Is it safe to add a bigger battery (Galaxy S3)?

[too lame to come up with a good username]

So I bought a Samsung Galaxy S3 on eBay and I also found some extended batteries on the site, ranging from 3000 mAh to 4800 mAh. I would love to replace the S3's tiny 2100 mAh battery with a battery that can last a lot longer but I want to make sure it's safe. Would it kill the phone or cause overheating issues? (The batteries are specifically for the S3 but they're not made by Samsung).

 

[Sophiania]

So I bought a Samsung Galaxy S3 on eBay and I also found some extended batteries on the site, ranging from 3000 mAh to 4800 mAh. I would love to replace the S3's tiny 2100 mAh battery with a battery that can last a lot longer but I want to make sure it's safe. Would it kill the phone or cause overheating issues? (The batteries are specifically for the S3 but they're not made by Samsung).

The most important specification of the battery you should pay attention to is the output and input. If they are same with your original battery, i think it's safe. If it's much different, you should be careful to choose.