I have a new (out of box, but new) rhino 2250mAh 4s 40c lipo pack I want to sell. Does anyone know if there are special rules, and what they are, when mailing LiPo's? Standard US mail, or the least expensive.

USPS will do it. I've sent them before.

A few years ago there was the superstition that your Lipo's would puff if you sent them airmail but I don't know if that is still true or not.

Officially...USPS will not ship lipos nor will any other carrier. At the end of the day, you have to lie to ship lipos. I've tried and even shipping little heli lipos was frowned upon and they sent me packing.

I'd just avoid the question...

Not true guys. I asked usps same question yesterday. You can ship Lipo just not airmail as the altitude will damage the batts

I don't know about USPS rules and regs. But I have bought lipo's directly from manufacturers, and they ship USPS...

Wrong. I've shipped lipos in the last month USPS and didn't have to lie about it. The postal clerk may have been misinformed.

A little both ways I guess. Well, I've got the battery for sale if anyone wants it. Make offers. I'll work out the shipping

They ship separate, ground only. Same with spray paint or any other aerosol product. Their considered hazardous.
When they ship from overseas, they have to come by boat, and are regulated.

The problem is the clerk (or even the Postmaster) may read the rules for shipping LiPos international (which rule specifically says: NO) and think it applies to domestic shipments. I had this problem at my local P.O. and insisted they do some more research because they seemed unable to comprehend that shipping within the same state (just happened to be the case that time) was NOT International shipping.

Yeah that is definitely false info about shipping a Lipo. My box I got 5 days ago from ups has a large yellow sticker on it saying it contains a Lipo battery

So like I thought, you still can't ship them via air Ground only.

You got it, and by the way, for all you rebels, it's a federal offense to ship hazardous materials without declaring it.
If something were to happen, and you got connected you wouldn't see your RCs except in your dreams for a long time.
Not worth saving a day or two in shipping.

I've heard of Li-Pos puffing because of altitude. I often get questioned about aeresols and liquids but never about battery packs. Good luck.

You really have to wonder how much truth (or myth) is in the statement that Lipos can't be shipped via air. I recently read an article about liPo battery use by NASA on the SPACE STATION. Seems to me if they can be used in space they can withstand the relative short flight on a commercial jet.

But I could be wrong ............ LOL