How are battery systems constructed?

Every child knows batteries from the remote-controlled car, the wall clock or the TV remote control. And yet the term battery often causes confusion in the context of electromobility. We clarify.

Common household batteries are battery cells and these come in many different forms. From the button cell, to the round elongated, to the large angular battery shape. In addition, we distinguish between primary batteries and secondary batteries. The former are disposed of after use and discharge and, in the best case, sent for battery recycling. Secondary batteries, on the other hand, are rechargeable and are therefore also suitable for installation in electrically powered commercial vehicles. They are also called accumulators.

Secondary batteries have different chemical compositions and modes of action. In our Futuricum e-truck we use lithium-ion battery cells of the NMC type (lithium nickel, manganese and cobalt oxides). These are characterized by their high energy density, low self-discharge and, compared to other cell types, a more uniform, high power output.

A world apart: the high-voltage battery system
In this article, we will focus on the various components of a high-voltage battery system of the Batteriewerk brand, as we find it in our Futuricum e-truck in daily use.

Our battery plant battery system consists of battery cells packed in modules, a battery management system (BMS), climate control elements, safety systems such as contactors, a manual service disconnect (MSD), and an insulating protective layer inside the battery system housing.

Battery cells – nothing works without them
Let’s start with the smallest unit – the battery cells. Electrical energy is stored in the battery cells and retrieved as needed. Battery cells come in different formats. The most common shapes in electromobility include the prismatic, cylindrical and pouch cell shapes. Different manufacturers have settled on different shapes: LG mainly manufactures pouch cells, Samsung mainly produces prismatic cell shapes and Panasonic mainly produces cylindrical shapes.

Different aspects play a role in the selection of cell shapes. Cylindrical battery cells, such as those used in passenger cars, are said to have an inherently better cooling effect due to their large surface area. At the same time, they require more space and are considered less safe than the other cell formats.

Larger cylindrical and pouch formats are still frontrunners in terms of module-level energy density, according to a study by the Frauenhofer Battery Alliance. When considering the overall system, the prismatic formats pull ahead of their battery counterparts. Both in terms of cooling, safety and durability, the advantages of a large battery system with prismatic cell shapes surpass. The prismatic format also catches up in terms of energy density and reduction of cobalt and lithium.

In addition to energy density, heat generation and safety, geometric dimensions, the possibility of integrating the cells into modules, cost and availability all play a role for most OEMs. Currently, the big players in the automotive industry are using different technologies to make themselves less dependent on one supplier. The massive increase in demand for battery cells repeatedly leads to fluctuations in availability worldwide.

At Batteriewerk, we focus on an optimal combination of safety, energy density and durability with the use of prismatic cell formats with NMC lithium-ion battery cells.

Modules – energy connected
Single cells would be impractical to handle and so they are assembled into a module by a cell compound. We mount these modules directly on air-conditioning panels and thus achieve optimum temperature control, almost independently of the outside temperatures. The modules can thus be cooled down to 15 degrees or heated up to 40 degrees. The optimum operating temperature is 25 degrees. At Futuricum we install modules from BMW with 5.2 kWh. In addition, we install VDA355 modules, which are often used in customized solutions due to their somewhat smaller dimensions and thus more flexible use. These modules have a capacity of 2.2 kWh.

Battery system – The whole is greater than the sum of its parts
Again from the beginning: Nothing happens without the energy storage in the battery cells. These form the smallest unit. These become battery modules that help organize and manage the individual cells in a system. And finally, the cells in the modules and many modules with other components in a housing form our battery system.

Our battery system is composed of the following components: Depending on the battery capacity, between 8 and 96 modules are installed in a robust and waterproof battery housing. Around the modules and their cooling or heating plates, insulation plates provide thermal and mechanical protection against external influences such as impacts and extreme weather conditions.

As a control element, the battery management system (BMS) monitors all vital functions. Temperature, voltage, state of charge and voltage balance are constantly monitored and regulated when necessary, protecting the accumulators. Voltage diagnostics and power prediction provide overvoltage protection, deep discharge protection and proper charge state balancing.

Contactors and a Manual Service Disconnect separate positive and negative poles as an emergency stop and protect against overcurrents. Overheating of the battery system – as in the early years of electromobility – is thus a thing of the past.

The modular principle allows individual adaptation to the application area in terms of room dimensions, battery power and capacity.

With the high-voltage options of 400 volts and 800 volts, charging times and power losses can be optimized and costs can even be saved by using less material.

And how do you decide?
Purpose and area of application are decisive in all considerations regarding the choice of battery system. The ecosystem in which the battery will perform is critical in finding the right mobile storage solution for your vehicle.
Contact us and we will advise you free of charge which solution is right for you.