ADCs and MCUs for a low-cost electric car BMS

Ray Vincent Aranzaso

Other Parts Discussed in Thread: ADS131B04-Q1, BQ76PL536A-Q1, BQ79616

Hi,

Good Day. I have a customer who is working with. Please see below his query for your reference. Thank you very much.

I am a part of a project at my university that aims on building a BMS for a low-cost electric car to increase electrical mobility in my country by 2030. My goal in this project is to acquire the battery data, such as voltage, temperature and current, to estimate the State of Charge, State of Health and other crucial information. To accomplish that I must find a good ADC and a good MCU for each module of the BMS and with all the variety of products you have available I'm having a bit of a hard time finding the best solution, so I would like some help to choose the ones that suits my purpose better. May you help me with this challenge?

Best Regards,

Ray Vincent

over 3 years ago

0 LeonardEllis over 3 years ago

TI__Guru 71526 points

Hi Ray,

We will need a lot more information regarding this design. What is a "good ADC" or "good MCU" pertaining to this design? And has he looked at BMS devices that are designed to monitor the battery conditions he describes?

Please ask for at a minimum a block diagram. Also suggest he review the BMS products: www.ti.com/solution/battery-management-system-bms . There are also many design considerations discussed in the references on this page.

Regards,

~Leonard

0 Joachim Wuerker over 3 years ago in reply to LeonardEllis

TI__Mastermind 23275 points

Hi Ray,

you might want to look at ADS131B04-Q1 in this case which is an AFE targeted at those measurements in BMS.
I can't comment on suitable MCU's unfortunately.

If you need solutions to measure individual battery cell voltages then we need to look at our BQ79xxx-Q1 portfolio.

Regards,
Joachim Würker
Systems Manager - Precision ADCs

0 Ray Vincent Aranzaso over 3 years ago in reply to Joachim Wuerker

TI__Mastermind 18180 points

Hi All,

Good Day. Please see below the response of our customer to your reply. Thank you very much.

Nominal voltage: 266.6 V

Power: 28.2kWh

Capacity: 106Ah

Max discharge rate: 3.5C

Topology: 72s1p

It will be divided into 12 stacks of 6 cells or 6 stacks of 12 cells all connected in series

I have never seen the link you just sent me, it helped a lot. I was looking at the BQ76PL536A-Q1 to monitor the cells for each stack, is it enough (for the 6 cells stack) or should I change it? Also, the BQ79xxx-Q1 models can do the passive balance between cells by themselves or they need other modules to balance? Can I implement a passive balance between cells with this component and an active balance between stacks with the main BMS?

Best Regards,

Ray Vincent

0 Alexander Scheuermann over 3 years ago in reply to Ray Vincent Aranzaso

TI__Genius 14890 points

Hello Ray,

Yes the BQ79616 device may be what you are looking for. They can monitor up to 16 cells and be daisy-chained together for a stack of 72 cells. They can do up to 240mA of passive balancing. https://www.ti.com/product/BQ79616-Q1?keyMatch=BQ79616-Q1&tisearch=search-everything&usecase=GPN

0 Ray Vincent Aranzaso over 3 years ago in reply to Alexander Scheuermann

TI__Mastermind 18180 points

Hi,

Good Day. Please see below the reply of our customer to your suggestion. Thank you very much.

The BQ79616 looks like a good idea to me too, do you have the library of this component for Altium Designer? I could not find it at Altium's site.

I would also like to know what is the TIDA - 00817 and TMS570 maximum voltage for active balancing?

Best Regards,

Ray Vincent

0 Ray Vincent Aranzaso over 3 years ago in reply to Ray Vincent Aranzaso

TI__Mastermind 18180 points

Hi,

Good Day. Is there any update on latest query of the customer? Thank you very much.

Best Regards,

Ray Vincent

0 Alexander Scheuermann over 3 years ago in reply to Ray Vincent Aranzaso

TI__Genius 14890 points

Ray,

For TIDA - 00817 it says 16 cells at 5A.

0 Alexander Scheuermann over 3 years ago in reply to Alexander Scheuermann

TI__Genius 14890 points

Ray,

Also here is an Altium file for the BQ79616 device

PAP0064A.STP

0 Ray Vincent Aranzaso over 3 years ago in reply to Alexander Scheuermann

TI__Mastermind 18180 points

Hi Alexander,

Good Day. Please see another query from the customer. Thank you very much.

I understand that the TIDA can balance up to 16 cells, but if I wanted to connect a 50V stack in each input for example, would it be possible? What are the limitations for the cell input?

Also, the 5A is the balance current (like the 240mA of passive balance in the BQ79616) or is the maximum current that the device can handle?

Best Regards,

Ray Vincent

0 Ray Vincent Aranzaso over 3 years ago in reply to Alexander Scheuermann

TI__Mastermind 18180 points

Hi Alexander,

Good Day. I would like to follow up about my latest post. Thank you very much.

Best Regards,

Ray Vincent

0 Alexander Scheuermann over 3 years ago in reply to Ray Vincent Aranzaso

TI__Genius 14890 points

Hello Ray,

The BQ79616 has internal FETs for cell balancing up to 240mA per cell. It can cell voltage of up to 5V. If you are asking if you can connect 50V between two VC channels, the answer is no since the maximum is 5V.

For TIDA00817, that design uses external balance FETs which are designed for larger balancing currents - in this design for 5A. Typically our customers find that the 240mA balancing capability of the BQ79616 is sufficient for their applications, but some customers do end up wanting more and look to designs using these external FET circuits.

0 Ray Vincent Aranzaso over 3 years ago in reply to Alexander Scheuermann

TI__Mastermind 18180 points

Hi Alexander,

Good Day. Please see below the response of our customer to your reply. Thank you very much.

I would also like to know if the BQ79616 has any restrictions regarding cell chemistry or capacity. I plan to use it on NMC 106Ah cells, is it ok or do I need to make adaptations?

Best Regards,

Ray Vincent

0 Ray Vincent Aranzaso over 3 years ago in reply to Ray Vincent Aranzaso

TI__Mastermind 18180 points

Hi Alexander,

Good Day. I would like to follow up about the latest query from the customer. Thank you very much.

Best Regards,

Ray Vincent

0 Alexander Scheuermann over 3 years ago in reply to Ray Vincent Aranzaso

TI__Genius 14890 points

Ray,

We are typically used for Lithium-ion cells - NMC is a subset of that so I don't expect any issues.

0 Ray Vincent Aranzaso over 3 years ago in reply to Alexander Scheuermann

TI__Mastermind 18180 points

Hi Alexander,

Good Day. Please see below the another query of the customer related to BQ79616. Thank you very much.

Good to know that the cell chemistry won't be a problem.

I'm having a bit of a hard time finding the BQ79616 schematic for Altium designer, in the component manual I see that it exists but I can't find it either at TI's and Altium's websites. I tried to download it from third parties but the pins are completely unorganized. Do you know where I can find it?

I'm also indexing a photo of the component schematic from the manual below.

Thank you again for all the support.

Best Regards,

Ray Vincent

0 Alexander Scheuermann over 3 years ago in reply to Ray Vincent Aranzaso

TI__Genius 14890 points

Ray,

I don't have anything more than the file I've given you. We recommend customers organize the pins however will best fit their schematic. Sorry I can't be of more help on this one.

Data converters

Data converters forum

ADCs and MCUs for a low-cost electric car BMS