i've tried fitting note 9 battery onto note 8 successfully swap over the connecting cable by soldering, phone works powering up but too bad the battery is too wide to fit in
the dimensions of the note 8 original battery are: 88 x 39 x 5 (mm) and the dimensions of the note 9 battery are: 87.7 mm x 41.5 mm x 6 mm
looking at the slot seems like it can handle the biggest battery of dimensions 91.5 x 40 x 6 mm
i found s7 active battery looks identical but couldn't get my hands on the dimensions
if anyone knows the dimensions or know any bigger capacity battery which may fit do share the info here, really appreciate that