To the thread's headline question, "does the plug in charger go bad," the answer is "yes." A charger is an electronic device, and electronic devices can go bad.
What I think you really meant to as was "Is it
common for the Note II's stock charger to go bad?" And the answer to that is "no"... but it's not
unheard of, by any means. And with regard to your purchasing what at least
appears to be a Samsung-branded factory replacement on such as Amazon,
be careful! Most -- and by that I mean so many that I could almost say "all" -- of those chargers are cheap Chinese knock-offs, illegally bearing the "Samsung" brand name; and, to the last of them, they can barely deliver even an amp, must less the full 2.1 amps. So stay away from those!
Sadly, if you want a Samsung-branded 2.1 amp charger for the Note II, you pretty much have to go to the Samsung website and purchase it -- for its outrageously-high price -- from there, as an add-on for the Note II. However, there are reasonably-priced -- usually two-USB-port chargers for both 120VAC wall outlets, and 12VDC automobile cigarette-lighter-outlets, by... oh... say... Ventev or Anker, for example, just to name two of the more reliable makers -- which deliver a full 2.1 amps from at least one of their ports; and since many of them are rated at 3-point-something to 4-point-something amps, combined, out of both USB ports, they can also simultaneously deliver another amp or amp-and-a-half out of their 2nd USB ports so that you can charge a second (smaller than a Note II) phone.
The thing is, though, that not just the charger, but also the cable, must be capable of handling the amperage that the phone's trying to draw... in the case of the Note II, a whopping (by phone charger standards) 2.1 amps. Obviously, the cable that came with the phone and its stock charger is capable of handling the 2.1 amps; however, not every USB charger/data cable -- even those made for Samsung Galaxy family phones -- can handle a full 2.1 amps...
...and some of that is because of the light weight of the stranded wires inside the cable; and some of that is because of that, combined with the cable being maybe too long. A lighter-weight cable can handle a full 2.1 amps if it's very short; and even a heavier cable cannot if it's too long. The shorter the cable, the less you have to worry so much about whether the wires inside are heavy enough; but if you insist on using a long (6- to 10-foot or longer) cable, then its wires, inside, must be heavy, indeed, in order to handle 2.1 amps.
There are also cables, out there, made expressly for charging, but which have no data capability... like the "charging only" cables made by MediaBridge, or Belkin, for example. The USB both charging and data cables made by EZOPower tend to be very high quality (for the price), and can often -- especially at the shorter lengths -- be counted on to be able to handle the higher amperages...
...something it's good to know, also, because the same cheap Chinese knock-off problem which exists regarding Samsung-branded chargers also exists with Samsung-branded cables. To get cables capable of higher amperages, you've got to get the known-to-be-of-higher-quality third party ones... from such as Belkin or EZOPower, for example, just to name two makers.
If you're not using the cable that came with the Note II and its 2.1 amp charger, then there's no telling what is the amperage capability of that cable you're using... especially if it's longer. All USB data/charging cables for cell phones are not equal; and if you're using a cheap and/or too long cable that's not the one that came with the phone and its charger (and remember that if you've got a few of 'em lying around, it's very easy to get 'em mixed-up), then that could, indeed, account for slower charging.
But so could, as your headline asked, a charger that's going bad... and they
can go bad.
So, too, can the charger port on the bottom of the phone... the place where you plug the small end of the charger/data cable. Gratefully, the part (at least if it's aftermarket/third-part) is
very inexpensive; but you shouldn't try to replace it yourself... it's very tricky to open-up a phone and not screw things up. Definitely take it to a qualified repair person if you want to get that part changed...
...but, of course, don't do even
that until you determine that that's really the problem. I'm just sayin' that that could be what's gone bad, too.
That's incorrect. Any charger -- of any amperage --
made for use with any Samsung Galaxy family phone (and that's the operative phrase) will charge a Note II. The charger's rated amperage (as well as the weight of the cable; more on that in a moment) will determine how fast.
The charger that comes with a Note II is a 2.1 amp charger, and so it will charge the Note II t he fastest (the Note II will only draw a maximum of 2.1 amps, so a higher-amp charger will not speed things up); however, even an old Samsung Galaxy "Captivate" .7 amp charger will fully charge even and almost-dead Note II, but simply slower. As long as one's charging overnight -- allowing all those hours to charge -- then the truth is that any charger, as long as it's made for a Samsung Galaxy family phone, will fully charge a Note II.
