3 hours ago, Davide DB said:

I did a quick test of the first option, connecting the camera with a full battery to a normal USB charger.

Upon connection, the camera warns you that the connected power source is weak and can only charge the battery when the camera is off.

I started recording in FHD (otherwise I would have filled the card) and after 50 minutes the recording was still going and the battery was still at 100%.

When the USB charger was disconnected, the recording continued without issues, using the battery.

So I would feel confident in confirming that a couple of small batteries in parallel with a step-up converter with the proper protections would be enough.

In my housing, the main problem is space.

Yes that's at 5V from an Iphone type charger, wondering if it might work better with two batteries in series as the readily available batteries are 3.7V.

Did you check afterwards did it draw power from the onboard battery or from the charger, the battery reading after pulling the plug will tell you? Your housing it seems has space for the mini flash and if so I would think you could readily fit two 18500 batteries in there and if the battery holder is not too big that should also fit and that's effectively a second battery. You probably won't have the issue mentioned in the video if you just use batteries without the voltage step up.

The 18500 batteries are short 18650s and are 50mm long. It seems like that option could be quite doable with minimal work apart from attaching a USB cable to the battery carrier and it looks like there is enough space where the flash trigger would go.

6 hours ago, Chris Ross said:

Did you check afterwards did it draw power from the onboard battery or from the charger, the battery reading after pulling the plug will tell you?

Yes once the usb-c was removed, the camera continued flawlessly recording using the internal battery, so it's a completely use case from the video you posted. Here the internal battery act a sort of last reserve.

6 hours ago, Chris Ross said:

wondering if it might work better with two batteries in series as the readily available batteries are 3.7V.

Good question, I guess it depends on how much current the camera draws while recording. So I can choose between serial or parallel circuit. I haven't a tester here now.

I'm not at home so the only test I could do is putting the camera battery in that space.The battery (55mm) fits only lengthwise, and just one millimeter more and the housing won't close. So with the 18500s, I wouldn't have space for the battery holder. If I use "bare" batteries instead, I have more freedom of choice.

Another option is using LiPo packs that usually have squared shapes.

45 minutes ago, Davide DB said:

Yes once the usb-c was removed, the camera continued flawlessly recording using the internal battery, so it's a completely use case from the video you posted. Here the internal battery act a sort of last reserve.

Good question, I guess it depends on how much current the camera draws while recording. So I can choose between serial or parallel circuit. I haven't a tester here now.

I'm not at home so the only test I could do is putting the camera battery in that space.The battery (55mm) fits only lengthwise, and just one millimeter more and the housing won't close. So with the 18500s, I wouldn't have space for the battery holder. If I use "bare" batteries instead, I have more freedom of choice.

Another option is using LiPo packs that usually have squared shapes.

I think the benefit of using some type of holder is you don't have to worry about battery management for charging.

I also found this one and 18350 which is 35mm long 18 dia, might be able to do something with them, but you'd need four of them. Ali express has holders .

https://www.liteshop.com.au/content/nitecore-nl1816r-1600mah-usb-c-rechargeable-battery/?gad_source=1&gad_campaignid=17182817440&gclid=CjwKCAjw2brFBhBOEiwAVJX5GD8NqXpZ7sSwOyl6OeguSdGD1zIFkTQVEi74Q9Cvz1gm6ajRUxZmeRoCXxoQAvD_BwE

1 hour ago, Chris Ross said:

but you'd need four of them.

Why four?

3 hours ago, Davide DB said:

Why four?

I think the capacity would be a little on the low side with two, 11 W-hr which is less than the on board battery, but it's not essential I guess.

On 8/27/2025 at 6:31 AM, Chris Ross said:

I think the capacity would be a little on the low side with two, 11 W-hr which is less than the on board battery, but it's not essential I guess.

If you go back to my post from Aug 21; that shows my 3 battery 18350 solution for the Canon V1.

Edited August 30Aug 30 by insomniac

1 hour ago, insomniac said:

If you go back to my post from Aug 21; that shows my 3 battery 18350 solution for the Canon V1.

Yeah I saw that, a nice solution, I'm thinking for people who aren't as comfortable spot welding battery packs together and if they have the space installing the same batteries in a holder that would be a good solution as you probably don't need any balancing for the batteries as you can pull them out and charge them in a dedicated 18350 charger, so you don't have to be concerned about getting them all fully charged.

On 5/1/2024 at 2:43 PM, boduoguo said:

If your housing has a space reserved for flash trigger. It can be used to install a lithium polymer battery. It's a rudimentary method, but it works and will last for a day's diving. No need to open the housing.
battery are cheap and can be recharged over and over again .

Woo! What a small world, this is my DIY battery pack which was used on Nauticam A7II case, so I assume you are the second owner of my case🤣

On 8/22/2025 at 11:30 PM, Davide DB said:

Old post but... From your photos I see you are using a 3,7V Lipo battery pack. 3,7V are enough to power your A7? camera?
I shot video only so I'm thinking for a similar out of the box solution for my GH5M2 that can be powered via USB-C...

There has a tiny charging board covered by heat shrink tube and silicon rubber, it will have consistent output in 5V, this is one of the model I was testing, but not the final version

And this is the final version

This was designed for the old sony camera which is using FW50 battery, and now I'm using the new version on my Marelux housing, larger battery and "smart" charigng board

Thanks a lot!

If there only has limited space inside housing, li-po pack would be the acceptable option, cause you can find almost any size of the battery pack from market (Aliexpress if you can order from it), but you must be caution that li-po pack is very susceptible to physical damage due to soft pouch construction. My previous battery pack was using a li-po pack but with metal shell for the advanced protection, but it takes extral space. Never worry about the charging board since the size could be around 16*14mm, you can put anywhere inside the housing.

On 8/27/2025 at 3:21 PM, Davide DB said:

Yes once the usb-c was removed, the camera continued flawlessly recording using the internal battery, so it's a completely use case from the video you posted. Here the internal battery act a sort of last reserve.

Good question, I guess it depends on how much current the camera draws while recording. So I can choose between serial or parallel circuit. I haven't a tester here now.

I'm not at home so the only test I could do is putting the camera battery in that space.The battery (55mm) fits only lengthwise, and just one millimeter more and the housing won't close. So with the 18500s, I wouldn't have space for the battery holder. If I use "bare" batteries instead, I have more freedom of choice.

Another option is using LiPo packs that usually have squared shapes.