Here's Mooch latest(?) battery chart.
If you plan on Vaping under 100 Watts get either Sony VTC6 or Samsung 30Q. If over 100 Watts get Sony VTC5A.
Try to buy your batteries from reputable stores or websites. Don't buy from Amazon or Ebay due to them selling fake batteries.
If you are new to Vaping and don't know what wattage you are going to run, tell us what tank you got along with the Gpriv and we can make suggestions.
And ask any other questions you may have. Good group of folks here to help you out.