Traction batteries – what they are and how they are designed
Buyers often have questions: what does it mean “traction battery”, how it differs from starter models, what are its advantages and features of operation? There are differences in the structure of batteries, and in the possibilities of their use. Starter models are designed for a short-term supply of high current at the time of starting the engine, and the rest of the time they “rest” and are charged from the generator.
Traction batteries are able to continuously supply power to electrical equipment – until they exhaust their reserve of energy. They must then be recharged from the mains. Once the charging process is complete, the traction battery is ready for continuous use again, i.e. it is designed to be used in a charge-discharge cycle. The number of operating cycles depends on the type of battery used, e.g. lithium batteries have an operating life in excess of 1000 cycles.
What are traction batteries for?
Traction batteries are installed on various types of electric vehicles and electric-powered vehicles. In particular, they are used for autonomous powering electric bicycles, electric cars, electric boat motors, wheelchairs, golf carts, forklifts, tractors, stackers, hydraulic carts, floor cleaning machines and other equipment equipped with an electric drive.
The difference between traction batteries and starter batteries
Starter batteries are mainly used in automobiles. They supply the starter with the necessary starting current and ensure that the engine is started. Starter batteries are characterized by:
- short-term supply of high starting current – 250-1000 A for a few seconds, and after starting the engine, the battery replenishes the spent energy;
- voltage 12.7 V;
- capacity 55-65 Ah;
- sensitivity to discharges – after several deep discharges the battery loses much of its capacity.
Traction batteries are also installed in vehicles and propulsion mechanisms, but have a fundamentally different principle of operation. Instead of supplying high starting currents for a short time, they are designed to continuously supply power to the electrical equipment throughout its operation. Traction batteries work in cyclic mode – they give the stored energy to the electric motor and the rest of the power consuming devices, and then replenish the energy in the process of charging from the mains.
Traction batteries are also called deep-discharge batteries. They are not afraid of considerable discharge, but in order to prolong the service life it is better not to discharge them below 5%. The battery is not susceptible to continuous loading, and their operating time on a single charge depends on the battery capacity and the power consumption of the equipment it powers.
Traction battery design
Like starter batteries, traction batteries have electrode plates (cathode, anode) and electrolyte inside. In lead-acid batteries, the electrolyte is liquid and gel-like. The main difference in the design of traction batteries is the thickness of the electrode plates. Starter batteries have thin electrode plates, but traction batteries have thick plates, capable of maintaining a long supply of current without loss of performance. Therefore, traction batteries are more resistant to wear and have a longer service life.
Starter batteries have a solid body, which contains the electrode plates and the electrolyte. Traction models are made as a monoblock that contains several batteries interacting with each other. Lead-acid traction batteries consist of several batteries of 2 V each. The most commonly used 12-volt assemblies consist of 6 sections connected in series.
The casing of traction batteries is made durable, resistant to external influences and corrosive environments. Traction batteries of lead-acid type are large in size and heavy in weight. Lithium-based traction batteries – Li-ion, LiFePO4, NCM – are more convenient to use. In addition to all the advantages of traction batteries, they are maintenance-free, have no memory effect, light weight, compact size and working life of over 2000 recharge cycles.
Lithium Traction Batteries Design
Li-ion batteries consist of a metal oxide as a cathode, porous carbon as an anode and a conductive electrolyte. The chemical composition of Li-ion batteries varies. To increase the specific power capacity and improve the performance of batteries, manufacturers experiment with materials for the cathode and anode.
In combination with a graphite anode, cobalt oxide cathodes LiCoO2, lithium manganese spinel LiMn2O4, lithium-nickel-manganese-cobalt oxide LiNiMnCoO2 (NMC), lithium-iron-phosphate LiFePO4 and other materials. Traction batteries of LiFePO4 and NMC types have the best characteristics. They are assembled from individual batteries in the form of cylinders, prisms or packs.
The connection is made according to a certain scheme – depending on the required values of battery capacity and voltage. The control electronics in the form of a BMS board (Battery Management System) ensures safe and durable battery operation, preventing overcharging, current overloads, overheating and other dangerous conditions. The cell management and balancing system regulates the discharge and discharging of cells, preventing premature battery wear and tear.
Advantages of Traction Batteries
Traction batteries based on lithium have:
- wide operating temperature range;
- low self-discharge;
- long service life, even in harsh operating conditions;
- high indicators of chemical and thermal stability;
- high values of specific capacity;
- resistance to deep discharges;
- possibility of uninterrupted operation for a long time in cyclic mode, in conditions of constant current output.
To continue the topic we offer to read the article about the best batteries for warehouse equipment.
Features of traction batteries: how they differ from conventional batteries
About the existence of the so-called traction batteries probably heard every motorist. But what they are designed for, as well as what, in fact, differs from conventional batteries, oddly enough, not every driver knows. Meanwhile, such knowledge could help many in practice.
Therefore, the main purpose of this material is to give a wide range of our esteemed readers, regardless of their driving experience, important information about modern traction batteries. In particular, we will consider their device, the main types, the scope of application, the criteria for selection when buying such batteries and the basic rules of their operation.
