How to Use a Dummy Battery with the Sony A7iii

It all started when I was using a Sony A7ii, which never really had a good battery life. Whenever I went out on a shoot, either for photos or videos, I would have need to bring at least 3-4 batteries, and sometimes even then I was really pushing it, having to be religious in powering off the camera when it was not needed and not chimp too much.

Back then I bought a dummy battery for the A7ii, hooked up to a DC coupler (which would up the voltage from 5v to 8.4v), connect it up to any old USB power bank, and that was more than enough for any video work I did. I say video as I recall that whenever I tried to take a photo, the mechanical shutter of the A7ii would lock up, but there were the very rare occasions when it would perform with no issues.

Fast forward a bit, now armed with the A7iii and with its fantastic new NP-FZ100 batteries, one would think that there would be no need for the use of a dummy battery because one normal Sony battery should give you 800+ shots, and it has a micro-USB and USB-C port that allows you to power the camera whilst in use. But after playing around with the A7iii for a little while, and with a little research on the internet, I found that:

  1. I really do like to power off a power bank when shooting videos, it’s just less battery changes, and charging multiple batteries afterwards, and
  2. Even with power bank plugged into the camera via the micro-USB or USB-C port, you must have a battery inside the camera AND it slowly depletes, and once it is depleted, you cannot use the power bank to power the A7iii anymore

An alternative solution was to get the Sony NPAMQZ1K Multi Battery Adaptor Kit:

This lets you plug in 4 batteries, either the A7ii’s NP-FW50 or the A7iii’s NP-FZ100. It is compatible with both the A7ii and A7iii via the use of a plastic bracket you can sheath onto the dummy battery part. But the downside? It costs HK$3090 (nearly USD$400) and if you lose the plastic bracket, you can’t just buy a replacement bracket, you need to buy the whole thing again….

With the above 2 points in mind, I furiously searched the internet for a NP-FZ100 dummy battery for weeks and eventually a dodgy listing on Taobao popped up with one. I say dodgy as the photo of the dummy battery was out of focus, and did not show much detail. But at less than HK$200, it was worth a try. A week later, the dummy battery arrived:

I quickly went about testing this with my A7iii, along with a USB powerbank and a 5v to 8.v DC coupler:

My initial test results were as follows:

  • AF works
  • Video recording and playback works, even prolonged shooting (over an hour) with no heat issues
  • Taking photos with the electronic shutter works
  • BUT taking photos with the mechanical shutter would lock it up


At this point I was quite pleased with this new dummy battery for the A7iii, it was performing as well as the ones I had for me A7ii. But then remember I mentioned near the beginning of this article that I would occasionally get the dummy battery on my A7ii taking photos with the mechanical shutter fine? I was determined to find out.

I purchased a little USB in-line power tester (I just needed to know if power was being drawn really) that lights up with all sorts of LEDs when power is flowing through it. I tested both an ANKER 5v 3.0A USB power bank and an ecco 5v 3.0A USB power bank, but both would lock up the mechanical shutter on the A7iii. At this point I also noticed that whenever the shutter locked up, the power tester would also power off as well, which leads me to believe that the camera draws more than 3.0A at the point of releasing the mechanical shutter and that both power banks would turn itself off to protect itself.

This is when I remembered I had a Xiaomi 20000mAh USB powerbank that has an output that was rated slightly higher; 5v at 3.6A. I plugged this in and viola, the mechanical shutter works perfectly, even hi-speed shots enough to fill the A7iii internal buffer was fine. So if you are on the look out for a dummy battery for the A7iii, make sure your USB power bank can produce 3.6A to power it fully.

So armed with a 20000mAh power bank, this is equivalent to over 9 NP-FZ100 batteries worth of charge!! I’m going to need more SD cards!

Final costs of this setup? Around HK$450, that’s less than USD$60 compared to nearly USD$400 for the Sony NPAMQZ1K Multi Battery Adaptor Kit.

I’ve since seen the dummy battery for sale on AliExpress, and as for the 5v to 8.4v DC coupler, I got this packaged with an A7ii dummy battery from before, so I’m sure these packages will spring up soon for the A7iii equivalent.



If you don’t want to bother trying to find a DC coupler to convert 5v to 8.4v, you can try using a battery mount plate like this one.

This takes those big NP-F batteries used for LEDs, video monitors or camcorders. As these batteries are already the same rating as a NP-FZ100 battery, but these batteries are quite heavy, they won’t hold as much charge as a big capacity USB power bank, will cost more and you lose the versatility of being able to use different power banks.

Another option I am going to test out in the next few days that would hopefully enable the use of ANY 5V rated USB power bank (2.4A or 3.0A) is the use of a dual USB enhancer cable, the ones you can find packaged with some external HDDs that take up 2 USB ports; one for power and one for power and data. I’m hoping the combined use of 2 USB ports at the same time on a USB power bank would mean I will not be limited to a 3.6A power bank.


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About Wing Lui 2100 Articles
aka Proplus. Constantly looking for innovative ideas. Prefers tech that doesn't waste time. Gone are the days of overclocking, cascade cooling and watercooling. Gadgets, give me more gadgets!!