How to replace the battery and fix solar sensor in a boktai cartridge?

@giwifruit same idea for this cartridge than the others. First you want to replace the battery. It is a CR2025 battery. Here is the guide for that ゲームボーイアドバンスカートリッジのバッテリー交換. After that I would probably try and replace the " solar sensor" Check for any damage on the circuit board since it appears as if broken traces are fairly common. The other thing would be to run this Solar Sensor Patch Kit and see if that will work for you. Of course, you also want some 99%isopropyl alcohol and a cotton tip applicator to clean your photodiode. If that does not yield the results you are looking for, you can replace it with another BPW34. Replacements can be purchased at places like this Remember, that will require soldering as well.