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Received: February 11th, 2023 ; Accepted: April 30th, 2023 ; Published: May 10th, 2023 ; Correspondence: dainis.berjoza@llu.lv, inara.jurgena@llu.lv Significant changes are expected in the percentage distribution of vehicles in the world over the next decade. It is planned to gradually replace conventional internal combustion vehicles with electric drive ones, thereby reducing environment impacts and the production of gases contributing to the greenhouse effect. It is necessary to foster similar trends regarding watercraft, replacing the internal combustion engines with electric motors. An experiment used a solar-powered catamaran equipped with a standard electric motor Minn Kota Endura 34, a 450 W monocrystalline solar cell and a 40 Ah lithium iron 12 V battery. A pyranometer was used to measure solar energy. The experiment used a data logger GL 220 that measured the energy flow to the battery and the electric motor. The experiment was conducted in Jelgava on 5 July 2022, with the maximum altitude of the sun reaching 56.7°. The experiment identified that at an average solar intensity of 500 W m-2 on a sunny day, the solar catamaran could be moved by means of solar energy without discharging the batteries at all power settings.

Received: February 2nd, 2021 ; Accepted: May 8th, 2021 ; Published: May 13th, 2021 ; Correspondence: dainis.berjoza@llu.lv Due to the fact that the world's energy resources are declining, various alternative energy sources are being sought. One such source of energy is solar energy. However, due to the large size of solar photovoltaic panels, solar energy is not widely used in mobile vehicles. In some electric automobiles, solar energy is used as an additional energy source, yet usually the sun is not able to provide more than 15–20% of the energy needed for their propulsion. There are some experimental design solutions for water vessels that are propelled by solar energy only. A recumbent electric tricycle was designed, constructed and tested within the present research. The recumbent electric tricycle used a 330 W solar battery, which was designed as a tricycle roof. During the tests with the solar battery, the electric tricycle reached a maximum speed of 32 km h -1 . On a sunny day in May under the conditions in Latvia, a distance of 50.20 km was experimentally covered without battery recharging, compared with a distance of 17.14 km covered without the use of a solar battery. By skilfully operating the solar electric tricycle and limiting the speed to 20 km h -1 on a sunny day, the expected distance covered could be unlimited. The acceleration and braking parameters of the solar electric tricycle were identified by using a scientific radar Stalker ATS.

Article A pack of batteries is one of the most important and expensive assemblies for an electric vehicle. A pack of batteries is comprised of several batteries connected in series. The number of the batteries connected depends on the operating voltage of the vehicle’s on-board system as well as on the individual characteristics of the batteries used, e.g. the operating voltage of a single cell. One or several cells of a pack of batteries could be damaged if improperly exploiting an electric vehicle– excessively discharging the batteries or overloading the electric vehicle. If a self-converted vehicle does not use an intellectual BMS (battery management system) that can identify and register voltage drop for any individual cell in the high-load regime, e.g. when accelerating, it is difficult to identify and change the cells damaged. In case a cell does not demonstrate a complete failure, it is almost impossible to identify a defect in any regime other than the load regime. The research developed and compared three different methods for identifying defective battery cells. The methods were approbated on a converted Renault Clio. The experiment involved making voltage measurements in road tests, running the electric vehicle on a roll test bench and making voltage measurements of maximally discharged batteries in the no-load regime. A comparison of the measurement results revealed that the measurements made in the road tests were the most accurate and useful. After the experiment, the defective battery cells were replaced, thereby restoring the performance of the battery pack.

Article Fossil fuel deposits are constrained in the world. Various alternative energy sources are introduced in vehicles to limit the depletion of fossil fuel reserves and to reduce environmental pollution. One of the alternative energy sources is electricity. Th e use of electric automobiles has begun in the Baltic States too, yet accurate performance parameters of the automobiles, which could sometimes differ from the technical characteristics specified, are not always known. Road testing an electric automobile w as performed using a data logger that recorded the battery’s voltage, current, temperature and the automobile’s speed. These parameters allowed computing changes in the electric automobile’s power output under various driving regimes, e.g. acceleration or braking. Road testing the electric automobile was done under two driving regimes – urban and non - urban – on a certain route. The experiment represented a full cycle road test, with the batteries fully charged, that lasted until the batteries were discharge d to a minimum level, which was limited by the battery management system (BMS). The experiment identified the maximum current as well as the effectiveness of the regenerative braking system.