And many experts in how batteries work will tell you that a battery routinely charged more slowly than it's capable of being charged wil cause it to give-up its charge less readily, and make the battery seem to last longer. My experience is that if that's true, it certainly isn't by much; and so re-charging at the full 2.1 amps is fine... especially with lithium ion batteris of the type that come in the Note II.
Agreed; and I've just written, above, about why.
Agree, yet again; and I've herein, above, covered why.
If you bought a Samsung-branded battery from such as Amazon, then it may be very sub-standard... yet another cheap Chinese knock-off; and, if so, then that, right there, could be the problem. If you insist on the battery bearing the Samsung brand, then the only truly safe way to get one is, again, to go to the Samsung website and pay through the nose for it; or you could take the phone to an
AT&T Device Support Center (not a store, mind you, but a true
device support center) and they can give or sell you a Samsung-branded battery that's really made by Samsung; and, as long as you're there, you could have them completely troubleshoot the slow charging problem.
If a third-party/aftermarket battery will do, then such as the RAVPower branded one (3100mAh) is my number one choice; however, that said, my second choice is QCell; and then Anker makes a decent one, as does the earlier-mentioned EZOPower; and some other well-known and reliable brands include Onite, ZeroLemon and Hyperion. Get the RAVPower, though (for typically only around ten bucks) and you'll be
very happy!
Again,
this Anker (the port on it labeled "Apple" puts-out a reliable 2.1 amps, even with something plugged-in to the other port), or
this Ventev (which delivers only 2.1 amps across both ports, so only one port could be used with the Note II plugged-in to it), or
this Ventev (which can simultaneously deliver 2.1 amps out of both ports, so you could simultaneously charge two Note II's). I've used all Anker and Ventev products, and they alwyas deliver their rated amperages out of all ports... with no Chinese knock-off problems! Or, of course, there's always
this.
Well, I've herein talked about the possibility of some of all that not being true, and what it could mean; and what you should do to correct it. Beyond that,
this app (though preferably
the PRO version) will help you to see exactly at what amperage your phone is being charged... either at any instant, or over time. It's simple, but very slick and useful. The problem is that that still won't tell you why...
...and so maybe a trip to the device support center is ultimately what you should do. However, if you could talk a salesperson at an AT&T store into letting you try charging your phone using a brand new charger and cable from an unsold phone, then that aforementioned app will let you see, in realtime, in an instant, whether even a new charger and cable is doing the job. If it's not, then perhaps the earlier-mentioned port is bad...
...though before you go in any of those directions, properly power the phone off; then put your old battery (the one that came with the phone) back into the phone; and then power the phone back up and let it finish booting-up... give it a few minutes to ensure that it's still not loading things; then properly power it down/off; then remove the battery and go get coffee... at Starbucks... preferably one on the other side of town, while that phone sits, with no power applied to it at all... for... oh... let's say a half hour... maybe even an hour... believe it or not.
Then put the came-with-the-phone-battery back in it; power it up; wait for it to finish powering-up; and then try what you believe is the original factory charger and cable that came with the phone, and see if it suddenly charges faster. You could also use the aforementioned app to see what is it's true charging rate.
If you've been doing things like not power-off the phone properly, or swapping-in/out batteries without proper power-off/on, or if you've simply plugged-in the charger, then unplugged it, then plugged it in again too quickly, or any of a number of other little things like that...
...then the phone can become "confused" about whether it's plugged-in to a charger or to a USB port on a computer; and it definitely doesn't charge at 2.1 amps if it's thinking it's plugged-in to a computer's USB port. Definitely determine if that confusion has, for whatever reason, kicked-in. Doing the little exercise that I herein described (wherein I said to go get coffee) can help with that one...
...as can the infamous factory reset. When all else fails, back-up everything on the phone, and then do a factory reset to restore the phone back to however it came from the factory.
There are more things you can try, but I'm guessing that this post has pretty much filled your plate.
Let us know if you need additional suggestions/help.