I had a pile of switch batteries sitting here and decided to have a go at trying to fix them.
(for those who don’t want to read the whole thread I had 8 knackered batteries and managed to recover 6).
So the symptom of all these batteries was the switch would show a charging Icon on the screen but the switch wouldn’t charge the battery up. No amount of power off’s, factory resets etc would make these work. Even leaving it to charge for hours made no difference.
To do the same technique as I use you will need a TP4056 power charger board and I bought 5 of these in a pack for about £6 ($10 approx) from Amazon
You will also need a USB voltage/Amp monitor but most people will have one of these as its the same one you use to check the volts and amps going into a Switch.
To set this all up you will need to solder a red wire to the B+ point on the TP4056 and a black wire onto the B- point on the TP4056. There are 2 other solder points on this board (out+ and Out-) but don’t use these points.
The setup will be 5v PSU in a wall socket going to the USB volt/amp monitor and a USB cable going from this to the Micro or Mini USB socket on the TP4056. The TP4056 can be bought with either Mini or Micro USB sockets and it’s your choice which one you want to use.
With the power off at the wall socket plug the red cable from the TP4056 into the outer red cable on the Switch battery connector. Plug the black cable from the TP4056 into the outer black cable on the Switch battery connector.
To make the cable fit into the Switch battery plug I had to crush the end of the tinned cable but now I know this fix works I’m going to take a battery socket off an old switch motherboard and solder it to the cables on the TP4056 to make this job easier to do.
Once you are happy that the cables are connected, switch the 5v power supply on at the wall socket and check the TP4056.
There will be 3 options now that the battery is getting power:
Option 1: Red light on the TP4056 and the USB volt/amp monitor will have an ampage of somewhere between 0.90 and 0.65 amps. Voltage will be around 5V
Option 2: Red light on the TP4056 and the USB volt/amp monitor will have an ampage of 0.06. Volts will be around 5v.
Option 3: Solid blue light on the TP4056 along with a rapidly flashing red light and no ampage on the USB volt/amp monitor.
If you have option 1 leave it to charge until the ampage on the monitor reads around 0.60 - 0.65 amps. You can now plug this into a Switch and will get around 15% to 20% showing on the Switch. You can then charge as normal using the dock or Switch PSU.
If you have option 2 then you need to leave it charging for 30 to 60 minutes. Eventually it will stop showing 0.06a and switch to around 0.85 - 0.90 amps on the display. Leave it to charge until it gets to around 0.60 - 0.65 and then plug into a switch and charge normally.
If you have option 3 (Blue light) then this battery is pretty much knackered. The cells are probably ok but the circuit board inside the battery is either corroded or a component has gone. I have 2 batteries here with this problem and at some point I’ll take them apart and try to figure out a fix.
Hopefully this info will be of use to other people out there with a pile of knackered batteries.
Disclaimer: Don’t do this if you aren’t comfortable working with Batteries. There is always a chance that the batteries can catch fire if you do something wrong. If you decide to do this type of work make sure you work on a surface that is resistant to fire. I’d recommend using a Lipo battery bag to charge the batteries in