Safe Use Guidelines for Li-ion Batteries

General information

If we want the motor with propeller to deliver the required performance, it is necessary to supply it with enough energy. For long and efficient flights, Lithium-ion batteries (abbreviated Li-ion) offer an excellent ratio between capacity and weight. Unlike LiPo batteries, they offer higher energy density, but are intended for lower to medium discharge currents. Batteries do not suffer from memory effect. They can be recharged from any state of charge, do not need forming, and self-discharge is minimal. However, Li-ion batteries still require proper care.

The battery cell has a nominal voltage of 3,6V to 3,7V (depending on the specific chemistry). The actual voltage depends on the battery's state of charge. Li-ion packs consist of individual cells connected in series (or also in parallel) – hence the designation 4S (14,4V), 6S (21,6V), etc., and for parallel configuration e.g. 4S2P.

You will usually find two connectors on the battery. The main power connector, which you use to connect the battery to the drone, and a service balance connector. The main connector is connected to the first and last cell of the battery and carries the total battery voltage. The connector type is usually chosen according to the expected current draw. The balance connector has more contacts (number of series cells+1) and is used to monitor and equalize the voltage of individual cells.

Capacity is usually stated in mAh (milliampere-hours). Capacity indicates the current the battery is able to deliver for one hour. The stated capacity is nominal. The actual usable capacity may vary depending on the current draw and ambient temperature – at high current draw, a greater voltage sag occurs and usable capacity decreases.

An important value is the maximum discharge current. For Li-ion cells, it is more often stated directly in Amperes (e.g. 35A maximum). When the battery is continuously loaded at the maximum stated current, there is a significant voltage drop and the battery may heat up. Therefore, it is necessary to cool the battery sufficiently, for example by airflow from the surrounding air when used in a drone. With Li-ion packs, it is essential not to exceed this limit. Extreme overheating shortens its service life. The charging current is specified by the manufacturer and is usually significantly lower than with LiPo batteries.

Use and safety

Li-ion batteries must be properly cared for. When used correctly, they are safe. Failure to follow safety procedures can lead to battery damage, loss of the drone, or in extreme cases even fire. The seller is not responsible for damage caused by incorrect use of batteries.

• Do not use damaged, dented, or otherwise defective batteries (cells in a rigid case usually do not swell, but mechanical damage to the casing is dangerous).
• Follow proper charging practices.
• Discharge batteries at temperatures of 0–50°C. In colder months, the battery must be preheated to operating temperature before takeoff.
• Monitor the minimum voltage. With Li-ion, it is safe to go lower under load than with LiPo; usually land around 2,5–2,8V per cell. The minimum permissible voltage must always be checked according to the selected battery. If the voltage drops below the minimum value, there is a risk of permanent cell damage.
• Do not exceed the pack's maximum discharge current. Li-ion batteries do not have as hard a discharge characteristic as LiPo – a sudden throttle punch (freestyle/sprint) causes a large voltage drop. Li-ion is intended for smooth, long flight (cruise).
• Never short-circuit the battery terminals – the short-circuit current of Li-ion cells is enormous and there is a risk of melting connectors or fire.
• After flying, always disconnect the battery from the drone.
• Do not throw batteries into fire.
• Store batteries away from flammable objects at temperatures up to 25°C. A non-flammable case (LiPo bag or metal box) is suitable for both storage and charging of batteries.
• Store batteries (when not used for more than 14 days) at a storage voltage of approx. 3,6V to 3,8V per cell.
• Do not put batteries in water and protect them from moisture.
• Do not puncture, disassemble, or modify their spot welds – there is a risk of short circuit and ignition.

Charging batteries

After each discharge, the battery must be charged again. For safe and reliable charging, follow the rules below.

• Always charge Li-ion batteries only with a professional charger supporting Li-ion / LiPo mode. Cells with a maximum voltage of 4,1V are charged using the Li-ion mode, and cells with a maximum voltage of 4,2V are charged using the LiPo mode. Always choose the voltage according to the specification of the specific cell.
• Follow the recommended charging current. The usual charging current for Li-ion is 0,5C to 1C (e.g. for a 4000mAh pack, charge at 2A to 4A). Fast charging with high currents damages Li-ion cells and shortens their lifespan.
• Always charge batteries with the service connector connected and use the Balance mode.
• NEVER LEAVE BATTERIES CHARGING UNATTENDED! Continuously monitor the voltage of individual cells and the pack temperature.
• Charge batteries on a non-flammable surface or in a non-flammable case.
• Before charging, carefully check the set number of cells (S) and the charging current.

Battery disposal

Damaged or worn-out batteries must be disposed of in an environmentally friendly way. Li-ion batteries do not belong in regular municipal waste. A battery intended for disposal should be fully discharged. Hand in the discharged battery at a collection point or throw it into the red container intended for electronic waste and batteries.