I've been searching for this answer, but I keep getting conflicting information. When the Switch is unplugged, does it charge the Joycon controllers?

So far the answers I've found are:

  • They don't charge at all
  • They do charge
  • They only charge up to 50% - Source: 1 2

Which is correct?

2 Answers

I tested this personally, and the most correct answer is: They charge up to about 50% and then stop.

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I let the JoyCons completely discharge until they would no longer function, then attached them to the console in handheld mode. As you can see in this picture, the JoyCons are indeed marked as charging. Ultimately, they got up to each half full, but there is no way to tell the exact percentage with the current GUI.

My best guess is that the Joycon batteries are simply wired in parallel with the main battery so they charge up to, but never exceed, the voltage of the main system battery because the system does not boost the voltage to charge them which is why Nintendo doesn't list this as an official charging method.

Official charging behavior is, per Nolanar's answer, console must be connected to the AC adapter.

This does not mean it is exclusively ONLY on AC and nothing else ever works. It simply means it is the officially supported method.

If you contact Nintendo support, that will be their answer and that's what they will ask you to do.

Just because the Joy-cons are able to charge without AC through the console fresh-out-of-the-box, doesn't mean it has to. No support documentation says that is the expected behavior, so it is possible that this behavior can change depending on the health of the battery or future updates.

Further explanation:

My guess for all this is due to the nature of Lithium Ion batteries. Li-Ion batteries degrade. Under perfect storage condition (storage, not usage), Lithium batteries will end up with about half its total maximum capacity after 2-3 years, from simply existing. Normal usage will degrade this faster (1.5 yrs to 2 yrs). Incorrect usage (deep discharge, overcharge) degrades this much, much faster, and possibly permanently damage it after only one cycle. However, manufacturers know users are idiots and won't let you damage the battery though, so that's why consoles will shut off automatically even though it still has power. Of course, if you're really dumb, and insist on repeatedly powering on the device when low in power, then you can fully drain the battery, but that's your own fault.

As the main console's battery goes through usage cycles, the battery capacity will lower, and the console will have data on how long it lasts. Internally, it has the option to change its charging behavior for the Joy Cons to avoid draining the console's battery. By not telling you it is capable of charging the Joy Cons without AC, it does couple of things:

  1. Train the user to properly charge the console
  2. Option to disable the function if it proves that users are too dumb
  3. One less thing to support and document

The fact that it charges without AC is simply a bonus. If they didn't document it, it isn't an accident, but a deliberate business decision. You won't find official documentation on it because they don't want to officially support it.

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