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Thanks Stuart,

To clarify I am looking to build a 7s powerwall with 100 cells per 1S so 700 cells in total, can this be handled by the diyBMS ?

22

You will have to determine if the design is suitable for your needs as every DIY powerwall is different.

You could also split your power wall into 50 cell groups and have 7S50P x2 and then use 14 modules to provide more granular control/higher balancing.

23

Awesome, that would work,
Next question, you have a part list are there any services out there that offer assembly, I am in South Africa so would prefer to order the 14 modules, controller assembled, shipped to an office in the uk and then they come over every month or so would bring it onto me, I can solder find just SMDā€™s are not a simple.

But again I really like this project and feel it has and can have a major impact, Is there any plan to include a shunt ?

Thanks again

24

The main forum is over hereā€¦

https://community.openenergymonitor.org/t/diybms-v4

Plenty of people have used JLCPCB to assemble the boards - you just have to add the ATTINY and solder the sockets.

25

Thanks Stuart, I appreciate the help.
After some reading and more investigation I think I am either going to hold out for the v5 active balancing or, just buy an active $15 balance on aliexpress, I still will do the BMS but my just take a look at the code and disable itā€™s balancing options.

Again thanks for the help. Iā€™ll be watching these threads keenly

26

I wonā€™t be making an active balancer myself, this forum is a sub-project.

You wonā€™t need to make any code changes to DIYBMS v4 to stop it balancing, just set the voltage to a high number and it wonā€™t do anything except monitor and control relays etc.

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I am interested to know if any further development has been made on this ?

28

The active balance isnā€™t my project so Iā€™ve not been working on that.

29

Hi!

@stuart Thanks for initiating the diyBMS project back then, and for supporting it for so long!
@hitech95 Thank you for taking the next step and thinking about of active balancing.

I have some experience in electronics, but I am totally new to BMS, making lithium batteries and so on! However, I want to replace the two Pb engine starter batteries (12 V / 12 Ah each) on my ship with a lithium starter battery. Some of my requirements and constraints made it impossible to find a suitable solution so far. So, here I am, doing it myself :slight_smile:

As a start, I have two questions from the very top of my list:

  1. Would it be possible to use this v5 to manage LiFePO4 cells?
  2. Would it be possible to manage bigger cells (e.g. 38120) instead of 18650 cells with v5?

Thank you!

Cheers,
Willy

30

Iā€™m not sure the v5 boards are progressing very much @hitech95 was working on it, Iā€™m not directly involved in it.

31

Development is on hold, due to some issues with the welll know Virus.
Iā€™ll come back on the development once, this emegency passes away.

Anyway, some progress on the code has been done. Iā€™m unfortuantly having issues on finding a source for the active balancing chips.

With some research we could try to implement our own buck boost circuit!

32

NicolĆ², what I like most about @stuart 's approach is using a multipurpose microcontroller instead of a specialized cell controller chip. This not only avoids ā€œissues on finding a source for active balancing chipsā€ but also allows for implementing features that chips made for mass markets normally donā€™t have (e.g. communication interface).

So, letā€™s do some research, yes! My present field of ā€˜researchā€™ is to work through the diyBMS-passive material (v4 and earlier) to learn as much as possible about cell balancing in general. Since you are some steps ahead, you may think about other activities. Please share you ideas with us.

OT: My thoughts go out to you guys in Italy. You suffer so much from that micro monster! Keep on singing from your balconies. Itā€™s so heart warming!

33

Hey @hitech95 greetings from fellow Altium user.
I was looking into the diyBMS Rev5. Awesomeā€¦
I use normally PSOC controllers in favour to Atmel Controllers. Why would take too long now.

I saw You had problems with the Memory stuff. This was one of my main reasons to switch to PSOC.
Also the PSOC has custom Logic and changeable pins. but more on that in a different text.

It might be that the PSOC4 could replace the ETA3000 and the Atmel chip. ( PSOC4 from Cypress, up to 256K memory, about 1.30$ at Mouser as 32K version)

The development software is also free to get.

I did a lot of projects with it. one version was with a custom HW designed SPI multiplexer inside the chipā€¦ Yes You can design also small custom circuits inside the chip.

