Electric vehicles will enter the mobility market en masse, as soon as engineers and designers construct the BEV around its central component, the traction battery, . Today fuels meet minimum requirements, of course. These are defined as European fuel standards EN228 (Otto-fuel), bzw. E590 (Diesel) likewise. Engineers construct their units, of course, according to these standards. Similarly, the traction battery must be part of the standardisation for traction energy. This way it becomes a reliable starting point when developing the BEV powertrain.
Standardization of the traction batteriy is the key to a number of systemic benefits. It leads to low production costs and, as a result, to high demand in the consumer market. Product quality will rapidly evolve, if many manufacturers compete within the limits of given standards. At the end of the life cycle standardized batteries can be recycled under automated conditions, thus cheaply and to a high degree. The amount of raw materials required decreases as market saturation is reached.
The traction battery has usually a nominal voltage of 350 to 400 volts at E-cars and vans on, which corresponds to the usual three-phase AC. It makes sense, to basically maintain this standard for the traction battery, for instance. to minimise the diameter and weight of power cables . Likewise, manufacturers must agree on robust couplings, to reliably connect batteries with the electrical system. These elements should be easy to maintain, to be replaced when necessary.
Particular importance is attached to the standardization of the outer dimensions. A reliable way to determine the optimum is an analysis of the vehicle fleet in terms of dimensions between axes, height of sandwich floors etc found in vehicles today.
Individual galvanic cells, battery cells, often resemble small columns. In appearance they are similar to standard household batteries. A greater number of such cells constitutes a battery module. A plurality of modules constitute the traction battery. The height of a cell is significantly defining the overall height of the traction battery as well. A European cell production therefor gaines additional significance, because own dimensions hold constructive advantages for European manufacturers .
Since, in the automotive industry, the dimensions of vehicle floors, in particular the height of the sandwich floor on the one hand and the dimensions of battery cells in mass production on the other hand, are limited, defining a binding standard height for the traction battery is relatively easy.
The overall- bzw. traction voltage of the battery results from connecting the individual cells. Changing the size of the cells or interconnecting cells in parallel, will increase storage capacity and voltage. The product of traction voltage (Volt) and electric charge / galvanic charge (Ampere-hour) yield the energy potential of the resulting traction battery.
Theoretical limitations in vehicle design are thus facing significant benefits from the standardisation of the battery module:
- Use in any vehicle and vehicle type, regardless of the date of manufacture.
- favorable conditions for mass production
- Simplification of repair and maintenance
- effective and extensive recycling at industrial level
- Use in standard stationary racks
Relating to highly loadable, lithium-ion batteries, the maximum current load (instead of specifying the capacity) has prevailed. It is often referred to as C-coefficient. In this case charging- or discharge current respectively are based on the maximum capacity of a the battery, in order to compare different types. A C-rate of 1C means, that a battery is completely charged- or discharged within an hour. A C-coefficient less than 1, that it takes more than an hour and a C-coefficient greater than 1, that it takes less than an hour.
The capacity of a typical cell 3,2 volts and 100 Ah, the case of standard discharge with 0,5 C ( 0,5 CA) thus was detected, has thus been determined with a discharge current of 50 amperes over two hours. The capacity figures at 0,5 C 1 or C are now common, wherein the permissible continuous load certainly 3 or more C (in the example at 3 C So 300 A), short-term load may even be significantly higher ( 20 C, also 2000 A) respectively.
Frequently, the capacity of traction batteries no longer specified in the individual cells' ampere-hours , but indicated in watt hours. Therefore different designs become comparable., because voltage is taken into account, too.