Diy 18650 4s battery pack [How to charge, how to build?]

C

CyPF

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Hello,
I'm building a bluetooth portable speaker. However, I have some questions about building my first 18650 battery pack. I have 4 pcs of Panasonic unprotected NCR18650B 18650 3.7V 3400mAh.[size=small]image_drpkas.jpgMy goal is to build a 4s 18650 pack with these batteries, and the battery pack must: - be inside the portable speaker - Fully protected - Safe[/size]
My question is, how do I design this battery pack? I have a idea, but want to know if it is a good way to build it?:[size=small]image_oojfih.jpgI also have some others questions: During my searches on internet some people use balanced charge, is it necessary to it use in my case? If yes how? Do I need to use a power adapttor or lithium li-ion battery charger adaptor?[/size]
Thanks for your future help Cordially,
 
Hmm have you looked at my build? :)


With those BMS boards you can potentially just charge it with the DC adaptor. Just make sure the voltage is not to high and it should be fine. Thats how most commercial builds are done.
 
daromer said:
Hmm have you looked at my build? :)


With those BMS boards you can potentially just charge it with the DC adaptor. Just make sure the voltage is not to high and it should be fine. Thats how most commercial builds are done.
Click to expand...

Hello nice bluetooth speaker ! :)
During my searches on internet some people use balanced charge, is it necessary to it use in my case?
It's a good way to charge without balance only with bms?
 
you should check your pcb's specs, usually, a bms also provides balancing. If not, use one that does ;)
 
BMS i used do balance when charged to the top. So it basically does what it should.
 
owitte said:
you should check your pcb's specs, usually, a bms also provides balancing. If not, use one that does ;)
Click to expand...
Please can you advice me a Good bms compatible with myPanasonic unprotected NCR18650B 18650
https://www.fasttech.com/p/1345500
daromer said:
BMS i used do balance when charged to the top. So it basically does what it should.
Click to expand...

I saw your video, i can't see the balance wires?

I found a board on aliexpress, what do you think ? https://goo.gl/bNeiCL


image_ihhsis.jpg

Or i have an other idea, what do you think if i put a balanced charger in the speaker, does it possible the wires stay always connected to the charger and the speaker circuits? image_lehtnv.jpg
 
He specifically says he's putting the balance leads on the pack shortly afterthis location:

If it's moving to fast, just slow it down with the Youtube controls. Click the gear icon and change the speed to .5 or .75.

He doesn't specifically show soldering the balance leads to the bms, but he does show putting the wires on the pack for the bms.
 
Please can you give me the link of the BMS you use?
Cordially,
 
I checked the existing BMS on the market, but i noticed that Over-discharge Protection is too low compared to my batteries specs. The common bms on internet cut the current at approximately 2.55 this is too low for my batteries. Indeed minimum voltage of my batteries is 2.75 V. So i found a new BMS with balance charge function:[size=small]link[/size]

I have several questions, i made a wiring diagram and i want to know if don't have made mistakes:[size=small]image_ocasig.jpgHowever, several questions remain vague in my mind: The Positive cable and the negative cable are the same cables to charge the battery pack and use it? On the diagram (Output / Input Positive + and Output / Input Negative -) Can i use the battery pack at the same time as it charging? For me it seems odd to me because I wonder what the intensity and the voltage sent to electric circuit of the bluetooth speaker. On the diagram(Intensity: A? Voltage Rating: V?)Those of the adapter or the battery?[/size]
 
The charging circuit will actually charge each cell individually. That's why the mosfets to do disconnections during charging.
No, you can't use the batteries while charging because of previous statement.
Amp/Volt output will be what the bms will allow as max. Should be listed on the specs of the bms. Voltage should be 4.2v*4 = 16.8V.

Wiring diagram looks good to me.
 
Thanks for your answer is more clear for me,
So per example, to avoid someone connect accidently the power adapter while the speakers work.
What componement can i add on my wiring diagram to avoid this situation?Do you have an idea?
 
add a mosfet that turns on the load when there is no power on the charger port. When the charger is connected, the mosfet gets grounded and shuts off

(i might have that backwards in the way it needs to be implemented)

Another option would be to have a similar type connection like that of a headphone jack. When a plug is inserted, it disconnected the speaker. In this case, it'd disconnect the load. Not sure if these are available for power connectors, tho.
 
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