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[SOLVED] Bluetooth Speaker battery issue

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Ollie Elmes

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Hi everyone,

I'm a complete electrical novice but I have a solder, a power meter and lots of enthusiasm to learn!

I have a broken bluetooth speaker that arrived broken from e bay but I got a replacement sent out, so I'd like to try fix the original as a project.

The issue is, it doesn't charge.... It was working when I first got it but it would power off after 10 seconds till eventually it wouldn't power on at all. When you plug in the usb to charge it, no light comes on to indicate charging.

I've taken it apart, and feel I have 2 options...

1) try and find the replacement circuit board, where the micro usb plug is located OR

2) buy x2 3.7V mAh 2000 (what it currently takes) rechargeable batteries. The batteries it came with our the flat lipo type and I'm unsure how to charge them without using the in built micro USB plug. If I purchased x2 cylindrical style batteries that I could charge externally, then I'd be up and running. I just can't seem to find that style of battery at 2000 mAh.

This is the type of battery with the same connecter


If I rigged up a 9V battery to this, would that blow the circuitry? Do I need to find exactly 7.4V at 2000 mAh to make it work?

I should also add, there appears to be no damage to anything that the eye can see on this, internally and externally.

This is the speaker


Thanks in advance,

Ollie from the south of England
 

Audioguru

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A lithium battery is extremely dangerous. If you charge it with the wrong voltage or current It could explode and/or catch on fire.
You do not know if the problem is with the battery or with the charger so why buy 2 batteries?
You do not know if the battery has a "protection" circuit in it and if you replace one that has it with a battery that doesn't have it then it might blow up/catch on fire.

The lithium battery is 3.7V, a 9V battery voltage is way too high and will destroy the circuits in the speaker.
Why are you talking about 7.4V when the battery is 3.7V, 7.4Wh (NOT VOLTAGE!). 3.7V x 2000mAh= 7.4Wh.
 

Ollie Elmes

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Thanks for your reply.

You do not know if the problem is with the battery or with the charger so why buy 2 batteries? Because I can bypass the charger and just recharge the new batteries externally.

Why are you talking about 7.4V when the battery is 3.7V, 7.4Wh (NOT VOLTAGE!). 3.7V x 2000mAh= 7.4Wh. You've kind of answered your own question there, there are 2 batteries, each 3.7v so a total of 7.4v is needed to power the device. Or is that not correct?

What would you recommend?
 

Audioguru

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Why would the speaker use TWO separate batteries when a battery with 2 cells in it costs less??
Oh, maybe the factory had many single battery cells for a drone that they do not make anymore. Then in series the battery would be 7.4V.
Oh again. Maybe the circuit is designed for single 3.7V battery but its charge did not last long enough so they put two batteries in parallel??

The batteries and charger for them from RS are way overpriced.
 

Ollie Elmes

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@Audioguru I'm not sure, having googled them, they do seem very popular with drones. RS? @KlausST I'll take some photos tonight and post them in the morning.
 

Audioguru

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My local hobby store sells drones and batteries for them at reasonable prices.
Amazon also sells the drones and batteries but also at very high prices.
 

Audioguru

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It uses two batteries that are thin enough to fit behind each speaker.
It uses USB which is only 5V to power the charger for the two batteries that are probably in parallel.
 

Ollie Elmes

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Does parallel mean that the battery power is used simultaneously? What would you suggest I try, having seen the photos? Thanks
 

KlausST

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Hi,

* do a battery voltage measurement (wihtout USB charger plugged in)
* do a battery voltage measurement when USB charger is plugged in and powered
* do step by step voltage measurements from UCB connector to battery on the PCB following the traces.

Tell us the results.

Klaus
 

Ollie Elmes

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Thanks @KlausST. Bit of a beginner with the power meter, what settings should I use? I might take a video
 

KlausST

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Hi,

not POWER.
I said "Voltage measurement" thus use the "Volt setup for DC".

There are many internet videos how to use a voltmeter. I couldn´t make a better one ;-)

Klaus
 

c_mitra

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You need to follow #11; that is the best advice; begin at the beginning.

1. You have a digital multimeter, right? Use that to measure the DC voltage. Use the DC volt function. If it is auto ranging, that is all you need to do. Do not forget to power on the multimeter first.

2. Select battery 1; (say the left one):there will be two wires connected to the battery. Most likely they will be color coded: red and black. See where they are going. Use your multimeter to read the voltage at the two points. It should be around 3.7v. Note the exact value.

3. Repeat the same with the other battery.

4. Is there a power on switch? You need to figure out whether it is a software or a hardware switch.

5. Next look at the charger: the charger is a 5V and use a fine wire to check whether the charger is giving the right voltage (you need to connect to the plug). You will have to wrap some fine wire on the probes (of the multimeter) to see the voltage.

6. Then connect the charger and see the battery voltage. Is there any LED on the PCB? that should light up!

Please come back and report the results.
 

Ollie Elmes

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Hi @c_mitra Thanks for your list. Yes, I do have a digital multi meter, I've watched a video now, so combined with your guidance I should be good to go.

I'll post back soon.

Thanks
 

Ollie Elmes

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Hi @c_mitra Thanks for your list. Yes, I do have a digital multi meter, I've watched a video now, so combined with your guidance I should be good to go.

I'll post back soon.

Thanks
--- Updated ---

So I went to do the voltage test last night, I plugged the speaker into the mains, I poked around a bit, and then I realised the charge light was on!
There was obviously a loose connection somewhere. Anyway, I’ve put it back together now and it still charges.
Thanks for everyone’s help.
I still have a guitar pedal from the 70s to fix, so I’ll post a video about that soon.
 
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