Building a "better" BMS

[Craig]

I am currently trying to build my own BMS. The reason why is that I cant find any suitable products that allow custom cell ranges and networked communications that are not Bluetooth. I need WiFi or Ethernet capabilities. I posting this thread for other peoples ideas of what a BMS should include.

My requirements

1. Network connectivity
2. Data logging each cells voltage
3. Active balancing
4. High and low voltage cut off
5. Temperature cut offs
6. High amp capabilities around 200

please if you have any ideas what such a system should include post them here.
if you know of a commercial product for less than $200.00 post that here as well.

Im figuring I could make something that works for around $100.00 from my experimentation so far.

The thing is if I build this thing I dont want to be wishing I had added additional features when its completed.


My end goal is to make a DIY solution that anybody can make on their own.

 

[JIMMY]

Hi Craig,

I have been looking for the same things in a BMS.

~5amp active balancing would be good.
150amp+ charging capacity

Otherwise it looks like you have my wish list covered. ?

Jimmy

 

[norbert66]

Hello Craig,
I have the same in mind. First I thought to measure the cell voltages via OpAmps, multiplexer and adc controlled by Raspi.
But then I found this - see the last 2 pages of http://electrodacus.com/SBMS100/manual/SBMSmanual.pdf
https://www.mouser.de/ProductDetail...GAEpiMZZMsfD%2BbMpEGFJaoYkyd819eelrFQOpKDO5A=

Might work for 8S but I have 16S, so I found this: bq76PL455A-Q1

My inverter has a low current On/Off switch, so I plan to use this to handle LV cut off and not dealing with the high current battery line.
Similar for my charger.

What might be your design?

 

[Stingy49]

Y'all should check out the diyBMSv4. Relay output so you can run contactors and support whatever amperage you want.

DiyBMSv4

Pretty neat for those of us comfortable with assembling pcbs and loading Arduino code. Fully modular, web interface, programmable relay outputs. Here is someone's video on it vs the last gen. A link to the GitHub with firmware and boards...

www.diysolarforum.com

 

[Craig]

Hello Craig,
I have the same in mind. First I thought to measure the cell voltages via OpAmps, multiplexer and adc controlled by Raspi.
But then I found this - see the last 2 pages of http://electrodacus.com/SBMS100/manual/SBMSmanual.pdf
https://www.mouser.de/ProductDetail/Renesas-Intersil/ISL94203IRTZ-T7?qs=sGAEpiMZZMsfD%2BbMpEGFJaoYkyd819eelrFQOpKDO5A=

Might work for 8S but I have 16S, so I found this: bq76PL455A-Q1

My inverter has a low current On/Off switch, so I plan to use this to handle LV cut off and not dealing with the high current battery line.
Similar for my charger.

What might be your design?

Wow these things you have found are very interesting I like this ISL94212INZ from mouser I have no clue how to use them yet but it looks promising.

Right now my design is to use and adc to measure and monitor cell voltages then use an acs758 to measure current. from those i would use some capacitors to active balance the cells. All this controlled by a raspberry pi. Using Pi mainly because Im familiar with them and I would rather have a full computer over a micro controller.. Im also toying with these cjmcu-226 for measuring voltage but all theese things have their drawbacks one of these mouser chips may be the ticket. The electrodacus is a nice unit but wont handle higher voltages or extra cells.

 

[Danny]

I am currently trying to build my own BMS. The reason why is that I cant find any suitable products that allow custom cell ranges and networked communications that are not Bluetooth. I need WiFi or Ethernet capabilities. I posting this thread for other peoples ideas of what a BMS should include.

My requirements

1. Network connectivity
2. Data logging each cells voltage
3. Active balancing
4. High and low voltage cut off
5. Temperature cut offs
6. High amp capabilities around 200

please if you have any ideas what such a system should include post them here.
if you know of a commercial product for less than $200.00 post that here as well.

