Hello everyone!!

As the title suggests, this will probably be a piece of cakes for most of you guys on here!
But me as a newby to electronics and circuits have a much more difficult time to be sure of my schematic.

I want to make a battery pack made out of 4 18650 battery hooked up in series.
Another requirement is being able to charge the batteries whilst in series. Now I am aware of the existence of circuits that charge series of batteries as well as levelling them but I want to be able to charge my battery pack with 5v (Planning on making a beefy 5v usb charger).

So here is my idea:
If I'm able to use 1 DPDT switch per battery to disconnect them from the serie and connected them to a TP4056 charger.
I think I got the schematics figured out -albeit it looking more like kids painting with the different colours, I'm not sure of my case and want to double check with someone who has extended knowledge of these things.



I'm all up for trail and error and believe it's (one of) the best way to learn. But since we're dealing with 18650 and I don't want to put everyone in my direct radius in danger as well as potentially cause a fire in my room, I want to be sure this thing is save.

Thank you if you made it this far and spending some of your time on my humble little problem, truly appreciate it!

Ps. I did search this forum for similar threads and although "doby" over at this thread comes very close to what I want, there were unfortunately no answers given that could help me.

Pps. please don't skin me alive for my schematic drawing and/or skills in CircuitLab

 

My apologies for having uploaded the pictures multiple times, I retried uploading them a couple of times thinking that my internet wasn't working.

 

A lithium battery will explode and/or catch on fire (a very hot fire) if you connect it with "trial and error". Buy a battery and charger made for it that will be safe.

 

well i can say a bought unit is best, time cheep as well but all require removing the bats from the circuit

but if you willing to put on the safety googles this will work ok

be also VERY AWARE of cloned 4056 chip fakes out there and they can cause big problems so only get the manufacture originals or replace clone pcb with original 4056chips , MOST ebay / aliexpress pcbs are clones
do a google of the fake 4056 chip and you see what i am referring to

The circuit also use pair mosfets to stop the 4056 from going crispy when putting the bats reverse polarity and try to charge 4056 not like reverse polarity

i put a fuse on each bat set at 1.5A, you need to look at what your current draw is and change the resetable fuse as required

the 4056 pcb will have about 8.5v on MOD1,12.5 mod3, 15.8v mod4 , present at the output pin of each , when the usb power is not on , and although this is not great it will should not harm the 4056 as it is disabled while usb power is not on.


also each 4056 pcb can charge at 1A unless you change the charge current resistor reference on each pcb resulting in usb current requiring 4A input


as i say i did this quick , so wait for those that look at close to comment

cheers

 

also note the NCh mosfets are in effect in series so need to be rated at the max current draw of the load for each NCh

 

@Audioguru That's why I wanted to ask people who understand these things before I start hooking things up! Definitely don't want to put myself in danger and in the worst case the whole building!

@longpole001 Those fake 4056 modules are definitely something too look out for! I already ordered mine so there is no turning back, luckily I always check the reviews thoroughly (also be aware of fake reviews!) before buying.
Good idea about using a fuse! I will do these tests when I get the 4056.

As for this schematic, decided it's not worth the risks tied to charging the 18650 this way so I will make the batteries removable and charge them outside the speaker and with a proper set-up.

Thanks a lot guy!

 

Do your cells have internal protection boards?

It is absolutely essential that there are two levels of independent circuitry to prevent over-charging. The charger itself should accurately regulate the voltage applied to the cell. A secondary protection circuit should disconnect the charger in the event that the charger fails and applies excessive voltage. This is not a completely fail-safe arrangement, but it greatly reduces the probability of causing the cells to rupture or catch fire. The protection circuit must not be relied on to limit the voltage for normal charging. Most will allow a voltage that is higher than the normal full-charge voltage but low enough to prevent disaster. Even a few cycles of allowing the higher-than-normal charge voltage can greatly shorten the life of a cell.

Protection circuits also disconnect the load to keep the cells from over-discharging (damaging, but not dangerous) and most will disconnect the load for overcurrent.