unfortunately there is no link to this document. What document are you reffering to?This document on page 10 outlines some of the details
The document I cite is online @https://pe.usps.com/text/pub52/pub52c3_028.htm
349.222 Lithium-ion (Rechargeable) Cells and Batteries — Domestic
Small consumer-type lithium-ion cells and batteries (also called secondary lithium cells or batteries) like those used to power cell phones and laptop computers are only mailable domestically under the following conditions. See 622 or IMM 135.6 when mailing batteries internationally or to and from APO/FPO/DPO destinations.
1 General. The following additional restrictions apply to the mailability of all secondary lithium-ion or lithium polymer cells and batteries:
2
1 The watt-hour rating must not exceed 20 Wh per cell.
2 The watt-hour rating must not exceed 100 Wh per battery.
Later floyd