Designing a Motorsport Battery in Seven Steps
We use batteries daily so we will use the whole lot from our electrical toothbrush to the automotive. Nevertheless, batteries used in motor sports are removed from the card behind AA's TV distant controls. So how do you propose to design a motorbike battery? We talked to main specialists to seek out out.
1. Low Voltage and Excessive Voltage
Trendy racing automobiles have two foremost forms of batteries:
- Low Voltage (LV) – 12V System Using Low Voltage Know-how and Security Methods similar to BMS, Cell Control Models, Insulation Control, Power Sensors and Knowledge Collection
- High Voltage (HV) – Controls electric motors and inverters while storing the power amassed during regenerative braking. Additionally uses a power supply unit (PDU), a bus community, and a guide upkeep interface (MSD).
An instance of a circuit diagram of an electrical racecourse
Electrical and hybrid motors require excessive energy, which is why a excessive voltage battery is required. "In general, if you want to give the same amount of power, you can do it in two ways," says Billy Wu, Imperial School London Power and Manufacturing Know-how. “Due to the Ohmi regulation, the facility corresponds to the voltage multiplied by the present [P=IV] you’ll be able to obtain the same power at high voltage, but with low present or excessive current, however at low voltage. The issue is that when pushing the current by way of the wire, there’s a finite resistance that causes the wire to heat up into the square. Thereby the warmth produced corresponds to the present square value multiplied by the resistance [P=I2R]. Subsequently, with a view to reduce the warmth generated and enhance effectivity, you need to scale back the current, which signifies that the battery have to be high voltage. "
2. Energy Density and Power Density
Nevertheless, the design, measurement and format of these high-voltage batteries differ tremendously on the hybrid, electric, or racetrack. “We need to understand what is important for an ERS battery in F1 and what is important for the Formula E battery as they are different animals,” emphasizes Douglas Campling, Williams Superior Engineering's motor sports activities supervisor. “The biggest difference is that the ERS battery is discharged and charged several times per cycle compared to the formula E, which has one single discharge in the whole competition. That's why you're looking for the best power density in F1; F1 is about having the power to boost efficiency in the smallest package, so volume and gravimetric power densities are key, ”continues Campling. “Fully electric it is an energy equation. You have to get all the cars to the end and you have a fixed amount of Joules for energy. Therefore, the purpose of Formula E is to get as much stored energy as possible and use it efficiently when it meets the power required by the championship. ”
Mercedes F1 2016 unit with ERS proper. CREDIT: Mercedes F1
Thus, the facility density of F1 ERS cells is greater (about 10-17 kW / kg), however lower power density (about 90-120Wh / kg) in comparison with Components E Gen2 (about 2.2 kW) / kg). and 232 Wh / kg). These variations are because of the totally different chemical compounds used in F1 and Method E. “But even within the same chemistry you get some cells that are“ powerful cells ”and others which are“ energy cells ”, Wu says. “There’s all the time a compromise between power and power. As a tough rule of thumb, if you need more energy, it’s a must to take successful on power intensity. "
three. Cell Varieties
Example of a bag cell. CREDIT: Xalt Power
The cells needn’t simply be the suitable chemistry, but in addition the dimensions and shape they need to fit the racing automotive. “The cells could be in three totally different varieties. Firstly, a cylindrical cell that is just around the globe. It’s in your energy tools or in a wi-fi vacuum cleaner. They are named based on their dimensions, so probably the most used cell on the planet is 18650, which is 18 mm in diameter and 65 mm in size – a lot to the dimensions of the thumb. This has a constructive terminal at one finish and a damaging terminal within the different, says Campling. “Then there’s a bag cell that can grow to be totally different dimensions, but it is a substantially flat set of electrodes within the polymer bag in comparison with rolled electrodes in cylindrical cells. Constructive and damaging tabs could also be at one finish or opposite ends. Lastly, there’s a prism cell with a hard housing around flat electrodes, which can be custom-made dimensions. "
four. Collection vs. Parallel
When a cell sort is chosen, the subsequent question is what number of? This can be calculated initially by dividing the helpful power required by the whole battery pack with that of a single cell. The required system voltage, steady power and the required charging velocity have to be thought-about subsequent. Thereafter, the power required for the battery affects the sort and number of car engines and the anticipated deterioration of the battery.
The number of cells within the collection determines the battery voltage. “Each cell has a voltage range. Completely charged it is usually about 4.2V and the lower limit is typically 2.5V to 2.7V, but each cell is different, ”says Campling. “You might have a variety of voltages, especially in Method E, where you’re on the lookout for one of the best performance, it’s worthwhile to be fairly accurate on the required battery voltage vary. In case you have related all the cells within the collection collectively to the voltage of each cell, you reach the higher battery voltage limit earlier than you attain the required usable power. Subsequently, you sometimes need to connect a number of cells in parallel to regulate the capability with out altering the output voltage. On this approach, you’re designing a battery compartment that meets the power target and the output voltage target. It is very important maximize the operating voltage, as a result of the upper the voltage, the lower the present, which leads to smaller buses and wiring and thus vital weight financial savings.
