Can you trust a high-voltage lithium battery? All the elements that guarantee its safety
12 September 2024
The transition of industrial vehicles to electric power has been under way for some time and is leading to growth not only in the number of electrified applications, but also in their size and power.
Indeed, more and more manufacturers are deciding to support a process of technological conversion, motivated by the many benefits of lithium electrification in terms of Total Cost of Ownership over the long term, sustainability and flexibility of use.
Current technological developments and the great strides made in the sector mean that even those segments with higher power requirements can look to lithium electrification as a viable option for increasing the sustainability and efficiency of their vehicles.
These needs find a concrete answer in high-voltage batteries capable of supporting applications requiring high levels of power and playing a key role in driving the electrical revolution also in these areas of application.
What is a high-voltage battery? Areas of application, benefits and concerns
Before analysing its functionality and potential, it’s essential to clarify what’s meant by high-voltage battery and what its main features are.
In the industrial world, batteries up to a nominal 102.4V are commonly defined as low-voltage, although regulations officially limit this category to a maximum of below 60V. High-voltage batteries, on the other hand, start from 300V and run up to more than 800V.
When high-voltage batteries are used
The costs of a low-voltage electrification solution are lower than those of a high-voltage option, as they include commercial components that are more readily available on the market, as well as not requiring specific high-voltage components, e.g. connectors and devices that cost more due to their increased degree of safety.
However, a low-voltage power supply cannot be used when the power requirements rise. What very often dictates the choice of voltage is the power of the electric motor: in industry, motors above 20-30kW require a higher voltage to remain compact and efficient.
Many OEMs are still sceptical about adopting high-voltage solutions, mainly due to safety concerns, frightened by the potential risks associated with high voltage.
High-voltage batteries: a good solution for high-power applications
High-voltage batteries are therefore essential to meet the needs of vehicles with high-powered engines and which as a result require high performance and long-lasting autonomy, such as in heavy-duty industrial applications.
A representative example of this is the Flash Battery 396.8V – 420Ah 166.6kWh, the customised high-voltage battery pack we made for a hybrid crawler crane.
The project required an in-depth mechanical study to find the best solution for housing the battery in the vehicle. Given its high energy demand, a structure was designed consisting of four units connected in series, separated and positioned in two separate compartments of the frame. Moreover, the integration of the battery with specific insulation control systems and HVIL made it possible to meet the stringent safety standards required of high-voltage applications.
But there’s more! High-voltage batteries are key components of electric vehicles, offering the benefits of superior performance, long range and fast recharging. While in most cases the nominal voltage of a lithium battery in an electric car is 400V, as in the well-known Tesla Model S, there are auto manufacturers that have already decided to switch to batteries with an 800V system, as in the case of the Porsche Taycan.
Benefits in terms of efficiency but concerns about safety
As in every area, however, we must also consider the other side of the coin: high-voltage lithium batteries can be as dangerous as they are high-performance if not designed correctly.
The voltage required by a high-voltage battery mean that stringent safety measures and protocols are needed to ensure system reliability and operator safety.
This is why it’s essential to rely on an experienced lithium battery supplier. It’s the manufacturer that must adopt strict design and production standards, implementing advanced technologies and thorough testing to ensure that the battery functions safely and reliably in all operating conditions.
Safety and the role of the manufacturer: the Flash Battery approach
Since the founding of Flash Battery in 2012, we have chosen to develop an advisory process that allows us, starting with discussions with the customer, to precisely define the characteristics the battery should have and the needs it should meet.
This approach has enabled us to produce hundreds of fully customised battery models tailored to work requirements and developed with a concept of efficiency and safety suited to the demands of each application.
Safety first: the key words for a safe lithium battery
There are three fundamental aspects we work on each and every day to ensure the total safety of our batteries starting from the design stage: chemistry, intelligent assembly and the development of advanced proprietary control electronics.
LFP (Lithium Iron Phosphate) chemistry has proven to be the most suitable for the specific needs of industry, not only in terms of efficiency but also safety. Indeed, it not only guarantees a long life for vehicles, with over 4,000 charge cycles, but is also the safest and most stable available on the market.
After chemistry, the assembly of the cells is the second crucial element to be considered for lithium battery safety. Specifically, the capacity – the number of cells connected in parallel within the battery pack – is decisive.
Using small cell sizes requires many parallel connections to achieve the desired capacity, greatly increasing the risk of short circuits. To avoid this risk, Flash Batteries are made with a maximum of four cells in parallel, a solution that, based on tests and studies by our R&D department, has proven to be the best to guarantee maximum safety in all situations.
However, all this would still not be enough without intelligent control electronics. Only by paying close attention to this aspect is it possible to have a reliable, safe lithium battery.
