There are more and more modern devices which require more and more technologically advanced batteries. Mobile devices are becoming smaller and smaller, but much more efficient than a few years ago. Drones have appeared, the possibilities of which are also expanding every year, apart from large flying devices, they are also small, very discreet. In some cases, the popular and commonly used lithium-polymer and lithium-ion rechargeable batteries do not work well. What we need is something more, something that will match the pace of development of modern electronic equipment market. The answer to all the requirements and expectations on its part is a Li-Fe battery, i.e. a lithium-iron-phosphate battery. It is an alternative to other batteries, where limited mass density or the adverse effect of the increase in current capacity on the operation of the device may prove to be a disadvantage. This can result in an increased risk of burns and damage. Li-Fe batteries therefore appear to be the best option for the most demanding and technologically advanced projects.