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chemical fuse

Other Parts Discussed in Thread: CSD, BQ20Z45-R1, BQ29412

Hi all,

I've been reading the datasheets for the BQ20Z95 and its Evaluation Module. There's mention of a 'chemical fuse' but no suggested part number anywhere. I haven't come across this kind of fuse - is there another name for it?



  • From the FAQ Knowledge Base
    These two companies are known to manufacture the 3-terminal chemical fuses:
    Sony Chemicals Corporation
    Electronic Devices Business Group
    1-11-2, Osaki, Shinagawa-ku, Tokyo, 141-0032 Japan
    TEL +81-3-5435-3943 FAX+81-3-5435-3072
    Uchihashi Estec Co., Ltd.
    Headquarters and Overseas Sales Department
    9-14, Imazu-Kita 2-chome, Tsurumi-ku, Osaka 538-0041 Japan
    TEL (06) 6962-6661 (INT-81-6-6962-6661)
    FAX (06) 6962-6669 (INT-81-6-6962-6669)

  • Hi

    There is something to know about the Sony product: You mustn't use it for medical applications

    An Other Company offering such fuses is NEC but I dont know the exact type name


  • I tracked down the NEC fuses,



    Also, why do you say that the sony fuses cannot be used for medical applications? Do they state that somewhere? Is there another reason other than liability?

  • Sony wants to know the end Application and if it`s a medical there will be no dellivery

    I don't know why but we had this @ two customers

  • They will also refuse to supply fuses for any military projects

  • Hi  I have a large selection of chemical fuses.  NOS of about 200 on hand.  Let me know and I can send out what you need.  I have tons of NOS tubes and transistors as well.  Todd  540-641-4536 

  • Is there any alternate solution (logic) for the chemical fuse?

  • Sony Chemicals has recently become Dexerials, and the devices referenced can be found here:


    However, I have contacted them regarding purchasing and samples and haven't heard anything back from them.  Which is putting an unfortunate cramp in my development, I would have thought triggerable fuses like this would be easier to get.

    As for an alternative, you'd need a way to fire the fuse very quickly without that surge reaching the load.  Maybe force the series-pass MOSFETS off, then short the pack across the fuse to blow it?  might be able to pull this off with a small device like a 2n7002 to drive the series-pass devices out of conduction and then something with a large peak current capability like a CSD series device to short the pack across the fuse.  But that's assuming you can get enough current out of the cells to blow the fuse quickly and reliably.. not a lot of safety in that I think.

  • Hello,

    I am wondering if these Chemical Fuses are a mandatory element of Lithium-ion battery packs.  I am working with a Chinese Li-ion pack
    supplier, and they produced a pack design based on a bq20z45-R1 fuel gauge IC, but there was no Chemical Fuse circuit.  Also, there
    was no secondary-overvoltage-protection IC such as the bq29412.  Are the Chemical Fuse and bq29412 (or similar IC) required for commercial
    Li-ion battery pack applications?  Is there a Regulatory requirement? 

    BTW, I am working on a medical device design.

    Thanks for any advice.


    Mohan Gurunathan

  • Hi Mohan,

    there is no regulatory reqirement to have a chemical fuse but some of the test made be UL will not be passed if you don't have one. Testing procedure depends on how your application is designed an what test are neccesary for your product.

    For a medical equipment it will be fine for your risk analysis if you have a 2nd Protection

    BTW: Since the company firmed from Sony to dexerials they alow to use the fuse also for medical if it is not life supporting.
  • Hi Jorg,

    Thanks for the advice.  I also have advice from another source confirming that there is currently no regulatory requirement to have a chemical fuse, but it is highly recommended, especially for high reliability applications.