blog Innovation & Development

Vattenfall Solar Team TU Delft

The new Nuna11 is under development with Cleantron. Students from the Delft University of Technology commit themselves for 1.5 years to build the fastest solar car to race in the Bridgestone World Solar Challenge 2021 in Australia!

Watch the video.

blog Innovation & Development

The automation robot

Up to 4 times higher output

One of the corner stones of the new production line is the robot that places the tested cells in the Battery tray. The robot makes sure that each cell is placed in the correct location and of course with the plus and minus on the right side.
This way the robot creates the required cell configuration by putting cells in parallel and series. In order to meet the required cycle time of the production line, the robot must place a cell each 0,2 s. This means that the robot must move super fast, but also high accuracy is required to place the cylindrical cell inside the cell holder. The high speed in combination with the accuracy means that a very stiff machine frame  is needed. Inhouse Computer simulations are performed on the frame in order to check the natural frequencies and the frame stiffness. Also, the exact movements of the robot are simulated in software to optimize the robot movements and to make sure that the robot is not crashing in any other machine parts during the first trials.

The robot can be used to fill different cell types like 18650, 21700 & 26650, different Battery Pack configurations and even completely different Battery Pack models. This allows an optimal flexible production line that can make multiple Battery with short change over times.

Finite element simulation on the frame natural frequencies.

As explained in an earlier blog, the first step in the production process is that we test all cells, but we do not only test the cells. We also would like to know their exact position in the final Battery Pack.
Therefore, the cells are picked up from a buffer in which the tested cells are buffered in a fixed order. This way the robot knows exactly which cell is placed at which location in the Battery Pack assuring full Track and Trace ability. This allows us to trace back potential issues in the Battery Pack to the tested data of an individual cell and to the cell ID and production batch ID.

The communication between the robot and the operating system of the line is programmed by one of our Software engineers, in cooperation with our subcontractors. The Robot programming is done inhouse. The inhouse programing enables us to have full control and to enable quick implementations of continuous improvements or even introduce completely new products on the line quickly.

blog Innovation & Development

Functional Safety

The safest Battery is never on.

The dangers of Lithium-ion cells are well known, and not just to engineers. Stories about phones violently exploding in people’s handbags or an entire fleet of planes being grounded because of Battery related fires make for great news bulletins after all. Despite this, Li-ion batteries keep being used in basically everything because they are just, so, darn, useful.

The good news is that engineers experienced with these Batteries know exactly what they need to do to keep Li-ion cells safe. Don’t let them get too hot or too cold, don’t overcharge them or discharge them too far, and whatever you do, don’t forget to protect against short circuits.

Consumers don’t have to worry about these kinds of things because any Li-ion application where safety could be an issue has a Battery Management System (BMS) included that measures voltages, currents and temperatures in the Battery Pack, and ensures the cells are disconnected from the application whenever any of its parameters threaten to go outside of safe limits.

So that’s it then, right? No Batteries ever explode, and we all live happily ever after? Unfortunately, the universe can be a bit of a cruel place. For a variety of reasons that take longer than a 750-word Cleantron blog post to explain.
Electronic components can randomly fail without any prior warning. If this electronic component just happened to be part of a safety-critical circuit of the BMS, then we may have just lost the only system that was keeping watch over the cells and that could prevent dangerous failures. So, the one-million-dollar question is: how do you design a BMS that you can trust to do its job? That is where functional safety standards come in.

There are many standards that apply to the field of functional safety, often specializing in various applications (IEC 61508, ISO 26262, ISO 13849, to name a few), but their core purpose is always the same. If you have an electrical, electronic or programmable system performing an automatic task with the specific purpose of keeping a system safe for people, then these standards will remind you that electronics can randomly fail, and that you should implement circuits that can automatically diagnose faults in your safety-critical components.

If any of these diagnostics ever find a fault that could impact the safety of the application, then the BMS should assume the worst and turn off the Battery Pack. This design philosophy of “anything could break at all times” makes for an incredibly challenging design process. For every single component and subsystem on your BMS, an engineer must separately analyze if the component or subsystem is safety-critical and in what ways this component could fail.

If a fault in the component automatically results in the BMS disconnecting the cells, then the component is fail-safe, and you don’t have to worry about it. In any other case, diagnostics need to be implemented, and before you know it you are designing a management system for the management system. Of course, these diagnostics themselves may fail as well, but fortunately the standards recognize that an electric scooter requires a different level of safety than a nuclear power plant (this is what (A)SIL levels are for), so for most applications simple redundancy, or one level of diagnostics, is enough.

