Max1757/8 Li-ion Battery Charger DIY

Recently, I have built a battery charger and have used it to charge my battery packs for a month. I would like to share the joy of DIY with you guys.

Home made PCB.

Assembled PCB


The IC, Max1757/8, will heat up to about 70C. I glued an Al slug with thermal epoxy on the top surface of the IC to conduct the heat to the Al case.



The yellow LED glows to indicate the charger is in Constant Current Mode, the green LED for Constant Voltage Mode and the red LED for Fault Mode.
No LED is on indicate that the charge cycle is completed. The IC is selectable to charge 1 Cell, 2 Cells, 3 Cells or 4 Cells. I fixed it only to charge 2 Cells. The maximum charge current is 1.5A. It takes about 3.5 hours to full charge my 2S1P 7.2V 2600mAH battery pack.

Looks nice. Do you have more info to post, like details of circuit diagram, parts list and external power supply?

Dear Mr. Happy,

You can download the circuit diagram and part list here.
http://datasheets.maxim-ic.com/en/ds/MAX1758.pdf
http://datasheets.maxim-ic.com/en/ds/MAX1757EVKIT-MAX1758EVKIT.pdf
The external power supply is a switching type 12V DC power supply which I borrow from my PC speaker.
The components lay out of the PCB

Dear Microa
Can I please have the footprint of this chip max1757? would be very useful! thank you.

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Dear Albertalp,

The details of the package can be found on the page 17 of the data sheet. If you want the 1:1 scale solder pad footprint of the chip, please send your e-mail address to my private mail of this forum. I don't know how to set up a direct download link for you to dwonload.

Recently, I have upgraded the layout of the PCB.
A) use a RBG Stat Led instead 3.
B) move all the components which higher than the chip to the solder side.
The result is
A) the chip can be directly attached to the heat sink.
B) the PCB shrinked to 28 x 28mm.

Component Side


Solder Side


Test Run

Another easy way to get the footprint is going to www.cadsoftusa.com to download the free version of EAGLE V5. Open the Libraries and find the maxim.lbr. Looking for the package SSOP28 which is under the devices, Bingo you find the footprint of SSOP28. Good luck.

I would like to post the components layout for your reference.
The Component Side

The Solder Side

The Component Side of the PCB

The Solder Side of the PCB

The comparison of different generations of the PCB

And what about cell balancing? Isn't it dangerous to charge li-ion packs without individual cell monitoring?

The protection circuit is built in the battery pack which is a Ricoh R5460N 2-Cell protection IC.

I know this is an old thread.
Can you provide the eagle files?

I'm very interested in this design.
I tried to do it myself but was unable to do it.
Would be awesome to get the eagle files if possible.

Dear Sir,
Please provide the schematics of MAX1758 ic. Thanks in advance
my email address is [email protected]

Hi @Microa,

I'm also wondering if you would be able to share you EAGLE files, or at least share the schematics. I'm also trying to get this to work, and it would help tremendously if you can share your work,

Hope to hear from you,

R.

Dear mohsin qau and ruben vleuten,

Sorry for my late reply. Please find enclosed EAGLE files in the dropbox
https://www.dropbox.com/s/iuirss44epjf24i/MAX1757_2-3_Cell_23x40.brd?dl=0
https://www.dropbox.com/s/vv2mjmo4zpiouwp/MAX1757_2-3_Cell_23x40.sch?dl=0
https://www.dropbox.com/s/k8wpm61ba12h7hq/MAX1758.pdf?dl=0
https://www.dropbox.com/s/wxu8ksz4wkrumma/MAX1758EVKIT.pdf?dl=0
My version of the EAGLE files is very old EAGLE 5.6.0. I am not sure whether EAGLE 6 and EAGLE 7 can open the files.
I hope these files can help.