Blackmagic Forum

Yes, that confirms what I wanted to communicate.

But their is no single “magical” voltage level you could feed the camera to reduce this conversion process, any power applied to either the external or internal battery requires conversion to the varied voltage levels required internally.

My question is if there's a voltage and input which is more efficient than the others because there will be less conversion inside the camera compared to the other possibilities.

Short answer not really, any voltage level used will require some type of conversion. Most batteries do not output a constant voltage output anyway, unless connected to a regulated power cable (another conversion process), so get get a battery or other power source with the correct voltage level.

The advantages of using a normal 14.5 VDC camera battery is, the higher voltage and MA provide more power, and 14 VDC an given amperage will provide the required 12 VDC level longer than a battery that only outputs 12 VDC at the same amperage, See Ohm’s law to see how this works.

I have tried running the original Pocket camera with a large 7.2 VDC battery (which was around 9.x VDC fully charged, and it would power up the small Pocket camera if I had an internal battery in it (not a BMD recommended practice when using a 12-VDC upscaling source) the original Pocket camera was combining the two batteries together at the DC-DC power supply, but this was not very good, and only Extended the run time by around 50 percent, not 2X as one would think.

The new Pocket 4K has a much higher 22watt average pier requirement, and it is the power load, along with the required voltage that drives an external power source. The internal battery is connected to the DC-DC board at s different tap, so it might have some if it’s voltage stepped up. So to answer your question as to which voltage is more efficient, the larger external 20-12 VDC input is only going to require down conversion, which is more more efficient, less loss, than up-conversion.

I use Dmitry’s Micro camera battery pack, which uses 4 18650 batteries and outputs around 14-16 VDC. It gives around a 2-3 hour run time, which works for me. For longer runs, I use a Anton Bauer 14.4 VDC Camera Battery on a Gold Mount plate, which runs for 6-10 hrs. I like the smaller form factor and reduced weight on Dmitry’s battery pack.
For Dmitry’s better pack, See https://lavky.com/handmade/home-and-hob ... t=UW590888
Cheers

Thanks a lot for your profound and helpful answer. I'll concentrate on the external input then. This suits me anyway since the higher voltage around 12V also works for many other of my applications as well. I've already tinkered and used some packs with 10 AA batteries but they were not sturdy and reliable enough and had no good mounting options.

The Dmitry’s better pack looks nice and seems to be similar to what I have in mind with lithium-ion battery cells. Like initially stated I like the fact of an open battery pack in general because it's better for the environment not to through away the complete barrel if one apple is rotten. Are the cells in the Dmitry’s better pack regulated individually and do you hand select your cells?

Dmitry has a list of recommended batteries, just gel four from the same manufacturer/series, and his battery pack will regulate charge and discharge cycle, keeping the cells balanced. I got is recommended battery charger also, which does a grand job. I ended up with two packs, and got the batteries from the Battery Store Mail order in USA, but you should be able to locally source the same batteries. He ships the pack without the batteries to reduce shipping issues.
Cheers

Great, thanks. That seems to be a really nice project. I'll seriously consider it if I'm not satisfied with the outcome of my experiments. Thanks again for your help!

You are welcome.
Cheers

...And to Reiterate what BM Engineers have stated; When using an upscaling battery source (ie NPF with a 12v base going to the 12v input) the P4K camera should NOT have a battery inside as that may lead to internal circuit damage.

Thanks for the heads-up. I've read something like this too. But also that it should not be a problem. Better safe than sorry. Anyway this probably means it's also not recommended to power the camera through the 12v input and a dummy battery simultaniously. It probably doesn't make sense anyway but it could happen accidentally in a hurry to attach both cables.

I've managed to tinker me some solution as I intended to. I can use Sony NFP batteries with this and I have two adapter plates so Canon LP-E8 will work as well. And in the pictures you can see two 6xAA battery packs with NFP output. This is the main reason I built this. So now I can use my AA batteries and can charge or replace them individually.

I can either use the D-tap output which combines the voltage of the two batteries in a series circuit for the 12V input of the camera (or other applications like LEDs). And I also have one power output on the side which is wired to one of the two batteries. That one I can use for example as an output for a dummy battery.

I yet have to test the solution with the camera. I'll do it as soon as I buy one.

Does anyone know if it's sensible to charge the AA packs in one piece? I assume this is not as good for the batteries than charging them individually. But maybe it's okay to do so on set once in a while to have a quick and dirty additional solution.

Thanks again for your input!

Hello,
quick question.
Which solution will make my bmpcc 4K last longer?
1) 1 x np-970 via dummy battery (internal power)
2) 2 x np-970 on v mount battery plate via D-tap port? (external power).

