Wet Battery DG Transport Guide: UN2794 / UN2795 / UN2800 vs UN3171
Acid vs Alkali, Non-Spillable & Battery-Powered Equipment — SP238 Exemption Explained

Storage batteries (secondary batteries) are among the most frequently shipped — and most frequently misdeclared — categories in international freight. Many companies shipping a forklift, UPS, e-bike or energy-storage battery for the first time simply declare everything as "Class 8 corrosive" and get rejected by the carrier or the maritime authority. The root cause is simple: for the same "battery", the UN number and transport requirements differ completely depending on whether there is free electrolyte, whether that electrolyte is acidic or alkaline, and whether the battery is shipped alone or installed in equipment.

1. Complete comparison of the four UN numbers

Based on the Dangerous Goods List in Chapter 3.2 of the UN Model Regulations (TDG) and the aligned IMDG Code 42-24 amendment (used for sea transport), the four high-frequency battery entries are:

2. UN2794 vs UN2795: the acid-vs-alkali difference

Both UN2794 and UN2795 are wet batteries that still contain free electrolyte, both are Class 8 corrosives with no packing group, both carry Special Provision 295 and both use Packing Instruction P801. The only difference is the chemical nature of the electrolyte:

A frequent misconception must be clarified here: not all lead-acid batteries use UN2794. Only traditional flooded batteries that still contain free-flowing acid fall under UN2794. If the acid is absorbed in glass-fibre separators (AGM) or immobilised as a gel (gel battery) inside a sealed, leak-proof case, the battery belongs to UN2800 in the next section.

SP295: one label on the pallet, no individual labels required

UN2794 and UN2795 share a practical simplification — Special Provision 295 reads:

"If the pallet is appropriately marked and labelled, the batteries do not need to be individually marked and labelled."

In other words, when multiple batteries are shipped on a single pallet, only the pallet needs the Class 8 label and marks; each battery inside does not need to be labelled individually — a significant saving for bulk battery exports.

3. UN2800 non-spillable batteries + SP238 exemption (core of this guide)

UN2800 covers "wet, sealed" batteries — NON-SPILLABLE in the proper shipping name — i.e. batteries with a sealed case that cannot leak electrolyte under normal transport conditions. Valve-regulated sealed lead-acid batteries (VRLA, including AGM and gel types) and maintenance-free batteries fall into this category.

The core value of UN2800 lies in its special provision SP238: once a battery is proven "non-spillable", it is not subject to the dangerous goods regulations and can be shipped as ordinary cargo. For exporters this means — no dangerous goods packaging certificate, no DG declaration, and significantly lower freight. The original text of SP238 (IMDG Code 42-24 amendment / TDG) is:

238

(a) Batteries can be considered as non-spillable provided that they are capable of withstanding the vibration and pressure differential tests stated below, without leakage of battery fluid.

Vibration test: The battery is rigidly clamped to the platform of a vibration machine and a simple harmonic motion having an amplitude of 0.8 mm (1.6 mm maximum total excursion) is applied. The frequency is varied at the rate of 1 Hz/min between 10 Hz and 55 Hz. The entire range of frequencies and return is traversed in 95±5 minutes for each mounting position (direction of vibration) of the battery. The battery is tested in three mutually perpendicular positions (to include the filling and vent openings, if any, in an inverted position) for equal time periods.

Pressure differential test: Following the vibration test, the battery is stored for six hours at 24℃±4℃ while a pressure differential of at least 88 kPa is applied. The battery is tested in three mutually perpendicular positions (to include the filling and vent openings, if any, in an inverted position) for at least six hours in each position.

Note: Non-spillable type batteries which are an integral part of, and necessary for, the operation of mechanical or electronic equipment shall be securely fastened in the battery holder on the equipment and protected against damage and short circuit.

(b) Non-spillable batteries are not subject to these Regulations if, at a temperature of 55℃, the electrolyte will not flow from a ruptured or cracked case and there is no free liquid to flow, and if, when packaged for transport, the terminals are protected from short circuit.

