DIY Lithium Battery Balancer and monitoring (BMS)

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(Robert Wall) #751

Unfortunately, I don’t feel able to start splitting the thread because it doesn’t fall strictly within our code of conduct: “posts shall be edited only when absolutely necessary.”

So your best hope is that all contributors see these last few posts and create a new thread if they feel that is warranted.

(Vela Nautica) #752

Hi Stuart,

but why do you think PCA9601D is not right to solve problems?

In my case I do not have issues with I2C but like to extend the distance from controller to the modules.


(stuart) #753

You are trying to solve issues with i2c - however i2c isn’t the best solution for this BMS problem, so rather than trying to work around the problem, it would be better to replace i2c with something else - like CAN or RS485 etc.

(Chance Schraeder) #754

Howdy gents! Before I get too far into the weeds with the LEDs.
Do I have them correct here? The green tinted side facing down are the cathodes.
Blue on the Left and Green on the Right

(Brett) #755

from what i can see Chance Schraeder

The green line on your LEDs need to be near the D2 D4 that in the negitive side of the LED as i found out the hard way as my LEDs i got never had any making on them so i replaced all my LEDs with the same style that have a grean mark on the negitive side

(Chance Schraeder) #756

Okay thank you! Based on the limited information on the version 3 board it appeared the cathode was facing the discharge resister. Thanks I’ll switch them

(Chance Schraeder) #757

One more question. Will either the green or blue illuminate upon applying power?
This is before I’ve programmed the ATTINY.

(Brett) #758

If you have a multimeter and put it on continuity the led should light up if black on negitive and red on positive, but looking at the board should be able to see the tracks which would be positive.

D4 should light up and D2 is discharge of cells

Iv changes my colours to D2 red discharge and D4 to green Activity i did have both on blue but i see the colours would have been better choice RGB leds would have been a better choice

For an unprovided module the D4 should little up for a few seconds then go out then using test connection provision all connections if in factory D4 should should stay lite

(Vela Nautica) #759

Hi Stuart,

So far on my side the diyBMS does a good job and has no issues since some weeks now.

As you see there are some guys building this project and for now we don´t have any better so adding PCA9601 is a small task to fix problems. But some of these problems seam to me homemade by wrong installation of I2C or using noisy chinese inverters.
I will try to use PCA9601 to gain some distance up to 3 meters between controller and modules to get it out of the batterie compartment.
As my controller also offers a display, I like to place it visible as one view all OK.
I designed small breakout boards to test it also at module side. Now waiting for JLC :slightly_smiling_face:

Maybe Version 4.0 comes with CAN ot RS485? yes RS485


(Brett) #760

Dont you mean RS485 ?
I have TTL to RS485
but looking into using TTL to RS485 to see if i can get my wireless DB6 wifi plug to using ttl to rs485 communication

(stuart) #761

V4 is using serial comms (again) but not i2c (this is not released or finished yet)

The move to CAN or RS485 doesn’t make sense in the small scale DIY world - you may as well buy Batrium !

(Brett) #762

yeah very true.

we are on a budget and DIY is much better and much cheaper then buying batruim
For my own self batrium in out of my ball park.

(Dirk Walde) #763

For all information:
Adam Welch has posted a new video on the net. Where he points out problems of the NTC at the reset port of Attiny85 from temperatures of 5 C or less. - YouTube - diyBMS issue - Voltage Divider Maths -

(stuart) #764

I’ve already updated the schematic diagram to show possible change in resistor values. This is only a problem if you are running the cells outside or in very cold environments.

As mentioned in the video, 18650’s don’t really like cold conditions!

(Chance Schraeder) #765

So green should illuminate upon power without any programming in place?
If so my first module is broken. I get no status LEDs

(Dirk Walde) #766

My Powerwall is in front of my house :wink: Germany with winter and snow and sometimes cold weather.
Not everyone wants a battery with up to 4200 x 18650 cells in the basement.

What resistance values have you now changed my V2 modules still after the status of 09/2018.

(Brett) #767

led should flash on and off when power is connected once programmed or factory reset led will stay on

the led should flash with your tx led when running the program to the attiny

(Chance Schraeder) #768

Okay makes sense! Thanks for the info.
I’ll be tinkering a bit this evening with them.
Just now finishing up the modules.

(Brett) #769

ill have to look and see what updates i need to do with my modules
due to one of my modules going into reset all the time now not running at all but waiting for some new componets to come maybe in the new year they be here.

(Chance Schraeder) #770

So far I’ve programmed two of these modules using the USBasp.
I tried several times using my uno with no luck.

Both modules report they are done uploading the sketch.
Upon plugging in power to the module the green LED flashes once then stays illuminated.

Am I on the right track?