Electronics > Beginners
Solder directly to NiCds?
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CarsonReidDavis:
I'm in the process of repairing a portable Tektronix 214. I disassembled the scope and removed the batteries. Then I powered it directly with two 6 volt sources and it seems to work, although there might be some connection problems while disassembled.

So I set about getting replacement batteries for the scope. It originally took two Ax5 NiCd packs, but I settled for AA for cost reasons. I had a local shop weld the NiCds because I have been told that soldering directly to NiCds is inadvisable because of reliability problems that can be introduced if the nylon seal is over-heated.

I didn't realize until I got the new packs home, but the technician did not solder to a hanging solder tab. Instead he cut a tiny solder tab that just covers the head of the battery and soldered directly to the top. I fail to see how this is thermally distinct from soldering directly to the battery.

I have included detailed pictures of the scope, the original packs, the new packs, and some diagrams I drew at this link: https://imgur.com/a/1sSIH3a

Do I need to have these packs remade? I do not plan on opening this unit again after the repair, so I will have no way to monitor corrosion or other problems.
bd139:
I used to solder to NiCds all the time. Apply some flux with a flux pen to the end then get some solder on the cell. Then let it completely cool. Then do the other end. Then assemble the pack. Tin everything.

NiCds I used had the shit hammered out of them in RC cars. Never had a problem.
BrianHG:
Use Mr. Carlson's wet rag method.  Here is his battery pack upgrade for your scope.
Watch at 13min 30sec for just the battery soldering instructions.

helius:
If the terminals are nickel-plated stainless steel, it should be possible to solder to them directly with normal alloys for electronics. If the terminals are pure stainless steel, other alloys like Sn96Ag4 may be required. Orthophosphoric acid can be used to activate stainless steel for very solid connections.
CarsonReidDavis:
Thanks everyone for your replies, however, I don't need to know how to solder to the batteries. The soldering has already been done, against my expectations. Please refer to my original post and the pictures I submited.

I paid a decent chunk of money to have a professional weld the batteries for me, because I have read from several sources that soldering directly to a NiCd can compromise the integrity of the battery if the seal is overheated. However, when I received my packs, 4 of the 10 batteries had been soldered instead of welded.

I'm trying to find out how big of an issue this is, and whether I need to go through the effort of fighting with a technician who might be very reluctant to replace some of the batteries and redo the work.
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