This was a surprise, batteries from the old DJI Mavic Mini DO fit into the new DJI Mini 2 and appear to work perfectly well!! Unfortunately the batteries for the Mini 2 don't fit into the original Mini but this is likely to do with the change in battery chemical platform (LiIon vs LiPo).

Hello sergeant, I appreciate the video you have shared and thank you for reaching us out. The Mavic Mini Intelligent Flight Battery of the international version of Mavic Mini are compatible with the international version of DJI Mini 2. Although the international version of DJI Mini 2 can use Mavic Mini’s battery, the power will decrease and the total weight will exceed 250 g, requiring registration in some countries and regions. Please check local rules and regulations before use. Thank you for your support.

DJI Paladin Posted at 11-6 14:51
Hello sergeant, I appreciate the video you have shared and thank you for reaching us out. The Mavic Mini Intelligent Flight Battery of the international version of Mavic Mini are compatible with the international version of DJI Mini 2. Although the international version of DJI Mini 2 can use Mavic Mini’s battery, the power will decrease and the total weight will exceed 250 g, requiring registration in some countries and regions. Please check local rules and regulations before use. Thank you for your support.

You guy's need to remove International JP part, everyone who's doing these tests are using the 249g mini 2. Clearly it works, but it will require you to register it. So unless they are planning to patch the normal mini 2 to prevent users from doing this, the only hiccup is the additional weight and requiring to be registered.

Just be mindful of the weight!

Probably best not to swap them around.

sergeant, Thanks for letting us know about that