Li ion battery charger, adapting power bank

[Steve B]

hi everyone, new here!

I have some very expensive wireless gaming headphones (my daughters) which do not charge up after 1.5 years (extensive) use. I suspected the battery was dead so ordered a replacement, but after soldering it in I’ve discovered it’s probably a problem with the charging circuit? The battery had some charge from new, and using the usb charging cable activated the ‘charging’ led indicator, however after charging for 5 hours the battery has died. Topping up the battery directly from a PP3 I again tried charging with the cable cable without success. A multimeter showed battery voltage steadily decreasing while it was ‘charging’.
So my question: can I take the regulating circuit board from a cheap power bank and wire this to the battery instead? I’m aware these batteries can explode if overcharged, that usb supplies 5.0 volts and the battery requires no more than 4.2 volts. Many thanks

 

[WHONOES]

Can we safely assume that the battery in question is a Li-Po?

 

[Steve B]

Hi, yes it is, model SRP603443

 

[Arouse1973]

Can you post some pictures please Steve of the battery and where they are used?
Thanks
Adam

 

[Steve B]

Hi Adam, just tried uploading a photo. The headphones are Astro A50 generation 1. I’ll add a photo now of the internals...

 

[Audioguru]

A power bank uses a battery much more powerful than the little 800mAh battery so its charging current will be much too high.

 

[Steve B]

Thanks, perhaps power bank was the wrong term then, but I was thinking of the small portable chargers for mobile phones etc?

 

[WHONOES]

Charging your battery is not as straightforward as it may first appear. As you correctly say, fire could ensue. You need to limit the charge voltage to 4.2V and limit the current to about 1/4 battery capacity or less.

 

[Steve B]

I was thinking of using the regulator board from a small power bank, basically wiring in my battery where the battery would normally be wired in the power bank. That way the board provides the correct voltage and overcharge protection? The attached photo is off the internet, but shows the type of board I’m thinking of using , top middle of photo. Thanks

 

[Arouse1973]

Hi Adam, just tried uploading a photo. The headphones are Astro A50 generation 1. I’ll add a photo now of the internals...

Thank you Steve. It makes it easier for everyone to see what you are talking about.
Thanks
Adam

 

[Audioguru]

Look at the battery in the power bank. Isn't it much more than the 800mAh of the little battery you want to charge? Like 3000mAh? Then the charger will seriously over-current the little battery which might cause it to explode and/or catch on fire. Have you ever seen the metal Lithium burn? A VERY hot fire.

 

[Steve B]

Hi Audioguru, the power bank I have is slightly less at 2000mAh but I’ve no idea of the tolerances hence I’m here seeking advice. The videos I’ve seen have used significantly higher power outputs to trigger a fire or explosion. However this is for my daughter and I’m absolutely not going to take any risks here. Just seeing if this is a viable option before I trash a very expensive set of headphones. Thanks for your thoughts though, I appreciate everyone’s input. Thanks

 

[BobK]

The current used to charge a battery is proportional to it's capacity. If you try to charge an 800maH battery with a charger designed for the 2000 maH battery, it will give it 2.5 times the correct charging current.

If you really knew what you were doing, you might be able to take the little board and replace a resistor that might exist on it to set the charging current down to the correct amount for your battery.

Bob

 

[Steve B]

Hi Bob,

Unfortunately I think replacing resistors would be beyond me. I think im going to abandon the project and will have to bite the bullet on replacement headphones.

Thanks everyone for taking the time to reply, much appreciated.

Steve