Im figuring I could make something that works for around $100.00 from my experimentation so far.

The thing is if I build this thing I dont want to be wishing I had added additional features when its completed.


My end goal is to make a DIY solution that anybody can make on their own.

You have got to have a lot of time on your hands. How much is your time worth say if you had to pay $400. That extra $200 will make you a slave. 123 bms and Orion jr to name a few if you are stuck on $200;

 

[Craig]

You have got to have a lot of time on your hands. How much is your time worth say if you had to pay $400. That extra $200 will make you a slave. 123 bms and Orion jr to name a few if you are stuck on $200;

Thanks for the reply. Yes this could be a huge waste of time but learning new things is never a waste of time. the 123 bms will not work for my purposes The orion probably would but the cost is extravagant.

Im sure I could hook bluetooth up to a SBC but in general bluetooth doesn't work for me since the system I want to monitor is 900 miles from my home.

Dont get me wrong Ive probably already spent more than 400 bucks finding out how not to do things.

 

[Danny]

Thanks for the reply. Yes this could be a huge waste of time but learning new things is never a waste of time. the 123 bms will not work for my purposes The orion probably would but the cost is extravagant.

Im sure I could hook bluetooth up to a SBC but in general bluetooth doesn't work for me since the system I want to monitor is 900 miles from my home.

Dont get me wrong Ive probably already spent more than 400 bucks finding out how not to do things.

Perhaps just getting rid of the Bluetooth constraints would get you into the cheap bms zone? Check this out . I just got myself a cheap used android for my bms. https://www.addictivetips.com/mobil...control-of-android-over-wifi-via-web-browser/

 

[norbert66]

Did not checked the details, but there are also some smart bms with rs485 around 70$. Maybe the rs485 provides the individual cell voltages.

 

[Danny]

Did not checked the details, but there are also some smart bms with rs485 around 70$. Maybe the rs485 provides the individual cell voltages.

I have one 80a 4s but the clients are BT android and windows so you to remote control the clients at the remote location. Here are clients in this video

 

[Jack of all trades]

Try Elite Power Solutions. https://www.elitepowersolutions.com/bms
Has all of the functions I believe your looking for. I am real close to commisioning my system which incorporates an older version as part of an oem product.

 

[JIMMY]

Try Elite Power Solutions. https://www.elitepowersolutions.com/bms
Has all of the functions I believe your looking for. I am real close to commisioning my system which incorporates an older version as part of an oem product.

Any idea of price JoaT?

There is no distributor for my neck of the wood.

Jimmy

 

[offgriddle]

I'd never even heard of a raspberry pi, very cool! https://www.raspberrypi.org/

 

[gnubie]

There's a whole world of SBCs out there to suit any application you can dream up at a price point that anyone can afford. I have a few nanopi neo SBCs doing various things.

 

[ScoTTyBEEE]

I've come to the conclusion that every bms worth using costs similar to my batteries which defeats the point. I have a balance monitor with alarm hooked up and an ammeter. I lived in a van for 1.5 years so far and stopped my lead acid going under 50% by using a ammeter so I can't see why it won't work with life batteries either.
I agree with Will that in the near future a decent bms will come out of China with all the features and low price. I'm going to hold off until such a product arrives.
My main issue is running 150A loads with an induction cooker. Any bms that can handle this requires expensive solid state external relays. If I was sub 100A I'd just use a Daly. I bought the 200A Daly but the wires are too thin to safely use and quite frankly I don't trust it.

 

[MisterSandals]

Does it make sense to others to have a BMS that can be used with 4s to 16s? I saw some monitors that worked that way based on the connector (and number of wires attached or cells detected?).
This is appealing to me because i am considering different systems (4S and (2P4S or 8S)). Buying a single, nicer BMS that is flexible for different battery banks is appealing not only financially but the weeks long order/shipping delay is significant too.

 

[offgriddle]

RS 485, the industrial cousin of RS 232, ahh analog memories ..