Recommendations on BMS

SeRiusRod

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I'm currently building a new 17kWh battery (14s176p) and I would add an affordable BMS system. What I want is to get as much as possible data in my server, to thinker on it. And I hate all those bluetooth apps.

I was thinking on an active balancer, like: https://es.aliexpress.com/item/32788338337.html
And for a BMS a DIYBMS: https://github.com/stuartpittaway/diyBMSv4

But I don't know if both those would collide or if there's a better approach.
 

daromer

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Skip the balancer. The diybms have enough balancing Power!
Diybms Will work and i add more and more to the data Collection :)
 

SeRiusRod

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Skip the balancer. The diybms have enough balancing Power!
Diybms Will work and i add more and more to the data Collection :)
😄 Ok. But are you sure it has enough balancing power? I've read about people doing tricks with mosfets to replace the stock resistances.
And i didn't know that diybms was able to transfer energy from one bank to other. I thought it only drains the topped ones.

I'm used to (and like) to do things with arduinos. I'll go this route, then.
 

daromer

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DIYbms does not transfer energy it only burns off energy. You cant compare an ebike chinese bms with a proper BMS. A proper BMS can balance alot higher current. Ebikes are between 20-50mA meanwhile a larger bms 250-1500mA. DIYBms is around 600-800mA depending on version and its more than enough for your battery bank
Do note that if you need to shuffle energy around all the time you have issues! You dont want the balancing to happen to many times per year. yes i said year!!

Active balancer can extend the depth of discharge by moving energy but every time you move that energy you loose energy as well. They arent 100% so if you balance 2 times each time you discharge you might loose a couple of Ah in total. To what use in the long run?
Balancing is generally only needed if you have a cell that drifts and you should make sure that drift is as small as possible.

DIYBMs also shows you when or what cells is being balanced and how much.
 

SeRiusRod

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Ebikes are between 20-50mA meanwhile a larger bms 250-1500mA. DIYBms is around 600-800mA
I understand. I suppose that was the problem I was intuiting. Having a secondary balancing system that masked a possible problem.

Btw, the device I linked is advertised for 6A balancing. 🤷‍♂️
 
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daromer

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Yes when one cell is at 4.2v and one is at 2.0V. But do you need to move that much energy back and forth??

Look at the datasheet:
1621251851898.png
 

daromer

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Those active balancers are great for applications where you have very very demanding cells. they are first made for lead acid where on lead acid you dont have bms and instead of overcharging you move the energy to the cells that need to be equalized longer than others. They then took the same type to Lithium. On Lithium you very very rarely need that amount of balancing power. Electric vehicles will for sure not need it since they have very good cells that are matched for IR.

Some Evs even have like 70mA balancers only ;)
 

SeRiusRod

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@daromer I just saw your video on the DiyBMS. Nice one. (I better understand you english ;) )
But I see you preferred to assemble the esp8266 controller. Having the esp32 available, is there any reason for the preference?
I'm a little confused with all those versions. Do you know what I would have to order?
 

Wolf

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But I see you preferred to assemble the esp8266 controller
That's because @daromer is cheap he won't spend the money on ESP32s. Plus I believe the sketch is written for the ESP8266 and it would need to be adjusted for ESP32. Probably not much.

Wolf
 

daromer

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Wolf: No thats not it. The old board can run both the ESP8266 and 32. Thus the old board also does not fancy the 32 there is no need to use that extra power. And lastly when i edited the video (Months back) the new board was not even public.

There are basically 3 different versions you could say.

The old version with ESP8266
The old version with ESP32.

Those both run the same code base and they work great. There is not much use going the 32 for the old board to be honest.

The new board with the ESP32 and ALL the ports breaked out.

So what version to choose?
If you only need main BMS function with cell monitor and dont need the shunt built into that base nor external display go for it with ESP8266. You can controll everything externally after and its so much cheaper overall.

The new board have these functions among some extra:
* All extra ports breaked out like RS485, RS232, the display, more IO and more
* It therefore can connect to the shunt that is being developer. I get mine in short for testing before release
* The board have touch screen
* The board have built in SD card holder for logging all events
* The board have both relays and SSR built in so you dont have to add extra
* The price point is still very good


With all that said DIYBms is DIY and developed by Stuart and contributors on the spare time.
 

SeRiusRod

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Wolf: No thats not it. The old board can run both the ESP8266 and 32. Thus the old board also does not fancy the 32 there is no need to use that extra power. And lastly when i edited the video (Months back) the new board was not even public.

There are basically 3 different versions you could say.

The old version with ESP8266
The old version with ESP32.

Those both run the same code base and they work great. There is not much use going the 32 for the old board to be honest.

The new board with the ESP32 and ALL the ports breaked out.

So what version to choose?
If you only need main BMS function with cell monitor and dont need the shunt built into that base nor external display go for it with ESP8266. You can controll everything externally after and its so much cheaper overall.

The new board have these functions among some extra:
* All extra ports breaked out like RS485, RS232, the display, more IO and more
* It therefore can connect to the shunt that is being developer. I get mine in short for testing before release
* The board have touch screen
* The board have built in SD card holder for logging all events
* The board have both relays and SSR built in so you dont have to add extra
* The price point is still very good


With all that said DIYBms is DIY and developed by Stuart and contributors on the spare time.
I understand, somehow.

And all those extra data ports in the new version... you think that they aren't necessary? That with the esp8266 I can still get the data? I prefer to do my own dashboards and tooling, and I would want to have info to be able to monitor banks and find bad cells.
And the shunt management, I suppose that it would be useful if it could communicate with the Victron. If not, I would still need to add a BMV702, isn't it?
 

SeRiusRod

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It seems that the new version could handle two batteries. Looking at those ports.
 

daromer

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It can only handle 1 battery. Doesnt matter what version you choose. With that said they can handle up to and around 100 cells in total. That can potentially be several strings.
 

SeRiusRod

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It can only handle 1 battery. Doesnt matter what version you choose. With that said they can handle up to and around 100 cells in total. That can potentially be several strings.
I had seen that the board had two sets of data connectors (rx1, rx2,..) and I thought it could handle two strings. Perhaps where added for future implementation?
The shunt capability will be interesting, as I still don't have one system for that. I hope that in the future it will be possible to communicate with the Victron inverter. I'll be placing an order the next days. If I can't find someone the has excess boards to sell me.
BTW, nice review! (y) https://youtu.be/gEXGgrDNMJQ
1621942459349.jpg
 
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daromer

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Currently its only for One string. The nice features is that Stuart have brought all ports so its easily to code what you want in the future :)
 
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