Hacking EZ4 with capacitor

[TecXero]

I've started using my Game Boy Micro again for GBA shenanigans and I bought an EZ4 flashcart for it. It's one of the models that doesn't have a rechargeable battery, which is fine.

I was thinking about replacing the battery with a capacitor when the battery dies, if I still have a need for it. Has anyone tried this and does enough power pass through from the Micro in this version of the EZ4 to charge it?

Normally, I'm fine with replacing batteries in cartridges, but I don't really see a need to have anything that holds a charge for long in the EZ4 since I just turn off my Micro then turn it immediately back on to save. I figured, in the long run, this would be a better solution for me.

 

[FAST6191]

I guess it could work, though if memory serves (and it may well not in this case) the non recharge stuff would have a diode leading off the positive pin of the cell. You could always fly a lead to somewhere else in the cart if you wanted.

I have no idea what you would want as far as capacitance. Probably not a piddly signal smoother but you should not need to go supercap either. Do make sure you put a resistor in line though as I hate to think what would happen during the initial jolt of a fully charged cap. Likewise when doing some cart swap tests for one of the dumping programs a dead save battery alone was enough to cause the device to reset on inset, to that end I would definitely make sure you have a resistor in there for when you have a discharged capacitor.

Is it not worth putting in some kind of coin cell holder? Ones with pins already welded are a pain to source (or at least expensive) but I buy trays of coin cells for next to nothing in real world shops.

 

[TecXero]

I guess it could work, though if memory serves (and it may well not in this case) the non recharge stuff would have a diode leading off the positive pin of the cell. You could always fly a lead to somewhere else in the cart if you wanted.

I have no idea what you would want as far as capacitance. Probably not a piddly signal smoother but you should not need to go supercap either. Do make sure you put a resistor in line though as I hate to think what would happen during the initial jolt of a fully charged cap. Likewise when doing some cart swap tests for one of the dumping programs a dead save battery alone was enough to cause the device to reset on inset, to that end I would definitely make sure you have a resistor in there for when you have a discharged capacitor.

Is it not worth putting in some kind of coin cell holder? Ones with pins already welded are a pain to source (or at least expensive) but I buy trays of coin cells for next to nothing in real world shops.

I'll probably go with your recommendation then. I figured I'd have to put in a resistor but if I have to make a modification for it to receive enough power to charge, well I don't have enough confidence to try something like that on a $40 flashcart for something this minor. I'll just put a holder in it instead when the time comes. That's always simple enough.

Thank you for the information and recommendation.

 

[Jayro]

How do we tell if our battery is rechargeable or not?

 

[TecXero]

How do we tell if our battery is rechargeable or not?

Just open it up and take a look at the part number on the battery. If it's rechargeable, it should be "VL2020". Anything else is probably a regular battery and your cart isn't designed for a rechargeable battery as well.

 

[Jayro]

Just open it up and take a look at the part number on the battery. If it's rechargeable, it should be "VL2020". Anything else is probably a regular battery and your cart isn't designed for a rechargeable battery as well.

I've purposely left on my GBA SP overnight with the lid closed just to see if it would charge the battery (that shipped dead), and nothing changed. I can still do a quick power off/on to save just fine, but otherwise, the battery is pretty dead.

 

[TecXero]

I've purposely left on my GBA SP overnight with the lid closed just to see if it would charge the battery (that shipped dead), and nothing changed. I can still do a quick power off/on to save just fine, but otherwise, the battery is pretty dead.

I'd imagine replacing it would be as easy as any other cartridge battery. Just need a 3V watch battery and a bit of solder. FAST6191 was recommending a battery holder be installed, which makes swapping out batteries quick and painless. I'll probably go with that myself just so I don't have to worry about screwing it up just for a capacitor.