Replacing cordless drill battery pack batteries.

Discussion in 'The Projects Forum' started by agroom, Nov 10, 2011.

  1. agroom

    Thread Starter Active Member

    Oct 15, 2010
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    Okay, so I have a cordless drill and one of the battery packs went dead and I'm attempting to replace the batteries in the pack. I've read a few forums online and found that even an amateur can do this pretty simple. However, I do have a few questions that I wasn't able to find out.

    The batteries in my pack are labeled "Panasonic 0507 S". From what I found this is a 1.2v Ni-Cd sub-c class battery and the S means high capacity (mAh?) and quick charging. However, I can't find much about this specific battery, like how many mAh it actually has.

    1. My first question is, where could I find the specs for this specific battery or what is a good mAh for a cordless drill? I've seen them up to 2500, maybe higher.

    2. I found many batteries setup to make into a battery pack with the tabs already included. My other question then, is can I just solder the tabs to the other battery or is there some other kind of "weld" or adhesive I should use? Maybe someone has done this already and suggests a good battery I can use?

    Thanks in advance!
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    You can't solder the tabs to the batteries; the heat would cause them to rupture. They are spot-welded together at the factory. Someone posted schematics for a home-made spot welder back in The Completed Projects Forum that you might have a look at.
     
  3. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
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    What is the make and model of the drill? Sometimes manufacturers put the mAh rating on the battery pack itself or you can find out when looking for a replacement battery pack.

    I haven't done this myself and SgtWookie is right that trying to add tabs would likely damage the batteries, but I'm told you can make them using copper braid and a high wattage gun iron. The trick is to quickly make the joint and remove the heat. The joint is made with heat, but using a low wattage iron means applying heat for a long period of time until the surface is hot enough to melt the solder and stick to the metal casing of the battery. This will cause the internals to get hot too which results in damage. Using a high wattage iron allows to quickly heat the surface, make the joint, and remove the heat, in theory applying less heat to battery internals and causing damage. In effect, this is what a spot welder is doing - applying a ton of heat for a split-second and removing it.

    All that said, I've bought the iron but haven't actually done this myself. For about 20 cents extra a battery, you can get batteries with the tabs already spot-welded.

    While rewarding to do it yourself, note that depending on the total number of batteries needed, it may well be the same price or cheaper to buy a replacement pack and save time.

    The mAh rating isn't critical to operation. The battery charger will charge it just the same. If you get a lower mAh rating than what you had, you'll have less runtime, more if you get a higher rating. You just want to make sure you get the right chemistry - I assume you have a Ni-Cd or Ni-MH, not a Lithium - so the charger works properly with the battery pack.

    As another way to save money, you can pick up a cheaper battery pack from Harbor Freight and rearrange (possibly needing some soldering) the batteries to fit your pack. I've come across $5 and $10 18VDC battery packs. Note these are generally rated between 1200-1300mAh, so they probably won't give you the same runtime as your original battery pack, but considering most sub-C batteries run $2-$3 a pop, $10 for 15 cells ain't bad.

    Good luck.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    There is a trick to soldering tabs onto a battery: I have a special solder flux that makes the solder "wet" on instantly so I don't have to heat the terminal much.

    In general, trying to rework cells in a pack is a fool's errand. If one cell is bad, others soon follow. Better to replace the pack.

    There used to be a standing joke that the cordless tool industry provided an essential service: a place battery makers could dump all their reject batteries. Bottom line, it's a zero profit margin industry and quality is not a consideration.
     
  5. sonofptolemy

    New Member

    Nov 10, 2011
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    I've tried soldering to battery terminals before and it is not really a wettable surface (Solder wont flow).

    Not only that, like Sgt said the battery might explode. My experience is it will just heat up the battery and hurt the capacity and you will not make a successful solder joint.
     
  6. sonofptolemy

    New Member

    Nov 10, 2011
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    Where can I get that flux?
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    No I do not agree to that. Unless we are talking about small button cells. The can be soldered. But most batteries need some preparation. As they most often have some plating that in many cases are very hard to solder using solder for electronics. IF you grind down the plating you will often find a more easy material to solder. And if you have some soldering experience. It can be done. I have done it a lot of times. HOWEVER making your own battery packs using rechargeable cells is big NO-NO. Unless you provide appropriate fuses. Quite often battery packs have both current and thermal fuses. So unless you do this, you may end up with a very potential hazardous item. My advice do not do it. You will only save nickel and dimes. compared to a safe commercial battery pack
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    It's liquid acid flux so it's not really recommended for electronics, but works great for soldering to steel. It has to be handled VERY carefully and thoroughly cleaned after soldering. You can probably still find it somewhere, not sure where. Maybe home depot or hardware store? Plumbing supply?
     
