I noticed the back of my Game Boy Advance SP was bulging and found the battery like THIS. I'm not sure how common this is or how it happens, but I'm hopeful
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Best Buy: Nintendo Game Boy Advance SP Donkey Kong Country 3 Bundle AGTSBB03
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Hobbyist adds a hinge to the Game Boy Pocket, delighting everyone | Ars Technica
K1 (GBA SP clone) puffy battery | GBAtemp.net - The Independent Video Game Community
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Amazon.com: Nintendo Game Boy Advance SP - Graphite : Unknown: Video Games
900 mAh Battery for Game Boy Advance SP — Retro Modding
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FunnyPlaying GBA SP Rechargeable 950mAh LiPo MaxPlay Battery – Retro Game Repair Shop LLC
Did my childhood Gameboy advance sp of 20 years develop a spicy pillow? Hard to tell. If so, where can I get an official replacement? All I can find is 3rd party
Handheld video game:Nintendo Game Boy Advance SP Game System - Flame Color - Nintendo — Google Arts & Culture
Cobalt Blue Game Boy Advance SP System used
I Can't Believe This Game Boy Advance SP Still Works
The (Nearly) Definitive Nintendo Battery Test | WIRED
I Can't Believe This Game Boy Advance SP Still Works
Game Boy Advance SP w/ Funnyplayin Laminated IPA & Expanded Battery 950 mAh | eBay
GBA SP Battery Replacement- XYAB Rechargeable - YouTube