I am looking to implement the active balancing into the PSOC as separate HW/SW combo. the dedicated ANALOG subsystem could handle also the measurement. I think we can do better than the 30mv stuff and You dont need the separate Serial com to the ETA3000ā€¦

It is still DIY but more advanced. Programming is different to Arduino IDE.
Dont get me wrong I use the Arduino IDE also for ESP32 and other stuff too.

It would be like the diyBMS_V5_Plus or similar.

One thing i want to know is the hookup of the BMSv5ā€¦
for instance if i have a 5S Systemā€¦

Could You create a wiring diagram or pinpoint me to a ressource for it ?

I check with my friends in CN for a source for the ETA3000 chip. I think i can import and distribute the chip.

So enough for now.

Greetings to all the ppls out thereā€¦ especially to You NicolĆ³ (sorry didnt find the other accent ) and Stuart Pittaway for creating the v4 and other circuit parts

34

Glad people are interested in expanding other ideas.

Please do me a favour though, donā€™t use the diybms or v5 as part of the projects name, it will be confusing to end users.

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Okay i will look about naming.

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@stuart Just found out that You are the father of the diyBMS plattformā€¦ Hats upā€¦ Awesome stuffā€¦

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Hi @hitech95 I will keep and eye in your code as I am begining to do my own diybms but with promini boards and other components that I have in home. I not feel confident with smd soldering.
I understand that you code is compatible with ATMEGA168/328 an ā€œsimilarā€ to diybmsv4 code, isnā€™t it?
Thanks

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By the way,
This is NOT active balancer.

39

This is still a proof of concept & a discussion on how to implement the acrive balancing. Take a look to the original v4 version.

Iā€™m using a bigger general purpose micro controller, the fact that to keep the boards the same size of the v4 I had to make some decision:

1.Active balancing require a lot of discrete stuff, using an external dedicated IC require less space. Discrete solutions require multiple opamps, mosfet drivers, mosfets, ?..
2. The current solution is cheaper. the IC require fiew passives.
3. Implementing the DCDC Buck boost on the FW require a ā€œlotā€ of resources that during initial phase of the development were not available (Initially I wanted to use the same AtTiny)

But Yes, youā€™re right I would prefere to have only a programmable chip with FOSS instead of a proprietary solution.

Thanks, things are looking better now!

This in my opinion could reduce the community ability to change and improve the software for their needs. That is why Iā€™ve chosed to work with the Arduino/Platformio. (the initial debug code is for arduino)
An STM32 could also be another good alternative.

The problem to implement the ETA3000 is the fact that we need three differential ADC channels to measure the local cell and the next cell to properly know if we can dump power to the next cell. One of which is used to monitor the balancing current.

Right now I donā€™t have a schematic for that, the connection is the same of V4, but you also have a sense cable that connect the cell balance of cell N to the positive of cell N+1 to read itā€™s voltage and provide the power if we need balancing.

Yes the V5 code has been tested on the 328P variant (except the sleep mode see below).
Take a looks that you cannot put the IC in complete sleep due to a lack of Serial RX wakeup ISR on the 328P variant but the PB have it but the AVR studio C library have a bug:

This is another reason Iā€™ve put on hold the project.

Why you say so? Instead of loosing the energy we move the power to the adiacent cell. Both UP and DOWN. This can be done on both charging and discharging process.

Iā€™m open to suggestions, the fact the you want to keep the DIYBMS make sense. Even if this is a directly derived project. In fact as you requested Iā€™ve also implemented your protocol. (We could mix and match modules - THIS REQUIRE TESTING)

Suggestions for the name are OPEN.

To sum up the current status:

Once I get some time for the project I will order the components that are missing and Iā€™ll show you a prototype.
Batteries, MCUs, Connectors, Passives, and PCBs are here.

I have created an Arduino Uno based prototype and used a scope/logic analyzer to troubleshoot the code and it was fine (The sleep wakeup from Serial was not tested due to HW limitation. Also the active balancer section is missing on that prototype.)

40

ā€˜SOLOBMS with ABSā€™ is my name suggestion.

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