Charging chime wakes me up

If this is the "same tri-tone that one hears when plugging in the charger." the charger may be disconnecting then reconnecting at night, so it would be worth testing with a different USB power adapter and wall socket.

Do you have a Apple watch?

Do you have any third part Alarm apps installed?

I know you were talking to the OP. The point is that it is often pocket lint in the charger. It isn't a question of people not taking care of their device. It's just very easy to get stuff in there and once you do, it tends not to come out. I say this after having worked for a major U.S. cellular carrier for 20 years in a variety of customer facing positions.

Regardless of when it happens, iPhones NEVER, EVER beep when they reach full charge. They only beep when they start charging. So knowing that you should be able to troubleshoot what is removing power from the phone, then restoring it. The answer might be a periodic power company glitch as they switch power sources, or an appliance that is on the same circuit that causes the line voltage to drop momentarily when it turns on.

If you're hearing that tone, it means that, at some point, the phone disconnected from the charger and is reconnecting (or the electrical supply to the charger was interrupted but that seems less likely). If it's happening with multiple chargers, the problem most likely lies in the charging port. I'd start cleaning the port. Under a bright light, with a magnifier if you have one, use a non-conductive tool such as a wooden toothpick to gently remove any pocket lint or other debris you find. Also, remove any case you have on the phone while charging. That might be interfering with the connection.

If none of that works, make arrangements to have Apple evaluate the phone.

Genius Bar Reservation and Apple Support Options - Apple

No, I mean NEVER, EVER. It is an absolute. As I said, if you are hearing a chime it is because power has been removed and restored.

You said “tri-tone”. When you connect a phone to a USB power source it makes a single “ping”. It does not make the tri-tone alert. So if you are sure it’s the tri-tone then it has nothing to do with charging. Plug in the phone and listen; is that the ping you are hearing?

I have an older Lightning cable that when connected to a certain port on the Mac and the i8+ on the other end will chime and chime again if the USB connector is jiggled in the least bit. Will work just fine in the other ports as well as backing up and syncing. A new cable won't do that anywhere, so there's something bad in that particular connector.

if you are beset by similar cable woes, maybe the pet cat/dog/mouse/parrot makes its nightly rounds and jiggles the thing?

BORg529 wrote:

It do not matter if ends are clean! It could be the internal wiring of Lightning is breaking up. That would cause beeping, you try with another cable?

Dirt in the port is a frequent cause of this sort of thing. Less common is dirt on the ends of the cables.

You try with another genuine Apple Lightning to USB cable, to see if issues continue? If yes, go to Apple Store, or Authorized Apple Service Provider to have iPhone SE check out.

The phone will only beep when it starts charging; it does not beep when it stops. So something is causing it to lose power, then to resume charging.