# Energy Sources of Mobile Robot Power Systems: A Systematic Review and Comparison of Efficiency
## 6 Conclusions  
In this paper, power systems based mainly on batteries from different materials for mobile robots were presented. Different energy sources were considered, and a detailed analysis of the electrical sources was performed. This can be summarized as follows:  
* Comparison of different types of batteries (lead-acid, AGM, Gel, NiMH, LiPo, LiFePO\({}_{4}\)) shows that the most versatile solution currently available, characterized by high specific energy and specific power, low self-discharge rate per month, and good safety, is LiFePO\({}_{4}\) technology. * New types of batteries with excellent qualities are the subject of research (batteries based on seawater, iron-flow batteries, silicon as the anode in a lithium-ion battery, organosilicon-based liquid solvents, magnesium metal batteries, lithium-sulfur battery technology made of B4C-hemp, lithium-tungsten batteries, gold nanowire gel electrolyte batteries). * An important parameter of batteries in applications is energy efficiency, which depends both on battery chemistry and the drive system of the robot. * A summary of the bipedal walking robots and driving robots is presented with examples. * AMRs are a very important factor in the development of Industry 4.0. Distinct types of AMR are available: fetching, picking, or sorting. These robots with different structure require different batteries (voltages, current supply, and capacity) to function efficiently. Li-ion batteries are mainly used as the power source. * The use of Li-ion batteries containing a LiFePO\({}_{4}\) cathode and a graphite anode is increasing. For AMR application, batteries from 12 to 96 V and capacities from 10 to 200 Ah are used. Individual (3.27 V) cells are combined in series/parallel connections to build such battery packs. The run time of robots is mostly targeting (\(\sim\)8.4 h), which is more than 3 times than the charging time (\(\sim\)2.7 h). * Modern batteries in applications have many benefits, including: \(\bigcirc\) Higher operating voltage and higher capacity; \(\bigcirc\) Longer operating time; \(\bigcirc\) Shorter down time; \(\bigcirc\) Longer cycle life. * Based on the review of power systems in the paper we propose:An algorithm for selecting the main energy source for robot application in which we can consider the main source type (hydraulic, mechanical, pneumatic, electric);  
An algorithm for selecting the electrical system power supply, which can help to find the optimal electrical source (NiMH, LiPo, LiFePO\({}_{4}\), supercapacitors). Current mobile robot battery solutions are still a trade-off between weight/size and capacity, making them the biggest limitation of robots. Progress in battery development is too slow, limiting the development of mobile robots themselves and their autonomy and range. Considering the broader perspective, we need to see changes taking place in the perception of the importance of sustainability, environmental pollution, energy costs and the availability of fuels, components, and raw materials, including those based on AI-assisted optimization [89; 90]. Intelligently managed, more efficient, more cost-effective, and less environmentally damaging powering of mobile robots will not only allow the further development of manufacturing, transport, and services, but will also contribute to the development of new business models, including in the area of public transport (subscription model, vehicle sharing), which will have important scientific and technical, but also economic and social, consequences  
Further intensive research and implementation work is needed in the field discussed in this paper. In addition, the current global economic situation, including the energy crisis, may make the use of mobile robots too expensive and their expected market success will be postponed for many years, as may happen in the near future with the implementation of electric cars. Conceptualization, T.M., D.M., A.K., E.M., T.P. and A.L. ; methodology, T.M., D.M., A.K., E.M., T.P. and A.L. software, T.M, D.M. and M.M.