A battery pack consists of multiple battery cells that are technically interconnected to form a single unit. By choosing the appropriate cell types (usually identical) and circuit configuration (series, parallel or mixed connection), it is possible to create battery packs with practically any voltage, current level and capacity.
In addition to the cells themselves, battery packs also contain other components, such as:
 spacers and connectors (e.g. H-type, Y-type) for electrically and mechanically
 connecting the individual cells to each other;
leads and plugs or soldering lugs, or contact connections for connecting the
battery pack to the consumer and the charger;
protection and control electronics, e.g. to protect against overheating or
explosions, for monitoring power limiting, function or aging and for charging
optimization.
A battery pack always fulfills more or less sophisticated housing functions as well. In the simplest case, the components are simply attached in a short-circuit-proof manner (e.g. using shrink sleeves), whereby care must be taken that heat dissipation and mechanical stability are sufficient. In more complex cases, a sturdier housing (e.g. plastic half-shells) must protect the battery pack against hostile ambient conditions or an injection-molded housing according to customer specifications is required to ensure seamless technical and optical integration of the battery pack as a system component of a device, such as an easily interchangeable battery pack of a power tool.
The development and production of battery packs – as prototypes, one-off units or for series production – is the business of battery pack assemblers like EMB. The development of a battery pack usually begins with an inquiry from a customer who needs an individually configured regenerative energy source for a specific mobile device. The battery assembler then refines the technical description together with the customer (e.g. voltage, capacity, lifespan, shelf life, ambient conditions, safety requirements and much more) to arrive at the current profile and the specification for the battery pack. It is the development of this definition that enables selection of the cells and other components. As the data sheets of the cell manufacturers seldom permit useful conclusions with regard to the behavior of the cell under specific load conditions, the practical expertise of the battery assembler plays a key role in the selection of the components. However, particularly challenging cases may still require on-site tests with various cells and configurations and using the most realistic possible current profiles before a battery pack is ready for series production.
© Marc Stenzel
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