bluetooth BMS?

[methods]

Marking this thread to read - thanks for putting it together, all who were involved.

Agreed that a BLE based BMS is FTW bigtime.

This opens the door to low cost, BLE enabled, modules which can be networked. All that must be agreed upon is the interface.... and that can come long after hardware is in the wild.

With a networked system of independent modules (that play nice together, and do not try to lock each-other out of the market) you can have a battery that requests a current reduction to a controller and then a primary contactor that waits to open until loads are low. . . all of these things working together let you use smaller, lighter, lower cost parts which do not have to survive "worst case" where 60V is blowing open at 50A.

JSON RESTful-type API on BLE in UART mode
Phone app to link all the different parts together with tokens

-methods

[john61ct]

Besides BLE, lorawan gives more range, important when the pieces are more spread out like homes, and bigger RVs and boats

other protocols I've seen for BMS, chargers etc

SMBUS, I2C/HDQ
MQTT
IOT-bus
CAN-BUS
isolated SPI, isoSPI
M-BUS

[maccoa]

Hello.
I wanted to calibrate my smartbms (antbms), it shows me 57.7v while in reality I have 57.9v.
I cannot change "Total Voltage Reference Value" which is set to 3000N
is there a tip?

similarly I don't understand too much to limit the charge to 4.1V, I can't lower the voltage of my charger.
I tried to set totalvoltage Highprotect to 65.6v, once this voltage reaches, the charger turns off and on all the time.

my pack is a 6P16S 15Ah (67.2V at 4.2V).

Thanks for your help

[john61ct]

Do any of these allow for calibration?

The charger of course is a separate issue, which do you have, link?

[maccoa]

I cannot modify them.
my smartbms is this one
https://fr.aliexpress.com/item/32826820 ... 6c37TbEu0e

the charger is this
https://fr.aliexpress.com/item/32778132 ... 6c370gPl5H
but it does not drop below 67.1 V

[john61ct]

So cheap!

Open it up and look for a pot adjustment.

[eee291]

So cheap!

Open it up and look for a pot adjustment.

We aren't talking about chargers here

[eee291]

Hello.
I wanted to calibrate my smartbms (antbms), it shows me 57.7v while in reality I have 57.9v.
I cannot change "Total Voltage Reference Value" which is set to 3000N
is there a tip?

similarly I don't understand too much to limit the charge to 4.1V, I can't lower the voltage of my charger.
I tried to set totalvoltage Highprotect to 65.6v, once this voltage reaches, the charger turns off and on all the time.

my pack is a 6P16S 15Ah (67.2V at 4.2V).

Thanks for your help

It's not that big of a deal, off by only 0.3%
I doubt you'll get any closer to 0%

[izeman]

Hello.
I wanted to calibrate my smartbms (antbms), it shows me 57.7v while in reality I have 57.9v.
I cannot change "Total Voltage Reference Value" which is set to 3000N
is there a tip?

similarly I don't understand too much to limit the charge to 4.1V, I can't lower the voltage of my charger.
I tried to set totalvoltage Highprotect to 65.6v, once this voltage reaches, the charger turns off and on all the time.

my pack is a 6P16S 15Ah (67.2V at 4.2V).

Thanks for your help

It's not that big of a deal, off by only 0.3%
I doubt you'll get any closer to 0%

Totally agree. 57.7 or 57.9 doesn't matter at all. Voltage sag will be much more and difference in SOC is minimal within 200mV.

[john61ct]

Again, do any of these BT BMS allow for calibration, at least of voltage accuracy?

[quamau]

Yes, they do. Once you have a reliable source for good measurement, you can easily calibrate each cell (parallel string) individually via the PC software. AFAICT, this is not yet doable via the phone app.

[quamau]

I am almost through this process, which I hoped would be smoother.

After finding the right spots to desolder (informative pictures at p.37 of this thread), I had to (re)discover the fact that the new cells need recalibration, otherwise each cell is seen with a 25V voltage... This needs to be done via the PC software, the phone app does not deliver.

Since the BMS is on my desk right now, with UART box connected, I was hoping to recalibrate the shunt value that provides current values that are off by 50%. Error msg when I attempt to write. Erro pops is if I simply read the BMS parameters and, before changing anything, try to write them back again.

Steps to reproduce:

1. fire up the software, connect to the BMS
2. from tab "Parameter", click "Read" (which succeeds)
3. from same tab, immediately thereafter click "Write"

Error message is: "The overvoltage protection and release value of the monomer is set wrong; the release value is set lower than the protection value 100mV" and I have trouble interpreting.

I guess it's an inconsistency where the phone app lets you change something that the pc app does not. PC sw is V1.E 20190807, phone app v.3.1.1013. Any hint? Any new version around?

