Low cost / High performance universal BMS

[nlc]

Originally Posted by esoneson

nlc,

Your contribution to EVs is much appreciated and making the protocol open is also commendable.

Thank you

Originally Posted by esoneson

In the light of the "bricking" of the Tesla which is caused by leaving your vehicle alone for a long period of time with no way of "turning off" the drain on the traction pack, is there any state of the slave board where it does not drain any power? Can you "turn it off"?

The slave board turn automatically OFF when there is no communication for more than 10 seconds. It's not a true OFF state but a deep sleep state, and the current consumption on the cell is a few µA, thus much less than self-discharge of the cell. The slave board wake up automatically when it receives a request frame form the mother/master board.

And the mother/master board is completly OFF until ignition key is ON or charger is plugged.

Originally Posted by esoneson

This is the one characteristic that the slave board that is powered by the mother board that would enable total power off of the vehicle.

No possible at my opinion, cost will be too high and wiring more complicated.

Originally Posted by esoneson

EDIT: sorry, that was a very poorly constructed English sentence.

It's my case too

[sawickm]

Originally Posted by nlc

More important decision for example is to tell the charger to pass to low current charge mode for balancing, completely stop the charge, tell controller to stop discharging the pack (at a first low voltage threshold for example), and why not cut completely the power by opening the main contactor at a second lower voltage threshold.

From my side I have not finished the development of the master board, because I want to take time to really think it to be perfect for EV usage.

NLC,

Are you going to design your “Master Board” to interface with the ReVolt Controller ?

A new version of the ReVolt Controller PCB that has the BMS master on-board would be very nice! You just directly plug in the distributed BMS slave boards to the new controller.

The ultimate would be an integrated BMS/Controller/Display & Charger?, just add batteries.

-Mark

[nlc]

I am not a big adept of the "all in one" philosophy (BMS/controller/display/charger), but more adept of the linux philosophy : a single and simple tool for a single/simple function.
And combine these simple (and then highly reliable because very specialized) tools together to do complex and sophisticated things.

For the openRevolt controller, there is absolutely no obstacle to directly connect and read the BMS slave board daisy chain, and do all we can imagine in internal controller firmware. For example SoC, limit discharge current to not have a brutal power off when battery are low, and so on.

To connect my BMS slaves, just need a free uart and very very simple interface, just some resistor/transistor, opto-isolation is directly on the BMS, on the first and last slave boards.

From my opinion, the perfect EV infrastructure is :
- A mother board calculator (brain of the EV), manage all input/output, precharge/main contactor, throttle/breake, charge relay, current measurements, motor temperature and so on.
- The daisy chained slaves board directly connected to calculator to always have in real time all cell voltage and temperature, and be able to do SoC and other useful function
- One or more controller which receive their torque consign from the mother board (with CAN bus). Very useful configuration for multiple controller/motor EV, because the differential gear is totally natural in torque consign mode (current mode).
- A tactile optionnal display, connected on the mother board calculator, and deported on the dash board. Display which can be a smarphone if motherboard implements bluetooth

I designed the power train of this without driving license vehicle, and exactly used this architecture. There is a controller on each hub motor wheel, thus 4 motors/controllers (the controller I talked about in the Paul and Sabrina AC controller topic), connected to the mother board with CAN bus, and this architecture is really simple, evolutionary and reliable !!

[skeeterb]

Originally Posted by sawickm

NLC,

Are you going to design your “Master Board” to interface with the ReVolt Controller ?

A new version of the ReVolt Controller PCB that has the BMS master on-board would be very nice! You just directly plug in the distributed BMS slave boards to the new controller.

The ultimate would be an integrated BMS/Controller/Display & Charger?, just add batteries.

That sounds like a good idea sawickm. That makes for a very revolutionary system that gives the EV user good control over management of the EV systems, as few as they are. It would probably ease the conversion of EVs from ICE.

[nlc]

Yes but with all in one concept, there is no modularity to work with absolutely all user :
- What controller voltage ?
- What controller current ?
- What charger input voltage accepted ?
- What charger output voltage/current ?

Easiest at my opinion to have 3 separate system but with easy wiring and configuration, every one choose the best component for its personal use. It can be also revolutionnary to have some bms / controllers / charger / mother board specially designed to work easily together with open protocol.

[Elithion]

Originally Posted by nlc

I begin with a photo where you can see a similar product from Elithion. But It have some flaws, I can list them if you are interested !

I wrote you privately, but you must have not seen it, as I did not get a response.

Since you state that our BMS has flaws, could you be so kind as to please write us directly and tell us what those flaws are? (This forum will not allow me to post links, so I must ask you to please use the contact page on the Elithion website.)

