First, watch this video for two power solutions for the Sony A7s:
The Sony A7s comes with an AC to USB adapter (AC-UB10) which also charges the battery.
For a more ‘regular’ AC adapter, you will need to purchase the AC-PW20 ($80 for original Sony, about $20 unbranded). The camera does not have a DC port, and the adapter has a battery attachment instead.
The camera comes with a charger (BC-TRW, which retails otherwise for $48) and two batteries (NP-FW50: 7.7Wh, 1080mAh, $40 for original Sony, about $5-7 for unbranded). Some of the unbranded batteries, like this one for $7, are rated at 2300mAh, or twice the capacity. Be extremely careful before using unbranded batteries. I’ve generally had no problems using them, but you must buy after reading many reviews. Don’t blame me if something goes wrong!
You can also extend the recording times by using a vertical grip, like the original Sony VGC1EM, which sells for $298. You get to use two batteries at the same time, and it might help you handholding the camera as well. The negatives are:
- It adds weight, almost double with two batteries
- It might interfere with the mounts on the lens adapter, especially the Metabones adapter.
How much battery life does the NP-FW50 provide? According to the official specifications, here are the ratings:
- Approx. 55 min with viewfinder, approx. 60 min with LCD screen – if you also zoom while recording
- Approx. 90 min with viewfinder, approx. 90 min with LCD screen – if you are not using any functions except recording.
In real world use, one can estimate about 60 minutes (one hour) of usable battery life in video mode, using a 1080 mAh battery. The viewfinder draws more power than the LCD.
What about charging time? The stock charger takes about 220 minutes (just shy of four hours) to charge one battery! Now that’s a problem. Therefore, I recommend getting a Wasabi Charger+2 battery kit for $26.99. It will also charge the stock batteries. Even though the Wasabi is rated at a higher energy level, you get about the same or slightly lesser battery life. For professional use, I recommend getting two Wasabi kits to supplement the Sony kit. You’ll end up with three chargers and six batteries. Consequently, you can also use dual chargers.
The Atomos Shogun takes a Sony NP-F970 (6300 mAh, retails for about $120) battery which will give it about 2.5 hours of life. You could get a Wasabi kit with two batteries and a charger for $84 instead and that would be the route I would take.
Of course, you could power up an entire rig with Anton Bauer batteries as well, which is what I’m doing. Ultimately, I highly recommend getting a V-mount of AB mount brick. Nothing beats that solution, unless you specifically need to lower weight.
Check out the options at B&H:
These are important topics raised by subscribers that shed more light on this lesson.
Q. Does the camera display battery life correctly on an external battery?
A. No. In fact, it is totally misleading, and just shuts off quickly. I rely on the indicator on the battery instead.