Hello, i'm a bit new to using batteries in my projects but i do know that if i connect the + to each other and - to each other on multiple batteries they act as one battery and won't add up the voltage per battery. Therefore the voltage stays at 3.7V no matter how many 18650 i add together but will i need to have a charging board (tp4056) for each battery or can i just use one board and it will charge all batteries at once?
...but i do know that if i connect the + to each other and - to each other on multiple batteries they act as one battery and won't add up the voltage per battery. Therefore the voltage stays at 3.7V no matter how many 18650 i add together...
You shouldn't put batteries in parallel, especially rechargeable batteries. They will never be "exactly equal" and one battery can discharge into the other which is not efficient and could potentially damage the batteries and maybe overheat and start a fire!
You can put batteries in parallel if you add a diode on each battery to prevent reverse current, but you'll get a voltage-drop across the diode (0.7V for a regular silicon diode) and you'd have to bypass the diodes for charging.
In series, the voltage will add-up but the current capability (and Amp-hours) remains the same.
will i need to have a charging board (tp4056) for each battery or can i just use one board and it will charge all batteries at once?
You can probably charge the batteries in series with one charger circuit. Normal battery packs are wired in series and they are charged at once. (Lithium batteries are "tricky" and I'm not a battery charging expert.)
hmm. All 6-cell HP_laptop_batteries has 2 cells parallel. Works perfectly OK
6-cell HP_laptop_batteries has 2 cells parallel
Yes, But.
Cells matched by the manufacturer, from the same manufacturing batch are probably OK...
Other: 18650's have a built-in chip that does some protection. Research that some more...
You can put multiple LiPo cells in parallel, as long as they're similar cells, and they are at the same open circuit voltage when you put them in parallel. As long as that restriction is met, once they're connected, you basically treat them like they were a single battery. Whenever they are disconnected, you need to again be super careful that they're at the same voltage when you connect them together again. In this situation you need only one charger.
It's series connections, not parallel that you have to be much more careful with - imagine if one has higher self discharge than another. Then you try to discharge them - it looks like all is well on the output voltage, but the individual cells may not be in the same state of charge, so you may be overcharging some and underdischarging others, since all cells in series are getting the same current, but may not have the same capacity or self-discharge rate. This damages the cells as you cycle them and can eventually cause failure - that's why batteries that are connected in series require a "balancing" charger.
I have one situation where I have a huge array of 18650's in series, and can't balance charge them - they get recharged a few times a year in place, with a conservative charging arrangement, and at the end of the season, the system is disassembled and all batteries get taken out and charged individually to put them all in the same state of charge. So far this has worked, but I'm sure it won't do any favors for long-term battery life (we're okay with tossing the batteries when their performance starts to suck). And we always charge it away from flammable objects in case the worst happens 
@OP,
you can't use TP4056 to charge multiple 18650s simultaneously.
If you want to really use TP4056 then you will need to use separate modules for each battery since these modules are rated for only a single cell. Like what this crazy guy did https://www.youtube.com/watch?v=KoHtxZG7leQ
Also do not connect these batteries in series since the max charge output of TP4056 is only 4.2v.
My advice if you really want to charge multiple 18650 at the same time, you can either take apart an old powerbank (eg:xiaomi powerbank) and use it's circuitry to charge all of your batteries at once or you can buy a power bank diy kit case from aliexpress or banggood or ebay that allows you to charge multiple 18650 cells simultaneously as they have dedicated charging circuitry for multiple cells. They cost around 5 or 6$.
FYI: All your batteries have to be same capacity and same manufacturer and same chemistry.
Note: Why not use a power bank? or a laptop battery pack? saves you the trouble. 
DVDdoug:
You can probably charge the batteries in series with one charger circuit. Normal battery packs are wired in series and they are charged at once. (Lithium batteries are "tricky" and I'm not a battery charging expert.)
Not with his TP4056 module, it's max input is 5v and charging voltage is about 4.2v, So he can't charge series with his module.
knut_ny:
hmm. All 6-cell HP_laptop_batteries has 2 cells parallel. Works perfectly OK
Laptop battery packs have a cell balancing circuit module as protection.
terryking228:
Other: 18650's have a built-in chip that does some protection. Research that some more...
Not all of them have a protection chip on them.
Thanks, i'll be doing some testing.. Either i'll go with using multiple TP4056 boards (one for each battery) and put the output in series and i might just include some poly fuses just in case or i might just go with harvesting a diy powerbank and use the circuit to charge the batteries.
Thanks!
My name is Renato and this is my first post in this forum so I'd like to apologize in case it's the wrong place to add some doubt about the subject.
It's not strictly about Arduino but searching all around I didn't find better place...
I'd like to build a portable music player based in these chineses MP3, BT, FM and USB players for the signal and a PAM8403 amplifier.
Studying the player, despite of the manual information (this needs 7v to 12v) I've discovered that there is an regulator 7805 type before all the circuit, soldered in this board. So I've jumped the IN and the OUT pins and the player works fine with 5v. The same manual says it takes kind of 200mA.
The amplifier, based in PAM8403 chip, deliver 3w@4ohm x 2 (stereo) and uses 5v. It's eficiency, as the datasheet says, can be near 80%, what means that in low volume it can take, say, 1A. But what if somebody likes louder sound? This gadget probably will end in my grandaughter's hand, rs...
To feed both circuits I've build a real 5v/3w PSU. But it doesn't makes my gadget portable. So I thought I could use a 18650 Li-ion battery that promisses 8.800mAh. And now I have to recharge this battery. I've found a circuit based in TP4056 to manage the charging. And as this battery says it deliver 3.7v, I thought using a XL6009 stepup mini board between the battery and the sound set (player + PAM8403).
Finally (excuse if this posts became bigger), I thought I could double all the power source schema, as can be seen below, to prevent overloads. Every device, except the amplifier, works, as far I understood, near 1A.
My questions:
1 - Can I, at the same time, charge the batteries and use the sound set? Won't that overload the charger manager (TP4056)? Or, at least, get the charging manager "a little confused"?
2 - Can I build an output after the batteries to charge a cell phone via USB? In another words, can this gadget works as a power bank and yet playing music?
3 - What if I put an capacitor, say 1000uF/16v, between the power and the sound sets. I ask this because this batteries, as long as I know, are made for continuos uses like lighters to hunt and the amp could ask the batteries for instantaneous current.
Any other comment or suggestion will be very appreciated, as I'm just starting electronic as a hobby.
Thanks.
P.S.: Excuse my not-too-good English.
P.S.2: As I've clicked "preview", I don't see the picture I'm uploading to show you what I say. But I'm sure it's attached. If you can't see the too, please ask and I'll try to show in another way. Tks.
Noobian:
@OP,My advice if you really want to charge multiple 18650 at the same time, you can either take apart an old powerbank (eg:xiaomi powerbank) and use it's circuitry to charge all of your batteries at once or you can buy a power bank diy kit case from aliexpress or banggood or ebay that allows you to charge multiple 18650 cells simultaneously as they have dedicated charging circuitry for multiple cells. They cost around 5 or 6$.
Thank you very much for this advice but in the images that you have posted they have connected all the anodes together and all the cathodes together. My question is that wouldn't they also do the same thing as a single TP4056 charging multiple cells? Please reply fast I'm already working on my power bank project
