DIY Lithium Battery Balancer and monitoring (BMS)

Jonisonveapa · 2019-07-15T22:22:12.179Z

Hello new to this forum hi

Really interested in bms solar, electronics microproceasors ect. I would like to build this bms could someone show me where the latest board is so i can buy it as i have many 18650s that need a home i have been trying to build a battery packs.
I have been a pcb deaigner could help in future with new designs if needed and help with design or hardware ect.
Am an expert in design spark, and protel, pcb packages Dos version, im old, could help with pcb advice ect.
Is now a final fully working design?
Or is there some of the latest boards for sale?
Wonder if someone could send a pm to
Chitu_Mihai-Georgehanks asmi am unable he has some boards for sale
Im so excited i wont be able to sleep tonight
Thank you

Jonisonveapa · 2019-07-15T22:34:44.158Z

@Chitu_Mihai-George
Hi have you any pcbs for sale and are they the latest veraion?

Jonisonveapa · 2019-07-15T23:07:54.247Z

Hello david, i am new to this board, interested in your bms, wonder if you have any spare boards for sale thanks jon

DavidBTB · 2019-07-16T03:04:13.481Z

Jonisonveapa:

Really interested in bms solar, electronics microproceasors ect. I would like to build this bms could someone show me where the latest board is so i can buy it as i have many 18650s that need a home i have been trying to build a battery packs.

It’s all Stuart Pittaway’s design. But I suggest you take a look at the most recent version.
https://github.com/stuartpittaway/diyBMSv4

Chitu_Mihai-George · 2019-07-16T05:39:59.300Z

Yes i have some more (~20 to spare). They are version v3.0, if you are happy with them i can send some.

stuart · 2019-07-16T07:47:17.042Z

Jonisonveapa:

I would like to build this bms could someone show me where the latest board is so i can buy it as i have many 18650s that need a home i have been trying to build a battery packs.

This is the older design - take at look at V4 over here…

DIYBMS v4 diyBMS

I’m having a chat with the OEM shop and also with some Chinese PCB builders to see what cost that would be.

stuart · 2019-07-16T07:53:53.726Z

Andy:

I measured 2 of the boards that wont provision and all reading are the same as a factory setting as a module that can be provisioned.

Hi @Andy do you get a voltage reading on the test point between that and cell negative? It should be about half the cell voltage.

Its strange that you are getting zero reading for both temperature and voltage - are the calibration values correct (if they are zero it would do this)

Does the web interface show the other voltages correctly?

Jonisonveapa · 2019-07-16T08:45:54.211Z

Helllo diybms
Thank you, is this version 4 board

Jonisonveapa · 2019-07-16T08:47:24.333Z

Hello chitu
Thanks for replying, is there any difference between version 3 and version 4?

Chitu_Mihai-George · 2019-07-16T08:52:38.622Z

It’s a huge difference and not compatible. Different components, power consumption, etc. As @stuart mention is nothing wrong with V3 but the project evolved and in V4 there are more possibilities. I did not build the V4, for the moment i will stay with the V3, but V4 looks very interesting!

Andy · 2019-07-16T08:55:49.172Z

hello stuart,
No i solved the temp and voltage problem. I found a short on the actual board and fixed the other short under the resister, so that took me to 13 boards working. I am now trying to get my 14’s working
This a new problem, 2 boards that I measure from gnd to each point on each of the components are the same as a proven good board, but these 2 wont provision. The wemos i working correctly. I have changed U2 several times as well. Thanks Andy

Andy · 2019-07-16T08:57:33.949Z

hello Chitu, are they fully completed boards and working and able to be provisioned.

stuart · 2019-07-16T14:14:08.710Z

Andy:

The wemos i working correctly. I have changed U2 several times as well. Thanks Andy

Okay, disconnect all the boards except the “bad one”. Reboot the Wemos (it only scans for modules on power up).

Can you provision the board now? If you can, select “factory reset” for that module and then try it again in the string with the others and see if you can provision it.

3xtr3m3d · 2019-07-16T17:17:05.443Z

Hi

is there a part list available to buy components at one place for v4? lcsc lists doesn’t seems to work in BOM tool

Regards

DavidBTB · 2019-07-17T04:34:41.132Z

Software question: If I wanted to make some minor changes to the controller / GUI code, would I end up having to re-provision all the cells every time I flash the wemos?

stuart · 2019-07-17T07:56:01.429Z

It depends…

If you are only changing the web interface, then no, the Wemos code is independent.
If you are changing the way the modules communicate/protocol or if you are moving logic into the cell modules then yes

Obviously if you make some good changes, please let me know so they can be pulled into the base code.

