3 lead cr2032 cmos battery.. Uhm. Why?

[SantaClaw]

So, I was about to replace the cmos battery in my Dell XFR E6400... and it's a regular cr2032, but it has three wires?

 MISC-S0479-1__13855.1526517166.JPG (99.26 kB - downloaded 259 times.)

Any clues as to why? It seems to have two negative leads..

https://www.upperedgetech.com/dell-3-prong-bios-battery-cr2032-3v-210mah-gc020012s00-latitude-e6510/

[ataradov]

210mAh implies that it may be a rechargeable battery, so extra lead is probably a temperature sensor.

[SantaClaw]

No, it was not a rechargeable battery, it was regular Maxcell cr2032 lithium, 3V, it's not a temp sensor either, both wires are connected to the negative side of the battery. I ripped the spot welded leads off and soldered them onto a new fresh cr2032

Old battery held a charge of about 1.5v

[ataradov]

In that case it is probably to make it universal. So that you could use a rechargeable battery and a primary cell with the same connector.

[SantaClaw]

I bet you are right. That would make sense. There is no room for any other type of battery than a coin-cell.

I think the rechargeable 2032's are called ML2032 if they are 3v?

[ataradov]

I think the rechargeable 2032's are called ML2032 if they are 3v?

Yes. But it is also not clear whether this is Dell nomenclature, or just sellers of the parts. That connector design is definitely special for Dell. Naming for parts like that can be tricky.

[Doctorandus_P]

Another possibility is battery detection, even with a dead battery.

Or they think you can not copy it and are more likely to use their USD120 battery replacement service.

[SantaClaw]

Well, the new battery works like a charm, I did order a replacement from ebay, just because I wasn't happy with my soldering, It's hard to get solder to stick to some cr2032's.

I sanded the surface a bit, and used a ton of flux.. I had the iron hot to keep the heat on for as short a time as possible

https://www.ebay.com/itm/184047991684

2.60$

I have Two D630 machines, and those use a two wire cr2032... It's just the XFR e6400 I have with three wires.

I think they are the same generation machine, or possibly 1 generation apart.

[Gregg]

The key to soldering copper wires to stainless or chrome plated steel is to first tin it with lead free solder containing silver and some of the nasty acid flux.  Then wash off the acid with detergent and water before soldering the wires.  After tinning as above, leaded solder will flow onto the tinned surface nicely.  If you plan on resoldering the joints in the future; the same lead free stuff will flow onto copper with standard flux.  I use the 4% Ag 96% Sn that I bought a long time ago, but 2% Ag should work OK.  The silver is the ingredient that wets the chrome or nickel; lead seems to prevent it from wetting.

[SiliconWizard]

The key to soldering copper wires to stainless or chrome plated steel is to first tin it with lead free solder containing silver and some of the nasty acid flux.

Thanks for the tip about silver. And beware of those acid fluxes. They tend to splash all over when reflowed. Wear safety glasses.

[Gregg]

The key to soldering copper wires to stainless or chrome plated steel is to first tin it with lead free solder containing silver and some of the nasty acid flux.

Thanks for the tip about silver. And beware of those acid fluxes. They tend to splash all over when reflowed. Wear safety glasses.

I started using the Sn96/Ag4 solder a long time ago when my next door neighbor had a restaurant and needed a rather large seam in a stainless steel steam table repaired.  I went to a welding supply and inquired about the proper solder that was also food grade.  They recommended this alloy and since it was only available in small lots or a 1 pound spool, I bought the spool for around $40 (this was 1968); now it sells for $150. I think they threw in a bottle of the flux.  It worked perfectly and I was amazed at how well it wetted alloys that regular leaded solder wouldn’t touch.  I’ve even soldered chrome plated plastic with this stuff.
I still have about ¼ of that spool and mostly use it with an old Weller soldering gun (cringe worthy on this forum) that I have a tip dedicated to this alloy solder.  It have used it to solder nickel strips to NiCad cells long before lithium cells became readily available and still use it today to replace lithium cells.  I believe the cross section of the soldered joint provides a better electrical connection than spot welds. 
To keep the heat transfer as low as possible, I use a hot tip and quickly tin the cell terminals and quickly wipe them with a damp sponge or rag to pull the heat away.  Then wash off the acid flux with detergent and warm water and an old tooth brush.  With both the nickel strips tinned and the batteries tinned, no flux is required to solder them together.