Bluetooth 10-15s bms review

[Inwo]

More testing of the China bt bms.
Honestly can't find anything I don't like.
Finished installing 100ah 14s pack in Tomberlin NEV today.
2016 Volt-as new. Balanced perfectly +- <5mv

Cell #1 was 50mv low. Started balancing, then though to check with meter.
All were perfect.
The bt bms has simple calibrate function. Enter actual voltage for each cell. How nice is that?

Presently finishing charge cycle to 4.1v to see what else I can learn.

 

[kocetoMR]

How work this calibrate function? I cant understand
You have to try this:

 

[Inwo]

You enter the actual cell voltages in the boxes.

Do you have a link to yours?

 

[casainho]

More testing of the China bt bms.

Only the price I would like to be lower like 15€ or less.

Chinese are top on electric vehicles, they produce a LOT and use them internally!!

 

[kocetoMR]

You enter the actual cell voltages in the boxes.

Do you have a link to yours?

https://detail.1688.com/offer/547125421401.html?spm=a360q.8258388.0.0.AD2h3w
http://www.smart-bms.com
You need use Taobao agent if you want to buy!


...and what happen when enter volt.cell in this boxes?

 

[cwah]

Any good?

 

[Inwo]

You enter the actual cell voltages in the boxes.

Do you have a link to yours?

https://detail.1688.com/offer/547125421401.html?spm=a360q.8258388.0.0.AD2h3w
http://www.smart-bms.com
You need use Taobao agent if you want to buy!


...and what happen when enter volt.cell in this boxes?

It calibrates each cell measurement.
Am I missing the question?
Let's say bms reads 3.95v for cell #1. A good meter shows it to be 4v.
Enter 4000 in the box (mv). Now bms reads 4v.
Each one can be set as needed.

 

[Inwo]

Looking for a firmware hack that will allow a wider range of settings.

Need it to go down to 1.5 volts uvp and ovp down to 2.6.

I know the hardware works that low.
By re-calibrating all cells to read 1v high, it seems to be working and balancing my 14s LTO pack.
ie. 2.8v reads 3.8v

 

[casainho]

Looking for a firmware hack that will allow a wider range of settings.

Do you have any information about the microcontroller on the board?? Can you please post pictures with detail??

 

[Inwo]

Mega328P
64c5f6

The voltage calibration spoof is working fine.
It thinks my lto 2.8 volts is 3.8 volts.




Download site:
http://www.lithiumbatterypcb.com/%e5%8d%9a%e5%ae%a2smart-bms-software-download/smart-bms-software-download/

 

[casainho]

Great!! so that is the very well known microcontroller Atmel Mega328P used on Arduino. We can also see on the board the programming header pins for it (but without soldered connector).

I wish that hardware could end to be the standard cheap chinese bluetooth BMS -- that way would be a good investment to develop the firmware for it.

We would also need to know what is the dedicated IC for cells voltage readings, etc and also the bluetooth IC. Wait, seems that the connector with labels TX and RX will connect to a serial bluetooth module that is now shown on the picture!!! So that is just a "simple Arduino" with added IC to read cell voltages and bleed circuit. Would be simple and fast to make the firmware!!!

Can you please post links for the cheap way to buy these BMS??

 

[Inwo]

Comes with bt module and pc cable.
There is an update button on programming screen.
Seller is not open to making changes.

https://www.aliexpress.com/item/14S-Smart-Li-ion-Battery-PCB-board-Bluetooth-Mobile-BMS-for-48V-58-8VLi-Ion/32794186005.html?spm=2114.13010608.0.0.mCFxL5


Dl center
http://www.lithiumbatterypcb.com/download-center

 

[casainho]

Seller is not open to making changes.

The only way is us develop our own firmware and document the hardware!!! We need to take advantage of cheap chinese products... at the same time we will help to make their products well known/boost sales.

 

[casainho]

Please find the reference for the IC of battery management!!

 

[Inwo]

Please find the reference for the IC of battery management!!

I don't understand.

 

[casainho]

Please find the reference for the IC of battery management!!

I don't understand.

That big one other than the microcontroller!! We need to find the reference and the datasheet.

 

[kocetoMR]

it is atmel 32 bit

 

[casainho]

it is atmel 32 bit

I am pretty sure it is not!!

The microcontroller is the ATmega328P, 8 bit microcontroller used on Arduino - datasheet.

The other big, rectangular IC must be a dedicated IC to read each cell voltage and control the bleeding circuits for each cell -- that's why that IC have so many pins!!

 

[Inwo]

I thought it was a pic.
I'll look it up.

 

[Inwo]

Found ti symbol on it.
Crosses to:
BQ76940
http://www.ti.com/product/BQ76940

Also, seller got back to me. It is not a sw issue. Hardware will not work at lower voltages.

 

[Inwo]

Looks like it will work down to 2v differential cell voltage.
Good enough for me.

 

[casainho]

The bq76920 device supports up to 5-series cells or typical 18-V packs, the bq76930 handles up to 10-series cells or typical 36-V packs, and the bq76940 works for up to 15-series cells or typical 48-V packs.
Are you guys sure that this BMS using the BQ76940 only supports 36V or 48V, like what the producer says?? is there any limitations on the hardware to not work also for 24V/ 7S ??

 

[casainho]

Found OpenSource firmware for Arduino + BQ76940 that should boost firmware development!!

I gathered all the information shared and put public on a page (inside another project I am working on for EBikes), including the datasheets and my notes, so anyone that will look for this BMS will be able to find this information and who knows, someone that will want to develop the firmware:

https://opensourceebikefirmware.bitbucket.io/Smart_BMS_with_bluetooth.html

 

[Inwo]

The 30a bms use 4 80a fets.
Default setting is 40a discharge.
I changed it to 30a

A 35a charger was connected by customer.

Smoke after 5 minutes. I wasn't there.

Replaced fets and tested. Trips properly on oc.
Added a copper heat sink to fets.
Gets very hot at 27a charge rate.

What has been the experience with these cheap bms?
Need heat sink?
Cut rating in half, even with heat sink?
Do I have a bad one?

 

[ninja007]

I have a couple of these, and some of the other BMSs from this company on the way for testing, let me know if you want more information on the boards, I'd be happy to share once they arrive. I'm interested in getting the Bluetooth outputs modified into a more user friendly interface for some packs I am working on.