Power bank idea

[bigone5500]

I am thinking that if I purchase one of those cheap power banks with a couple Li-Ion batteries, then I can rob the circuit board and use it for a larger array of batteries. I have several 18650 batteries that need to be used. I think I can make a 20 or 30,000 mAh bank with them. My only concern is that the board in the smaller bank will not be able to handle the extra current...

Thoughts???

 

[shrtrnd]

The only thought I have, is to avoid exploding your batteries.
I'm not familiar with the 'power bank' term you're using.
I've heard horror stories about lithium ion batteries exploding.
I don't know if a 18650 battery is lithium, or if you plan to remove the 'couple Li-Ion batts' from the original before, installing your 18650's. Maybe somebody else here will look-up all the applicable data.
I'd run the calculations on the board's current handling capability, ensure that the charge value and rate matches
your 18650's, and wear safety glasses when I powered it up.

 

[Gryd3]

I am thinking that if I purchase one of those cheap power banks with a couple Li-Ion batteries, then I can rob the circuit board and use it for a larger array of batteries. I have several 18650 batteries that need to be used. I think I can make a 20 or 30,000 mAh bank with them. My only concern is that the board in the smaller bank will not be able to handle the extra current...

Thoughts???

Just to be careful.
Mixing and matching cells is never a good idea. If all the cells are 3.7V Lithium-Ion then you can parallel them. Only connect cells in series that have the same mAh rating, and if you do so, please connect some kind of low-voltage protection on each cell in a series pack.
*Be mindful with the current charge state of each cell. Higher charged cells will discharge into the lower charged cells and can damage each other with excessive current. These batteries are very capable

The RC community often connects multiple batteries in parallel. It gives them additional capacity for longevity or for peak/sustained current draw...

 

[bigone5500]

I suppose it would be best to simply purchase a pack already containing the cell count I want. I just have all these 18650 3.7v lithium ion batteries and would like to do something with them before they go bad if they do.

Thanks.

 

[Gryd3]

I suppose it would be best to simply purchase a pack already containing the cell count I want. I just have all these 18650 3.7v lithium ion batteries and would like to do something with them before they go bad if they do.

Thanks.

You could always buy additional 18650 cells

You can do what you want with them, as long as you observe the limitations of your individual cells.
Mixing and matching cells means that in a series connected string, the current must not exceed the capability of any individual cell in the pack... This also means that the cell with the lowest capacity will dictate the run-time of the pack.
Of course, parallel is a different monster. Voltages must be the same of all the cells, although capacity can vary.
As the voltage drops in the less capable cells, the more capable cells will be drawn from instead. The over-all mAh capacity can still loosely be summed, but the 'peak' or 'constant' current draw of the pack cannot be.

The dangers with both packs is excessive current during discharge or recharge state, as well as under-voltage or over-voltage conditions. Some cells have built-in protection from the above conditions, some don't, and many have a very 'loose' enforcement of restricting damage conditions... (ie... short protection that trips at 10A for a cell rated at maybe 2A peak draw )
It's just so much easier to match the cells is all.

Lithium, when abused will begin to heat up, and the cell will begin to expand from gasses being created in the cell... Eventually, the cell wall will rupture and vent the gas which usually ends up in a small fire from the exposed innards.

Always be safe. If you venture into "you *can*, but probably shouldn't territory", some not so fun things can happen.

 

[BobK]

I believe power banks can be bought without the 18650's.

Bob

 

[AlenZGB]

Mine chinese power bank with ``12000mAh`` was around 1700 mAh tops, could charge phone one full time.
And inside it was bad 18650,rusted and in bad condition in first month or so. I use the same capacity, lowest 2100 to 2150 mAh, measured with Imax B6 charger. And connect it in parallel and on the power bank board, but i can tell that usb cable is a bit warm on connector. batteries inside wasnt warm at all but connector of that mini usb was.
not sure is thats good idea so i stop using it and, charge batteries with Imax B6 and place it in a box

Regards,
Alen

 

[Gryd3]

Mine chinese power bank with ``12000mAh`` was around 1700 mAh tops, could charge phone one full time.
And inside it was bad 18650,rusted and in bad condition in first month or so. I use the same capacity, lowest 2100 to 2150 mAh, measured with Imax B6 charger. And connect it in parallel and on the power bank board, but i can tell that usb cable is a bit warm on connector. batteries inside wasnt warm at all but connector of that mini usb was.
not sure is thats good idea so i stop using it and, charge batteries with Imax B6 and place it in a box

Regards,
Alen

Heat is caused by power loss.
That either means excessive current is flowing for the connector (or joints on the connector) , or that there is a high resistance fault of problem with connector or joints.
Power = Current^2 x Resistance

Now... depending on how warm it is, it might be normal.
Phones are charging in the 2000mA range now, and that poor little usb connector usually only deals with 500mA. (Which is still considered high for some USB standards)

 

[HellasTechn]

I just have all these 18650 3.7v lithium ion batteries and would like to do something with them before they go bad if they do.

Read here for info about how to prolong their lifespan.
https://www.electronicspoint.com/threads/how-to-preserve-18650-batteries.261318/

 

[AlenZGB]

Heat is caused by power loss.
That either means excessive current is flowing for the connector (or joints on the connector) , or that there is a high resistance fault of problem with connector or joints.
Power = Current^2 x Resistance

Now... depending on how warm it is, it might be normal.
Phones are charging in the 2000mA range now, and that poor little usb connector usually only deals with 500mA. (Which is still considered high for some USB standards)

not 100 C warm but on the touch id say around 40-45 C.
On the phone original charger it say 1000 mAh.

 

[bigone5500]

Heat is caused by power loss.

Phones are charging in the 2000mA range now, and that poor little usb connector usually only deals with 500mA. (Which is still considered high for some USB standards)

I have a galaxy S6 edge (SamSucks), and the adaptive charging causes the micro USB to deliver 9v @ 1.67A. This makes the connector very warm while charging. I wonder if it causes the connection points to prematurely wear out.