The SP238 exemption can be broken down into three actionable conditions:

• ① Pass two tests proving "non-spillable" — a vibration test (0.8 mm amplitude, 10–55 Hz, 95±5 min per mounting position) and a pressure differential test (24℃±4℃, ≥88 kPa, ≥6 h in each of three perpendicular positions), with no electrolyte leakage throughout.
• ② No leakage at high temperature — at 55℃ the electrolyte will not flow from a ruptured or cracked case.
• ③ No free liquid + short-circuit protection — no free-flowing liquid inside, and the terminals are protected against short circuit when packaged for transport.

4. UN3171 battery-powered vehicle/equipment: get the boundary right

UN3171 is an entry whose boundary has been re-drawn in the latest regulations: Class 9 miscellaneous dangerous goods, no packing group, with Special Provisions mainly 123, 240, 388 and 961. Its proper shipping name is "BATTERY-POWERED VEHICLE or BATTERY-POWERED EQUIPMENT". The key is when it applies and when it does not — the IMDG Code 42-24 amendment draws the boundary clearly through Special Provision 240: UN3171 only applies to vehicles and equipment powered by wet batteries, sodium metal batteries or sodium alloy batteries, transported with those batteries installed; vehicles powered by lithium batteries (lithium ion / lithium metal / sodium ion) are now separately assigned to UN3556/3557/3558 and no longer to UN3171. The detailed mapping is:

"Vehicle" and "equipment" are clearly defined: a vehicle is a self-propelled device designed to carry persons or goods — cars, motorcycles, e-bikes (pedal-assisted bicycles), self-balancing vehicles (hoverboards), electric wheelchairs, lawnmowers, self-propelled agricultural and construction equipment, forklifts, etc.; equipment includes lawnmowers, cleaning machines, boat or aircraft models. Two easy-to-miss reminders: ① a "vehicle" powered by lithium batteries (lithium ion / lithium metal / sodium ion) is no longer UN3171, but UN3556/3557/3558; ② "equipment" powered by lithium batteries (typically power tools, robot vacuum cleaners) is UN3481/UN3091, not UN3171 — both boundaries are very common misdeclaration points in foreign trade.

The main special provisions attached to UN3171

• SP240 (scope): the UN3171 entry only applies to vehicles and equipment powered by wet batteries, sodium metal batteries or sodium alloy batteries, transported with those batteries installed — this is the core scope definition in the latest rules.
• SP123 (mode of transport): vehicles/equipment under this entry are "subject to these Regulations only when transported by air or by sea" — i.e. road and rail transport are not subject to the TDG Model Regulations (but must comply with each country's land transport rules).
• SP388 (boundary with UN3166): the UN3166 entries apply to vehicles powered by flammable liquid or gas internal combustion engines or fuel cells — used to separate "combustion/fuel-cell vehicles" (UN3166) from "pure battery vehicles" (UN3171).
• SP961 (Class 9 conditions): qualifying vehicles must be assigned to Class 9 and meet requirements such as "no signs of leakage from the battery, engine, fuel cell, compressed gas cylinder, accumulator or fuel tank".

5. Classification table for common market products

Applying the rules above to actual products, one table tells you exactly how to declare each shipment:

6. Practical sea freight declaration points

For the four entries above, the common points for sea freight (IMDG) export declaration are:

1. Classify first, then prepare documents. UN2794/2795/2800 are Class 8, while UN3171 is Class 9 — different classes mean different DG packaging certificates, maritime declaration forms and carrier DG application processes.
2. DG packaging certificate. UN2794/2795 wet batteries and UN3171 usually require a DG packaging certificate; UN2800 claiming the SP238 exemption needs no certificate, but keep the non-spillable test evidence for inspection.
3. Short-circuit protection is mandatory. Regardless of the entry, exposed terminals must be insulated (insulating tape / terminal caps / individual packaging) to prevent short circuits in transit.
4. Marking and labelling. UN2794/2795 may be labelled at the pallet level under SP295; UN2800 (when not exempted) and UN3171 carry the appropriate class labels as required.
5. Maritime declaration. Submit the DG declaration to the maritime authority before loading, providing the UN number, proper shipping name, class, MSDS, etc.; UN3171 vehicles also need a short-circuit prevention statement and battery installation statement (subject to the practical requirements of the port, e.g. Shanghai).