4-channel BMS with daisychain bus

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Re: 4-channel BMS with daisychain bus

Post by wacomg »

Here is my setup
unnamed.jpg
when i connect batteries slaves blink 4-1 slow
when i connect power to the main board they stop blinking and after 1-3 sec first slave starts blinking 4-1 really fast
second module does not blink
in the interface it shows only first module
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

That wiring looks fine to me.

I had the similar issue of only seeing the first module in the interface. That was because I had the slaves connected to the battery the wrong way around so the first slave board was on the most positive side of the battery instead of the most negative which it should be.

I don't think that was flashing fast though when it did that. What is your shuntvtg set at? When I was balancing the cells that were being shunted down would flash rapidly.
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Re: 4-channel BMS with daisychain bus

Post by wacomg »

I have properly connected most negative side to the first slave module
but it doesn't help
It can see only first module
Screenshot-20220331171851-517x255.png
Screenshot-20220331171917-822x539.png
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Re: 4-channel BMS with daisychain bus

Post by wacomg »

when i set shuntvtg to 3400 it light up 2 diodes , as far as i can see, for second and fourth cells
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Re: 4-channel BMS with daisychain bus

Post by johu »

Is modcount set correctly? (2)
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Re: 4-channel BMS with daisychain bus

Post by wacomg »

where to check it ?
I don't see it either in the interface or in the sources
johu wrote: Thu Mar 31, 2022 3:38 pm Is modcount set correctly? (2)
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Re: 4-channel BMS with daisychain bus

Post by johu »

Oh right, the binary on github doesn't have it yet.
So both modules are flashed ok and give you a running LED when reset and not connected to master unit?
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Re: 4-channel BMS with daisychain bus

Post by johu »

I have decided to open source the master firmware as well: https://github.com/jsphuebner/bms-software

I won't be pushing commercialization of this BMS any further as doing so showed a number of issues:
- Mass production is difficult as every module must be calibrated and programmed. No pre-programmed Attiny chips can be fitted
- communication wiring was a constant source of mishaps

I have another idea up my sleeve, more on that in a separate thread.
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Re: 4-channel BMS with daisychain bus

Post by wacomg »

johu wrote: Thu Mar 31, 2022 9:20 pm Oh right, the binary on github doesn't have it yet.
So both modules are flashed ok and give you a running LED when reset and not connected to master unit?
Hello !
both modules give me running LED 4-1 slowly until i power on master unit
when master unit starts both modules stop blink then on first module one led blink onse
then on the first module i see running LED again but much faster
the second module no longer blinks at all until i reconnect power

Interface shows only one module
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

wacomg wrote: Sun Apr 03, 2022 5:55 pm
both modules give me running LED 4-1 slowly until i power on master unit
when master unit starts both modules stop blink then on first module one led blink onse
then on the first module i see running LED again but much faster
the second module no longer blinks at all until i reconnect power

Interface shows only one module
I've had that happen in the past when a data connection wire between the slave boards fell off, every slave board after that one in the line stopped blinking.


On a separate note, are the slave boards able to cope with an odd number of cells or do they need all four to work? In my new setup I will only be using 70s.

Also does the newly released master firmware have the isashunt canbus fix? If not was it a relatively simple thing to fix?
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Re: 4-channel BMS with daisychain bus

Post by johu »

You need to connect at least two cells to be able to generate stable 3v3 for the MCU. The last cell must be connected to channel 2 and 4 for power supply

Not sure what the "canbus fix" is but now with the source code released you can check yourself ;)
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Re: 4-channel BMS with daisychain bus

Post by m.art.y »

johu wrote: Sat Dec 11, 2021 10:03 am No, calibration would only affect the absolute values, not the jitter. I can compile a software later that has a configurable round-trip time or so, see if that helps.
Hi, Johannes, when hooked up to the full battery there is still the same ~10mV jitter on reported voltages. Which parameter would that round time be in your code and which values you'd recommend to try? Just wondering did you see any jitter like that when you tested your system?
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

The last slave board will only have two cells to monitor so that's lucky!

