I ship all the time, the USPS requirements are that Li-ion cells be inside a device. I know they get shipped in the little plastic boxes, and all sorts of ways, but the rules at USPS are quite clear. Even on Click-and-ship. The people at the counter usually ask if the package has Li-ion cells, and if you say yes, they ask if they are inside a device for protection against water damage and/or crushing. Just because the rules are always broken, doesn’t change the rules.
There are a lot of fine details, but primarily…
1. When a mailpiece limitation of 8 cells or 2 batteries is applicable, a mailpiece may contain either 8 cells or 2 batteries, not both.
2. Each cell must not contain more than 1g lithium content.
3. Each battery must not contain more than 2g aggregate lithium content.
4. Each cell must not exceed more than 20 Wh (watt-hour rating).
5. Each battery must not exceed 100 Wh.
6. Each lithium metal or lithium alloy cell or battery must not exceed 0.3 gram of lithium content.
7. Each lithium-ion or lithium polymer cell or battery must not exceed 2.7 Wh.
Yes, they are to marked ground only, no air, which throws 2-Day Priority Mail out.
General description of mailing rechargeable Li-ion cells through the USPS is as follows…
General. The following additional restrictions apply to the mailability of all secondary lithium-ion or lithium polymer cells and batteries:
The watt-hour rating must not exceed 20 Wh per cell.
The watt-hour rating must not exceed 100 Wh per battery.
Each cell or battery must meet the requirements of each test in the UN Manual of Tests and Criteria, part III, and subsection 38.3 as referenced in DOT’s hazardous materials regulation at 49 CFR 171.7.
All outer packages must have a complete delivery and return address.
All packaging must meet all applicable requirements specified in 49 CFR 173.185.
Except for mailpieces containing button cell batteries installed in equipment (including circuit boards), or no more than 4 lithium-ion cells or 2 lithium-ion batteries installed in the equipment they operate, mailpieces containing lithium-ion batteries must bear markings that indicate that the package contains lithium-ion cells or batteries; that the package is to be handled with care and that a flammable hazard exists if the package is damaged; that special procedures must be followed in the event the package is damaged, to include inspection and repacking, if necessary; and a telephone number for additional information. Mailers may use a DOT-approved lithium battery handling label, in domestic air or surface transportation, to meet these marking requirements provided all required elements are included.
Except for mailpieces containing button cell batteries installed in equipment (including circuit boards), or no more than 4 lithium-ion cells or 2 lithium-ion batteries installed in the equipment they operate, mailpieces containing lithium-ion batteries must also be accompanied by a document that indicates that the package contains lithium-ion cells or batteries; an indication that the package is to be handled with care and that a flammable hazard exists if the package is damaged; an indication that special procedures must be followed in the event the package is damaged, to include inspection and repacking, if necessary; and a telephone number for additional information.
Notice the discrepancy regarding “20 Wh” in line 4 vs “2.7Wh” in line 7? As with most things government, there are enough contraindications to pretty much flag anything. Tricky, as I don’t know that I’ve ever received Li-ion cells fully meeting the requirements.
So now you know. (part of the story, there’s a lot more)