When shipping UN3480, Lithium Ion Batteries (alone without equipment), the strictest safety standards apply to air transport under U.S. DOT and International Regulations published by ICAO (IATA). Primarily, this includes the requirement that they do not exceed a 30% State of Charge (SoC) as indicated in the IATA Dangerous Goods Regulation, Packing Instruction 965, Section IA. However, there is no advice or specific procedures provided in this packing instruction on the process of computing the SoC level.
On the surface, it would appear to be a simple method of measure such as determining the fuel level in your automobile’s gas tank: full if it registers 100%; half full at 50%; and 25% for a quarter tank. Of course, the unit of measure can be based on gallons or liters.
Consequently, it appears that the power rating for a lithium ion battery could be measured in a similar fashion. It has been established that lithium ion batteries indicate their power rating in Watt-Hours (Wh). Therefore, if such a battery has a maximum of 100 Wh, then 30 Wh would seem to reflect a 30% State of Charge (SoC). Unfortunately, the actual process to determine the SoC is not that straightforward.
Since the process requires a certain level of expertise to explain, we will borrow and give credit to such an expert from Power Tech Systems (https://www.powertechsystems.eu/). Below is their brief explanation of the methodology to determine SoC and a link to their website for full details about the process.
The state of charge (SoC) of a lithium-ion battery can be measured using two common methods: the Open Circuit Voltage (OCV) method, which estimates SoC based on the battery’s voltage after resting, and the coulomb counting method, which tracks the current flowing in and out of the battery over time. Both methods have their advantages and limitations, particularly due to the flat discharge curve of lithium-ion batteries, which can make voltage-based estimations less accurate.
Please visit their website for a fully illustrated explanation of the process for measuring the SoC of a lithium-ion battery.
Note that for UN3556, Vehicle, Lithium Ion Battery Powered, UN3557, Vehicle, Lithium Metal Battery Powered, when the battery is rechargeable, and UN 3558, Vehicle, Sodium Ion Battery Powered, the following requirements apply:
Until December 31, 2025, vehicles should be offered for transport with:
- The batteries at a state of charge not exceeding 30% of their rated capacity; or
- An indicated battery capacity not exceeding 25%.
From January 1, 2026, vehicles should be offered for transported as follows:
(a) Vehicles powered by batteries with a Watt-hour rating exceeding 100 Wh must be offered for transport with:
- The batteries at a state of charge not exceeding 30% of their rated capacity; or
- An indicated battery capacity not exceeding 25%.
(b) Vehicles powered by batteries with a Watt-hour rating not exceeding 100 Wh should be offered for transport with:
- the batteries at a state of charge not exceeding 30% of their rated capacity; or
- an indicated battery capacity not exceeding 25%.
(c) Vehicles powered by batteries with a Watt-hour rating exceeding 100 Wh and at a state of charge greater than 30% of their rated capacity or an indicated battery capacity exceeding 25% may only be shipped with the approval of the State of Origin and the State of the Operator under the written conditions established by those authorities.