Ryobi battery pack repair (replacing battery cells (Li-Ion))

Discussion in 'Power Electronics' started by Ljk2000, Nov 20, 2016.

  1. Ljk2000

    Thread Starter Member

    Nov 20, 2016
    30
    0
    So I am new to this and will say that I have done some electrical projects before and am pretty confident with what I am doing. But I will jump to the 'story'. This battery is about 4-7 years old and is dead. And of course I got some new ones and they work great. But anyway I wanted to just kinda experament and replace the cells in the battery pack. They are all 18650 cells. And this is the replacement I wish to get. It seems to be closed to these originals. Before taking apart I charged up what little it could hold and tested a battery. it measure (off top of my head) about 3.8 volts and almost 1 amp. being so old I think they where able to hold more than that. But there is a concern (hence this post). I know that batteries in series adds up voltage, and in parallel it adds amps/current. Does the circuit board control the amps/current because 8A would fry a tool I am sure. And because I fear this I will only replace the top half. Which would add to 7.5Amps! So I am kinda worried about this granted I still want to learn from this. I ordered a Imax b6 (something like that) to really determine some stuff. But how are they doing this because even with these it should be killing the tools. But maybe that is why there is such a "motherboard" to keep this in control. I would love any info on this, it is something I want to accomplish and learn to do. I hope yo all help! My other group (stack echange) let me down, answered with "Li-Ion batteries are dangerous, do not bother". I want to ensure I know the procuations. I read on safety with these. Thank you! DSC02158.JPG DSC02161.JPG
     
  2. tcmtech

    Distinguished Member

    Nov 4, 2013
    2,808
    2,705
    The amp rating on a battery its amp hour rating which means it can supply its rated amps into a load for one hour.
    Your tools equivalent resistance is what determines its amp draw.
    So whether you have one set of 4 cells in series or 100 sets of 4 cells in series paralleled to get the tool will only take what amps it needs.

    Also when dealing with battery packs you need should never mix new ans old cells together so either just run one set of four or run the two sets of four.
     
  3. Ljk2000

    Thread Starter Member

    Nov 20, 2016
    30
    0
    @tcmtech I see what you mean. So if there was a... say 15Amp battery it will not fry the tool since it simply will take what it needs. So I could use a 2Amp battery and make this huge thing. That sounds nice. That there was a help so I thank you kindly! And do not worry, I am replacing them all with new ones. I might however use the 'good' old ones to make another old battery my friend has just to make that one operate better.
     
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