Why can lead-acid batteries be transported as ordinary goods in international logistics under superpower conditions, while lithium batteries cannot? The main reason lies in the differentiated management of the two in international logistics transportation, which stems from their chemical properties, risk levels, and differences in international regulatory classification standards. The following analysis will cover three aspects: technology, regulations, and industry practices.

Essential Differences Between Chemical Properties and Risk Mechanisms

1. Stability of Lead-Acid Batteries

The electrolyte of lead-acid batteries is a sulfuric acid solution, and its chemical reactions are relatively stable. Even in cases of overcharging or physical damage, the main risk is electrolyte leakage (classified as Class 8 corrosive substances), but it is not prone to spontaneous combustion or explosion. Through sealed design and leak-proof testing (such as vibration, pressure differential, and 55°C leakage tests), lead-acid batteries can demonstrate their safety, thus exempting them from being classified as dangerous goods for transportation. For example, a notice from China’s Ministry of Transport in 2007 clearly states that sealed lead-acid batteries meeting specific conditions can be transported as ordinary goods.

2. Risk of Thermal Runaway in Lithium Batteries

The high energy density and chemical reactivity of lithium batteries (especially lithium-ion batteries) pose a risk of thermal runaway. When the battery is overcharged, short-circuited, or subjected to pressure, the electrolyte decomposes and produces flammable gases (such as hydrogen and methane), which can lead to fire or explosion. Even without exceeding power limits, lithium batteries must undergo UN38.3 testing (including puncture, overcharge, external short circuit, etc.) to demonstrate safety. When exceeding power limits, the internal energy accumulation in the battery intensifies, causing risks to increase exponentially; therefore, strict regulations for hazardous materials transport must be followed.

Differentiated Classification and Exemption Provisions of International Regulations

1. Exemption Mechanism for Lead-Acid Batteries

According to the International Maritime Dangerous Goods Code (IMDG Code), lead-acid batteries can be classified as UN2800 and subject to special provision 238 if they pass vibration, pressure differential, and 55°C leakage tests, exempting them from being treated as dangerous goods. For example, both the European Union and China allow qualified lead-acid batteries to be transported as general cargo, requiring only labeling for short-circuit protection and electrolyte leakage prevention measures.

2. The mandatory hazardous material properties of lithium batteries

Lithium batteries are uniformly classified as Class 9 hazardous materials (miscellaneous dangerous substances), and regardless of their power, they must comply with strict packaging, labeling, and transportation requirements:

• Lithium batteries transported separately (UN3480/UN3090) must pass the UN38.3 test and be packaged using Class II hazardous materials packaging.
• Lithium batteries contained in equipment (UN3481/UN3091) must be secured to prevent short circuits, and the equipment must have a function to prevent accidental activation.
• Super power lithium batteries (such as lithium-ion battery packs with energy exceeding 100Wh) require additional special approval (e.g., IATA’s A99 provision), and transportation on passenger aircraft is prohibited.

Differences in Industry Standards for Power Calculation and Thresholds

1. Power Calculation of Lead-Acid Batteries

The power of lead-acid batteries is usually expressed in ampere-hours (Ah), with a higher superpower threshold. For example, the capacity of lead-acid batteries used for automotive starting can exceed 100Ah, while international logistics limits the capacity of lead-acid batteries mainly based on the risk of electrolyte leakage rather than energy density. As long as they pass leak-proof tests, high-capacity lead-acid batteries can still be transported as ordinary goods.

2. Energy Limitations of Lithium Batteries

The power of lithium batteries is measured in watt-hours (Wh), and their risks are directly related to energy:

• Consumer lithium batteries: Individual battery ≤ 20Wh, battery pack ≤ 100Wh can be exempt from dangerous goods certification, but must indicate the Wh value and use short-circuit prevention packaging.
• High-power lithium batteries: Such as electric vehicle batteries (usually ≥ 100Wh), even if they meet UN38.3 testing, must be transported as hazardous materials and use specialized packaging and transport tools.

Historical Evolution of Industry Practices and Risk Awareness

1. Mature Transportation System for Lead-Acid Batteries

As a traditional battery technology, lead-acid batteries have been in use for over a century, and their transportation risks have been fully recognized and managed. The industry has established a mature exemption mechanism through standardized testing (such as vibration and pressure differential tests) and packaging specifications (such as acid-resistant casings).

2. Emerging Risks of Lithium Batteries and Regulatory Upgrades

The rapid proliferation of lithium batteries has been accompanied by multiple transportation incidents (such as cargo hold fires on aircraft), prompting a continuous tightening of international regulations. For example, the IATA DGR 66th edition (effective in 2025) introduces a classification for sodium-ion batteries and strengthens the charge limit for lithium batteries (≤30%). China’s “Several Measures to Accelerate the Improvement of Transportation Services and Safety Assurance Capabilities for Power Lithium Batteries in New Energy Vehicles” (2024) also requires tiered management for lithium battery transportation.

Typical Cases and Actual Impact

1. Lead-acid battery case: The German Sunshine Battery A512/40 G6 (12V40Ah) is exempt from IATA DGR’s A67 clause and can be air transported as ordinary cargo.

2. Lithium battery case: BYD large power lithium batteries (energy ≥ 35kg) require special approval under A99, and must be equipped with thermal runaway monitoring and emergency response plans during transportation.

Summary : Core Reasons and Future Trends

In the future, with the iteration of lithium battery technology (such as solid-state batteries reducing the risk of thermal runaway) and dynamic adjustments to regulations, transportation restrictions may gradually be relaxed, but strict controls will still be maintained in the short term. The exemption mechanism for lead-acid batteries is expected to exist long-term due to their stability and maturity.

If the shipment contains both lead-acid batteries and lithium batteries, can they be transported together ?

Of course. The specific arrangements depend on the condition of the lithium batteries and relevant documentation.

1. If the lithium batteries are within power limits, they can be transported as regular goods.

2. If the lithium batteries exceed power limits, they must be transported as Class 9 hazardous materials.