YES...you can ship LiPo batteries via Priority Mail within CONUS

rangemaster728 · Nov 4, 2018

In a review of the US Postal regulations, Division 9D, you can ship LiPo batteries installed in (and/or packed with) a Spark or Mavic by Priority Mail within the continental US.

Batteries for/with other drones may qualify for this...haven’t checked yet but the key is the number, types and mAH capacities of the individual cells in the packs.

I sat down with the local Postmaster and reviewed the regs, and ship drones/batteries regularly by Priority Mail.

There are limits to the type and number of batteries that can be shipped in this manner, and they must be properly packaged.

The package also needs to have this label, which you can download (or copy the pic below and print it out and insert your phone number):

Full info here:
Publications

Like most federal regulations it’s a long read LOL.

I also discharge all the batteries to storage level prior to shipment to lessen the energy contained for safer transport

Former Member · Nov 4, 2018

The read is not too bad if you start at:

349.222 Lithium-ion (Rechargeable) Cells and Batteries — Domestic

a. General. The following additional restrictions apply to the mailability of all secondary lithium-ion or lithium polymer cells and batteries:

1. The watt-hour rating must not exceed 20 Wh per cell.

2. The watt-hour rating must not exceed 100 Wh per battery.

c. Watt-hour (Wh) means a unit of energy equivalent to one watt (1 W) of work acting for one hour (1 h) of time. The watt-hour rating of a lithium-ion cell or battery is determined by multiplying the rated capacity of a cell or battery in ampere-hours, by its nominal voltage. Therefore, watt-hour (Wh) = ampere-hour (Ah) x volts (V).

MP battery = 3,830mah, 3 cells, 11.4 volts total, 3.8 volts per cell

3.8 amps x 3.8 volts = 14 wh which is under the max per battery

The limitation might apply since a shipper is limited to 8 cells or 2 batteries total in one package, whether installed or not installed in a drone.

and then Exhibit 349.222 Domestic Lithium Battery Mailability