I would appreciate some advice on my little BT speaker project

[Elijas]

Hi, I'm new to this, and I need some advice with my first Bluetooth speaker project. I'm not sure if my plans on doing a portable Bluetooth speaker are correct (is it going to work?). I have 4 18650 batteries (one battery has 3.7V 30A) that I'm going to use for the project. Also I'm going to use AMP (TPA3118 PBTL Mono DC 8-24V 60W Digital Audio Amplifier Board AMP Module Chip 9FR | eBay - https://ebay.to/2WBgsdp), PRE-AMP (NE5532 Tone Board Preamp Pre-Amp with Treble Bass Volume Adjustment Pre-Amp O1P1 | eBay - https://ebay.to/3b8jwD2), an on/off switch, a Decoder board (Bluetooth 5.0 Car Decoder Board MP3 Player FM Radio Audio Module Remote Nett | eBay - https://ebay.to/3ftX3Uw) and also a 4ohm 100w(not sure about the wattage of the speaker) speaker. I also might add an LED strip (AC220V DC12V Waterproof 3528SMD 5050smd LED Strip Light 30CM 1m 2m 3m 4m 5m | eBay - https://ebay.to/2SLzfl2) with a separate switch. The thing is that I'm worried about the decoder board as it's only capable of 12V, im not sure if I can use the 14.8V provided by the batteries or should I lower it with this board (DC-DC Adjustable Step Up Converter 2-15V to 5V-28V 2A Boost Power Supply Module | eBay - https://ebay.to/3fw4QRu), or is it good as is.

Also I haven't decided how I'm going to connect all of these parts (don't have the scheme yet).
Note: I'm going to connect all of it to the same circuit.


Links:
AMP: TPA3118 PBTL Mono DC 8-24V 60W Digital Audio Amplifier Board AMP Module Chip 9FR | eBay - https://ebay.to/2yAgDO0
PRE-AMP: NE5532 Tone Board Preamp Pre-Amp with Treble Bass Volume Adjustment Pre-Amp O1P1 | eBay - https://ebay.to/3bedMrB
DECODER: Bluetooth 5.0 Car Decoder Board MP3 Player FM Radio Audio Module Remote Nett | eBay - https://ebay.to/2L6Gos0
LED: AC220V DC12V Waterproof 3528SMD 5050smd LED Strip Light 30CM 1m 2m 3m 4m 5m | eBay - https://ebay.to/3bb8ayg
DC-DC CONVENTER: DC-DC Adjustable Step Up Converter 2-15V to 5V-28V 2A Boost Power Supply Module | eBay - https://ebay.to/3bkedAJ

More info in attached file, it might be useful.

 

[SJD]

The Bluetooth car decoder board is designed for use in a car, where the battery voltage rises above 12V when the car battery is being charged. The voltage could easily be as high as 14.8V.

So I would expect the Bluetooth board would not have a problem with 14.8V, but you'd need to see the specs of the board (if they are even available) to be sure. On the other hand, the cost of this board is so little that you could just try it and see!

However, you are going to need to charge your 14.8V battery, and I'd be wary trying to charge it with the Bluetooth board directly connected, as again the voltage would be higher that 14.8V while charging.

Is there some reason why you don't just use a 12V battery?

 

[Elijas]

However, you are going to need to charge your 14.8V battery, and I'd be wary trying to charge it with the Bluetooth board directly connected, as again the voltage would be higher that 14.8V while charging.

Is there some reason why you don't just use a 12V battery?

I'm going to use USB Type-C 5V 1A board (5PCS type-c USB 5V 1A 18650 TP4056 Lithium Battery Charger Module Charging Board 690100048486 | eBay - https://ebay.to/3dsEw9b) for charging the batteries.

I already have the batteries with me, so I want to use them all in this project (4x 18650). Also I use a lot of different devices, so stable voltage is important to me (can't drop below 12V). Also I don't want to underpower speaker, AMP and the PRE-AMP.

Is it possible to use 4 batteries, and use 14.8V for all the other devices except LED strip and the Bluetooth decoder board. And for those two I would use 3 out of 4 connected batteries, that way I would get the 14.8V (from my 4 batteries) for AMP and PRE-AMP, and 12V (from the same 3 batteries) for Decoder and LEDs.

 

[SJD]

The charger you link to says 4.2V output when batteries are fully charged, so you would have 16.4V from the 4 batteries across the equipment (I'm assuming you plan to charge the batteries while the equipment is in use).

If you try to run the Bluetooth board from 3 batteries, when the batteries are going flat, the voltage will drop to 11V or less. Personally I'd avoid the complication of trying to run this board from 3 batteries, power everything from the one supply and just make a simple low-voltage-drop regulator to drop the Bluetooth board voltage down to (say) 12V.