New SOK Bluetooth BMS for DIY

[FilterGuy]

@FilterGuy




So I originally said yes, from my understanding, since this is what I was told.

I have been looking into the MCU's flash and found today that my understanding was slightly incorrect..

The balance function will only turn on if the charge current is more than 1 amp. The 3.4V cutoff and 25mV difference is correct. As far as duty cycle goes, the MCU enables the balance cycle for 0.6 seconds, then keeps it off for the rest of the second.. in other words, a max of 60% duty cycle. The BQ76920 still has its own duty cycle limitation (70%), but the MCU's is lower for some reason.

OK. Thanks for the update. It is not what I wanted to hear, but at least I know.

With those parameters, the Ballance system is constrained to a fairly narrow window. With the weak balance current, this will make it quite difficult to balance any cell that is not in line with the others.

Is there any chance any of these parameters will be adjustable in a future version of the app.... or is this all 'hard coded' into the hardware?

 

[kinyoubi]

OK. Thanks for the update. It is not what I wanted to hear, but at least I know.

With those parameters, the Ballance system is constrained to a fairly narrow window. With the weak balance current, this will make it quite difficult to balance any cell that is not in line with the others.

Is there any chance any of these parameters will be adjustable in a future version of the app.... or is this all 'hard coded' into the hardware?

Sorry to be the bearer of bad news imagine my surprise when I came across that code!

This is programmed into the microcontroller flash, so as it is right now, it wouldn't be editable. The MCU's flash would have to be updated to allow this to be changed via the app. Unfortunately, the only way to update the MCU's flash at the moment is via a programmer that directly connects to the PCB.

One hackey way that you could force a balance would be to remove all loads and chargers so there is 0A, then do a current calibration but set the offset to something like 1.5A. This way, you could just keep it charged, and even when there is no actual current flowing the BMS will think there is and keep the balance function on. Once the cells are balanced you could reset the calibration.

If you're unfamiliar with the calibration procedure:

Tap the current on the app's main screen
Enter password 200010
Enter in 1.5
Click Set
Cancel out of Dynamic Current Calibration

Hope this helps!

 

[kinyoubi]

@FilterGuy

One last thing for now.. the flash I am looking at now is for the V1 BMS (2021-10 area date of production). This behavior MAY have changed with newer version BMS's. I plan to get the flash off a newer BMS in the near future and will report back my findings.

 

[jetjaguar]

Where are my non-Bluetooth homeboys at? I don't want bluetooth:

a) Another thing to break
b) Unwanted RF noise
c) I'm old and I don't like new things

If it can be disabled and still have a usable battery, great.

 

[Tomthumb62]

Where are my non-Bluetooth homeboys at? I don't want bluetooth:

a) Another thing to break
b) Unwanted RF noise
c) I'm old and I don't like new things

If it can be disabled and still have a usable battery, great.

I’m ABC as well, but having Bluetooth on my 3 month old battery has saved me a TON of headache diagnosing gremlins in the system. Found out that the BMS did it’s job properly when the charge controller was regularly spiking to 16-18v volts due to it being programmed at the factory to do that (why, I’m still trying to find out). I could see the BMS charge MOSFET was turned off when the SCC had spiked to 17v one day. The BMS kinda wigged out for a few minutes with the voltage bouncing all over the place from 12.8 to 14.0v, in which the load remained a constant 6.0A during the whole event.

So I’m thrilled to have a Bluetooth BMS to be able to see this data in real time.

 

[jetjaguar]

I’m ABC as well, but having Bluetooth on my 3 month old battery has saved me a TON of headache diagnosing gremlins in the system. Found out that the BMS did it’s job properly when the charge controller was regularly spiking to 16-18v volts due to it being programmed at the factory to do that (why, I’m still trying to find out). I could see the BMS charge MOSFET was turned off when the SCC had spiked to 17v one day. The BMS kinda wigged out for a few minutes with the voltage bouncing all over the place from 12.8 to 14.0v, in which the load remained a constant 6.0A during the whole event.

So I’m thrilled to have a Bluetooth BMS to be able to see this data in real time.

Can you disable the bluetooth and still have a usable battery?

 

[Tomthumb62]

Can you disable the bluetooth and still have a usable battery?

Just turn off Bluetooth in your phone. Then place a lead blanket over the battery (NOT the terminals!!) and it’ll be “off”. Or cut open the battery and clip the wire to the Bluetooth dongle.