Introduction: Lithium Battery Utility Board

Picture of Lithium Battery Utility Board

I use lithium batteries (mostly in form of the well known 18650 cells) quite a lot. For charging them, I used to use the TP4056 boards with protection, which are available from Ebay for about $0.5/piece. Then I utilized a separate boost converter. But a while ago, I saw a nice video from GreatScott which inspired me integrate this into a single board.

You see his original video here and the associated Instructable here. His work will be referred to as the original design. I reworked the circuit and made the following changes:

  • I included a Load Sharing circuitry. In the original design, it was not possible to charge the battery and output 5 V at the same time (or better it was possible, but it would damage the battery and disrupt the charging).
  • I optimized the layout of the SMPS a little bit, so it is now able to output 1 A without significant voltage drop. The schematics is done to be a little bit more organized and include equations for calculating output voltage, charging current etc. Also, all the source files are available as Eagle files, which at least in my opinion is better than that EasyEDA stuff.
  • I did add a few capacitors, resistors and a "Power Good" diode. Also, all diodes are using such a footprint that you can put SMD 1206 diode over it or solder two wires in there easily, so you can route the diodes to some front panel or similar.

Just for remind you what this board can do:

  • charge a Li-Ion or Li-Pol battery with a current of up to 1 A (the charging includes a precharge, CC and CV stages)
  • protect the battery from overvoltage, undervoltage and short circuit
  • boost the voltage of the battery to 5 V (or any voltage in the range of 4,5 to 28 V)
  • share the load between the battery and the charging input (that means you can charge and use the device at the same time).

All the source files are available in the last step.

Step 1: Performance

Picture of Performance

Of course, after you build such a circuit you want to know the performance. I have performed a variety of test, of which the most important is probably efficiency versus load current at different battery voltages. Another test is load regulation (that is, how constant is the output voltage at different currents). The last measurement I did was output ripple, which was about 50 mV average and 600 mV peak-to-peak during all tests.

The first two charts are attached to this step as pictures.

Note: because of resistive losses, at 1 A output and 3,0 V battery voltage the actual voltage at the protection circuit was lower than 2,9 V and the protection disabled the output. So you need to raise the battery voltage to about 3,05 or use short thick leads to have 1 A output at 3,0 V of battery voltage.

Step 2: Conclusion

Picture of Conclusion

I had the board professionally manufactured in China. After JLCPCB screwed me, I chose ALLPCB and I got the boards in like 8 days, thanks to the free DHL shipping. The quality was very good for the price, so I recommend them.

All of the passive components are 1206 size, so really easy to solder by hand. The smallest IC is the dual N-FET in TSSOP-8 package, but even that can be soldered by hand. Except for the ICs and passives you need just two special components:

  • microUSB connector (or you can directly solder wires to the board, if you want). I used the type with 5 pins and 2 holes, for example available here.
  • 22 μH inductor in 7 x 7 mm package.

The final board is 20 x 50 mm, so you can fit 10 of them on a 100 x 100 mm board. It is also just 2 mm wider than a 18650 cell. In the thickest point it is 6,23 mm.

All the files and photos are also available on my GitHub (and I recommend you download them from there, as there might be some future updates, new features and so).

If you have any questions, comments or suggestions, feel free to leave them below! Also, if you have hard time getting the components or boards manufactured, PM me. I have a bunch of the boards and components lying around, so I might be able to post them to you.

Comments

the_pi_and_i (author)2018-01-20

Hi, For space considerations, I'm considering one of the flat, thin batteries as sold by Adafruit and Sparkfun. These batteries have built-in protection circuitry. Will the protection circuitry of your circuit interfere and cause problems? I guess I could modify your circuit and remove protection but I also envision using 18650's, meaning I would need two versions. Thanks, I especially like the way you presented this project.

MartinD_CZ (author)the_pi_and_i2018-01-20

Hi,
firstly, thanks for your feedback. Regarding your question - that is honestly hard to tell. I would say that they should not interfere during normal operation, but the real question is what would happen if for example both of them enter the undervoltage lockout mode.
What I suggest is that you have the boards made with footprints for the protection, and then you do not populate the protection parts (that is R4, R5, U2 and U3). Then you just need to short all of the pins of the U2 footprint to complete the current path and voila - you have a board without protection...

the_pi_and_i (author)MartinD_CZ2018-01-21

Thanks, your solution makes perfect sense. What is the exact part you used for Q1. I can't find it on Sparkfun. Guess it's not very critical but would like to use what you used. Speaking of parts, I was curious about the pricing of parts here in the US. I was astounded to see that neither Digikey or Mouser carried any of the IC's.