  9. wayneh

    Expert

    Sep 9, 2010
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    I think it varies with metallurgy. I've had some that would flow nicely with a quick tap of a hot iron and others that reject solder like water on wax.

    Still, I wouldn't usually bother trying to solder to a battery itself. I try to maintain any hanging tab it might have and solder to that. I'd have a quandary if I had a new battery with no tabs. There is such a thing as conductive glue but it wouldn't be a good choice where you need high current and mechanical strength.
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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    Yes very often they have used some plating what is hard to solder. Instead of some flux, fine grade sand paper to remove the plating often works better
     
  11. agroom

    Thread Starter Active Member

    Oct 15, 2010
    60
    1
    When I took apart the factory battery pack it had no fuses in it. It was just 15 C-cell batteries all connected in series. My savings would be close to around $50 with prices I've spec'd out from places like Harbor Freight or Amazon as well as the local battery shop.

    My last pack that went bad I took to the local battery shop and for about $10 less than a new replacement, they replaced all the cells with new, higher mAh ones, but in the same case. The new pack works like a dream, 10x better than the original.
     
  12. agroom

    Thread Starter Active Member

    Oct 15, 2010
    60
    1
    Yeah, not sure why I never thought of this! *rolls eyes* thanks :)

    Yeah, I already plan to get the ones that have tabs already welded on. I've soldered wires to batteries in the past, but stranded copper wire, never a nickle tab. I've seen around online, and a few others have noted it's possible. I've got pretty good experience in soldering too.

    The idea is to create a pack that'll run for much longer than the stock. I noted in another post I had a local battery shop replace the cells in another pack for the same drill and it turned out to be a 10-fold improvement! I'm not stingy, but $20-30 is worth doing it myself.
     
  13. agroom

    Thread Starter Active Member

    Oct 15, 2010
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    1
    That is what I'm doing, replacing all the cells in the pack.
     
  14. agroom

    Thread Starter Active Member

    Oct 15, 2010
    60
    1
    Does anyone have a good battery site they use? It seems like they're a dime a dozen so I want to be sure it's a quality product from a legit site. I'm thinking this might be about as good a deal as they get.
     
    Last edited: Nov 10, 2011
  15. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Personally I would not try this except with tagged cells, of a type which are intended for soldering into circuit. A friend at work once tried to make up a battery pack, which failed VERY dramatically, with the contents splattered onto the lab. ceiling.

    I'm not sure it was soldering that did it, but it certainly put me off the idea.
     
  16. #12

    Expert

    Nov 30, 2010
    16,284
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    I keep a diamond fingernail file for damaging unsolderable coatings. Tin both parts. After the battery has cooled down, then solder the tab on while pushing the parts together with something made of stainless steel (it won't stick to the solder). If you are short on tabs, solder wick makes a good, flexible conductor.

    Fast is good! My Weller 250 is a miracle worker.

    No comment on whether rebuilding your own battery pack is a good idea.
     
  17. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Make sure they are all the same or there will be problems.
     
  18. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I've done the solder method a couple of times successful. But would highly recommend the tabbed batteries.

    I used basic solder flux but scrapped the battery terminals with some fine sandpaper. I have noticed that with the sanded surface and flux and a hot Solder iron I works fairly quickly. Without the sanding, but just the flux takes a whole lot longer and probably can get dangerous and damage the cells.
     
  19. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    I researched the rebuild cost for my Craftsman 19.2v battery packs. I could buy two new ones for $10 more than the rebuild cost of one! That was with the battery shop doing the rebuild.
     
  20. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
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    You haven't told us the make and model of your drill.

    If you're looking at spending $30 plus shipping alone for the cells and you're still saving $50, I assume you have a DeWalt, Makita, or similar. If they don't have a thermal fuse or the like, I'd be a little concerned.

    Was this battery pack for the same drill/pack you're trying to rebuild now? If yes, what was the mAh rating of the batteries the shop used? Was the price reasonable from the shop? If yes, I'd just have them build you another pack.

    Alternately, Home Depot sells a two-pack of 18V Ni-Cd batteries for $60. Those would include a thermal fuse and soldered tabs. You may need to move a couple of cells around to make it fit your battery case, but you'd save on shipping and assembly time.

    http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053
     
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