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What's the function(s) of the extra contacts on so many cellphone's batteries?

Discussion in 'Power Electronics' started by Benny7440, Apr 6, 2020.

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  1. Benny7440


    Jan 14, 2016
    Someone gave me a Zune device telling me that it was an iphone & I thought it was an ipod instead. It took 2 different persons trying to investigate this device & more than a week for me to get it right. Obviously, the batt. was fully discharged & there was no cable or base for it...

    I watched a video showing how to open it and got access to the batt. but it took just about 3.2 V after 3 trials. I then took a cellphone batt fully charged & managed to get access to its programs: it still works. The batt didn't lasted the amount of time I needed, so I found other cellphone batts (discharged) and thought of charging all of them and stacking all in parallel to increment time duration. Some of the batts have 3 contacts & others 4.

    My question now is how to charge them because their respective phones don't exist anymore or there're problems with their charger, cables or the phone itself? I know that maybe I can't use all of them because may not take a charge anymore, so I need to make sure that each one can be charged before making a "pile" of them. Once the pile is made then they must be charged either individually or at the same time, (this last scheme demands a more powerful power supply...).

    Think I'm not the first person to face this situation and more than one solution may be found. Thanks in advanced for any help with this!

    Attached Files:

  2. Ylli


    Jun 19, 2018
    Recycle all these batteries and buy the proper one with the proper charger. Otherwise, you are asking for catastrophic battery failure and perhaps a fire. Li-Ion batteries are not something that can be charged/discharged willy-nilly.
  3. Benny7440


    Jan 14, 2016
    I used to be an electronic technician in a computer factory by the late 70's and early 80's, so I'm inclined to use my own judgement after considering all or most of the available data. Having said so, what I want is to gain access to the knowledge applicable in this case.

    I know that Li-Ion batts are dangerous and should be handled carefully both, physically & electronically. I might do, at the end, as you suggest but, for now, I want to try to give those old batts a chance. In any case, this is so old that its' parts are scarce and pricy: not a good general approach.


    May 20, 2017
    Li-ion batteries need to be charged in a certain way, paying very very close attention to the charge voltage per cell plus a method of current limiting, termination of charge and preferably some thermal feedback that can also be used to terminate the charge process.
    Benny7440 likes this.
  5. bertus

    bertus Moderator

    Nov 8, 2019

    Have a look at this video and see waht happens at about 4:00,

    More info on the lithium batteries can be found in the battery university:

    Benny7440 likes this.
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