Cells are grouped to type modules and multiple modules type a battery. CREDIT: Bosch
There are various alternative ways to connect cells and modules to satisfy each the required power and output voltage targets. "Using a small cell with a low energy content is a larger compromise compared to a larger cell with a high energy content," says Anthony Regulation, McLaren, Applied Applied sciences, Director of Motor Sports Batteries. “For example, cylindrical 18650 cells supply far more flexibility in area, quantity, and how many you’ll be able to connect in a battery pack. You possibly can squeeze a lot of these cells into extra uncommon states, making it a smaller unit packet. Larger bag varieties are barely more limited. Thus, there’s a trade between the additional weight associated with a single cell sort and all their interconnection, the number of bus and connections and the pliability of the design. "
5. Temperature vs. Performance
The subsequent word is temperature. The hotter the battery, the quicker it should break down. However scale back the temperature too much and the battery loses performance. “The F1 batteries run above the batteries in terms of temperature, giving them the ability to get a lot more performance from the battery, but it degrades faster,” says Campling. “It's perfectly okay in F1 because they will replace the batteries a number of occasions through the season, however it's not acceptable in Method E, because these groups need the battery to final the entire season. Subsequently, temperature limits are strictly defined based mostly on the results of modeling and testing of degradation. “
The battery can break down in two ways:
- Cycle time: much less battery cost
- Growing older – lithium ion cells lose their capability even when not in use, which is extremely troublesome to model and predict.
In F1, the ageing of the calendar isn’t a menace, but the Gen2 Method E battery, which lasts two seasons, is the collection's factor. There’s additionally a danger of catastrophic disturbances, corresponding to thermal strain.
”You will get a discharge when the battery goes above 80 or 90 deg. This triggers chemical reactions within the battery which might be exothermic and thus release a large amount of heat, ”Wu explains. “You find yourself on this loop, the place exothermic reactions produce heat that burns the warmth out further. The battery typically has to burn because the electrolyte used in the batteries is flammable. It successfully turns into a mini flipper. “The delicate stability between battery performance and temperature makes designing probably the most challenging duties for right now's engineers.
There are two ways to scale back battery degradation. “You can use less available capacity and / or keep the battery in the optimum temperature window,” says Paul McNamara, Technical Director at Williams Superior Engineering. “If your battery ranges from 5% capability to 95% complete capacity, it’ll deteriorate from greater than 10% to 90%. Then you must compromise more on using cooling, which increases the load vs pack more cells to increase capacity. “
There are primarily 3 ways to cool the battery: 1) Air Cooling 2) Two-stage Cooling three) Single-stage Coolants (Liquid Cooling)
Motor sports are primarily driven by single-phase coolants similar to liquid cooling. “The question is whether you are flowing this liquid through the cold plate or whether the floods have been cooled,” emphasizes the regulation. “When using a cooling cooler, dielectric fluid is used because they’re non-conductive, so you employ this liquid to be in direct contact with the cells. So that you fill the battery with a dielectric fluid. This has the advantage of avoiding the additional heat resistance you get when utilizing the chilly plate. The cold plate is often a metallic cooling component, the place the cooling fluid flowing inside it’s hooked up to the bottom of the cells via a thermal adhesive. For this objective, you favor to use water as a result of it is a far more environment friendly coolant than a dielectric liquid and is less dense and subsequently lighter. The extra weight financial savings are as a consequence of the truth that you do not fill all of the battery pins and in the present day's chilly plates can now be made on very skinny walls, however still be capable of stand up to excessive pressures. “When the coolant has flowed into the battery, the heat is extracted after which discharged from the battery, it flows into a standard cooler, where excess warmth is discarded into the encompassing air, just like a standard inner combustion (IC) engine cooling system
Williams Superior Engineering designed by Gen1 Components E
It is fascinating to note that F1 and WEC use water for their cooling techniques. “In the racing application, you can only use dielectric fluids if the instructions are for safety reasons,” says Campling. "This was the first four periods of Formula E – security was not a compromise, and this has also been transferred to new Gen2 batteries."
Cautious monitoring of the cell temperature, voltage, and efficiency of each battery compartment, which may include as much as 5000-6000 cells, requires a posh wiring community, all controlled by a posh brain: BMS. "We had thermocouples and voltage measurements on each cell to monitor the voltage ranges and identify which cells were more difficult than others depending on where they were in the battery pack," McNamara explains. "That's why we could ensure that the performance of each package was fair to competition."
In addition to thermocouples, there’s additionally a constructive and unfavorable high present connection that passes from one cell to a different to ensure that the present to circulate between the cells and the low current detection connection. Finally, a cooling system which will require the cell to be related to a chilly plate by way of a thermal adhesive, both on the prime or bottom of the cell. "You also often have cellular rails that carry power from all cells in parallel to the next cell group or module," says the regulation, "The cells hook up with the sleeves either by a welded joint, thread ties or bolts
Gen1 by Williams Advanced Engineering Method Battery
The number, sort, and packaging of those diagnostic connections are one of the crucial essential areas of motor visitors improvement in at present's analysis and improvement, with the goal of extracting the maximum power from the battery as mild as attainable. Reduction, 56% efficiency increases while attaining 12 occasions the facility density and double power density. with ng
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