# A microprocessor controlled centralised BMS system idea.



## mnikhilesh (Jan 10, 2013)

If one can use a centralized version of BMS like MiniBms where wire from every cell is coming to BMS and HVC, LVC etc are being controlled by circuit, why not make one where a microprocessor controls everything. In my opinion it will be easier and use less components. For too many number of cells it may be cumbersome to have so many of wire but for small packs like 16 or 24 cells, it will be easier. Signal from each cell will be directly fed to microprocessor (through a multiplexer) everything will be calculated inside the micpro and signal can be sent to charger and load.
As for the temperature of cell one can install thermistors at several locations and read it through multiplexer. Many times cells are in parallel as well as in series so cell boards are not on all cell top but on one cell in each series cell. In that case we are not getting temperature of each cell, by using thermistors we can ger temperature at any number of places and have better control and look of temperature.

What I want to convey is shown in attached image.








http://www.flickr.com/photos/mnikhilesh/8782209540/

I am a mechanical engineer so kindly forgive me if there is any feasibility issue from electronics point of view. I am just curious to know if its possible to have such a system as it will be a simple BMS solution for small battery packs.


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## mnikhilesh (Jan 10, 2013)

I was looking at elithion and miniBms etc but while I was thinking about this thing I came across Orion BMS and I think they are doing the same thing I am proposing here, found just right now.
Can someone point me to advantage and disadvantage of both systems


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## Siwastaja (Aug 1, 2012)

mnikhilesh said:


> If one can use a centralized version of BMS like MiniBms where wire from every cell is coming to BMS and HVC, LVC etc are being controlled by circuit, why not make one where a microprocessor controls everything. In my opinion it will be easier and use less components.


No it won't. You'll have horrible time shifting and measuring the voltages and horrible PCB routing and wire spaghetti. It also get very sensitive to noise easily. This idea always rises up based on how things were in 1980's, when the CPU was a luxury item. Things changed in 1990's.

You just need to think a microcontroller as a simple basic component like a resistor, which it today is, with a price of $0.50 and a leg count of 8-10 and with very high level of integration.

Then it will appear to you that a distributed system is the simplest, extendable, least complex, cheapest and the most reliable, and by a large margin.

These microcontrollers have integrated voltage reading and integrated temperature sensors. No need to multiplex anything. Very few external components needed; only level shifting or isolation for communication. And digital communication is easier to level shift or isolate than analog voltage measurements you need to take care of in your proposal!

Of course you still need one microprocessor "control everything".


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## mnikhilesh (Jan 10, 2013)

Siwastaja said:


> No it won't. You'll have horrible time shifting and measuring the voltages and horrible PCB routing and wire spaghetti. It also get very sensitive to noise easily. This idea always rises up based on how things were in 1980's, when the CPU was a luxury item. Things changed in 1990's.
> 
> You just need to think a microcontroller as a simple basic component like a resistor, which it today is, with a price of $0.50 and a leg count of 8-10 and with very high level of integration.
> 
> ...


But Orion BMS is doing this same thing so its feasible, though I dont really know about their performance. This system can also remove the heat of top balancing from battery to BMS master. I intended to use multiplexer only because of wire spaghetti. By using multiplexer for voltage and thermistors PCB can be made real neat.
As for time shifting problem I am no expert in electronics, can you please elaborate why you think there will be problem?


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## mnikhilesh (Jan 10, 2013)

I was going through orions documentation and found that they are much concerned about electrical noise but in most cases they can suppress it by grounding the BMS body.


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## Siwastaja (Aug 1, 2012)

mnikhilesh said:


> As for time shifting problem I am no expert in electronics, can you please elaborate why you think there will be problem?


No, I won't start elaborating what "voltage" means and what a resistor is etc. I think if you want to design a BMS and think you have a great BMS design idea, you should start from the basic electronics. Once you understand the basics, go prototype something, and you'll probably understand the flaws of your idea by yourself. Good luck! A hint: you cannot measure cell voltages from one place with good accuracy and safety. That's why it's typically distributed, and even many of the "centralized" systems are something like distributed systems joined to one PCB.

tldr; Sorry, you need to be an expert in electronics.


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