Flash Battery’s patented proprietary battery management system, called the Flash Balancing System, doesn’t just balance cells. It’s designed to offer full, constant control of each battery pack, ensuring stable performance over time.
HVIL (High voltage interlock)
The High-Voltage Interlock system (also called HVIL) uses a low-voltage continuous circuit to monitor the proper connection of all high-voltage components within the vehicle.
If the HVIL signal should be interrupted for any reason, the high-voltage supply will be disconnected by cutting off the power in order to safeguard the safety of users.
MSD (Mechanical safety disconnect)
The Mechanical Safety Disconnect (MSD) is a safety device used in high-voltage battery systems to provide a physical method for disconnecting the electrical circuit. The MSD is typically designed to be operated manually to ensure the safety of operators and technicians during maintenance or in emergency situations.
Fuses
Fuses are the simplest and least expensive current-breaking devices, but they can effectively protect the system against overloads caused by short circuits.
The operating principle of a fuse is very simple. It consists of a glass, ceramic or plastic container that contains a conducting element (covered with sand so as to prevent the occurrence of an electric arc) that heats up when current flows through it and that melts due to the Joule effect when it exceeds a certain temperature, interrupting the flow of current.
Insulation control board
The main function of this element is to constantly monitor the insulation resistance between the high-voltage electrical parts of the battery and the vehicle chassis itself. This monitoring helps to ensure operator safety by preventing short circuits and other electrical faults.
Connectors
The connectors in a high-voltage battery differ from the conventional connectors in a low-voltage battery in that they must cover greater insulation distances, prevent direct contact with fingers, and include contacts for the HVIL circuit to pass through to monitor the proper connection.
Contactors
between the battery and the load (as in the case of an electric vehicle’s motor). In emergency situations or in the case of anomalies such as overloads, short circuits, overheating or other, the contactor can open to break the circuit and prevent damage to the battery or system components.
Contactors are essential for opening the circuit even when the vehicle itself is off, thus reducing further risks downstream of the battery. Furthermore, to improve the level of safety more than one contactor is usually used, e.g. one on the positive pole and one on the negative pole, to make sure that at least one is triggered when needed.
Battery Management System: when electronics make the difference
It has become clear to all that the choice of intelligent control electronics plays a key role in ensuring the safety of your system. Indeed, one element that really makes a difference in dangerous situations is the Battery Management System , the software used to manage the batteries.
The BMS is the battery’s brain, constantly monitoring the voltage and temperature of each cell, ensuring that none of them exceeds safety limits.
Should a cell reach a critical voltage or temperature, the BMS balances the cells or interrupts the charging/discharging process by dialoguing directly with the vehicle and the charger. Likewise, in the event of overheating, the BMS can reduce power or shut down the system to prevent damage or fire by opening the contactor and interrupting the current flow.
But BMSs aren’t all the same, some are better than others
Flash Battery was born out of the conviction that to really make a difference in the world of lithium batteries for industry it was necessary to focus on the electronics. Back in 2009, friends and founding partners Marco Righi and Alan Pastorelli, today respectively the company’s CEO and CTO, realised that a truly innovative product could only be achieved through a state-of-the-art battery management system (BMS).Together they began to develop their own lithium battery management system.
With its Flash Balancing System, the proprietary high-power (20A) combined active and passive cell balancing system, Flash Battery first hit the market in 2012, carving out a prominent place for itself in the emerging landscape of lithium batteries for industry.
“In the beginning we mainly focused on the production of electronics to make our customers’ existing batteries safer and better performing. But we soon realised that the real added value lay in the creation of complete battery packs, which, thanks to the Flash Balancing System, were not only reliable but also intelligent, safe and with a lifetime longer than that of the vehicle they were installed on. The Italian patent for industrial innovation earned by our BMS in 2022 was the culmination of more than 10 years of continuous efforts to make industrial electrification more efficient and safer for an increasing number of applications”.
Predictive maintenance: remote monitoring can anticipate faults
But there’s more! Just imagine the benefits of foreseeing a safety problem even before it occurs. If care is put into its design, a good BMS ensures stable performance over time, prevents faults, and performs self-diagnosis and preventive maintenance, providing a comprehensive check of the battery pack.
Thanks to the Flash Data Center, our remote monitoring cloud system, which uses artificial intelligence and machine learning, you don’t have to wait until it’s too late to notice a problem.
Our AI technology performs real-time collection and analysis of the operating data of all Flash Batteries in the world, and is thus able to proactively recognise potentially abnormal behaviour and communicate it directly to our After-Sales department, which can then take prompt action. This allows the battery’s owner to avoid costly downtimes and much more serious safety problems on vehicles.
