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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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spot welders for ni cad battery rebuilds.
It seems a lot of we DIYers want to rebuild ni cad packs from 12v drills etc.
Spot welders seem to be the ideal method. Q) anyone out there built / seen/ used a homebuilt version for this purpose.? Normal spotwelders for heavier joins are basic mechanics and electrical parts. Combining the knowledge of a group like this should get a basic design possible i reckon.. Any ideas out there. I can make gadgets in metal but have no idea re volts/ amps needed to make the spotwelder work.. RC modellers/ recycler fiends and DIYers would get a lot of use from such a machine in a community. Jewellers use them but high cost. Surely the junk brigade can cover the problem? Any ideas appreciated.. Nick Tasmania Australia |
#2
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This is from a current thread in "basics":
http://groups-beta.google.com/group/...2a8f0214ad3b43 and the DIY spot welder: http://users.frii.com/katana/spotweld.html I've done this for a long time. I replaced batteries in pro movie camera belts but those were soldered together. At least that's the way we did it. More recently I work on my own stuff, mostly Makita 9.6V sticks. I've been using a big soldering gun with the tip cut off. Pressing the open leads against the work firmly makes a lot of cool sparks but heats the work area so that it takes solder nicely. This method wouldn't do well around sensitive components. There's another guy working on heat sinks that uses a BIG iron. I also reassemble the batteries first and make the middle connection at the bottom last. This avoids most short circuit problems. I also don't leave out the cardboard sleeves and the plastic washers between the cells. Richard |
#3
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spudnuty wrote:
This is from a current thread in "basics": http://groups-beta.google.com/group/...2a8f0214ad3b43 and the DIY spot welder: http://users.frii.com/katana/spotweld.html I've done this for a long time. I replaced batteries in pro movie camera belts but those were soldered together. At least that's the way we did it. More recently I work on my own stuff, mostly Makita 9.6V sticks. I've been using a big soldering gun with the tip cut off. Pressing the open leads against the work firmly makes a lot of cool sparks but heats the work area so that it takes solder nicely. This method wouldn't do well around sensitive components. There's another guy working on heat sinks that uses a BIG iron. I also reassemble the batteries first and make the middle connection at the bottom last. This avoids most short circuit problems. I also don't leave out the cardboard sleeves and the plastic washers between the cells. Richard Short Answer: I've been workinng on and off on the problem for a couple of decades. Here's the result: http://nm7u.tripod.com/homepage/welder.html I stopped working on it when a Unitek CD welder fell into my lap. Long Answer: Welding something with an electrode on each side and no worry about temperature is pretty easy. Welding with both electrodes one side and not being able to heat the metal is MUCH more difficult. You need a LOT of power for a short time. The current has to go thru the contact points and the battery case, not the metal strip. Nickel is most used, but I've found .005" brass from the hobby store to work pretty well. Contact area is critical. Too big and it won't weld. Too small and it burns thru. You're on the right track when you get a weld that can't be pulled off without tearing the strip and the battery is still cold to the touch. One thing that helps is to cut a slot in the tab material between the electrode contact points. That increased path resistance forces more current thru the battery. If you cut it longitudinally, you can make the path length thru the tab arbitrarily long. If you use a transformer and run if off the AC line, you need to worry about saturation in the core. I solved the problem by using zero crossing turn on and running an integral number of cycles. You can have ZERO.Zero resistance in the welding path. I was improving the setup by taking out a couple of milliohms at a time. You'll see a lot of soldering on my system. That's all mechanical. No current goes thru a soldered joint. My welds were working but they were extremely sensitive to time,pressure and number of cycles of AC line. More turns on the scondary gives you more voltage and less sensitivity to time/pressure, but increases the input amps proportionally for the same output amps. Oh, I was sucking 40 amps for six cycles out of a 15A house breaker. Talk about dimming the lights ;-) I was about to give up and add a third secondary turn when the