There are so many SP batteries and I don't understand how they are all wildly different in battery life

First video:    • Testing Aftermarket GBA SP Batteries  

RGRS Battery: https://retrogamerepairshop.com/colle...
Helder Battery: https://heldergametech.com/shop/batte...
RM/Makho Battery: https://www.retromodding.com/products...
Makho Battery PCB: https://retrogamerepairshop.com/colle...
Funnyplaying Battery (RGRS): https://retrogamerepairshop.com/produ...
Funnyplaying Battery (Funnyplaying): https://funnyplaying.com/products/gba...

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