bluetooth BMS?

[tmho]

are there any programmable bluetooth bms that are just 1 cell high? i need to make a flat battery and 7cm is my thickness limit.

Mine is 70mm x 138mm x 17mm excluding the wires.

Mine is the 7s-16s 100A version. I got it from taobao.com. You can find it from https://www.aliexpress.com/item/Bluetooth-APP-Smart-display-7S-20S-Lifepo4-li-ion-Lipo-LTO-Battery-Protection-Board-BMS-400A/33004914212.html and there is a version suitable for you.

 

[thundercamel]

The PC software with the usb cable has access to all of the settings. Temperature limits, cell voltage calibrations, and more current limits.

 

[agniusm]

Ok. Giving another shot. Have 2 batteries, 20S and 10S.
Questions if i mey:
How do you hook up 10S battery to 15S bms? Just skip all the remaining connections ?
Can someone link me to a page with correct settings for these units? I stopped at page 15, too much for me
I will have relay connected on the bms output and dc/dc. so no real power discharge will go through bms

 

[flippy]

Unless its programmable you cant. It will constantly be in fault mode.

 

[john61ct]

Is this thread limited to specific units ?

I thought it covers many, from different makers?

Are there any product / model #'s to help identify which posts apply to which units?

 

[agniusm]

Unless its programmable you cant. It will constantly be in fault mode.

I have the same unit talked about in this thread. With bluetooth etc etc.
So yes, programmable.

 

[trazor]

Ok. Giving another shot. Have 2 batteries, 20S and 10S.
Questions if i mey:
How do you hook up 10S battery to 15S bms? Just skip all the remaining connections ?
Can someone link me to a page with correct settings for these units? I stopped at page 15, too much for me
I will have relay connected on the bms output and dc/dc. so no real power discharge will go through bms

Some information:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=88676&p=1444776&hilit=bluetooth#p1444776

 

[agniusm]

Ok. Giving another shot. Have 2 batteries, 20S and 10S.
Questions if i mey:
How do you hook up 10S battery to 15S bms? Just skip all the remaining connections ?
Can someone link me to a page with correct settings for these units? I stopped at page 15, too much for me
I will have relay connected on the bms output and dc/dc. so no real power discharge will go through bms

Some information:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=88676&p=1444776&hilit=bluetooth#p1444776

That is good one. Thanks

 

[flippy]

Unless its programmable you cant. It will constantly be in fault mode.

I have the same unit talked about in this thread. With bluetooth etc etc.
So yes, programmable.

then you can.

 

[agniusm]

What would be advisable settings for 42V pack? Its 14AH. this is what i have atm:

 

[agniusm]

BTW, what with the odd and even cell balancing? Does it do all cells eventually by balancing odd then even cells?
When it balances, to what voltage it does that? To lowest cell if its constant balancing?
Would it be better so set it to balance when on charger, off charger or both?

 

[john61ct]

BTW, what with the odd and even cell balancing? Does it do all cells eventually by balancing odd then even cells?

I am also curious about that, very odd

> When it balances, to what voltage it does that? To lowest cell if its constant balancing?

If it can actually balance with no charge source active, then capacitor-based "charge shuttling" would mean the energy taken from higher voltage cells / groups is diverted to the lower ones. Very unlikely in such a cheap unit.

> Would it be better so set it to balance when on charger, off charger or both

Depends on your charging profile and that pack's balancing needs, whether or not doing it only during charging is long enough.

Balancing at low SoC **and** at the top would be a waste.

There are dozens of different user philosophies about how you should do balancing, and some banks while in good condition don't even need it.

So a good design is to accommodate the various user preferences rather than impose only one fixed way of doing it.

But this does require you to make informed decisions.

 

[agniusm]

So i have my pack hooke up and sitting on a charger and i just dont understand how this works. Initially i have set start balance at 3900mV but it just sits and drains the cells. Now i have set it to 4180mV to see if it balances.
On PC app the ok on balance graph does not light up so is it still balancing?

 

[eee291]

what's the balancing accuracy set to?

 

[agniusm]

what's the balancing accuracy set to?

0.3V

 

[evblazer]

Well I went and search and saw an update for my app. It looks like a few days ago there was an update and today another now the iPhone app XiaoxiangBms has a version that shows config options for 5.99.

 

[izeman]

What would be advisable settings for 42V pack? Its 14AH. this is what i have atm:

Untitled.png

I guess this screenshot shows why your last battery FAILED. IMHO if you got "balance" activated it will balance ALL THE TIME. It will try to reach your 30mV delta ALL THE TIME. So it will never really sleep, and it will use power all the time.
At least this is what i found out. I activate "charge balance" only, so if there is some charging happening, it will balance. If not, it will shut down the BMS after short time.
That way i haven't got any drainage issues anymore.

 

[BotoXbz]

What would be advisable settings for 42V pack? Its 14AH. this is what i have atm:

Untitled.png

I guess this screenshot shows why your last battery FAILED. IMHO if you got "balance" activated it will balance ALL THE TIME. It will try to reach your 30mV delta ALL THE TIME. So it will never really sleep, and it will use power all the time.
At least this is what i found out. I activate "charge balance" only, so if there is some charging happening, it will balance. If not, it will shut down the BMS after short time.
That way i haven't got any drainage issues anymore.

No...
It clearly says "Start Voltage: 3900 mV", it'll only balance above that voltage.
I had some issues with ticking both "Balance" and "Chg Balance", only picking one of them worked.
Also the odd and even stuff is because of a limitation on the TI BQ76940 IC that you can't balance neighboring cells.

 

[izeman]

It clearly says "Start Voltage: 3900 mV", it'll only balance above that voltage.

It STARTS, but it doesn't STOP if cell voltage falls BELOW that value. At least it seems it didn't do with my battery.

 

[agniusm]

It clearly says "Start Voltage: 3900 mV", it'll only balance above that voltage.

It STARTS, but it doesn't STOP if cell voltage falls BELOW that value. At least it seems it didn't do with my battery.

I had charge balance on the dead pack. I have both on on this one as i have it sitting on a charger.
Can you post your setting screen?

 

[izeman]

 

[cycborg]

It STARTS, but it doesn't STOP if cell voltage falls BELOW that value. At least it seems it didn't do with my battery.

Then how is this useful? Seems to me the "stopping" is an indispensable part of the balancing process.

 

[izeman]

It STARTS, but it doesn't STOP if cell voltage falls BELOW that value. At least it seems it didn't do with my battery.

Then how is this useful? Seems to me the "stopping" is an indispensable part of the balancing process.

Theory is one thing. Reality a second one. I don't know if my assumptions are true. I am with you, that it doesn't make sense, but fact is, that the BMS was draining my battery pretty fast until i set it to how it is right now, and now everything works fine.

 

[john61ct]

The stopping should happen as a result of the biggest V delta falling within the tolerance spec'd by the user.

And of course only during the charging cycle unless you were manually monitoring.

Personally doing it that way, with a 4-6A balance current so it didn't take so long would be the way to go.

Not available in any BMS I've seen, but there are dedicated gadgets can do that.

 

[Taswegian]

Could anyone please advise on their approach to soldering the B- & C- wires to these BMS.

I have a couple from James at LTT power and the pads for these connections seem very small, there isn't much 'meat' around the hole to solder to.

Also, on one side they don't actually even connect to the main adjacent track, I suppose that's moot as Ill join it when soldering.

Hoping some others have pic of how theyve gone about it.