[Solved] Bluetooth speaker - information about low battery and auto power off

Good day.
I have a bluetooth speaker before Manty's branding - MA407.
Unfortunately, for some time constantly informs about the low battery and turns off after some time. The battery is not in it, I pulled out the external cables and powered everything using my own Li-Ion 3.7V.
Despite the voltage of 3.9V on the battery, the signal from the speaker constantly informs about its discharge (I checked various batteries, without changes).

I would like to get rid of this problem somehow, bypass built-in discharge protection.
I attach a photo of electronics:


I would be grateful if you would like to help, best regards.

Hello

Domen4 wrote:

Unfortunately, for some time constantly informs about the low battery

what caused such a message to be broadcast?

Domen4 wrote:

and after a while turns off

I propose to see what IC is included in the battery power supply-charging system, look for its data and on this basis to see how it works.

antek1cza wrote:

what caused such a message to be broadcast?

I would like to know it myself, above 4V it worked rather normally, while at 3.9V it started to turn off, from time to time there was a message about a low battery ..

antek1cza wrote:

I propose to see what IC is included in the battery power supply-charging system, look for its data and on this basis to see how it works.

The whole RDA5851S chip takes care of it, from what I read it in total it performs all the functions of this speaker. There is no minimum power supply, only a maximum 4.5V.

Domen4 wrote:

antek1cza wrote:
what caused such a message to be broadcast?
I would like to know it myself

After all, a colleague has already answered this himself

Domen4 wrote:

above 4V it worked rather normally, while at 3.9V it started to shut down

That is, you need to power it with 5V specified on the miniUSB socket (or pin on the board). Which is not surprising as if after reading the original instructions that I attach.

antek1cza wrote:

That is, you need to power it with 5V specified on the miniUSB socket (or pin on the board)

Of course not. The miniUSB power supply must be 5V, but the pins on the board are for connecting a battery, I can't give 5V there, because the whole system will probably burn. I am not interested in the miniUSB socket itself - the FM radio does not work, my powerbank sends only interferences, only with the computer is good, but then there is no mobility.
Therefore, I only have to power directly from the 3.7V Li-Ion battery, unfortunately the message about its discharge appears too early.

However, I decided to follow the Lord's advice @ antek1cza . The loudspeaker was activated after applying 5V voltage directly to the motherboard (instead of the battery).
It acted noticeably louder, even crackled at the highest volume. After about five minutes it turned off without any message and unfortunately I can't start it anymore. I will only add that it was warm around the record.
What can I do to bring him back to life again? After connecting the 5V power supply to the Mini USB also no signs of life ..

Dear friend, you haven't read exactly what I wrote:
1.

antek1cza wrote:

it must be powered with 5V specified on the miniUSB socket (or pin on the board)

The miniUSB socket is soldered to the pins that are on the board and about these pins I wrote.
Simply put the miniUSB plug with a 5V power cable or if you don't want to have spiders (wires) you can solder the wire directly to the pins of this socket!

2.

Domen4 wrote:

The miniUSB power supply must be 5V, but the pins on the board are for connecting a battery, I can't give 5V there

And that's completely right.

3.

Domen4 wrote:

all I have left is a direct 3.7V Li-Ion battery supply

And I wrote about it in post no. 2 where I propose

antek1cza wrote:

I propose to see what IC is included in the battery power supply-charging system, look for its data and on this basis to see how it works.

He found a colleague important information about this IC that says

Domen4 wrote:

There is no minimum power supply, only a maximum 4.5V

and it's strange that he didn't follow her! And it is not about exceeding the maximum supply voltage of the integrated circuit !!!
By the way, it is a pity that the datasheet of this system was not placed here.

4. The system located between the USB socket, battery and IC has not been analyzed, which task is, among others, to reduce the 5V supply voltage to a level adequate to the battery charge status.
To sum up, the miniUSB socket should be 5V all the time and the battery will rise and fall depending on the degree of its discharging and charging, but certainly there is no 5V (on the battery).

5.

Domen4 wrote:

However, I decided to follow the advice of Mr. @ antek1cza

He did not understand what my colleague wrote about in post no.7 (additional explanation now in p.1) and also noticed in the datasheet of the system where he writes that the maximum voltage is 4.5V.

6.

Domen4 wrote:

After about five minutes it turned off without any message and unfortunately I can't start it anymore

It looks like the IC has fallen . Maybe there is a protection in the form of a fuse (it can be similar to an SMD resistor) so it's worth seeing.

7. I propose to check all the elements that are in the battery circuit.
If you manage to restart it in no case on the IC system itself and also on the pins under which the battery is connected should not give more voltage than 4.2V (maximum voltage on the battery after charging).

8. Once you have managed to restart the speaker, I recommend following the circuits from the USB socket, battery to IC.
It will also be easier when the diagram of this part of the speaker is drawn.
Well, unless someone has or somewhere is his whole scheme.


p. forumnot yourself

Domen4 wrote:

advice of the Lord @ antek1cza

We "reign" only friends well, unless you don't want to.

Thank you buddy @ antek1cza for extensive message.
I checked everything thoroughly again. The speaker, surprisingly, works, lay down a little, cooled down and returned to efficiency.

I was looking for patterns. I found on Chinese pages:


I am not sure if they all refer to the same, however I hope they are helpful.
I would like to point out that I do not know their analysis, so I completely do not understand it.

RDA5851S datasheet available here: link

Connecting to a Mini USB cable is unfortunately not a solution for me, because my powerbank is interfering with the FM radio.
Anyway, at higher volumes the loudspeaker switches itself off (at higher frequency sounds).
I would still like to know how to clear the low battery message and the device to turn itself off.
Thank you.