Sebastian_Nobody · 2019-07-17T09:11:19.197Z

Hi Stuart, hi guys,

I want to give you an experience report about my current v3 build. Just some things I run into and which were not so easy etc. Currently I have done 9 of 14 boards. They are all working now…!
I need the BMS for a Diy Powerwall made out of 1120 18650 cells connected as a 14s setup. The total capacity is ~10 kWh.
Also I just ordered stuff for the v4. Just for fun

About the v3:

I used my 3D printed stencil (diyBMS stencil (v3 and v4) by seba_p - Thingiverse). It really works well!
I ordered most of the components via Aliexpress. To find the ATtiny85 was more difficult, at least at low cost!
I used hot air to solder the boards. No problem at all.
As discharge cement resistor I have chosen 10 W 2 Ohms as I have about 180 Ah (80 cells) in each pack. At 4,1 V (max. setting for me) the current flow will be ~2 A => ~8,5 Watts. Lets see if the resistors are really able to handle 10 W! As backup I have some 3.3 Ohms laying around. Of course I left a couple of mm space to the pcb not to heat up the whole circuit.
Programming work easily done. But I have done some Arduino projects before. I used an Arduino Nano which I flashed before as ISP. Burning the boot loader and writing the code went smoothly.
I use a NodeMcu ESP8266 ESP-12E as controller. First I didn’t read about the pull up resistors for SCL and SDA. And ofcourse nothing was working. But 2.2 kOhm between +3.3V and SCL and SDA works perfectly for me now.
The first problem occured around board 6. First all 6 were running on a 6s test setup. But suddenly one board dropped of. The green LED was flashing showing the “panic mode” then. I couldn’t reset the board as it was not shown anymore. Also reflashing didn’t help. After erasing the flash with the given Arduino expample code and reflashing it worked again. Took me a while to figure this out.
With board 7,8 and 9 more problems came. After flashing they all showed the solid green LED light. But provisioning didn’t work at all. So I started to reprogramm etc. No luck. After that I started to check the solder joints around the I2C isolater chip. I found out that 1-2 solder joints on each board were bad!!! So I hand re-soldered them. And that was the solution for that problem. I think my 3D print stencil is the problem as not enough solder paste comes through these tiny holes. Also the chip arms bend easly. Thus, they were not touching the pcb. But it didnÄt see it with my microscope.
The blue LED is very week with the updated 4.7 kOhms in series. I think 1-2k would be better. Or even lower. In earlier versions a 2.2k was given. What do you think?

About the v4:

I have chosen 5 W 3.6 Ohm cement resistors. I don’t want to have the heat on the board. Once the board heats up, the voltage devider which gives the cell voltage drifts. I tried this with my v3 just by heating the two resistors a bit with my hot air gun (like 80 °C). The voltage reading in the web interface went up about ~0.2 V!
I hardly found the LM4040BIM3-2.0/NOPB. At Farnell it is discontinued. Finally I fount it on Aliexpress. But 1 USD each and only 10 peaces together. Thus 20 USD for that …

Thanks to all of you working on such a great project!

Best regards from Germany,
Sebastian

Andy · 2019-07-17T11:53:49.263Z

Hello Seb
Thanks for your post, you helped me solve of problem i been having. It was point 8, had 3 boards that wouldnt work correctly, everything look correct and was even measured correctly. However your point showed me it could be the I2C chip and its legs, so i pressed down on the legs with my nail and did a scan using the BMS controller test software and finally it showed up. Did the same with the other and now i have spare boards. finally so thank you SEB.
Andy

Sebastian_Nobody · 2019-07-17T12:01:06.315Z

Ha! Yeah! I saw your post and I was facing the same problem more or less. So I started checking and checking. I couldn’t believe that the solder joints were bad. They looked so perfect.

Glad that I could help you.

stuart · 2019-07-17T13:36:18.842Z

Thanks for the great write up and feedback @Sebastian_Nobody highlights the importance of triple checking the soldering just to make sure.

Sebastian_Nobody:

I hardly found the LM4040BIM3-2.0/NOPB. At Farnell it is discontinued. Finally I fount it on Aliexpress. But 1 USD each and only 10 peaces together. Thus 20 USD for that …

They are expensive, but overall much cheaper than the v3 boards.

Farnell are restocking but under a different part number, no ETA on arrival either.

You can also order directly from Texas Instruments

ti.com

LM4040-N | Buy TI Parts | TI.com

LM4040BIM3-2.0/NOPB - 100-ppm/°C precision micropower shunt voltage reference in a SOT-23 (DBZ) package with 3 pins