Just try another battery. Galaxy S3 / i9300 fit as replacement. These are good quality (not fake) batteries:
1) Polarcell Akku (HQ battery): http://ebay.eu/2ad81ut
2) FourHeart (I have it and it is 100% Japan cell by etched code under sticker): http://bit.ly/2aJDupX
3) Anker (HQ battery): http://ebay.eu/2alByqs
There are also some good ones from asia also, like KINPS (I`ve bought it 2 times and they are good):
4) https://www.amazon.co.uk/Kinps®2500mAh-Extended-Battery-Samsung-GT-I9300/dp/B00HE9Y0Z6 (must be with orange/purple/white sticker)
but there are so many fake & bad quality batteries out there on web. Be aware!
I would go for Anker, Polarcell or re-branded Japan/Samsung cell (if You are 100% sure they have legit etched code under sticker). And also - don`t follow those absurdly high numbered "high capacity" asian batteries - they won`t last longer. HQ 2100mAh battery will last even longer as those cheap ones.
Used, bad-cell, smaller cell re-labeled batteries is very dirty business in asia (and hence resellers worldwide) and there can be even legit looking packaged Samsung batteries that are fakes and not Japan made. So, You are warned