Author Topic: Asus laptop battery BMS reset? TI BQ30Z55  (Read 22161 times)

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Offline Kureigu

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Asus laptop battery BMS reset? TI BQ30Z55
« on: April 11, 2015, 12:14:50 pm »
Hello all.

I'll try to keep this as short as possible while also providing as much information as I can. (And I failed. Italics = long version. Note form below)

Back Story

So a couple days ago I bought a (cheap, used) Asus X200CA notebook with no charger. As expected it didn't power up without said charger, and with, all was golden, or so it seemed. Windows reported that the battery was detected and charging. However it transpires that it wasn't charging, the percentage wouldn't increase from 0 and 3rd party software reported that the charge/discharge rate was 0mw. After seeing this, I proceeded to try various internet found methods to initiate an internal charge to no avail.

Disassembly time... having already popped open the case to disconnect the battery for above "methods", I figured in for a penny in for a pound. The battery pack itself fortunately reveals the cells by simply peeling back a film. Measuring the voltages confirmed that it had been without power for quite some time, less 1.50v a cell, eek! Being a 11.25v pack with 3.7v cells my trusty Li(Po/Ion) charger was of course having none of it and complained of low voltage. So I trickle charged them in turn under NiCad mode up to a more respectable 3v each. I then continued to charge them correctly until the charge currant dropped to 0.2A. This was to test if the battery would now charge in the laptop, nope, but 84% charge was reported by windows. Disconnected mains, instant off. hmm... Checked voltage at the header, nothing  :palm:  Next ripped the board out to have a general look, and do some research on the main BMS chip.

Notes (Short of above)

Asus X200CA Notebook. 3* 3.7v cell, 11.25v Li-ion pack. Cells good, battery pack doesn't charge or have power out at header. BMS seems intact as battery condition/state is reported to laptop.


The main chip in the BMS is from Texas Instruments and has the part number BQ30Z55. One of its many protection features is a series of "permanent" failure states, which is stored in flash and can be reset. I believed that the critical low voltage fail state was triggered during storage. Communication with this chip appears to be with a TI proprietary protocol called SBS 1.1 which I can't find any detailed information on. Their own Battery Management Studio "bqStudio" does not list my chip, and I'm not sure on how to interface with the chip anyway. Pins 13 "SBS 1.1 data line" and 15 "SBS 1.1 clock line" look like a good bet for access, but beyond that I'm not sure.


bq30z50-R1 and bq30z55-R1Technical Reference
bq30z554-R1 Data Sheet (Essentially the same chip, confirmed here
Texas Instruments Battery Management Studio bqStudio

And finally the Question.

How can I interface and communicate with the chip to reset the failure state? Can I use the main header (probably not) or do I have to connected directly to the chip? I have an Arduino, and a Raspberry Pi for GPIO at my disposal.

Any help would be greatly appreciated.
Regards, Craig (Kureigu).

Offline senso

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Re: Asus laptop battery BMS reset? TI BQ30Z55
« Reply #1 on: April 11, 2015, 01:27:42 pm »
There is a 3 pin fuse somewhere in the pcb of the battery, when the BQ signals the battery as faulty it kills the fuse.
There are also lots of keys to be able to change those registers.
I think SBS is just another flavor of I2C, plug it into the laptop and probe the pins, but there is also an 100$ Devboard from TI that talks all those protocols.

Offline amyk

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Re: Asus laptop battery BMS reset? TI BQ30Z55
« Reply #2 on: April 11, 2015, 01:46:31 pm »
Yes, SBS is I2C-based protocol. Download the specification and read it first.

Check the fuse first, as mentioned above.

The Russians seem to have the most expertise in "hacking" these ICs... do some Googling and translating.

Offline Fraser

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Re: Asus laptop battery BMS reset? TI BQ30Z55
« Reply #3 on: April 11, 2015, 02:12:12 pm »
Please also be aware that the BMS 'kills' the battery pack for a good reason. Lithium Ion cell chemistry is irreversibly changed if the p.d drops below the minimum threshold. The OEM ensures that the battery disables itself in such cases due to fear of cell instability and potential negative consequences. If you do re-enable the battery, I recommend that you charge it only in your presence until you are sure that it does not get hot or present other symptoms such as out gassing.


Offline Kureigu

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Re: Asus laptop battery BMS reset? TI BQ30Z55
« Reply #4 on: April 12, 2015, 09:21:22 am »
The fuse appears to be fine, although I'm not sure on the proper test methodology for testing a 3 pin fuse. Continuity is being read in all directions.

Aurora, thank you for your concern regarding the cells. I am aware of this and was present throughout the charging process. If I do manage to get the pack functioning again, I will be doing a few charge/discharge cycles at different rates to ensure that the cells are stable and still maintain a reasonable capacity.

Looking at the Toshiba TPC8073 MOSFETs on the board, the 1st one (left in image) is switched on, while the second is off. If I take power from the first and apply it to the second then it too switches on. So possibly there is a bad transistor some where, or the BQ30Z55 is not signalling to turn it on, permanent failure state or sleep state?

So far my Googling of Russian forums hasn't come up with much on my specific IC, but has given me some software options. Unfortunately again, they don't seem to support my IC and also require additional serial hardware and licencing fees  :--

I would like to make use of my Arduino or Raspberry Pi for I2C comms, however I am struggling to find useful addresses in the technical reference document.

Offline amyk

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Re: Asus laptop battery BMS reset? TI BQ30Z55
« Reply #5 on: April 12, 2015, 04:24:08 pm »
Check the MOSFET control pins of the BQ to determine if it is keeping them off or not.

The datasheets/references should have enough information to at least read the state of the pack from the IC.

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