DIY 18650 Lithium Ion Cells Charging Grid

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Introduction: DIY 18650 Lithium Ion Cells Charging Grid

About: Being a science student i love to indulge in projects related to engineering as i love to learn things practically...

I have been working on motorising my bicycle using a geared DC motor and now I need a battery pack for that. So to make a battery pack I have decided to go with the popular 18650 lithium ion cells from two old hoverboard batteries.

Since the cells are from used batteries so I need to balance charge all the cells before making the battery pack. Everytime I use these 18650 cells I need to go through this stage when I need to balance charge all the cells individually to get them at the same potential.

Now to get through efficiently I decided to built a dedicated charger for 18650 cells. Moreover, I have decided to make it a modular charger so that I can add up modules to form a larger grid that enables me to charge as many cells as I want simultaneously.

Don't forget to vote us in the PCB Design Contest.

Step 1: Design

Since we need the charger to be modular, easy to built and low cost so I came across these TP-4056 lithium cells charging boards. These boards are specifically made to charge lithium ion cells with a micro USB input, over charging protection and above all they are dirt cheap.

For each module I decided to go with two cell holders, each one of which can hold up to four cells. So for each module we are going to need eight TP-4056 modules.

For the main input of the board I have used an XT-60 connector but we have the option for charging two or three cells only using a cell phone charger as well.

Now to keep things simple and neat I decided to design the printed circuit boards.

Step 2: Ordering the PCBs

To save time I decided to order the PCBs. So I visited PCBWAY and after going through a couple of options I ordered 10 boards. These boards will be enough to built a charging grid thats capable of charging upto 80 cells simultaneously.

Once I uploaded the Gerber files I waited for the designs to get verified to make sure there is nothing wrong with the boards. Well thats one of their many useful services and this project is made possible by them so make sure to have a look at their website for great quality PCBs at an outstanding price.

The link to the PCBs and the Gerber files for the circuit boards is:

https://www.pcbway.com/project/shareproject/18650_Cells_Charger_PCB.html

For discounted coupons for PCBs have a look at the link:

https://www.pcbway.com/activity/christmascoupons.aspx

Step 3: Components and Tools

Within just a week the PCBs were on my workbench and the quality pretty much talks on its own so guy have a look at their website as they made this project possible by sponsoring it. I gathered all the components. The BOM(Bill Of Material) file is attached in this step.

For the tools we are going to need the basic soldering stuff.

  • Soldering Iron
  • Soldering wire
  • Pliers

TP-4056 modules:

https://www.banggood.com/custlink/GKGDDk05kP

Step 4: Assembling the PCBs

To assemble the PCB all we need to do is to drop all the components as mentioned on the board. I have started by soldering the charging boards and then moved towards the bigger components.

Once I finished soldering all the small components I then soldered the cell holders. Make sure to match the polarity on cell holders to that mentioned on the PCBs.

With all the components around it took me hardly 10 minutes to complete one module. Now before I make more modules,I tested this one.

Step 5: Testing the Modules

Now to test the module I plugged my cell phone charger to one to the TP-4056 board using a micro USB cable. This allows me to charge up-to three cells.

For charging eight cells I have used a PC power supply with the 5v input using an XT-60 connector. The module flawlessly charges each cell. As the cell is completely charged the light over that particular charging board turns blue from red and we can turn of the switch for that particular cell to save power.

Step 6: Making the Charging Grid

Now to form the whole charging grid I have made some more modules as I have to charge a lot of cells.

After making a couple of modules I then assembled the modules using some nut and bolts as I don't have the required standoffs. now to power the whole grid I have used the same power supply as in the previous step. As each module is connected in parallel across the standoffs so providing the input through any of the modules will provide the power across the whole grid.

Step 7: End Results

The whole project turned out to be a really useful one as now I have a customised charger that can charge as many cells that I want. The whole charging grid costs me a fraction of the price of a professional chargers available in the market and they don't have the capacity to charge as may of them.

The PCBs Made everything neat and the pre Made charging boards saved a lot of hassle and I am really happy with the end results.

For more fun projects stay tuned and subscribe to my youtube channel.

https://www.youtube.com/channel/UCC4584D31N9RuQ-aEUxP86g

Regards.

DIY King

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49 Comments

0
dubbby
dubbby

2 years ago

Good project. I ordered the PCB through your link.What is the name of the switch at the bottom, I've been on amazon, ebay, gearbest, etc., to find them and only find momentary or 4 or more prong switches and banggood doesn't recognize the search ?

0
tresjohnson92
tresjohnson92

Reply 3 months ago

Did you find them?

