12vdc power supply for a77

You'll not likely find a converter that goes directly from the 12v battery to the camera .
You could make your own with salvaged parts and a transformer cobbled together.
But as the 12v battery when charged might be nearly 13v steadily dropping , getting the voltage right to the camera might be an issue .
Personally I'd stick with a mains voltage power supply and just connect an inverter to the battery as you might carry in your car .
I have several that I typically charge batteries with while I'm on the road in my campervan.
Small ones plug into a cigarette lighter socket that could easily be adapted to have two clip on wires for the battery with a lighter socket on the other end .
For more power , like using a laptop computer or printer , I have a sinewave inverter ( check the correct name for it ) that produces clean electric for sensitive electronics , where the cheaper inverters might cause interference.

Once you've got mains voltage , external power supplies are readily available be it mains or USB powered .

As a sidenote , I use various power tools made by Ryobi both DIY , car repair and gardening tools, the ones that share the same battery , in the Ryobi 1+ range .

They do other than power tools that use these batteries , lights , radios etc .
But they also do an inverter that gives you mains power and two USB outlets .
The unit just clips on and the combined power pack is small and light depending on what sized battery is used . I've got upto a 9 amp hour battery , which lasts a good long time .
These might also be worth you looking into .

As you say in your OP "I'm using an a77m2 for astrophotography, so the camera is tethered and running on it's own for quite some time; changing batteries is a bit of an inconvenience."
It isn't clear on what your plans are , or what your power source is , or what you consider "some time" .
If its a car battery your using overnight , an inverter would be just fine , power wise , and the inverter fits in your pocket while carrying the battery to where your presumably leaving the camera ?
If your leaving the set-up in place for a month where the inverter will be using power while it's not needed , then yes , you might have a problem .
The smaller the battery , the more so .
But with very little information , it's hard to make suggestions .


WRT the 3a , are you using manual focus lenses only ?
As long as the AF doesn't kick in and no pop up flash is used , I can't see the camera using more than that .
If you build your own set up out of parts , it would be easy to temporarily fit an ammeter inline to check power consumption for piece of mind .

Thank you! This looks very much like it's exactly what I need.

No, I don't think you are missing anything :)

Just buy a DC-DC step down adjustable buck converter with the appropriate specs. I guess 5A output will do great (it's good to have a little extra ampere). They are plenty and cheap from China.

Then just add the proprietary connector for the camera and adjust voltage to about 7.6V. Getting the proprietary DC in jack may in fact be the biggest hassle, but you can of course buy an aftermarket AC power adapter to get one. Another option would be to use a dummy battery. This may have the advantage that you don't need a charged battery in the camera.

I haven't made a 12V adapter myself so far, but I see no problems. I think a XL4005 based buck converter will be sufficient (like ebay item 386688350847).

If needed in your setup, its easy to add a lager capacitor and ferrite core coil at the output to further smoothen the voltage.

(For reference, the AC-PW10AM AC Adapter is Sonys AC adapter. The aftermarket Glorich AC-PW10AM has an output rated DC 7.6V/3A 22.8W.)

kurja wrote: This winter I've used a motorized eq type mount, on top of it a small refractor telescope, a 50mm guide scope and camera, plus the a77 for imaging. These are controlled by a laptop, and there's a 10W dew heater for the telescope. I have 12V 26Ah batteries that I use to power all this, I've used one of those even when I have mains - eq mount slewing draws too much current for my 12v ac/dc charger to handle. During imaging the camera is essentially always shutter open, drawing some power, winter temperatures are hurting battery endurance too. Standard camera batteries really don't last that long. No AF, flash, camera body is just taking long exposures and sending the data to the laptop over usb. Next winter I plan to shoot a night or possibly two at a location where I have no ac power, and I also can not drive all the way, I'll need to carry or pull everything in a sled. So I'd rather avoid adding any unnecessary bulk and weight to the setup. Ideally I'd have enough battery power to run all this for 24 hours or so. Minumum, ten hours. I also dislike the idea of taking 12v dc and converting it to 230ac just so that I can then convert it back to dc at lower voltage than it was to begin with, yes I'm very fun at parties

Thanks for making that clearer , it's an interesting project you've got going .

I've been considering getting a motorised EQ mount for my scopes for tracking so I can attach the camera and leave it to it.

Typically when I've been observing I've driven to where I'm going in my campervan, parked up in a good dark sky area in the middle of nowhere and set up there .

For due heaters and so on , I just run a lead from my van for the 12 volt as it has a large leisure battery in it .

For moving further away from the van , I taken a 12v ride on mower battery with me .

For less usage I'm using the Ryobi one batteries .

Someone mentioned above a power adapter lead that plugs into a USB socket .
USB adapters are available for the Ryobi one batteries, which would be a quick win , but as you've already got the battery it would add unnecessary cost .

Good luck with your build , it sounds simple enough with readily available parts .

It'd be good to see your results .

kurja wrote: neilt3 wrote: I've been considering getting a motorised EQ mount for my scopes for tracking so I can attach the camera and leave it to it. I find there are a three big things when getting into astrophotography - first putting a camera on a tracking mount instead of a static tripod, second calibrating and integrating multiple light frames, third autoguiding the mount to get 15 minute exposures, and longer. Fourth step would be a monochrome camera with narrowband filters, but that's a step I've so far chosen not to take I've done astrophoto earlier with tracking and camera lenses - some vintage telephoto lenses from ebay and an a700. Now I've got a small telescope, an a77m2 and autoguiding. So I hope I can improve

Good luck with it , it's something I mean to get back into .
The auto guider is definitely what I need to pick up .

just googled "12vdc 3a battery power bank" with plenty of results

also found this thread that might be helpful:
https://www.dpreview.com/forums/thread/3990960

i just realized your thread is a year old :D i hope you already got what you need