We present here a brief overview of rechargeable batteries.

The consumer type is represented by cylinder Ni-MH type with voltage 1.2V. Often it is used instead of alkaline in spite of lower voltage. Ni-MH batteries also is used in some specific industrial applications. There are high power version (D-size cell provide current up to 150A), high temperature version (+90…+100℃), version with full industrial temperature range (-40…+85℃), version which can be charged at negative temperature, etc. Unlike lithium Ni-MH battery from several cells doesn’t need electronic protection and equilibrium circuit, simple fuse is enough. Main disadvantage – low energy density ~ 80 Wh/kg

New trend – lithium 1.5V rechargeable batteries with USB charging. Really battery consists of 3.7V li-ion cell and small PCB with DC/DC converter.

Li-ion batteries is divided on several types depends on cathode/anode material. From chemical point of view terms “Li-Ion” includes the following:

For our purposes it is better to classify “Li-Ion” by cell voltage.

Chemistry	Name, abbreviations	Nominal voltage	Voltage of 100% charged cell
{C} +NMC // NCA // LCO // LMO	Li-ion “classic” NMC, NCA, LCO, ICR, INR	3.6 -3.7V	4.2– 4.4 V
{C} + LFP (Li-FePO4)	Li-FePO4 LFP, IFR	3.2 - 3.3V	3.6 - 3.65 V
LTO + {LCO // LMO // NMC}	Lithium-Titanate LTO	2.3 – 2.4 V	2.7 - 2.8 V

Basic features of different Li-Ion types are in this table:

Chemistry abbreviations	Energy density	Number of cycles charge/discharge	Safety
NMC/NCA/LCO	200-300Wh/kg	500 –3000	Moderate
LFP	120-200 Wh/kg	1500 - 7000	Safe
LTO	80-90Wh/kg	10000 - 20000	Safe

Manifold of Li-Ion batteries allows to provide the most suitable for particular case solution. Sometimes it will better to use standardized 18650, 21700 and other cylinder cells. Sometimes the best solution will from prismatic or pouch cells.