FYI
Safety Notice — United Arlines
Effective July 9, 2018
Lithium batteries that are installed in any checked or carry-on baggage must be removed by the customer.
Once removed, these batteries can be transported on board.
Smart bags that do not have a removable battery cannot travel on any United or United Express® flights.
Reference
https://www.united.com/CMS/en-US/travel/Pages/BaggageCarry-On.aspx
I think that applies to luggage that has a lithium-ion battery installed in it, not laptops. They specifically say installed in baggage and refer to “smart bags”
That is how I read it, too:
Effective July 9, 2018, lithium batteries that are installed in any checked or carry-on baggage must be removed by the customer
I don’t read that as batteries inside computers/phones. If so, no apple product could go on a plane!
I have a non removable battery in my ‘laptop’ if they were to deny it I would just turn around and go home.
But it does read as smartbags, not laptops. You can’t put a laptops in checked bags now so they have to be carry on, if I remember reading correctly.
The battery in my MacBook Pro isn’t removable even if you open the case! It’s glued in and very difficult to replace (thank you Apple).
Won’t be an issue when flying, and non-removable batteries are now essentially the norm in high-end laptops, not just from Apple.
For overseas attendees who got used to other voltages then 110 volts, check this website:
Nearly all laptop and phone chargers are able to accept 110-240 volts ac and 50-60hz. Check the label on your charger, but it is extremely likely all you need is a plug adapter.
Therein is the problem with assumptions by the author of the UA Safety Notice.
The author assumes all readers are aware of the existence of bags that have built in batteries.
I’ve never heard of such a thing before today.
I read “Lithium batteries that are installed in any checked or carry-on baggage” to mean a battery installed in any device inside the baggage.
Before posting, I called UA this morning to confirm.
The UA support person immediately said,“Yes, the battery must be removed from the laptop.”
In a second call to UA this afternoon, UA says the battery does not have to be removed from the laptop.
In this call, the UA support person checked with two supervisors.
Post title edited … Sorry for the false alarm.
They can have my lithium battery when they tear it from my cold, dead laptop!
Obviously, I need to get out more as I’m dumbfounded by the existence of battery powered suitcases.
Next, they’ll figure out a way to utilize a microchip in an Estwing® framing hammer.
Too late! They already have. 
To my knowledge there is a limit as to the capacity of Lithium-Ion batteries that may transported by air as well.
But remember that, in most states, securely-cased and unloaded handguns may be included in your checked baggage, provided that any related ammunition in also either in that case, OR if > 0.75 caliber and/or not shotgun shells, it is carried in a separate secure-case, also in your checked baggage !
So at least you can’t carry them onto the plane !!
Also remember that the rules relating to the carrying of concealed firearms varies from state to state !!!
Nothing any consumer electronic device would exceed. Seriously. There is no conceivable issue here flying with batteries as long as you show them at security.
Are there any rules against Nerf guns?
Yep.
Here’s the relevant TSA web page.
What Can I Bring?
Planning ahead and packing properly can facilitate the screening process and ease your travel experience at the airport. Know what you can pack in your carry-on and checked baggage before arriving at the airport by reviewing the lists below.
https://www.tsa.gov/travel/security-screening/whatcanibring/all
To confirm, I have travelled on three United roundtrips since July 8. No issues with United or TSA with batteries in my laptop or phone. Cheers to a great Boot/Basecamp.
One notable exception, the self-igniting Samsung Galaxy Note7
DOT Bans All Samsung Galaxy Note7 Phones from Airplanes — October 15, 2016
Too bad for passengers of flight 93