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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44 Discussions

0
ParadoxNasha
ParadoxNasha

10 months 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 11 months 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 1 year ago

is it a momentary button or pushbutton

0
ottmannster
ottmannster

Question 1 year ago

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

0
АлексейВ12
АлексейВ12

Question 1 year ago

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

Answer 1 year ago

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

0
ghavican
ghavican

Question 1 year 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 1 year 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.

0
dubbby
dubbby

1 year 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 ?

3
Ardutronico
Ardutronico

Tip 1 year ago on Step 1

This charger is overkill for what you want. It's good for what I want (charge and test thousands of cells for my power wall project), but it's not the best option for a battery pack. You don't need to charge the cells separately for balancing, you can just use a BMS which automatically balances the cells and also provides overcharging, overdischarging and overcurrent/short circuit protection! You can either look for an appropriate BMS for your battery pack and buy it or make one yourself.

0
azipper
azipper

Reply 1 year ago

@Ardutronico Can you tell us a good example for a BMS you can recommend?
There are a lot of "BMS" on the internet and it is really hard to find something useful...
Thank you! :)

0
JohnC430
JohnC430

Reply 1 year ago

it is not overkill. what u are suggesting costs about $8 whereas these small modules cost less than $0.25 each. he would have to build the rest of the contraption anyway.

1
Ardutronico
Ardutronico

Reply 1 year ago

These modules cost $0.70 (not $0.25) each, and you need one for each battery. And add the PCB (which is big and therefore expensive, $6.20 each) and the other components to that and you have $20 per board (see ebaugh's question above for a rough calculation). Total $40 for 16 cells, plus the added inconvenience of moving the cells back and forth (time is also money, you know). Whereas the BMS would be just $2-$10 for the entire pack.

0
iqlogic
iqlogic

Reply 1 year ago

I've recently bought 10 modules TP4056 for only $1.70 on Ali ;)

0
Ardutronico
Ardutronico

Reply 1 year ago

Yes, but the OP bought them in Banggood, and even then, it's still about $15 per board.

2
JamesA41
JamesA41

1 year ago

Thanks for sharing this design. I've never seen the TP4065 module idea before. I wound up purchasing a small range of the multi cell higher current fault protected charge controllers to test out. This is inspiring to consider even using those range of modules. Thanks again!

0
Yonatan24
Yonatan24

Reply 1 year ago

You have these in all small, single 18650 portable phone powerbanks :)

0
DIY KING 00
DIY KING 00

Reply 1 year ago

Ya, its great na.... when I got through how useful and cheap these modules are I just realized that I must consider making something useful with them.