LTC6811 Implementation Thread

[okashira]

What's the possible programmable range of sensitivity?

Pretty large. Read the datasheet.
If you're designing a sensor the sensitivity is also a function of the iron core geometry and material you use.
One cool thing about hall sensors is you can have two in series, one with low and one with high sensitivity for good accuracy at low and high currents without adding impedance.

 

[okashira]

okashira thanks for the clarification! I have a half dozen sample chips in my lab and never got around to building prototype sensors... (the story of my life.) Glad to know they will work as stated in data sheet.

Just thought about one more thing on using them without reprogramming
Half of the reason for using their programmer is calibration. It's intended so that each sensor is programmed and calibrated in a temperature controlled test at various current levels and temperatures.
This way the sensor can compensate for the magnetic hysteresis and saturation curve specific to the sensor and iron used.
Something to keep in mind for a BMS. May affect 0 current offset and higher current accuracy. You can get around alot of this if you are clever with your code...

 

[NeighborVadim]

Hello!

Not to sure if this thread is dead, but I have been working with the 6811 for the past months too. Currently I am trying to set up a board with the ltc6820 to convert the IsoSPI into regular-spi, but it isn't working (no SPI at all, just straight 5v on SPI lines). I am testing this board with the dc1894 demo board.

Would love to contribute to you guys' project in any way I can, and would appreciate any help you guys can give!

 

[methods]

Update:

I am extremely busy with work but we were able to hit the FAST FORWARD button.

We have teamed up with a UK entity who has provided qualified 6811 slaves. Those should be coming in the mail any day now.

For my efforts here (strictly DIY for my boat... not for my close friends Electric Airplane...) I will be delivering an Arduino based Master which will serve to handle all tasks required. V1 simply exposes and controls the LTC6811 features for immediate use, testing, and evaluation. V2 integrates via CAN to a Contactor Drive, Precharge Drive, Current Sensor, Isolation Measurement, and whatever else you have around that you want to integrate.

I am forwarding the software I developed for BMS V4. It was paid for indirectly by the TTXGP, myself, Jozzer, and a 3rd party (who will remain unnamed...) who still has a $5k outstanding invoice. This software is a 100% working state machine which will take only a few days of fiddling to get moved over to the 6811.

I do not post these things publicly... for fear of the code ending up in someones Senior Project. If someone is building a BMS for School.. YOU NEED TO BLANK PAGE THE WORK YOURSELF!

SO DONT ASK!
I WILL NOT DO YOUR SENIOR PROJECT FOR YOU... EVEN FOR MONEY (tho... eh... er... eh hem... I have done a few in the past )

Yea... so ... I am on the grind hardcore. When I have some time I will comb back thru this thread and then post results. Anyone who is a contributing member is welcome to share in the loading and enjoy the fruits. My short term goals are to:

* Get a protected lithium starter battery running in all 5 of my cars in a non-ghetto way
* Get our boat running in a protected way
* Keep present and accountable in the BMS domain

Carry on

-methods

 

[ENNOID]

Hi,

Just have a look on this project:
- www.foxbms.org

seems like the thing you were looking at...

 

[ENNOID]

... It is based on LTC6811

 

[bradleyk]

Anyone managed to get anywhere with this?

I've just finished designing a low parts carrier for this. So far I can measure cell voltage and do 50mA per cell and 200mA per pack

about to start testing isobus chaining then looking at writing a standalone balance firmware for the esp32 master.

https://gitlab.com/bradleyking4/esp32-ltc6811-bms

 

[ENNOID]

I started to work om my own bms last year based on the software from DiebieMS. The BMS is functionnal, but we are still improving the software and making the final tuning.

https://www.ennoid.me/battery/bms

 

[bradleyk]

I've got this to the stage where it can now balance cells over multiple iso bus slaves. logging voltage every minute, accessable via a web interface. not yet talking over can. I'll be doing a pcb revision soon to clean up the layout to make assembly easier.

https://gitlab.com/bradleyking4/esp32-ltc6811-bms#firmware

 

[ENNOID]

Hi,

I managed to get multiples slaves LTC6811 working together with a master board with STM32 MCU for a complete up to 500A/400V BMS configurable with a nice graphical user interface through USB...

See thread:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=92952&start=25