0
tresjohnson92
tresjohnson92

3 months ago

Can anyone please give a link to the correct tactical switches?

0
mohammed breky
mohammed breky

2 years ago

Hey !
awesome Project dude
i have one question why did you add push buttons under the batteries ?

0
DIY KING 00
DIY KING 00

Reply 2 years ago

These button are added to turn off the charger for individual cell by cutting of the supply to that particular tp-4056 module.
Note:
These are not momentary switches

0
tresjohnson92
tresjohnson92

Reply 3 months ago

What switches are they

0
JohnW51
JohnW51

2 years ago on Step 7

Wow! That is impressive! I didn't know about the little charger boards. Those are so cool AND inexpensive too. I did want to make one comment about your schematic. It shows a momentary contact switch at the input to each of the charger boards. I think those switches must not be momentary or you'd have hold every one of them on while the battery charges. But that's a minor thing because we know what you meant.

0
DIY KING 00
DIY KING 00

Reply 2 years ago

You are totally right, while designing the schematic I mistakenly used this package which is usually available for momentary switches.
But later, somehow I managed to find the required switches. So these are not momentary switches

0
tresjohnson92
tresjohnson92

Reply 3 months ago

Why wasn't this updated is this why my grid is not working?

0
ottmannster
ottmannster

Question 7 months ago on Step 6

Welche Switches werden verbaut und wo kann ich sie bestellen?

0
ParadoxNasha
ParadoxNasha

1 year ago

I'd just like to point out a safety issue that immediately concerned me and also offer some suggestions on possible enhancements for this project. This is a great project, i dobr wish to take away from that despite my many suggestions.

Although anyone building more than one module is likely to be electronically aware enough to know this already, but the posts (screws in this instance, or stand-offs) are LIVE and can easily be shorted out, posing a safety risk. At 10A per module, this is not a trivial amount of potential energy.

In a grey area between being part of the power supply design, and also charger design, would be some fuses. Certainly would be nice to see some on-board fuses (My charger I built, on breadboard PCB to safe costs, I used 5A axial glass fuses to connect the TP4056 boards in parallel and 15A fuses on each board), as well inter-board and supply lead-in as PC or server PSU's converted for use as charger power supplies can be capable of extremely high currents .

I'd love to see a design where this risk of bare power supply lines mitigated. A quick fix, not requiring any redesign or component changes would be to heat shrink as much of the screw as possible.
Securing the bottom module to a piece of plastic or other such non-conductive material easily takes the risk of shorting out the circuit if placed on a steel work bench etc.
Some cost could be saved (and a smaller PCB size) if only using a single XT-60 plug, and connecting it's wire to the board. This is based on building a charging module of fixed size, to meet the output of a charger.

Also, this is not a balance charger. This is a bulk charger, allowing many batteries to easily be charged from a single high-powered power supply. Balance charging (put very simpl, qnd technically inaccurate) is the process of charging all cells to exactly the same voltage. Simply charging all cells until cutoff by the TP4056 is not the same thing.

Lastly, when using Li cells for building a battery, ensure similar capacity cells are used throughout the battery. Second hand cells are likely to vary quite a bit.

Wow, I just wanted to point out the safety issue and that ended up becoming a thesis!

0
buell2236
buell2236

Question 1 year ago on Step 3

The switches 1-8 push button pcb latch switch data sheet rates the max current at 20ma
The max charging current is 1amp per cell
The current rating of the switches appears to be grossly over loaded

0
lasserjensen2004
lasserjensen2004

Question 2 years ago

is it a momentary button or pushbutton

0
ottmannster
ottmannster

Question 2 years ago

Hello, I am looking for a source for the switches Sw1 to Sw8. Can someone name this to me?

0
АлексейВ12
АлексейВ12

Question 2 years ago

What software did you use when creating the PCB image?
0
edgiru
edgiru

Answer 2 years ago

Я так понял что он прям на сайте создал PCBWAY. Могу ошибаться конечно.

0
ghavican
ghavican

Question 2 years ago on Step 7

You mentioned a 5 volt charger, but didn’t see what amperage the charger was. I assume it was a minimum of 4 amps, which would give 500mA per cell. In addition, why not use a barrel connector for the charger to plug into since most chargers come with one? The 5.5mm x 2.1mm would be perfect since a lot of chargers have this plug. I plan to build a couple of these and will be substituting a barrel connector if I can get it to work with your board design.

0
edgiru
edgiru

Answer 2 years ago

xt-60 connector is likely to be compatible with SkyRC IMAX. there is a suspicion that the current will not be evenly distributed among the banks.