Lithium Batteries FAQ

Although they have become essential for many modern devices, batteries have a number of hazards that make them dangerous in transportation. When damaged, or if improperly manufactured, they can form “internal short circuits” that lead to heat buildup that can result in fires. They can also ignite if overcharged, or when operating equipment and not enough cooling is provided. Lithium metal in non-rechargeable batteries can ignite on contact with water, so cracked casings can be dangerous when batteries are exposed to the elements. Making matters worse, extinguishing lithium battery fires can be difficult and require special extinguishers (Class D). Finally, swallowing a lithium battery (although a rare situation) can lead to potentially fatal damage to the esophagus and digestive tract.

Although people tend to use these terms interchangeably, they have specific meaning in dangerous goods regulations. A cell refers to a single anode and cathode separated by electrolyte used to produce a voltage and current. For example, think of a single “AA” cell that is not connected to another cell. When two or more cells are connected together to share their output, this is called a “battery.” For example, a typical computer battery pack contains several cells connected together.

Lithium metal batteries, as the name suggests, contain metallic lithium typically used as the anode (negative electrode). These batteries were originally non-rechargeable (also known as primary batteries), although rechargeable versions are now in development. Lithium metal batteries are known for their high energy density but also pose greater risks if damaged or improperly handled.

In contrast, lithium ion batteries do not contain metallic lithium. Instead, they operate using lithium ions that move through an electrolyte between electrodes during charging and discharging. These are typically rechargeable (also called secondary batteries) and are widely used in consumer electronics, electric vehicles, and other applications. Some lithium ion batteries use a polymer-based electrolyte (commonly known as lithium polymer batteries), but for transport classification purposes, they are still considered lithium ion batteries.

Sodium batteries, including sodium-ion and sodium metal variants, are emerging as an alternative to lithium-based technologies. Instead of lithium, they use sodium a more abundant and less expensive material. Sodium-ion batteries work similarly to lithium ion batteries, using sodium ions in the electrolyte. While their energy density is currently lower than that of lithium-based batteries, sodium batteries are gaining attention for their potential advantages in cost, sustainability, and resource availability. Like lithium batteries, sodium batteries may also fall under transport regulations depending on their chemistry and risk profile.

The United Nations Recommendations on the Transport of Dangerous Goods establish criteria to differentiate between “high-powered” batteries, which must be shipped as fully regulated dangerous goods, and “low-powered” batteries, which may be eligible for exemptions from many regulatory requirements. These criteria have been adopted into national regulations such as the U.S. Hazardous Materials Regulations (49 CFR) and Canada’s Transportation of Dangerous Goods (TDG) Regulations.

For lithium metal batteries, classification is based on the amount of lithium content:

• Lithium metal cells are considered low-powered if they contain no more than 1 gram of lithium each.
• Lithium metal batteries are considered low-powered if they contain no more than 2 grams of lithium in total.

Since lithium ion batteries do not contain metallic lithium, their classification is based on Watt-hour (Wh) ratings:

• Lithium ion cells are considered low-powered if rated no more than 20 Wh each.
• Lithium ion batteries are considered low-powered if rated no more than 100 Wh per total unit.

The same Watt-hour-based thresholds apply to sodium-ion batteries, which are now recognized under a separate UN number (UN 3551 – Sodium ion batteries). Like lithium ion batteries, sodium-ion batteries are typically rechargeable and do not contain reactive metals in solid form. As a result, their transport classification is determined by their energy capacity rather than by metal content:

• Sodium ion cells are considered low-powered if rated no more than 20 Wh each.
• Sodium ion batteries are low-powered if rated no more than 100 Wh per total unit.

In all cases, proper classification ensures appropriate packaging, labeling, and documentation.

For lithium metal batteries, the best approach is to consult the manufacturer’s documentation—such as a specification sheet, Safety Data Sheet (SDS), or product datasheet. If this information isn’t readily available, but you know the ampere-hour (Ah) capacity of the cell or battery, you can estimate the lithium content using the formula:

Lithium content (grams) = Ah per cell × 0.3 × number of cells

For lithium ion batteries, the power rating is typically expressed in Watt-hours (Wh). On most recently manufactured lithium ion batteries, the Watt-hour rating must be marked directly on the outer casing. If it’s not listed, you can calculate it using the battery’s voltage and ampere-hour capacity:

Watt-hours = Voltage (V) × Ampere-hours (Ah)

This same approach also applies to sodium-ion batteries, which are regulated under UN 3551. Like lithium ion batteries, sodium-ion batteries are classified based on their Watt-hour rating. You can find this value marked on the casing of newer sodium-ion batteries or calculate it using the same formula:

Watt-hours = Voltage (V) × Ampere-hours (Ah)

Whether you’re dealing with lithium metal, lithium ion, or sodium-ion batteries, the key data are usually available in the manufacturer’s specification sheet or SDS. This information is essential for determining how the battery should be classified and transported.

UN specification packaging is generally required when shipping high-powered lithium or sodium-ion batteries on their own or packed with equipment (but not installed). If the batteries are low-powered or installed in equipment, UN packaging is usually not required—though other packaging rules still apply. Always check the specific regulation (e.g., IATA, 49 CFR, or TDG) to confirm.

High-powered lithium and sodium-ion batteries shipped as spares or packed with equipment must use UN outer packaging authorized at least to Packing Group II (PG II) standards. Acceptable packaging types include metal boxes, wooden boxes, fiberboard boxes (4G), solid plastic boxes, plywood, fiber (1G), or plastic drums.

Non-metallic inner packaging must fully enclose each cell or battery and prevent contact with equipment, other devices, or conductive materials. Common options include plastic bags and protective inserts.

The US has some special domestic rules for shipping lithium batteries. For example, except when lithium cells or batteries are packed with or contained in equipment in quantities not exceeding 5 kg net weight, the outer package that contains lithium cells or batteries must be appropriately marked: “PRIMARY LITHIUM BATTERIES-FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT”, “LITHIUM METAL BATTERIES-FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT”, “LITHIUM ION BATTERIES-FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT.” Alternately, the packages may be labeled with a “CARGO AIRCRAFT ONLY” label. The US regulations also have reduced requirements for lithium batteries up to 5 g/cell or 25 g per battery (lithium metal) or 60 Wh/cell or 300 Wh/battery (lithium ion). These are only allowed to be transported as exempted by ground, so must be marked “LITHIUM BATTERIES-FORBIDDEN FOR TRANSPORT ABOARD AIRCRAFT AND VESSEL.”

The UN Recommendations on the Transport of Dangerous Goods established that there was too much confusion regarding the phone number, which did not enhance safety, so the requirement was removed. The 49 CFR, IATA, and IMDG have also amended their regulations so that a phone number is no longer required. Note that a transition period in place allows you to continue adding a phone number if you wish.

The Transportation of Dangerous Goods Regulations in Canada have not yet been amended to reflect this change.

The UN Recommendations on the Transport of Dangerous Goods have recently allowed for a reduction in the size of this mark to a minimum of 100 mm per side (from 110 by 120 mm). IATA, IMDG, and now the 49 CFR by way of HM-215Q also incorporated this change. The TDG regulations in Canada is the only regulations that is still pending.

Yes. A completely black and white design will not be acceptable.