LG Energy Solution (frueher LG Chem) INR21700 M50 (M50T)

The LG INR21700 M50 is an energy cell in the 21700 format from LG Energy Solution (formerly LG Chem), a South Korean cell maker. It is used in lithium-ion batteries for long range and is intended for small FPV drones that are to fly long and steadily. The format 21700 stands for 21 mm diameter and 70 mm length.

The cathode is NMC811, a nickel-manganese-cobalt oxide in the ratio 8:1:1; the anode is graphite with silicon oxide. The cell stores 5,000 mAh at 3.63 V nominal voltage, which is 18.2 Wh, at 267 Wh/kg and 68 g ±1 g. Continuous discharge is limited to 1.5C, which is 7.5 A, within a temperature range of 5 to 60 °C. That is a figure for gentle loads, not for freestyle with fast throttle changes. The dimensions are at most 21.10 × 70.15 mm.

Six cells in series (6S1P) come to about 109 Wh and so lie between the IATA limits of 100 and 160 Wh; there the airline must agree to carriage of spare batteries. Lithium cells must meet the tests of UN 38.3 for transport, and spare cells are protected against short circuit. In addition, IEC 62133 covers the safety of lithium cells in portable devices; whether a cell is tested to it is stated in the manufacturer's data sheet. Joining cells into a pack belongs in a specialist workshop with test and protection equipment.

When choosing, the pack current must stay below 7.5 A per parallel group; with two parallel cells the current per cell halves. Because the 7.5 A only holds between 5 and 60 °C, the pack should be brought up to temperature before flight in winter. With increasing cycles internal resistance rises and capacity falls; store partly charged and do not charge in frost.