How to replace the battery with a larger one on the bluetooth receiver?

Question

Electronics

All the best!
Brief background: I bought a bluetooth receiver on Ali Express so that I could listen to music from my phone in the car without a wired connection. A year later, the microUSB connector fell off on the receiver. I repaired the connector, but in the process of repair, the idea came to me to replace the battery with a larger one, since the regular one lasts no more than two hours of work. Moreover, I just had an ownerless battery from the Samsung Galaxy Tab 4 tablet in good condition.
Actually the question is: since I have not done anything like this before, I have no experience, but I would like to know how this can be done, what are the subtleties when replacing and how to find out if a new battery is suitable or something else is needed?
Nothing is known about the regular battery, there is no marking on it, it is soldered directly to the board. On a Samsung battery 4000 mAh, 3.8 v. There is a black casing at the end, some kind of board is felt through it, I can assume that this is a charge / discharge controller.
PS Since the pictures for some reason do not want to be attached to the message, I uploaded them to the dropbox:

1. https://www.dropbox.com/s/obgu94q0w8dp335/20191006...
   
2. https://www.dropbox.com/s/mgho04rt36ufino/20191006...
   
3. https://www.dropbox.com/s/62muq8pqz7evgpp/20191006...
   

Thanks in advance!

Answer 1

The board at the end is a protective board that protects the battery from overcharging and overdischarging.
Actually, you determine the polarity of the standard battery, the battery from the Samsung and solder it, observing this polarity. Actually, everything.
Naturally, the receiver will take longer to charge, but it will also work longer.