If you shoot with Sony a7 series cameras you’re going to want to carry a few spare batteries to get you through a full day of shooting. I always recommend using genuine Sony NP-FW50 Lithium-Ion Batteries in your Sony E-mount camera.
Here’s a great deal on genuine Sony NP-FW50 Lithium-Ion Rechargeable Battery (7.4V, 1020mAh, Bulk Packaging) (Order Here $29.95). Buying in bulk packaging will save you $20 off the $49.95 street price.
You can also save on a bulk packaging version of Sony BC-VW1 Battery Charger for $24.95.