Answering my own question: Q1 Mosfet is IRLML2244. It's available on ebay.

HippyNerd (author)2018-01-08

I used to do this. but I found that its just a whole lot easier and better to get a phone bank charger because its all in one nice package. You do have a couple problems with the phone bank devices though, one is that they shut off if there is not enough draw on them (they think the phone is charged...), The other is that they dont have really awesome batteries, like the good 18650s (AW, panasonic, ...)

FoxtrotOscar (author)2018-01-07

Nice!
I would really like to see you do the same for 2x batts - (8.4 - 6.4v)!
Im looking to power an arduino-rfid-HC12 package where I need the battery life two of these will provide.
Any chance you could get back to me?

MartinD_CZ (author)FoxtrotOscar2018-01-08

Actually, that's the thing I am working on right now :) It should be out in a week or two...

FoxtrotOscar (author)MartinD_CZ2018-01-08

Diamond Geezer

YLBright (author)2017-12-25

Thanks, but the board has to ordered from the manufacturer?

MartinD_CZ (author)YLBright2017-12-25

No, you can order it from anywhere you want. Just download the zip file and there are either gerbers or eagle source files...

YLBright (author)MartinD_CZ2017-12-25

Thanks, sorry, I didn't phrase that correctly: the board is not avaible for purchase without manufacturing it?

MartinD_CZ (author)YLBright2017-12-26

Hi,

yes, unfortunately you have to manufacture it yourself. Maybe I could post some of the PCBs to you, as I have about a 100 of them, but they will not be populated with components...

AAndy (author)MartinD_CZ2018-01-07

I would love to obtain one or 2 of these & would be glad to pay for them...
If this is possible, please drop me a note at andy at aschmitt dots com.
Thanks... & GREAT Instructable!!

MartinD_CZ (author)AAndy2018-01-07

thank you too, I sent you an email...

AAndy (author)MartinD_CZ2018-01-08

not to prove to be a complete idiot but I sent the wrong dot com address... it's awschmitt....... sorry & thanks again

MartinD_CZ (author)AAndy2018-01-08

I sent you an email.

YLBright (author)MartinD_CZ2018-01-08

Martin, that was the purpose of my query: can I purchase 2 or 3 of these boards from you. I don't need a hundred. YYLBright@gmail.com

MartinD_CZ (author)YLBright2018-01-08

Hi,

okay, sorry for that, maybe I misunderstood you. I have sent you an email.

chunkysteveo (author)2018-01-04

Neat little board, like it! How does the load sharing work?

Steve

MartinD_CZ (author)chunkysteveo2018-01-07

Hi,

it's kind of hard to explain, so I made a picture, see below:

RandyKC (author)MartinD_CZ2018-01-07

I couldn’t view the drawing. The resolution was too low to make out the writing. Any chance you could attach a higher resolution image of it? Beautiful instructable.

MartinD_CZ (author)RandyKC2018-01-08

Hi, well, for me, it shows up just nice, so I do not know what is wrong with Instructables. I put the files on GitHub, in the "load_sharing_explanation" folder

tomontee (author)2018-01-07

I just uploaded the gerbers zip file to OSH Park to see what the cost would be. They directly understand zip file from Eagle or KiCad. The upload failed with the following errors: 1) could not file drill file, and 2) could not find board outline file. I am using KiCad and don't know enough about Eagle to create a zip file with these two file include. Any help you can give will be apprecieated.

keesj (author)tomontee2018-01-08

I use kicad as well.
Use edge cut layer and draw a line around your pcb save your pcb file. When you plot your kicad file confirm the edge.cut
layer in the left column.
By default this edge cut layer is not marked.
Now you have your outline of your pcb.
You can see the edge cut layer with a seperate gerber extension
beneath.
A pcb manufacturar asks for outline of the pcb.
You can also look this up in the kicad manual.

MartinD_CZ (author)keesj2018-01-08

Hi,

my gerbers were optimized for AllPCB, but I see that OSHpark requires different format. I used the CAM tool from their official GitHub. You can find the Gerbers here, but I can not guarantee anything! Please let me know if they work, if they do, I will put it on my GitHub.

keesj (author)2018-01-08

Hello,
can this charger also be used in a serial setting of the 18650 batteries.
?

