Hello and good day Nigan. Thank you for reaching out and for these information you have shared with us. DJI does not recommend using different or 3rd party batteries on your DJI Phantom 3 for compatibility and reliability purposes. Using 3rd party batteries might cause damage or harm to your DJI Phantom 3 and might lead to an unwanted incident. Thank you for your understanding and fly safe always.
You're asking of you can use an aftermarket battery to replace the stock OEM battery. The answer is maybe. It's best to use an OEM if you can find one that is worth buying. There are plenty of them being sold on eBay that are used. New DJI stock batteries still exist but are hard to find and may be dead on arrival. I've heard people say good things about the Powerextra battery. Good luck