You can use a connector that is similar looking to the old CD-ROM audio cable headers.
Here is a site that provides some alternatives and tips: http://pc-restorer.com/replacing-cmos-b ... n-old-pcs/.

I have the same setup on my 486. I ended up jury-rigging this:

I took a PC Speaker cable and cut the speaker off.
Then I desoldered a coin battery cradle from a spare dead motherboard.
I soldered the cable to the leads of the cradle. The connector on the cable plugs right into the battery headers and you just drop a CR2032 battery into the cradle.

That's just one way of doing it. Mine looks kind of ghetto, but it works.

The internal and external batteries are more or less guaranteed supposed to be connected in parallel. Just do continuity tests between the internal battery poles and each pin, and you'll find out which pole of the external battery to connect to which pin 😀

Any .10" hole pitch connector will do, the suggested CD audio connector for instance. If you don't have one of those, you could always trim down a spare IDE or floppy cable to size.

> It looks like only pin 1 is connected to anything.

Multilayer PCB. The dark green (vs light green on the edge of the board) is copper of the inner layers. The ground pin will be connected there.

Why is it that 486 systems have stand alone batteries, but even right up to Pentium MMX/Socket 7 boards were shipping with those dumbass RTC modules? I legit don't understand why those were a thing at all and I was so happy to find out the 486 I was getting in a trade didn't have one.

SRQ wrote:

Why is it that 486 systems have stand alone batteries, but even right up to Pentium MMX/Socket 7 boards were shipping with those dumbass RTC modules? I legit don't understand why those were a thing at all and I was so happy to find out the 486 I was getting in a trade didn't have one.

Who knows ? Perhaps this was about the same on late 486 boards, too.
The only explanation I can think of, is the rapid increase in CPU speed in the early-mid 90s.
Board makers *perhaps* simply didn't expect their boards to be so long in use. And so new designs were made this way.
I was around these times, but I was still using an 8Bit machine and then I also had a 286.
So I wasn't into the newest hardware and can only speculate.. However, I noticed all the jokes about PCs beeing
slow and outdated, as soon as you left the stores with them. Which makes me think there really was some truth within.
I mean, there were 486 overdrive chips for a reason. This was also mentioned in an earlier LGR video.
https://www.youtube.com/watch?v=Qt-0lqkJUKE
https://en.wikipedia.org/wiki/Intel_80486_OverDrive

The 486 was another beast. When it was introduced in the late 80s, it was considered to be absolute high-end.
This was before multimedia was a thing and before the 486 became a consumer's product.
Intel even made the RapidCAD chips for "old" 386 machines.
https://en.wikipedia.org/wiki/RapidCAD

PS. Sorry for my bad English, I've got a cold.

Thanks for all the responses guys!

I confirmed with a multimeter that pin 3 and 4 both were connected to ground. The internal and external batteries are not connected, there is a jumper that switches between them. This is fortunate, because the internal battery is rechargable so there is a current supplied to the pins, but not to the external battery which meant I could use any kind of battery.

I used an internal speaker cable and soldered onto it a CR2032 holder. I'm not very good at soldering, so it looks like some kind of Frankenstein's monster contraption, but hey, it works like a charm! 😀

SRQ wrote:

I legit don't understand why those were a thing at all and I was so happy to find out the 486 I was getting in a trade didn't have one.

It's not like they were expecting the machines to be in service almost 20 years later or something. 😒

But these 486s were expected to be?

SRQ wrote:

But these 486s were expected to be?

Apparently yes. 😎

Although my opinion is heavily biased: I'm always in favor of 486 era machines when 386 (486 SX-25!) or early Pentium machines (486 DX4-133!) are involved. Just a personal flavour.