Completely remove solder

Discussion in 'General Electronics Chat' started by kyle7119, Feb 15, 2011.

  1. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    I am thinking about doing a small hack which would involve me soldering some wires to battery terminals. However, if the hack does not work well, I want to be able to undo the job and remove any solder that I put on the terminals.

    Is there a way to *completely* remove solder from a surface? Will desoldering braid be sufficient for this job?
     
  2. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    Here is a picture of what the battery terminals look like. Very similar to what you would find in a laptop.



    [​IMG]
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You don't solder wires to battery terminals as the heat can (and does) cause the battery to rupture, often quite forcefully. This can lead to bodily injury or property damage.

    Rather than solder your wires to a battery, use a battery holder (Radio Shack stores carry a variety of battery holders) or purchase batteries that have tabs welded to them.

    Either that, or make your own battery tab welder. You'll find the prior two options much less expensive and time-consuming.
    [eta]

    Whoops, I thought you meant regular batteries like AA or D cells.

    No, you won't be able to remove the solder completely without damaging the gold plating.

    You might consider using miniature alligator clips, but that could be a bit dicey.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    Yes, good quality braid will remove solder effortlessly but u will melt the plastics with it.
     
  5. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    Yes, but leaving a silvery area showing the sign of previous soldering attempt.

    You will never see the shinny gold color surface again.
     
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    Nonsense. Tens of thousands of modelers have been soldering to old-style cylindrical batteries for more than 50 years. Commercial vendors did it too, before tab welding was prevalent. The cheap battery holders to which you refer just don't hold up in a model aircraft environment.

    I have never had nor do I know anyone who has had a battery destroyed, much less swell and explode. This applies to old style dry cells, alkaline, NiCd, and NiMH. I have not done it to any of the lithium types.

    John
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Many battery are plated with an alloy what make them difficult to solder on. The soldering job may be much more easy if you use a fine sand paper to remove this alloy. I have never heard of a flashlight type cell exploding because you solder a wire on it. But I can see the potential risk then soldering on very small coin cells
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Molten solder absorbs gold.
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    Of course, but there is no chemical reaction. One simply has an intermetallic layer of that alloy to address. Depending on the thickness of the gold (if it is really gold) one might be able to remove the lead chemically. It has been reported that mixtures of sulfuric acid or an alkane sulfonic acid plus nitric acid will remove lead. That makes sense, but I have not tried it. Be sure to keep all sources of chloride out of the mixture.

    If the lead is on copper, the initial bulk removal as described above can be followed by immersion in a bath of sulfuric acid or alkane sulfonic acid with copper (II) ions (e.g., cupric sulfate) to get rid of the last traces of the alloy.

    That does seem like a lot of effort to cover up an unsuccessful hacking job.

    John
     
  10. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    Just to clarify, these terminals are not attached to the battery itself. They are attached to the device and make contact with the battery pack when it is inserted.
     
  11. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    Okay, so it is looking like soldering is probably not the route that I want to take. How about crimping? Any possibilities there?

    I added some pictures that will hopefully help clarify the issue. For those of you who followed my last thread, these should look familiar. :)

    Pictures:

    1: The configuration needed to wire a 7.4V battery to the device
    2: A picture of the hack (not mine)
    3: Another picture of the hack
    4: The connector on the stock battery
     
  12. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    Crimped connections work well. Maybe if you gave us a clue as to what it is you are trying to do, we could be of more help.

    John
     
  13. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    The stock battery for this device is a 7.4V LiPo battery. It cost $80 and performs terribly. For $10, I can get a 7.4 LiPo of the same capicity with far superior performance. However, that LiPo doesn't come with the proper connector so I have to make my own connection to those terminals. I don't want to do anything completely permant, though, just in case I want to switch back to the stock battery for some reason.

    Don't worry about the battery aspect. I know what I am doing there. It's just the connection that's really holding me up.
     
  14. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If the stock battery performs poorly, why would you want to go back?

    One thing though, that 10k resistor is likely supposed to be an NTC thermistor that measures 10k when the battery is room temp, and decreases in resistance as the battery heats up. This is an important safety feature, and should not be overridden by the use of a fixed resistor.
     
  15. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    I'm not sure why I would want to go back. I just like to keep my options open, especially if I even need to ship it back for returns.

    Yes, I would agree that the 10k resistor is a thermistor. I was looking around at the pinouts on other batteries, especially laptop batteries, and this seemed to be pretty common.

    So how would I go about crimping a wire to these connectors?
     
  16. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    The system needs at least 10k of resistance across these two pins to power on. I assume that this safety feature forces a power-off if the battery gets dangerously hot?
     
  17. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    If you modify it, then the warranty is almost certainly void. How would a little residual solder on the terminals change that?

    As for crimping to those terminals in the case, I suspect that would be somewhat difficult to get to physically and would leave just as obvious marks as solder would leave.

    Apparently the device is designed for on-board charging. Bypassing a safety device so you can substitute a cheaper LiPo battery without that associated internal circuity is not safe. If there is an event, like a fire, are you in a position to accept total responsibility for it, or is that when you would want to go back to the manufacturer? Similar things have happened with people putting aftermarket batteries in cell phones -- there was one in the news in Cleveland a few years back. The lady wanted to sue the manufacturer for something she screwed up. I don't know how it turned out, but the costs of such fraud are not insignificant and are passed on to other customers.

    John
     
  18. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    I knew that this was going to happen...

    Please guys, no more posts ranting about the safety aspect of this.
     
  19. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    I was focused mostly on the fraud that you seem intent upon. Sorry, if you missed that point.


    John
     
    Last edited: Feb 17, 2011
  20. kyle7119

    Thread Starter Member

    Feb 11, 2011
    71
    17
    What are you talking about!?! I haven't said a thing about fraud.
     
Loading...