Thank you for your time, and I wish you the best with your BMS project.

Davide

[nlc]

Originally Posted by Elithion

I wrote you privately, but you must have not seen it, as I did not get a response.

I just checked for that but I have not found any message for you
Maybe you just have clicked on "preview" and not "send", I made this mistake one time or two.

Originally Posted by Elithion

Since you state that our BMS has flaws, could you be so kind as to please write us directly and tell us what those flaws are? (This forum will not allow me to post links, so I must ask you to please use the contact page on the Elithion website.)

Hummm, I don't know what to say to you !! Yes from my opinion your board have some flaws, but give them to you will be the best way to explain you how to improve your products !! In another situation it would have been a pleasure to do that, but because I want to try to propose a high perf low cost BMS and more generally a complete master board / display system for DIY EV conversion, I think you will understand I prefer to not list these flaws now

Originally Posted by Elithion

Thank you for your time, and I wish you the best with your BMS project.

I don't know if it's really sincere, but thank you anyway

[Elithion]

Originally Posted by nlc

Yes from my opinion your board have some flaws, but give them to you will be the best way to explain you how to improve your products

Of course we're striving to make our product the best that it can be: you can't blame us for that.

We are flattered that you chose our BMS, presumably because you felt it was the best one out there, and the one that you wished to reverse engineer; I see from your description of your BMS that you were successful in doing so, as you copied most of the features, technologies and functions of our BMS. Good for you! And thank you for the compliment implied by your choice.

Originally Posted by nlc

>Thank you for your time, and I wish you the best with your BMS project.

I don't know if it's really sincere, but thank you anyway.

Oh, absolutely! I meant it. I am sorry if you may be so jaded that you can't accept a sincere well wish without suspicion. I can prove that I meant it: on our site we take pain to list every BMS out there (again, I can't put a link because this forum will not let me); that is because we wish success to all the BMS companies. We all are doing something good for the world, and we need to work together, not against each other.

[nlc]

Originally Posted by Elithion

We are flattered that you chose our BMS, presumably because you felt it was the best one out there, and the one that you wished to reverse engineer; I see from your description of your BMS that you were successful in doing so, as you copied most of the features, technologies and functions of our BMS. Good for you! And thank you for the compliment implied by your choice.

In fact I have not wished to reverse engineer any BMS, not chosen yours. I developed for a customer some month ago a special BMS for the car it develops (I also developed for him the FOC controller I talk about in the Paul and Sabrina topic). But it's a more sophisticated BMS because it uses capacitive balancing. For installation cost he asked me to have one small board by cell, same principle than a lot of other BMS manufacturer. But on this BMS, there are 4 wire between each cell, for the communication daisy chain (there is not a lot of way to do a Tx/Rx daisy chain, not necessary to look how other do that !!), and capacitive balancing needs.

After that I thought it would be a good idea to simplify it in a extreme way for my personal use (I try to convert a gazoline car to electric), and why not propose a low cost high perf BMS based on this principle for DIY EV conversion community, in France and world wide. More generally I want to propose a generic calculator to manage all the EV car, the slave BMS being just a part of the complete system.

During development of my board I talked about my project to some friends some week ago, and one of them told me that it already use this kind of BMS, and it was yours ! He asked if I can be able to repair some broken board, I say yes I can try and this is at this moment I studied your board and saw some flaws I did not have on my own board (from my opinion of - maybe too much !? - perfectionist developer !!). Also, at this moment I seen that your hardware daisy chained principle is even simpler than mine, but I prefer mine anyway because I don't like directly input a signal in a microcontroller, even trough a resistor.
Also, I don't know how your protocol works, and it's better like this, I prefer implement it myself, it's really exciting to try to simplify it in an extreme way keeping high perf and high reliability (as you know the internal clock of this microcontroller can severely deviate in all the -40/+125° range).

Originally Posted by Elithion

Oh, absolutely! I meant it. I am sorry if you may be so jaded that you can't accept a sincere well wish without suspicion. I can prove that I meant it: on our site we take pain to list every BMS out there (again, I can't put a link because this forum will not let me); that is because we wish success to all the BMS companies. We all are doing something good for the world, and we need to work together, not against each other.

Happy to hear this, thus I gladly accept your wish and I thank you very much for that !

[z704w40]

Great work.
May I suggest the "brains" for your BMS. There is a single credit card size motherboard available. It's called raspberrypi (.org)
It's has a lot of connection possibilities and it is cheap and based on arm linux. Do you want to make this BMS project open source?

regards