Adding "buttons" to flat-top cells

[FBsLights]

I have a bunch of NiCd flat top cells that I want to use around the house but they need button tops to make contact in most items (including flashlights!)

What would make a good button? I have access to a punch and scrap copper in various thickness. Would a small round copper piece soldered to the top work well? I'm concerned that it may corrode quickly and not make good contact. I've done a couple and it seems to work but wanted to ask for opinions before potentially ruining a bunch of cells.

I know how to quickly solder to the batteries and then cool them with a damp sponge to minimize heating of the entire cell. I have a good soldering iron that allows me to do this.

Thanks,
FB

 

[jwyj]

Well, you could use some of those small super magnets.

 

[ama230]

Well, you could use some of those small super magnets.

This is the best alternative as its reversible and cheap. Also you have to make sure you buy the right size magnets as getting a kit with a bunch of them is fun to play with a serves great purposes. Like some of my aaa's have extra material around the ends and dont touch properly on the charger and the small neodymium magnets do the perfect job and would fit your need(s) as well.

 

[Lynx_Arc]

I used to buy cell phone nimh packs and strip the batteries out of them. Most of them are flat tops with arc welded strips on them. I removed the strips and using a dremel ground off the leftover welds then took a 50 watt soldering iron and basically built up a nipple using solder and it worked pretty well I have used most of them for years with about 25% of them going bad from me mostly from charging them on a 1 hour charger and discharging them too low. The magnets would be easiest if I had an easy way I would have used copper nipples and just tinned them to prevent tarnishing.

 

[FBsLights]

Good advice.

I would prefer not to use magnets as I want to keep the use of the batteries as simple as possible for everyone in the house. Otherwise, they won't get used!

I don't know why I didn't think to just tin the copper tops to prevent corrosion. I already have the copper buttons punched out. They have been sitting on my bench for a couple days and I noticed they were already darkening. It will be simple to tin them.

FB

 

[Lynx_Arc]

Good advice.

I would prefer not to use magnets as I want to keep the use of the batteries as simple as possible for everyone in the house. Otherwise, they won't get used!

I don't know why I didn't think to just tin the copper tops to prevent corrosion. I already have the copper buttons punched out. They have been sitting on my bench for a couple days and I noticed they were already darkening. It will be simple to tin them.

FB

If you are going to solder them on, pretin both top and bottom and the flat top before you attach it so that you will minimize heating time. I have a tray of 48 1600mah nimh AAs that are flat tops that I ended up finding a sale on rayovac hybrids so I never put them in use I was considering putting tips on but the solder blob fix is too difficult for more than a few cells trying to get them the right height and not too fat a top is a mess. I bought some brass rod stock and was going to try and cut it for tips but couldn't figure out an easy way to do it.

 

[alpg88]

i use magnets too, but to make sure they aren't moving and shorting, i cut circles of the same diameter as cells, from a hard foam, as thick as magnet, or close to it. cut out a hole for magnet. this way magnet stays.
it is ok to solder nimh\nicd cells, but i never do it with 50w iron, i use my 25w, and i try not to heat up the cell much. i use plumbers flux, i spread a bit on the cell , and solder stick very quickly, no need to use a lot of heat.
if i take apart a pack i rip the tabs only from negative end, i end up having almost intact tab on positive side, i just fold it in half, or 3 times, depending on its length. and that is it, positive end becomes a bit longer, enough for good contact.