CR2032 Cartridge Battery Replacement

That new Retro cart you just picked up, you know the one, that lengthy RPG.  How old is it?  Maybe the battery inside it which is going to keep your save games is on its way out soon’ish?

It’s easy to replace it, and there’s a couple of options.  Chances are the battery that’s in there (assuming it’s a SNES, Mega Drive as that’s all I’ve done so far) is a CR2032 with solder tags on.  Pop your cartridge open and remove the old battery.  Depending on the system you’re working on, you may need a GameBit to open the cart up, the SNES uses 3.8mm, some Mega Drive carts use 4.5mm.

I find it easier to heat up the solder on the Positive + solder pad first, I prefer to use a desoldering pump to suck the solder up, you might prefer desoldering wick though.  You may get away with just heating it up and pulling the battery from the other side at the same time.  Make a mental note which was positive and negative on the cart circuit board (in my limited experience, the postive side went through a larger hole on the board, with a bigger solder pad, and the negative should be easy to spot and they generally just connect to the massive Ground bit of the circuit board – which is why it’s harder to desolder, as the heat dissipates).

Now that you’ve removed the positive tag from the cartridge board, bending the negative leg, it’s easy to heat up the negative tag and pull the battery free.   Remove as much solder from the hole as possible so that you can get the next battery through easily.

Now, you can pick up a new CR2032 with solder tags from a couple of places.  The one I bought from differs the most from the original battery, the tabs are flattened out and need bending at right angles to the battery, making sure you get the polarity correct.

Another place is bitsbox, the battery I got from there is a closer match, the solder tabs are a tiny bit too far apart, but it’s just a quick bend with some pliers, or even just put one solder tag in place, and manipulate it so that the second lines up.

Battery Holder

Another option is to fit a battery holder, I’ve only tried this on a SNES cart so far.  I hunted on eBay until I found the smallest CR2032 battery holder, I searched for cr2032 smd and chose the smallest ones I could find.  They were from a seller called wonderco_buy.  It’s not too difficult to fit one of these, and then you can easily replace the battery next time, you could even replace the battery whilst the cart is out of it’s casing, but plugged into your console – make sure it’s plugged in the correct way around!  (Although, I’m sure the first battery I replaced, I did it quite quickly and the cart retained my saved game, so there could be a grace period)

I had to start by cutting off the two little nobbly bits on the underside of the battery holder.  Then carefully straighten the solder tabs.  I found the positive one to be delicate, I snapped my first one, and on the second I decided not to straighten it out completely.

This was a direct fit, the positive tag only just pokes out through the circuit board, but as you add more solder it will go down into the gap and get a good contact on the tab anyway.  In fact, to strengthen that bent tag, I usually add a bit of solder to the leg from the parts side of the board too and allow it to go down into the hole again.

Here you go, finished, and a brilliant fit in the cart case.

Small Update

After I broke the positive tab on one of the battery holders, I decided to mount the next one a different way.  So I heated up the the old battery’s negative leg and pulled it through.

Then gripped the positive leg with a pair of long nosed pliers and kept bending it back and forth until it snapped off, leaving a perfect tab to solder the battery holder onto :-)

 Conductive Glue

There was one other way I was going to try, but didn’t finish off.  I’ve put it here as a last resort, you may find it interesting, especially if you can’t solder.  I heard of a conductive glue, and found it on eBay, called Wire Glue.  So I guess this is like cold solder.  I used a regular CR2032 battery, and some short pieces of wire.  I got a blob of the glue, and stuck the first wire in place.  The glue I tried needed 24 hours to dry, when it was ready I did the same for the other side of the battery.

That was as far as I went, as I really intended to use either battery holders or tagged batteries.  I did test the battey using the wires I glued on, and sure enough it was reading 3volts on my meter.  So, if you aren’t soldering at all, you could do this to the battery, and then cut the old batteries solder tabs, then glue the wires to the old batteries tabs (is it tabs, or tags?!).  Probably a good idea to stick it in place using double sided foam tape stuff.