Hi,
I'm looking to build a few bluetooth speaker systems and was wanting to find the optimal way to deal with the power situation.
Ideally I want a system like most consumer bluetooth speakers, which have a single power input port (usually micro USB), and the device can operate while plugged in, batteries will also charge, and it will seamlessly transition to being powered by the battery when uplugged.

I've done a bit of research and it appears this is not as straightforward to achieve as it may seem.

There are 2 cases I want to handle:
1. Low power speaker system (5v power/amplifier, about 5W)

For this I was thinking of either using a standard USB power bank with pass-through capability (apparently Xiaomi ones do, and for example: https://www.zendure.com/products/a3)
Alternatively, there are simple single-Li-ion cell charger modules like: http://www.ebay.com.au/itm/Mini-Cha...818210&hash=item3d4ad52df3:g:oUQAAOSwjghZ1taR
This is used in the following project:
http://www.instructables.com/id/Powerfull-Portable-Bluetooth-Speaker-2x5W/
Although, I am not sure how they would work with pass-through power capability (power device while charging battery)

2. Higher power speaker system (12v power/amplifier, about 15W)
There are 12 v car jump starter power banks, but I'm not too sure about any pass-through capability.
https://www.aliexpress.com/item/Hig...ry-car-Charger-for-Phone-SOS/32702791438.html
Alternatively I was thinking of going for a 3S Li-Ion cell system (up to 12.6V) using a protection board like this: http://www.ebay.com.au/itm/3S-12-6V...harger-BMS-Protection-PCB-Board-/142476751433
This is used in following project: http://diytechandrepairs.nu/build-bluetooth-speaker-box/
But it seems the protection board in its own is not ideal for charging the batteries using a standard 12v DC supply, as discussed here:

I found it hard to come across a 3S lithium battery charging module similar to the single cell one, however there is this:

Seems a bit overkill though ($10 each, and still need protection board)

So basically, is there some nice streamlined solution to all this?
Or do I need to go down some more messy route of using diodes to merge power source input & battery output to load?
Or use a manual switch to choose between charge & direct power modes?

Thanks for any help

Cheers

 

Here is a 3S bms pcb, from china, you can get them in Aus,.

https://m.ebay.co.uk/itm/3S-12V-12-...%3A059c127c15f0a99b93219fbcfffcfa89%7Ciid%3A4

Just put the charger on P+/- and that's where the load is wired to, when the charger is disconnected, the battery pcb takes over and provides DC until the lithium-ion needs to be charged and cuts off the batteries for safety.

 

Ok, but what do you mean by charger? A standard 12v dc supply or one dedicated for li-ion charging? Because I don't think the charger will be good at powering the load during charging because it changes voltage/current during charge cycle, and a basic 12v dc supply don't charge ideally as mentioned in that video