Battery Pre-Shipment Inspection: What to Actually Check
A working checklist for LiFePO4 power stations and BESS. Written for buyers who will open the carton and test the unit themselves, or who need to tell an inspector exactly what to look for.
Why Battery Inspection Is Different
You cannot see the defect. A power station that looks perfect can have mismatched cells, a BMS that never trips, or 12 percent less capacity than the label claims.
With most consumer goods, inspection is visual: stitching, paint, printing, whether the box is dented. With lithium batteries, the failure modes are electrical and invisible. That is why a proper pre-shipment inspection for this category has to include measurement, not just a look-over.
The three that matter most, in order: actual capacity, cell consistency, and whether the BMS protection actually trips. Everything else is secondary.
Part 1 · Electrical Checks
These require instruments. A visual inspection cannot substitute.
| Check | How it is done | Pass criteria |
|---|---|---|
| Actual capacity | Full discharge at 0.2C, measured Wh vs nameplate | Within ±5% |
| Cell internal resistance | AC internal resistance meter, all cells in a pack | Spread under 10% within a pack |
| BMS protection | Over-charge, over-discharge, over-current, short circuit, temperature | Every function trips and recovers |
| Output waveform | Oscilloscope at 50% and 100% load | Pure sine, THD within spec |
| Rated power | Resistive load ramp to rated and to peak | Holds rated; peak within stated seconds |
| Thermal at full load | Continuous run at rated power, measure case and exhaust | Within design limits, no derating |
On capacity testing: test at 0.2C, not 1C. A 2048Wh pack discharged at 0.2C should give roughly 2048Wh; at 1C it may give noticeably less purely from rate effects. If your inspector does not state the discharge rate, the number is not comparable to anything.
Part 2 · Safety & Documentation
The paperwork has to describe the thing in the box. This is where most problems hide.
| Item | What to look at | Red flag |
|---|---|---|
| UN38.3 test summary | Document lists the exact cell and battery type | Model on paper = model in carton |
| MSDS | Current revision, matches the cell chemistry | Consistent with the unit |
| Shipping marks | UN number, lithium battery mark, orientation arrows | Correct for air and sea |
| Packaging drop test | Drop from the height your forwarder requires | No cell damage, no fault codes after |
| Carton & label check | Model, capacity, warnings, plug type, serial range | 100% match to the PO |
How Many Units to Check
AQL sampling, in plain terms.
AQL (Acceptable Quality Limit) is a sampling standard, not a guarantee. It tells you how many defects a plan tolerates before you reject the lot. For power stations, most buyers use General Inspection Level II with Major 2.5 / Minor 4.0.
| Lot size | Sample (Level II) | Major 2.5 allows |
|---|---|---|
| 20 units | all 20 | 0 defects of consequence |
| 51–90 | 13 | 1 |
| 151–280 | 32 | 3 |
Critical defects are zero-tolerance regardless of AQL — a BMS that does not trip, a missing UN38.3 summary for the cell used, or an exposed conductor. Do not accept a lot because the math allows three majors; a safety fault is not a "major".
Our Own Procedure
Same list, applied to every batch before it is packed.
We run the checks above on every order, photograph each step, and send the record before the goods are closed. You approve the goods, not the promise. The process itself is described on the pre-shipment inspection page.
If you already have your own checklist, send it and we will run that instead — provided the tests are within what the unit is designed for and do not require destructive sampling.
Questions Buyers Ask
Including the one about UN38.3 that trips people up.
Does a UN38.3 report mean the product is certified?
No, and this is a common misunderstanding. UN38.3 is a transport test requirement for shipping lithium batteries — it confirms the cell or battery passed eight tests in the UN Manual of Tests and Criteria. Your forwarder needs it. It does not replace CE, FCC, IEC 62133 or UL requirements, and it is not a product safety certification.
What should be checked before shipping lithium batteries?
At minimum: actual capacity against nameplate, cell internal resistance consistency, every BMS protection function, output waveform under load, thermal behaviour at full load, packaging drop test, and a UN38.3 test summary that lists the exact cell type inside. Documentation and physical unit must match.
What is AQL and which level should I use?
AQL defines how many defects a sampling plan tolerates. For power stations most buyers use General Inspection Level II with Major 2.5 / Minor 4.0. Critical defects — safety faults — are zero-tolerance regardless of the AQL number.
How is capacity actually verified?
By a full discharge at a defined rate, usually 0.2C, from full charge to cut-off, comparing measured watt-hours to the nameplate. About 5 percent tolerance is common. Testing at 1C gives a lower number and is not comparable.
Can inspection be done without visiting the factory?
Yes, and most small orders are. A third-party inspector, or a supplier-run inspection with photo and video evidence of each step, is standard. What matters is that the test is defined in advance, recorded, and that you approve the goods before they are packed — not after.
Want the checklist as a file?
Tell me which model you are buying and I will send the inspection record format we use, plus the document set that ships with each order.