltage device sign and a sign that the device is turned off. Then a person with a lower qualification can work on the car.

When the battery is out of the car, diagnostics are carried out that can reveal a fault. A high-voltage expert is already needed for work here. After acclimatization to the ambient temperature, e.g. overnight, the battery is tested for tightness. After that, the battery can be opened by removing the top cover. Its interesting feature is that it has a foam seal stuck on it, which does not need to be changed if it is not damaged. If it is damaged, the entire cover must be replaced, as the seal cannot be scraped off the cover.

According to Roman Pošva, one of the trainers, it looks a bit like Lego inside the battery, but it’s not. Experts must work with special protective equipment, which includes, in addition to overalls, insulated boots and gloves, as well as a helmet with a darkened face shield. The tools are also special, insulated.

The expert must also follow the correct procedure exactly. If he didn’t do this and for example disconnected or connected a component in the wrong order, the electricity could find its way somewhere else and possibly destroy the control unit in the process.

Together with Radek Nekněz, the second trainer, he demonstrates the replacement of a defective high-voltage module. They must always work in pairs; one of them is the work leader, controls the diagnostic devices and checks the correctness of the actions performed by the other.

When a module in the battery is changed, it must first be balanced to the mean value of the voltage of the cells of the other modules in the battery. It is not possible to install a module that is charged to a higher or lower value in a battery that arrived for service with a state of charge of 30%. Balancing, during which the voltage is set with an accuracy of thousandths of a volt, is a rather lengthy process, so the service sometimes tells the customer in advance to come to a certain operation with the car charged to a certain degree.

Experts will gradually disconnect the necessary connectors between the modules that are connected in series in the battery. Then they remove the screws holding the module in the frame and lift it up with a jack. It is not that heavy, it weighs around 30 kg, but pulling it out with your hands would mean the risk of inaccuracy or damage to some of the surrounding components.

They pull out the old layer of heat-conducting paste, clean the space of residues and apply new paste. For this, there is a precise mold into which the paste is extruded with a pneumatic gun. It is not a cheap matter, the application for one module only costs less than five thousand crowns in material.

This is followed by positioning the new module again using a jack. This is also used here especially to ensure that the module lands exactly in its place on the first try. After it has landed, it must not be lifted, as there is a risk of air bubbles forming, which would stand in the way of proper heat transfer from the module to the cooling circuit in the bottom of the battery.

This is followed by the return of the couplings and screws, tightening to the prescribed tightening torque – the second expert checks this and marks with a marker which screw is correctly tightened – and a final measurement of the tension, which will tell whether the error has been eliminated. The battery management experts then enter through the computer that there is a new module in the battery, and the battery can go back into the car. The car gets new coolant – the interesting thing about it is that it is not changed periodically, but only at service operations that include it, but at all such, even if they follow a week in a row – and can drive again.

Replacing the module with the exact prescribed procedure is a job for the service for about eight hours. The new module itself costs around 35,000 crowns, with the heat-conducting paste we are around 40,000, and to this must be added the work, which includes at least two highly qualified people.

The total price for the customer therefore depends mainly on the hourly service rate, and module replacement is therefore a matter of higher tens of thousands of crowns to hundreds of thousands, if more modules need to be replaced.

It’s not a cheap repair even for a car that’s a few years old, unless it’s already covered by warranty. In the realms of ten- to fifteen-year-old used cars, it can easily reach a large part of the purchase price of the car.

On the other hand, we are not yet in a situation where there would be a large number of fifteen-year-old used electric cars on the market. It can be assumed that when we are there, even unauthorized services will be able to repair batteries. And if we speculate a little, perhaps modules with cells will also be available from secondary production at lower prices, just as it is today with common car parts.