The issue with the isashunt canbus was that you occasionally had to reselect isacan1 in order for the board to correctly read the canbus data from the isashunt. I'm sure I can probably get it working by just deleted all the code for any other option, that's my go to method of coding!
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Re: 4-channel BMS with daisychain bus

Post by johu »

Oh now I remember. No that's not fixed. The reason why it works after re-selecting is that the init sequence is sent again. It seems that better (=delayed) timing of the init sequence should fix this
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

That makes sense, I have been looking through the firmware a little tonight. I should be able to figure out some adjusted timing for that. Thanks for the pointer.
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Re: 4-channel BMS with daisychain bus

Post by wacomg »

LRBen wrote: Sun Apr 03, 2022 8:14 pm I've had that happen in the past when a data connection wire between the slave boards fell off, every slave board after that one in the line stopped blinking.
If you have issues with data connection between modules then master module cannot receive any information from modules
am i right ?
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

wacomg wrote: Mon Apr 04, 2022 6:36 pm
LRBen wrote: Sun Apr 03, 2022 8:14 pm I've had that happen in the past when a data connection wire between the slave boards fell off, every slave board after that one in the line stopped blinking.
If you have issues with data connection between modules then master module cannot receive any information from modules
am i right ?
Thinking about it I think it might have been one of the slaves losing power, the rest of the boards after that wouldn't report to the master module. I'll have a little experiment tomorrow and see if I can't recreate it.
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

Would it be possible to add the compiled binaries for the slave boards to the repository? I'm having issues trying to configure code blocks in order to compile the slave board firmware.
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

johu wrote: Sun Apr 03, 2022 8:17 pm You need to connect at least two cells to be able to generate stable 3v3 for the MCU. The last cell must be connected to channel 2 and 4 for power supply
How do channels two and four need to be connected to the last cell? I have tried a number of different combinations and do get power but the voltage reading is way off.
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Re: 4-channel BMS with daisychain bus

Post by m.art.y »

johu wrote: Fri Apr 01, 2022 8:16 am I have decided to open source the master firmware as well: https://github.com/jsphuebner/bms-software
Hi, does the source code include balancing feature as well that you had previously removed? Would you be able to tell which is the round trip time parameter which you suggested to adjust regarding reported jitter on the cell voltages? Thanks.
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Re: 4-channel BMS with daisychain bus

Post by johu »

So has anyone ironed out some of the remaining bugs? Any running systems?

BTW Literally nobody: "thanks for publishing the code"
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Re: 4-channel BMS with daisychain bus

Post by LRBen »

I shelved it in the end and went with Tesla slave boards and SIMP BMS. I just didn't have the knowledge to get anywhere with bug fixing.
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Re: 4-channel BMS with daisychain bus

Post by joeflickers »

m.art.y wrote: Thu Jul 29, 2021 4:48 pm Johannes, so I flashed the firmware on the 5.3 slaves and also on the master unit. I can see BMS settings on web interface and slaves are flashing in sequence from LED 4 to LED 1 when connected to battery cells. However when I try to connect slaves to master unit I get no data at all and slaves keep flashing as they were. On the first slave (counting from the most negative cell) I did not put a jumper on the programming header but I put a jumper on the 2nd slave on the 4th pair of pins counting from the top (the only free pair not used for flashing). It is only a 2 slave board test setup. I tried to put the jumper on the same pin pair on the 1st board but no change. What could be wrong? How do we select first board (or not) on the 5.3 slaves? Thanks 😊
im having a problem copiling the attiny44 firmware via arduino ide,,idd appreciate a way to do it
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Re: 4-channel BMS with daisychain bus

Post by johu »

It's not meant for arduino, you need to compile in CodeBlocks IDE
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Re: 4-channel BMS with daisychain bus

Post by joeflickers »

johu wrote: Mon Jan 23, 2023 2:30 pm It's not meant for arduino, you need to compile in CodeBlocks IDE
thanks,i had a no clue of the IDE used ,ill try that familialise myself with codeBlocks tommorow,
I believe the cell-module firmware is what I will compile.Lastly have a querry about the type of current sensors compatible with this hardware.I happen to have a nissan leaf current sensor around.
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