Powermaster: Smart Power Distribution System
In the electric motorcycle market, models featuring removable batteries which users can charge at home are especially popular. When the range requirements are high, the weight and size of the battery grows substantially, so the usual approach is the strategy of using different battery modules.
Even though they are more convenient for the user, multi-module battery architectures impose some complexities in power distribution that affect the motorcycle's performance in several areas.
EEVAM's R&D department has carried out different studies analysing the impact of using a modular architecture on vehicle performance, compared to a single fixed-module battery with the same capacity.
The results show that this type of architecture, although more advantageous for the user, has a number of drawbacks and penalizes the performance of the motorcycle.
Among the drawbacks, the penalization of the vehicle's autonomy with the use of two battery modules stands out. Furthermore, to prevent cell damage due to high discharge currents, which adversely affect battery cell integrity and lifespan, some manufacturers include power limitations on the motorcycle. Vehicle performance suffers due to this power limitation, both in terms of acceleration and maximum speed. This effect is noticeable enough to negatively affect customer perception.
From the EEVAM R&D department, we identified the most promising technology to face these market need. We are developing Powermaster, a Smart Power Distribution System (SPDS) that optimizes the energy flow among the different systems on the vehicle.
Powermaster has a series of power inputs coming from different battery modules, keeping the electric insulation between them. The main function of Powermaster will be distributing the electric power among the battery modules, as well as controlling the discharge power required by the electric motor.
Powermaster is also equipped with sensors able to gather data. This data is later processed through algorithms that control the smart power distribution, based on the following criteria.
- Maximize the range of the vehicle.
- Optimize the lifespan of the batteries preventing the lack of balance among modules.
- Guarantee the security avoiding high discharge currents in the cells.
- Improve the performance of the vehicle by limiting the power losses.
The development of a product has four stages: ideation, design, engineering and validation.
In the ideation stage of Powermaster, we successfully simulated and implemented the first working prototype. For the validation of the control algorithm bases, we executed different tests using a Hardware-in-the-loop (HIL) system. A HIL system includes both physical and simulated components.
This HIL system is composed by the physical implementation of Powermaster and the virtual implementation of the batteries. By doing this, we managed to streamline the validation and development of the control algorithm without having to charge and discharge batteries. The batteries have been replaced by power supplies that provide the necessary power, while their HIL implementation simulates the discharge curve of a real battery, which the control algorithm uses to smartly distribute the power to each battery.
In the following graph, we represent the voltage on each battery module on its HIL implementation during the execution of one of the tests. A higher voltage implies a higher state-of-charge (SoC) level, so in this implementation, we represent a situation where a battery has a higher SoC than the other one. Throughout the test, each module is discharged according to the power it's providing to the system.
According to the control algorithm implemented in this prototype, the power is distributed in such a way that both modules are finally balanced, optimizing at the same time their lifespan. The following iterations of the control algorithm implement a more complex and more equilibrated control of the discharge currents. In this test is represented a scenario of cruise speed: the necessary acceleration and therefore the necessary power is kept constant to keep the established speed.
After the ideation stage, and following the validation of the of tests executed on this prototype, the development of the product goes to the design and engineering stage. This is an iterative stage where we implement more and more advanced prototypes, each one closer to the final product.
Powermaster is just one of EEVAM's product. Our team keeps working non-stop in developing the technology of Powermaster, with the objective of powering the new generation of electric vehicles and proposing new alternatives for a sustainable mobility. Soon, we will be announcing news on our latest results.
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