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Battery name is GARDA31, based on bq29330 and bq8030.

Most probably I killed it myself when soldering by shorting terminals with solder wire :( Controller is alive (communicates through SMbus), but shows "critical" and 0% charge in the OS.

enter image description here

The marking seems to be

R005 FZ81

but I am not sure in first 0 as the defect is exactly in its place.

It has relation to the - terminal of battery. I would think it is a current sense resistor Rsns (see circuit diagram of page 4 of datasheet), but my colleague says that it does not look like resistor but rather like semiconductor; I measured it to be a short (voltage is 0 across it and Ohmmeter shows the shortage), and if it would be a current sense resistor then battery would start or/and catch fire?

Battery pack was replaced and is fully charged.

I have another battery controller with current sense resistors, and they really look differently:

enter image description here

I did not desolder the battery pack yet, seems will have to do it to perform signal tracing.

Update:

I removed the batt pack, and desoldered the device. It appeared to have two terminals. Also found out that fuse is blown - and that's why there's no further damage.

This "resistor" is going to the notebook battery connector. I can not trace it more precisely because I have no datasheet for bq8030.

Update 1:

I shorted the fuse with solder (expected to melt in case of emergency), and replaced defective current sense resistor with two R010 resistors in parallel.

No change. OS still says 0%, and "Online, Critical". There's something else, up to gas gauge chip's firmware defecting the assembly because it thinks pack is damaged.

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  • \$\begingroup\$ I would still guess shunt resistor. Can you trace out the schematic around it with a multimeter? \$\endgroup\$
    – winny
    Commented Sep 23, 2019 at 15:49
  • \$\begingroup\$ Updated the question. \$\endgroup\$
    – Anonymous
    Commented Sep 23, 2019 at 17:36
  • \$\begingroup\$ Measure (and charge) the cells individually! \$\endgroup\$
    – winny
    Commented Sep 23, 2019 at 20:31
  • \$\begingroup\$ Other then the markings the top picture looks exactly like DALE (now vishay) WSR series resistors. I also see them commonly fail like that. Sometime they are not even be bad its just the package thats damaged by overheating. 95% sure its a low value resistor. considering the markings probably 0.005 ohms and your meter probably will show it as open. vishay.com/docs/30101/wsr.pdf \$\endgroup\$
    – narkeleptk
    Commented Sep 24, 2019 at 0:06
  • \$\begingroup\$ @winny already done, it was first step in identification of dead cells (they were in pairs - cut the wire at the negative teriminal side to access each cell individually, and then charge each individually). \$\endgroup\$
    – Anonymous
    Commented Sep 24, 2019 at 6:14

1 Answer 1

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Its a current sensing resistor, probably 5mΩ maybe a cree because they make resistors that neck down and have FZ in their ordering name (but the ones made now do not print the FZ on the resistor, so this makes me somewhat unsure, might be an older version of the same part):

https://www.bourns.com/docs/Product-Datasheets/CRE.pdf

I'm 80% sure it's a 2512 (you did not supply dimensions and should have), I'm 90% sure its a 5mΩ resistor.

You need to be sure of the value though. Maybe contact cree and see if this is one of theirs.

Edit: It's possible that the battery pack reached a critical or short circuit condition, and BMS protection fuses. Check the battery voltage and make sure it's above the danger levels for li ion

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  • \$\begingroup\$ Anything capable of destroying a 5mOhm resistor in so drastic a fashion is too likely to have destroyed something else - and something safety critical - on the way.... \$\endgroup\$
    – rackandboneman
    Commented Jan 23, 2020 at 20:38

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