Keystone Battery Retainer Project

Last update: June 27, 2006



This project is for owners of the Capcom CPS2 units who want to change their batteries in a simple and elegant manner. To combat bootleggers, Capcom used encryption in their CPS2 based arcade hardware. The decryption key itself is stored in battery backed RAM. When the battery dies, the game will no longer work since the decryption key has been permanetly lost. At this point, if your battery had died, you would be greeted with an unwelcome solid blue or green screen upon starup. Therefore, it's important to change battery every 5-6 years to prevent the board from commiting suicide.

Changing the battery is straightforward but requires a bit of soldering. A much better method is to mount a battery holder instead. That way the next time you need to change battery, you can do it in 10 seconds (after you have opened the case that is)! I had seen holders for the 1/2 AA batteries before, but it was not until MKL (shmups forum) showed me the Keystone holders with retainers that things became interesting. The retainers prevent the battery from being dislodged!





Keystone battery holder retainer (Mouser part #534-108A)


Keystone battery holder (Mouser part #534-108)


One 3.6V Lithium battery, size 1/2 AA (Mouser part #667-TL5902S, Elfa part #69-282-12)






I take no responsibility whatsoever for any damage you might cause to your hardware, yourself or your surroundings when attempting this project. Lithium is an extremely volitile and hazardous substance and must be treated with respect. If you puncture the battery, it will spray nasty liquid on you, your board and the surrounding area. In a matter of seconds, it will start eating whatever it landed on. Skin, PCB, clothes, eyes, whatever! The battery changing procedure is only for those who are familiar with electronic components. We are NOT responsible for you killing your own or anyone else's game boards. Please do not even attempt unless you know what you are doing.

Torx 20 Security Bit

If you have all the necessary parts and tools, and are confident you can complete the project in a safe and timely manner, then go to the next page to get started!



Time is of the essence here so prepare and lay out everything you need before you start the procedure. Open the CPS-2 B Board using the Torx 20 security bit (and void that warranty you never had to begin with). Remove the PCB and put it down on an antistatic flat surface. Look at the Keystone battery holder. There is a small plastic alignment tap underneath, near the positive (+) terminal. Remove it with the utility knife so the surface becomes level.

Make sure the drill and drill bit is ready.

I do not use a helper battery because I can perform this procedure in around 6 minutes. Normally the board will survive without a battery for at least 40 minutes but this varies. If you are unsure about your ability to perform this procedure within the time limit, I strongly advise you to use a helper battery.





1. Make a note of where positive (+) & negative (-) are on the existing battery before you remove it.

2. Remove the existing battery by cutting the wires. Remember the clock is ticking as soon as you cut the first wire!

3. Turn the board around where it's "solder-side up" and use the solder wick to suck away as much solder from the solder pads as possible. Hold the remains of the battery leg with the tweezers, touch the soldering iron to the solder and gently lift up the leg. Use the desoldering braid to clean up all excess solder. Use the desoldering pump if necessary to open the terminal holes.

4. The terminals of the Keystone battery holder are a bit wider than the existing holes so the existing holes have to be expanded slightly. Use the 1.5 mm drill bit to slowly and gently widen the holes. This must be done from the "solder side" of the PCB to avoid destroying the solder pad.

5. Insert the new battery holder, making sure you align it with the correct polarity. Solder the terminals.

6. Insert the battery making sure, again, you align the correct polarity.

7. Once you've inserted the battery, you can breathe a sigh of relief. I'd recommend you double-check the quality of your soldering work by using a digital multimeter to check and ensure the board is getting power from the battery. Just touch the tips of the multimeter terminals to the appropriate spots on the board as shown in the picture:

If everything was done correctly, the multimeter should read somewhere around DC 3.68 volts.

8. You will need to shave off a small bit of plastic to make the battery retainer cover align correctly. There is a small SMD device (D5) just in front of the positive (+) terminal which will block the side of the lid. I use the Dremel with the sanding disc to shave of a little corner.

9. Mount the retainer on top of the battery holder.

10. Label the battery with the date, or make a note of the date somewhere in a safe location.

11. Prepare the board to be re-assembled and make sure to align the PCB with the "solder-side up" and oriented as shown:

Relax with the knowledge that next time, all you have to do is insert a 3.6v 1/2 AA battery!

This was a fun project to complete since I have several CPS-2 boards and had always worried about the battery dying and dreaded having to change it. Now, with this simple modification, every time you need to put in a new battery it will literally take seconds! Also, you are saving potential damage to your board from re-soldering over the same terminals every time. You may be surprised to learn that some original Capcom CPS-2 boards can last an extraordinarily long time without the battery dying. Just recently I pulled out batteries dated August, 1993! Almost 13 years! How is this possible? It all depends on how much usage the board has gotten over the years. If you bought your board from an arcade operator that had the PCB on location (in an arcade, laundromat, etc.), then the board itself was turned on and in use for the most part of every day...and therefore not using the internal lithium battery at all! However, waiting this long is a gamble since the battery could die at any point. Don't delay, save your board today!

If you have any tips to add to this project or comments, please contact us!

Originally written by Tormod Tjaberg:

Updates, revisions, additional pictures and clarifications by JAMMAPARTS