MartinD_CZ (author)keesj2018-01-08

Hi,

you would need to provide a galvanically isolated 5V input for each cell, and even then it would not be a good solution... but I am building a project which will be able to achieve that, so stay tuned, I want to publish it in like two weeks....

hpb (author)2018-01-07

Very neat. Good work and thank you for putting this out here.

Wild-Bill (author)2018-01-07

From all the crazies, innovators, and thinkers out there, I sincerely thank you for your instructable. When it comes to electronics, I typically clobber things together and then try to smooth out the corners by using software, as I am not where near as courageous or as knowledgeable you. I give you two thumbs up.

MartinD_CZ (author)Wild-Bill2018-01-07

thanks, I appreciate that!

nqtronix (author)2018-01-07

You really know how to make great circuits affordable by choosing the right components. PCB layout is neat and tidy, traces are as short as they can be. I like this, a lot! :D

That said, I noticed two minor things: The B340A diode for the load sharing circuit has a fairly high leakage current and might drain the battery fairly quickly. Unfortunately this is common for schottkey diodes. Second C4 could have been place a bit better to make the loop C-L-IC a little smaller. But yeah, that is absolutely nitpicking ;)

MartinD_CZ (author)nqtronix2018-01-07

Hi, thanks! :)
Regarding your feedback: the B340A has indeed a leakage current of about 0.5 mA. But this leakage current then needs to go through the 10k resistor and it flows only when the circuit is switched on. And the MT3608 will consume much more current when switched on, so I considered that an acceptable loss...
But you are right with the C4, it could have been closer, but I ran out of board space :)

Anyways, thanks for you feedback!

shootermatic (author)2018-01-01

Have you considered putting this on kickstarter? You could use kickstarter to raise the funds to allow you to manufacture and sell these on a larger scale which in turn would give you funding to make more cool projects.

MartinD_CZ (author)shootermatic2018-01-03

Well, thanks for the idea, but this is just a side project of mine, so I do not want to go through all the bother of putting it on kickstarter etc....

JohnW51 (author)2018-01-02

Very impressive. I was under the impression that a board like this is already commercially available. Don't recall where I saw it though, and i could be wrong.

MartinD_CZ (author)JohnW512018-01-03

Hi,

it can be available somewhere, I am not claiming this is something super new or innovative. I just needed a few of these boards for myself and decided to publish them afterwards, thinking they might be useful to someone...

KristjanK12 (author)2017-12-28

Yo man, have you thought of maybe selling them on ebay or smth? Also what about making v2 of it which would beef the circuit up? let's say up to 2A of charging current and max 2.5A output or smth like that. Good job on this one tho!

MartinD_CZ (author)KristjanK122017-12-29

Hi, thanks. Actually, I thought about selling them for a brief moment, but the thing is that I would have to assemble them by hand, which takes a lot of time and it is a very boring job. And anyways, I made them primarily for myself, not to make money. But if you want, I can post you the PCBs (but hey, you can have them made in China for a few dollars)

Regarding the beefed up version - that wouldn't be hard, but I do not have a use for such a beefed up version right now..

KristjanK12 (author)MartinD_CZ2017-12-29

Thank you for answering! by saying "have them made in china", do you mean prebuilt with chips or just pcbs? Also, how would you go on about beefing it up? I have some projects in mind that require more power than 1A but when it comes to designing pcbs or beefing things up, then it really muffles me. I have no idea how to do it, so if you have time and want to publish v2 some day, then i would love to see that.

MartinD_CZ (author)KristjanK122017-12-30

Hi,

by that sentence I meant just the PCBs, having them populated would cost a lot of money on such a low scale. You can populate them yourselves, it takes about 20 minutes each, and you don't need much skill, the components are big enough for hand soldering.
For beefing it up you would need to:
A.) increase the output current - the MT3608 should handle up to 4 A, so in this scenario it should be sufficient for 5 V 2 A output. You would need to upgrade the inductor, diodes (SS54 would do) and capacitors
B.) change or disable the overcurrent protection feature
C.) 2 A charging is actually the hardest part. You would need different IC, see for example http://cds.linear.com/docs/en/solutions-manual/Linear-Battery-Charger-Brochure-2016.pdf

Hope this helps a little bit...

randofo (author)2017-12-26

Nice board! I've thought about doing the same thing. :)

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