How could I make a rechargeable battery source for my Bluetooth amplifier project

Thread Starter

alexc064.302

Joined Jan 3, 2018
3
Hello all!

I am currently a student studying product design at A Level and have given myself the challenge of making a portable Bluetooth amplifier that can run off of its own power supply. This is so that a potential user can take one or two Hi-Fi speaker out anywhere and plug them into this amp, connect with a smart device via Bluetooth and then listen to music wherever you want to easily e.g. in a park etc...

I am using a PCB Bluetooth amplifier called "TDA7492P 2*25W Wireless Bluetooth V4.0 Audio Receiver" which I bought on Amazon. The specification of the board are as followed:

Supply Voltage: DC 8-25V
Power Interface: 2.1 DC Socket
Audio Input: Bluetooth Receiver V4.0
Audio Output: Terminals
Output Power: Add Pre-5532 Output Foot
Applicable Speaker Impedance: 4/6/8/16 ohm
Number of Channels: Two-channel Stereo
PCB Board Size: 82 * 50mm / 3.23 * 1.97in
Weight: 37g / 1.32oz

I had the idea of setting up the circuit something like this which I found online for a Bluetooth speaker build:

But due to me not knowing as much as I should I don't understand how to wire this up to the PCB and whether this would work when wiring it up to the PCB.

I found a video online where the person wires up the same PCB but instead of having a charging port they use a DC port that is plugged in constantly supplying power to the device. Their wiring guide other than the contact to the power contact (which is above where it says switch in green is) is more a less what I think I need to do. His wiring guide looks like this:

If someone could please help and explain to me how i could get this to work or to come up with a better method for powering and charging the batteries that would be so greatly appreciated!!

Kind regards,
Charlie
 

ScottWang

Joined Aug 23, 2012
7,213
How is the specification of boost converter as the links and the range of input/output voltage?

The range of input voltage of amplifier is 8-25V and the output voltage of boost converter is 30V, so you have to make sure that does the output voltage is adjustable? (it looks like that it can be)

If the output voltage of boost converter can't adjust then it could be damage the amplifier module.
 

Dodgydave

Joined Jun 22, 2012
10,319
You need to find out what current the amplifier takes at say 12V, then you can size your battery capacity in mAh.

I would be using a 12V lithium ion battery, and use the booster to charge the battery from the usb,
 

Thread Starter

alexc064.302

Joined Jan 3, 2018
3
You need to find out what current the amplifier takes at say 12V, then you can size your battery capacity in mAh.

I would be using a 12V lithium ion battery, and use the booster to charge the battery from the usb,
I tested this before with a similar board and the results that I got were that at 25V the max votage that the board said that it could take I would be getting a current of around 0.2A which is alot less current than I was expecting the amplifier to take.

And when you say charge the 12v battery from USB, dont USB charging modules only charge 5v at 1A before they stop power going to the battery? If not then how would I go about this and wire it up? Thanks
 

Thread Starter

alexc064.302

Joined Jan 3, 2018
3
How is the specification of boost converter as the links and the range of input/output voltage?

The range of input voltage of amplifier is 8-25V and the output voltage of boost converter is 30V, so you have to make sure that does the output voltage is adjustable? (it looks like that it can be)

If the output voltage of boost converter can't adjust then it could be damage the amplifier module.
Yes with the boost converter you can adjust the output voltage and I would set it to roughly 14v so that it could charge the batteries. I've already burnt out a board that I tested before by putting it up to 30v to see what current I would be getting and I burnt the board out due to over loading it.

My confusion is how I am going to wire this up to the amp. If you look at my original thread and the first image I had attached, that is the wiring that I will use for all the components but I don't know how to wire the toggle switch and power up to the board correctly (I'm quite new to the whole electronics side). If you could help me understand that it would be greatly appreciated! Cheers mate
 
Hi! You probably have the solution to this by now, but let me try. In order for your boost converter to work, you would need a 3(fully charged)-4 Li-ion in series to achieve the 12V so it can boost it up to your desired voltage. The problem with series setup is balance charging the batteries. For this, you would need a balance charger and a BMS, there are BMS with balance charging in them as well. For starters, I'd go for option two below:

You can purchase a boost converter that can boost from lower voltage to a higher one, let's say 3.7V to 12V so you don't have to wire the batteries in series. You can simply wire the batteries in parallel.
 
Top