Features of traction batteries
The principle of operation of conventional car batteries is clear: with their help, the engine is started. For this purpose, an energy jolt is supplied to the starter, as a result of which the flywheel begins to work and the engine starts. Given this functional feature, such batteries are called starter batteries. When starting a car, they give the opportunity to create a “starting” current of a very high value: from 250 to 1000 amperes.
Such batteries, as we know, have one problematic feature. Thus, they are very sensitive to deep discharge. Discharge them below the voltage indicator of 10 volts experts strongly advise against, since a few such discharges are quite enough to start the battery ceased to work at full capacity and became, in fact, useless.
In parallel with such batteries on transport (and not only!) are widely used batteries for other purposes – traction. Such batteries are of a completely different format, which do not have high starting currents. This means that they can give out some energy for a long time, discharging sometimes almost to zero.
Traction batteries are indispensable wherever long, continuous power is needed. Because of their nature, they are capable of working all day long! In addition, they are also valuable in that they are very resistant to high and low temperatures, not ceasing to work even at 30 degrees Celsius frost and heat in the plus 50-60 degrees. For a long time maintenance-free batteries (for example, several weeks of idle time), in contrast to the starter, practically do not lose their abilities.
Design: what are the similarities and differences
The key difference between the traction battery and the starter battery is in its functional parameters. In terms of voltage, they range from 2 to 24 volts, and in terms of current – from 30 to 300 amps, although the upper figure can be higher. In their structure they almost do not differ from standard batteries: they also have minus and plus plates, they are also filled with electrolyte and stored in a plastic case. But there are some differences:
- The plates are very thick, massive, they contain a lot of lead and other heavy metals.
- The case is also thicker, so that it can bear the huge weight of heavy plates.
Types of traction batteries
Modern domestic and foreign industry produces different types of traction batteries for consumers. According to technology, these are alkaline batteries and acid batteries. The latter are, in fact, lead-acid formats, because they use lead and electrolyte on sulfuric acid.
Alkaline ones use nickel-iron plates, which are filled with a special alkaline solution. They are considered very reliable even in the most severe frosts, but the price of such batteries is several times higher than that of lead batteries, and their charging is accompanied by caustic vapor. Because of this environmental aspect, the scope of their use is now a little narrower than other batteries show.
Recently traction batteries, which are based on new AGM and GEL technologies, have become fashionable. They are characterized by compactness, high energy, and, alas, a huge price.
The modern industry continues to improve such batteries in every way possible. According to experts, in the coming decades lithium batteries will confidently move to the forefront in terms of their reliability, efficiency, and affordability.
Scope of application
These days there is a wide application of traction batteries in different spheres of life. They are not only used with the same efficiency in automobiles, but also in many other tangential areas of technology. For example in fishing boats, during hunting, for propulsion of electric cars and other small forklifts. Very effectively they have also proven themselves as an indispensable support for alternative energy sources – solar panels, electric generators and so on.
Traction batteries selection criteria
Many drivers wonder how to choose a traction battery. First of all, it is necessary to clearly determine what it will be used for. If this is decided, it is better to certainly take into account the recommendations of specialists or those professionals who themselves use such batteries in practice and are well aware of all their features.
It is also better to review in advance through the Internet or special profile publications rating of traction format batteries. In the store itself, you should carefully read the instructions attached to each traction battery, paying special attention to its:
- Capacity. The higher the value, the longer the equipment will be able to operate on a single charge. The capacity of the battery varies. Thus, during the start of service increases, which is performed by the development of the active mass of the plates. Then there is a gradual decrease in the capacity.
- Number of cycles. They depend on the battery technology. For WET, the resource reaches 1000 cycles, AGM – up to 400, and GEL – has the ability to withstand more than 700.
- Self-discharge. This process occurs due to redox reactions. Preference should be given to batteries with a low self-discharge value.
- Cost of operation. For this purpose, the price of one cycle of deep discharge is considered. For example, the cost of an AGM product is 15 thousand rubles, and its gel “counterpart” with the same capacity costs 23 thousand rubles. The resource of the first battery 350 cycles, and the second – 700. It follows that their operating price of 42.85 and 32.85 rubles, respectively. (The total is calculated by dividing the price of the device by its cycle).
- The reputation of the manufacturer. Since it is impossible to check the quality of the battery at the time of purchase, the only guarantee may be the reliability of the manufacturer.
Rules of operation of traction batteries
The basic rules of storage and operation of traction batteries are practically the same as those for conventional batteries. If they obey the time-honored principle “God takes care of the right guy,” by providing them with normal care and constant preventive maintenance, such traction batteries are able to operate successfully for many years.
Can the traction battery be used instead of the starter battery?
Such a question from the motorists have to hear hardly more often than others. And this is understandable, since the traction battery has, in comparison with the starter battery, a number of important advantages and advantages. For example, they can be stored for a long time without operation, without fear that they will run out of power and fail (which is especially attractive to drivers).
Experts say that it is hypothetically possible to use a traction battery instead of the starter battery. It is not always possible to start the engine with it, because the battery has much less energy: the current to start the engine is unlikely to be enough. And if a powerful traction battery with the necessary current of 300 amps is used, it simply will not fit under the hood of the car due to its dimensions.