One of the interesting challenges in functional safety is to design a Battery Pack that is not just safe, but also still actually works! The safest battery pack is one that never turns on after all, and it sometimes feels like you’re designing a system that is preparing for an explosion at any moment, and you just filter out those few moments where a Battery Pack is just safe enough to actually briefly do its job. I admit there is quite some hyperbole to be found in the previous sentence of course, but nonetheless, increasing safety comes at the cost of Battery Module uptime. Finding a balance in this is quite the challenge.

There are many more aspects to functional safety that are deserving of a full blog post by themselves. For example: is software always safe? (absolutely not, look up the Therac-25); should we have diagnostics for engineers themselves? (we should, engineers are flawed human beings). For now though, I hope I have given you some idea of what functional safety is and why it’s important.

So next time you come across a Cleantron IEC 61508 certified Battery Pack you may just spare a thought for the engineers that processed hundreds of pages of functional safety standards to design a Battery Pack that – despite everything – may sometimes still just do its job!

blog Innovation & Development

Traceability cells

Traceability ''to a T''

From the very start to the very end of the production process, data of each step that is relevant to the product or its quality is gathered for traceability tracking and to make it available for (statistical) data analysis. Statistics is a very powerful tool in a production environment. A small set number of tasks is repeated endlessly in our production machinery, and when monitored closely for deviations this can contribute largely to improved product quality and efficiency. 

The new Cleantron production line is set up specifically to make this type of data analysis possible. At the start of the production line, each individual battery cell is tested for quality, the data is logged and then linked to the unique serial ID of the Battery Pack. This happens fully automated with all relevant information (both product and process) at each subsequent step too: cell placement, welding, programming and end of line testing.

By using unique keys and setting up the infrastructure to store this data in an easily accessible manner, at any moment during the product lifetime, we can exactly determine which individual cells, electronics and other important parts have been used in which Battery Pack. We can see what process settings were used, what the results of the process were and of course what the results of the final quality control steps were. In case any questions arise at a later date as to what happened during production and which components were used, this information is only a click of a button away. This perfects the traceability of Cleantron Battery Packs.

By using statistics and combining the data of multiple Packs, quality performance of production can be monitored and used for improvement initiatives. To accomplish this, Cleantron uses industry best practices such as Statistical Process Control, an advanced analytical technique for looking at quality data used in many high-tech industries (such as automotive). By setting the process limits based on observations and then using the statistical technique to check for deviations, any errors in the process can be caught early on. This means that problems can be solved in the process before they even have a chance to affect product quality. This leads to a more stable process, less rejected product and a deepened understanding of what is happening during the production of our Battery Packs.

blog Innovation & Development

Investment cell test capacity

The investment for the cell test capacity

A Battery Pack Production Line has multiple bottlenecks. Bottleneck where throughput has a large impact on the total production of the line. One of these bottlenecks is the Cleantron in house developed in line Cell Testing Station. Here each individual Cell is measured to prevent that any (micro) deviation in a Cell may eventually, over time result in a failure in a Battery Module.

These tests take up valuable time, especially when handling of the Cells to and from the testing position is considered. Up to several valuable seconds are spent on testing per cell. However, speeding up these tests, or removing them all together, impacts the accuracy of the cell tests and increases the risk of faulty cells ending up in the Battery Pack.

To solve this, Cleantron has looked at their experience & insights related to production lines and cell testing. Cleantron calls this ‘Knowledge Based Working’. This experience and knowledge is noticeable in the two main aspects of the cell testing station.
Firstly, it has been decided that the number of testing positions needed to be increased to allow for a better balance between test time and handling time. This has resulted in a Cell tester with 2 parallel testing lanes, each of which has 10 testing positions. Here the benefit is that one lane can be emptied or filled during the time the Cells in the other lane are tested. This parallelism means that the Cell handling time becomes virtually non-existent for the throughput of the cells in the production line, meaning a constant flow of Cells is available for the placement robot.

Furthermore, to ensure a high testing accuracy and a short testing time to match the total throughput of the production line, a solution had to be found for the cell testing equipment as well. Based on previous experiences, an new battery measuring technology has been selected. This technology has been used earlier in our R&D department of Cleantron to great contentment. Combined with a multiplexing unit, this allows for the connection of the 20 testing positions with just one impedance measurement tester. Use one advanced impedance tester has the major positive benefit that differences in measurement-accuracy is prevented (that could occur between different channels), while still allowing for a high throughput. Finally, to maximise this throughput, an optimal testing sequence has been specifically selected to generate the most important battery data at the quickest possible time.

blog Innovation & Development

Cleantron introduces High Power MPC

Cleantron introduces the High Power Multi Pack Configuration (HP MPC) technology to the world of Urban Mobility and Last Mile Logistics. This innovative dual battery system, with a Fixed Battery in the Vehicle for optimal Power and compact light Portable Battery Cartridges for Range, offers unique independency on Charging Infrastructure and an extended lifetime. Read more; High Power MPC