Expert Tips for LiPo Batteries

Mr. Offenthaler, how dangerous are lithium-ion batteries—which also include lithium-polymer batteries?

Dieter Offenthaler: When used properly, lithium-ion batteries pose no danger. I recommend buying only batteries from reputable brands. This is because rigorous, uncompromising quality control of both the batteries and the manufacturing process is essential. With major brands, you can assume that they adhere to the highest standards to avoid damaging their reputation.

Why can batteries catch fire?

Unlike other batteries, which use a water-based electrolyte, the electrolyte in lithium-ion batteries is flammable. The separator—a semi-permeable plastic film—separates the cathode (made of aluminum)

and the anode (made of copper) in a cell; only lithium ions can pass through this sheet. If the separator is damaged—for example, by excessive heat, a puncture, or crushing of the battery—this causes a short circuit; and electric current flows unimpeded between the two terminals. The battery heats up, and the electrolyte catches fire. The heat generated by this fire then destroys the separator of the next cell, and the cells catch fire one after another in a chain reaction.

What should you keep in mind with LiPo batteries?

What batteries really can’t stand is heat—for example, when they’re placed behind the windshield on a sunny day—and mechanical stress such as impacts. Under no circumstances should batteries be disassembled. To recharge a LiPo battery, use only a charger designed for that specific battery, and unplug it once the battery is fully charged.

How should I store my battery when I’m not using it for a long time, such as during the winter?

Store your battery in a dry, frost-free place. Ideally, charge the battery to half capacity.

Dieter Offenthaler is the director of Batrec Industrie AG in Wimmis. The company recycles used batteries and rechargeable batteries collected in Switzerland. "Regular" household batteries are recycled on-site, while lithium-ion rechargeable batteries are prepared for recycling. A French subsidiary then recycles the valuable raw materials, such as cobalt, nickel, and copper. www.batrec.ch

Dieter Offenthaler, Director of Batrec.

This way, you can prevent deep discharge, which occurs when the battery discharges on its own over time. Check the battery’s charge level from time to time and recharge it to half capacity if necessary. After a long period of nonuse, monitor the initial charging process.

Are fire-resistant containers recommended for storage?

Generally speaking, yes. However, these containers must be equipped with a vent. They must not be gas-tight under any circumstances to prevent dangerous pressure buildup inside the container in the event of a fire.

For LiPo batteries, safety bags that meet these requirements are available on the market. These are definitely recommended.

What should you do if the battery starts smoking or catches fire?

As far as possible, place the battery in a large container filled with water—ideally one that isn’t made of plastic. The battery must be completely submerged in water. Leave the container with the battery outside for several days. To dispose of such a battery, you should contact the INOBAT emergency service: www.inobat.ch/urgence. If you can no longer handle the battery, extinguish the fire with water, a fire extinguisher, or a fire blanket. Once the flames have been smothered,

also place the battery in a container filled with water and proceed as described above. It’s therefore a good idea to keep a container filled with water within reach while flying your model aircraft.

What are the signs that a lithium-ion battery has a problem?

There are several signs that may indicate a battery has a problem and should be returned as soon as possible to a designated collection point:

1. The battery is swollen. This indicates that chemical reactions—usually caused by moisture—have begun inside the battery. With lithium-polymer batteries, swelling becomes visible very quickly.

2. The battery shows external damage, such as dents or cracks.
3. It exhibits a noticeable drop in power.
4. The battery becomes extremely hot during use or while charging.

5. If you smell gas or notice liquid leaking from the battery, there is no time to waste.

If you notice any of these signs, the battery must no longer be used, let alone recharged. Insulate the terminals with adhesive tape to protect against a short circuit, and place it separately in a plastic bag. Take it immediately to a designated collection point so it can be disposed of properly.

A new INOBAT fact sheet provides model airplane enthusiasts and drone pilots with information on the safe disposal of LiPo batteries. It can be downloaded from the INOBAT website at www.inobat.ch under the “Information Materials” menu.