[john61ct]

Yes, they do. Once you have a reliable source for good measurement, you can easily calibrate each cell (parallel string) individually via the PC software. AFAICT, this is not yet doable via the phone app.

Excellent, thank you.

I'm a bit confused by the phrasing "to calibrate cells".

I plan on using a standard voltage reference device like this: https://www.amazon.com/ad584kh-precisio ... b07dnwqg2n

so that the **BMS** is calibrated, no matter what cells its sensors are reading.

Anyone see any problems with that approach?

[serious_sam]

Anyone see any problems with that approach?

If you only hook up your voltage reference to each cell "channel" one at a time (with no battery pack connected), I don't think the BMS will power up.

You would probably have to connect the full pack, and substitute the voltage reference for one cell at a time.

Probably just be easier to connect your pack to the BMS and use an accurate voltage meter to read each cell voltage and enter that value into the BMS software.

[john61ct]

I assumed the context was on the bench, PSU or various other sources would be to hand.

Either way works, just wanted to point out the reference devices are super accurate, 95% cheaper than a quality DMM, and suitable for calibrating your DMMs off as well.

[serious_sam]

When you say super accurate, what is that accuracy, and how does that compare to an "average" DMM?

I ask because most people will already have a DMM available, so a voltage reference is an additional cost. Wondering what is the added benefit vs cost.

[john61ct]

Even a DMM costing many hundreds must be regularly calibrated.

The benefit is knowing it is not just precise, but accurate.

If accurate voltage is not important to you, then don't spend the extra.

0.1% is the least accurate I see, that's a 5-digit readout

Lots are based on this chip
https://www.analog.com/media/en/technic ... 4_5045.pdf

https://www.tindie.com/products/JouleTi ... iy-project

https://www.markhennessy.co.uk/ad584_references
https://youtu.be/L5gAohxwOxU
https://youtu.be/PynyfLHXK-o

https://www.amazon.com/ad584kh-precisio ... b07dnwqg2n
https://m.banggood.com/AD584-4-Channel- ... 78638.html

https://dmmcheckplus.com

[serious_sam]

Even a DMM costing many hundreds must be regularly calibrated.

The benefit is knowing it is not just precise, but accurate.

If accurate voltage is not important to you, then don't spend the extra.

Do you plan on getting your voltage reference calibrated by a trusted source?

WRT accuracy vs precision, in this case precision is far more important IMO.

For example, I'm not too worried if my BMS is reading 10mV high, just as long as it is reading equally 10mV high for every cell. Then all cells are maintained at the same state of charge, irrespective of the actual voltage figure. If they're all the same, that's a healthy battery. Don't care if it's 37V or 37.1V.

Most DMMs have excellent precision (repeatability), so they're quite suitable for the task IMO.

[john61ct]

The reference is the calibration source, accuracy is its reason for existence.

Again even the best DMMs need periodic calibrations, whether or not cheap ones are within your desired accuracy range is lots more a roll of the dice.

And again, I'm not telling anyone what they should do, just posting options and info, your rig your choices of course.

[ElectricGod]

I've posted a lot of stuff on modding several smart BMS's in this thread.

The ones that use the cute elephant app have an LCD.
I thought I'd get a couple of them to try out.
This would supposedly eliminate the need for a phone app or the USB/PC app.

I have to say...do NOT waste your time. This is the dashboard screen.
All the other pages of data are even worse than this.
Since I can't read squiggly, I don't know what is what.
I've gone through all the menus looking for something to select or change and maybe get an idea what things do.
It appears that you can't change anything via the LCD...disappointing!
Assuming it uses settings from the BMS, you should see the battery at nearly full.
There's zero documentation for the LCD so I'm 100% guessing at functions.
It has a connector labeled speed, but what you connect it to is a mystery...maybe a motor hall?
Doesn't matter really as none of the screens list kmh or mph or RPM.
This was a waste of money!

[john61ct]

"cute elephant app"

Does that refer to what has been labelled the Xiaoxiang app?

are there lots of other bluetooth BMS that don't use that app?

And the Ant BMSs are completely different right?

And then there's the ones Em3v uses, any leads on how to get those?

I think it would be very useful, if we standardized some naming conventions?

[izeman]

Anyone has an idea if/where there are firmware updates for the BMS? I was wondering if there are some improvements.

[agniusm]

Got 4S 120A version of this. Was working and now it reads 0.1V on all cells. They are charged and 4.18V shows on the JST. Is it toast? Same on PC and Android. Also when i try to write to it, error is displayed:

BMS_error.png (5.71 KiB) Viewed 2278 times

[john61ct]

Got 4S 120A version of this

Can you be more specific? link?

So many different versions discussed in the thread

[agniusm]

Got 4S 120A version of this

Can you be more specific? link?

So many different versions discussed in the thread