Probably the most important and most criticized component in an electric car is - apart from the engine - the drive battery. In the real sense, however, the drive battery is not a battery, but rather a rechargeable battery in the physical sense due to its chargeability. In electric cars, several of these batteries are interconnected to form a traction battery. Compared to conventional batteries, this has a higher capacity, which is achieved by many battery cells connected in series.
Most of today's electric vehicles use lithium-ion batteries: They offer many advantages, such as high specific energy or low memory effects. One disadvantage of lithium-ion batteries, however, is their manufacturing process: this requires lithium carbonate. The largest deposits of the raw material are in the salt lake regions of Bolivia, Argentina and Chile - the so-called lithium triangle. In order to extract the lithium carbonate from the salt lakes, the water is evaporated, leaving a solution with a high lithium content. This solution is converted into lithium carbonate with the addition of soda.
After the life of the lithium-ion battery is over, it is either used elsewhere outside of the car - for example as storage for the home solar system or it is recycled. However, recycling processes for batteries in electric vehicles have yet to be developed. If electromobility is to advance, a recycling concept is therefore of the utmost importance.
In addition to lithium-ion batteries, nickel-metal hydride batteries are also currently used. We have summarized the most important information and technical data below:
Lithium-ion batteries
Like all batteries, a lithium-ion cell also has a cathode (negative pole) and an anode (positive pole). The cathode of this battery consists of a graphite electrode and the anode of a lithium metal oxide electrode, for example made of manganese or nickel. Lithium is a light metal that reacts violently with water. A necessary component of every battery is the so-called electrolyte, which makes it possible to transport electrical charge between the electrodes in the first place. An anhydrous but flammable solvent is used as the electrolyte in the lithium-ion battery. To prevent a short circuit between the electrodes, they are separated from one another by a separator, which in turn is permeable to the lithium ions. Lithium-ion batteries can usually be charged up to 2.000 times.
The lithium polymer battery (LiPo) is a subtype of the lithium ion battery. The main difference to the lithium-ion battery is the composition of the electrolyte. The electrolyte of the LiPo battery consists of a solid to gel-like film on a polymer basis. This property also offers the advantage that the battery does not necessarily need a solid housing and can therefore be produced in many different forms. LiPo batteries are mainly used in small mobile devices such as smartphones or in model making.
Nickel-metal hydride accumulator
In the case of the nickel-metal hydride battery (NiMH), the anode consists of the eponymous metal hydride in powder form and the cathode consists of a nickel oxide hydrate sheet. In this battery, too, an electrolyte between the two electrodes takes on the function of a separator and at the same time acts as an ion conductor.
NiMH batteries have a nominal voltage of 1,2 V, they can be deeply discharged and have a long service life when discharged. However, the high level of self-discharge makes the NiMH battery less attractive for manufacturers of hybrid or electric cars. One manufacturer that uses NiMH batteries for its hybrid models is Toyota, while other manufacturers prefer lithium-ion batteries.
In general, the following applies to batteries in electric cars: A battery is considered worn when it has less than 80 percent of its nominal capacity. The battery has had its day for the electric vehicle, but it can still be used elsewhere, for example as a buffer or temporary storage device for photovoltaic systems. How long the batteries of electric vehicles will last in practice will only become clear in the next few years. Nissan now offers an 8-year guarantee on the 30 kWh battery for the new Leaf model.
The most important parameter of rechargeable batteries or batteries in electric vehicles is the range. This is determined by the charging capacity of the batteries. While conventional electric vehicles have an average range of around 200 kilometers, the vehicle manufacturer Tesla manages to achieve a range of 560 kilometers with its Model S - but this range is also reflected in the price.
Tesla uses a relatively simple system for the longer range: Several lithium-ion cells are connected in series. The energy density of the round cells that Tesla uses in its vehicles is good
at 50 percent above the cells commonly used in the automotive industry. In order to achieve this long range, however, disadvantages such as a shorter service life have to be accepted - whether this affects the service life of Tesla batteries can only be observed in the coming years.
Will the future be heralded in Austria?
The Austrian company Kreisel Electrics offers real competition to conventional batteries with its self-developed batteries. The batteries from Kreisel Electrics are made from Panasonic round cells, such as in Tesla vehicles. However, unlike Tesla, the cells are not welded, but linked to one another by laser and can thus be built smaller and lighter as battery packs - but the company's batteries have not yet been tested very much in practice.
However, a VW eGolf retrofitted with gyro batteries was able to achieve a range of 430 kilometers in the practical test - the range from the factory on the tested VW model was "only" 190 kilometers. It remains to be seen whether and how the automobile manufacturers will adopt this new battery technology.
green car magazine 01/2017
Cover picture: Copyright Patrick P. Palej @ fotolia.com
Questions and suggestions under 01575/287 3616 or by email to leser@greencarmagazine.de.
Comments are welcome to be entered. They are activated after a content check.
- Renault Espace E-Tech Full Hybrid seven-seater – the team SUV - April 25, 2024
- Ora Funky Cat 400 Pro+ - The Purring Cat - April 25, 2024
- Pedelec accident numbers are increasing - April 25, 2024