Request for tldr fix for wrong woltage readout by cmu

[0tik]

I have read the other thread with 11pages but still don't get it. Can I just swap LTC chip? Analog.com have pinout of the chip. Is it possible to check voltages on its pins from cells? That way I could check if there's a fault between voltage tap and LTC chip. If LTC chip swap fails then I should get replacement CMU(any will do?) And swap eeprom from my faulty CMU. But then which chip is eeprom?

 

[kiev]

background on issue from PM:
Hello Kiev. I have 2 cells in my imiev that read 320Volts each. If you know what could be the culprit, can you give me your contact info for instant messaging or audio chat?
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i'll have to find the other thread; there is a thread with pictures of the CMU boards with all the components identified, LTC, eeprom, etc.

the inputs to the LTC chip can be monitored or checked with a voltmeter once the pack is opened.

One idea--what is the condition of the 12V battery, just to rule that out.

 

[0tik]

Thank you for fast help.
https://myimiev.com/forum/viewtopic.php?t=4866&start=10
I hope it is not this thread. Pictures are gone.
I charged 12v battery before checking car for the SECOND time. So that's not it.
Here's pdf with a description of LTC chip.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.analog.com/media/en/technical-documentation/data-sheets/ltc6802-2.pdf&ved=2ahUKEwih9-nxwbb-AhWOlYsKHTZyDw0QFnoECBMQAQ&usg=AOvVaw1PAuo36S6kyGRI_mZ_V619

I'm not quite sure yet which pins to check for particular cells.
One thing I could check so far is continuity between voltage tap and those springy things that connect it to the motherboard. All springs are okay. It's cells 25 and 26 that give 320v in canion/obdzero. Also checked in diagbox- 4v one cell and 3.61v on the other- I am sure the fault is somewhere around LTC chip. Although I wonder why it's different values for obd apps and diagbox.

 

[MickeyS70]

Hi there
You’re correct these symptoms point to a CMU fault, a blown smd fuse or a faulty LTC chip I would guess, both can be replaced using a hot air solder station..

 

[kiev]

The CMU thread that has the pictures:
https://myimiev.com/forum/viewtopic.php?t=4302

Do you have the pack open and access to the CMU boards?

 

[MickeyS70]

Might be helpful in tracing signals

https://imgbox.com/izI61UTr

 

[0tik]

Might be helpful in tracing signals

https://imgbox.com/izI61UTr

Be wary this is a single 4 cell CMU. Notice the lack of socket for the cable for the other slave cmu. Pinout of LTC is different for 8 way CMU. Not c1 but let's say c5.

Anyway it turned out to be a single blown smd fuse between cells with faulty reading. Yay easy fix Tank you guys for pointing it out.

 

[kiev]

What would cause the fuse to blow? Will it blow again when re-installed?

 

[MickeyS70]

.. in my case it didn’t blow again but LTC chip got damaged and needed replacement, hence the pic without chip, and yes, it was a 4 cell CMU, same PCB for an 8 cell, just fewer components installed…

 

[0tik]

The only reason for the fuse to blow that I can think of is that I placed CMU on th cell tray in the opposite direction and cell taps touched cell terminals.

@MickeyS70
It's not exactly same. "Cn" and "Sn" pins are leading to different cells. That's extremely important when checking continuity from cell voltage taps to LTC chip's legs.

 

[MickeyS70]

@MickeyS70
It's not exactly same. "Cn" and "Sn" pins are leading to different cells. That's extremely important when checking continuity from cell voltage taps to LTC chip's legs.

It is the same PCB layout as you can easily convert an 8 Cell CMU to work with a 4 cell tray, but you’re correct the routing changes depending what it controls.

 

[MickeyS70]

@MickeyS70
It's not exactly same. "Cn" and "Sn" pins are leading to different cells. That's extremely important when checking continuity from cell voltage taps to LTC chip's legs.

It is the same PCB layout as you can easily convert an 8 Cell CMU to work with a 4 cell tray, but you’re correct the routing changes depending on what it controls.