Unitek fell into my lap. The Unitek CD welder is MUCH more forgiving. It dumps a fixed amount of energy and is relatively insensitive to contact resistance. That's relatively. Still have to be careful, but I can make 10 good welds in a row without much trouble. Couldn't do that with the microwave transformer. Wear safety glasses and an old shirt. A mis-weld sprays molten metal at you. Keep a flashlight handy so you can find the fuse box when it blows ;-) Blows caustic stuff at you when you blow a hole in the battery. Been there done that. mike -- Return address is VALID but some sites block emails with links. Delete this sig when replying. .. Wanted, PCMCIA SCSI Card for HP m820 CDRW. FS 500MHz Tek DSOscilloscope TDS540 Make Offer Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. MAKE THE OBVIOUS CHANGES TO THE LINK htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/ |
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nick moore wrote: It seems a lot of we DIYers want to rebuild ni cad packs from 12v drills etc. Spot welders seem to be the ideal method. Q) anyone out there built / seen/ used a homebuilt version for this purpose.? Normal spotwelders for heavier joins are basic mechanics and electrical parts. Combining the knowledge of a group like this should get a basic design possible i reckon.. Any ideas out there. I can make gadgets in metal but have no idea re volts/ amps needed to make the spotwelder work.. RC modellers/ recycler fiends and DIYers would get a lot of use from such a machine in a community. Jewellers use them but high cost. Surely the junk brigade can cover the problem? Any ideas appreciated.. Nick Tasmania Australia -- nick moore I've rebuilt nicad battery packs by cutting the tabs that are tack welded to each individual battery so that there is a long tab left and then soldering the two tabs flat against each other between the replacement battery and the old battery left behind. It does not heat the batterys too much and works fine mechanically. |
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Charlie+ wrote:
On Wed, 23 Feb 2005 10:21:39 -0800, mike wrote as underneath my scribble : This tripod site tried to load 32 ads and cookies during the time it took to load this page - beware. I'm using Firefox with pop-ups disabled and a Flash-turner-offer extension; I had no problems at all, whole lot came up in less than 0.5s, albeit on half a meg of ADSL. However, comment well taken as all Tripod sites seem to "pollute" the browsing experience unless steps are taken to prevent it. Short Answer: I've been workinng on and off on the problem for a couple of decades. Here's the result: http://nm7u.tripod.com/homepage/welder.html I stopped working on it when a Unitek CD welder fell into my lap. snip |
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Charlie+ wrote:
On Wed, 23 Feb 2005 10:21:39 -0800, mike wrote as underneath my scribble : This tripod site tried to load 32 ads and cookies during the time it took to load this page - beware. Where's a good place to stash a FREE webpage that doesn't have ads? I'd be more than happy to move there. Popup and ad blockers seem to be a necessity to surf today's web. mike Short Answer: I've been workinng on and off on the problem for a couple of decades. Here's the result: http://nm7u.tripod.com/homepage/welder.html I stopped working on it when a Unitek CD welder fell into my lap. snip -- Return address is VALID but some sites block emails with links. Delete this sig when replying. .. Wanted, PCMCIA SCSI Card for HP m820 CDRW. FS 500MHz Tek DSOscilloscope TDS540 Make Offer Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. MAKE THE OBVIOUS CHANGES TO THE LINK htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/ |
#7
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"mike" wrote in message ... Where's a good place to stash a FREE webpage that doesn't have ads? I'd be more than happy to move there. Popup and ad blockers seem to be a necessity to surf today's web. Try your ISP. N |
#8
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"mike" wrote in message ... Charlie+ wrote: On Wed, 23 Feb 2005 10:21:39 -0800, mike wrote as underneath my scribble : This tripod site tried to load 32 ads and cookies during the time it took to load this page - beware. Where's a good place to stash a FREE webpage that doesn't have ads? I'd be more than happy to move there. Popup and ad blockers seem to be a necessity to surf today's web. mike There's no free lunch, somebody's gotta pay for the web space. You *do* need an ad blocker to surf the web these days, I too would strongly recommend Firefox with the free Adblock extension, you can even import a large list to Adblock so you don't even have to mess with it, brings the enjoyment back to surfing the net. |
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