Sorry for my terrible english.
Greeting from Italy

Option 2.

Sorry, I forgot to specify that I have two np-970 batteries, so I was wondering if the camera last longer using these in parallel via V-Mount on the external plug or using one at a time via dummy battery internal.

As far as I understand it's likely that the 12V input is a little more efficient. If you already have both options available you could try it out. For me it's a benefit not to switch batteries as often if I use both parallel. The other thing is that you could possibly load one battery while using the other one. Also two batteries are heavier than one. In general I assume these kinds of aspects are more relavant than the choice of input.

I cannot try it yet because Im looking to buy a VMount battery plate to connect my two np970 in parallel.
Right now I use 1 at time np970 via dummy battery but I would like to know which solution would last longer in terms of power.

I'll try to measure it, maybe soon. I could just power the camera via the 12V input and the dummy battery with two different power adapters and my meter for the wall socket and substract the consumption of the power adapters without the camera. It may not be extremely accurate but gives a ballpark. My guess is that it doesn't make much of a difference and can be ignored with regards to practicality.

If you're using Vmount, you'd want the two NP-F batteries in series, not parallel. Also, I think it is potentially dangerous to connect two batteries in parallel if they are not at the same charge state. Don't do this unless you really know what you're doing.

If Vmount is what you're considering, look at the following: https://www.amazon.com/gp/product/B075R ... UTF8&psc=1 It includes a charge monitor you can activate.

I think there may be equivalents from other manufacturers.

thats what I meant

Jan Kluczewitz wrote:I'll try to measure it, maybe soon. I could just power the camera via the 12V input and the dummy battery with two different power adapters and my meter for the wall socket and substract the consumption of the power adapters without the camera. It may not be extremely accurate but gives a ballpark. My guess is that it doesn't make much of a difference and can be ignored with regards to practicality.

Thank you, I appreciate

Don't forget that instead of dual NP-f to V-Mount monsters and heavy inefficient AA arrays, you can still get my custom made 14.8V 50Wh 18650 battery enclose and optional Charger. It works with Pocket4K as well as with any other camera that can accept DC 12-18V input. Only add quality Li-ion 18650 cells from this list viewtopic.php?f=2&t=71520#p410547 and DC to Pocket4K cable adapter.

More details here viewtopic.php?f=2&t=71520&start=50#p509842

Dmitry’s battery rig works great, I have one installed on my Picket 4K setup, much smaller and lighter than a 14.5 V/Gold Mount vattety, more compact than this and the NP battery sleds. Got a PC4K power cable from online, that connects the battery pack directly to the Pocket 4K power input on the side.

You can setup two battery packs in parallel for real long run times. I gat 2-3 hours on one charge, depending on shooting situation and camera settings.
Cheers

I second that. I like Dmitry’s solution a lot and would have bought it under different circumstances and still am thinking about that. Thanks for sharing!


I ran a test where I recorded 2 x 30 minutes with the pocket.
- 6 AA batteries via battery dummy
- 12 AA batteries via 12 V input and with my solution above

The AA batteries were fresh and fully charged. After that I recharged them with my charger that shows how much ampere were taken by the batteries.

The 6 batteries altogether took 6,21 A.
The 12 batteries altogethe took 6,58 A.

The interpretation of the (one time) experiment is up to you. If this is worth anything it seems that the dummy battery solution gives you around 4 more minutes per hour than the 12 V input. It may depend on several other aspects like the voltage of the source (both inputs have a fairly wide range) or other things.

Thank you for your help.
It sounds a bit weird to me because via dummy the camera sucks 7-10volts and via D-Tap 12-20 volts.
Should absorb more energy from d-tap battery pack and discharge them faster compared to the dummy one battery solution? Am I wrong?

To calculate power consumption (W) you multiply current (A) with electric potential difference (V).
1 W = 1V * 1A

Another way to look at this: Each of the 6 batteries needed around 1.04 Ah to recharge. Each of the 12 batteries needed around 0.55 Ah. So the 12 batteries have more voltage and were discharged less individually.

And that’s why I prefer solutions that use higher voltage to drive a given power demand. Since power demand can fluctuate, and higher voltage systems often have larger capacities, the higher voltage batteries can be more flexible and respond to changing circumstances.

will be harmful to power my pc4k using just a 7.4 volts via dummy battery?

No, as long as the 7.4 VDC source is regulated and has enough MAmps to support the current draw, it should work. However, this is not the best solution, but works with sleds that use two Sony NP batteries in parallel or a single NP battery.
Cheers

READ THIS!

YEs, youtubers tell you to buy the cheap and long lasting 7.2V battery. i was one of the dummies who followed. However this ruined my bmpcc 6k. First it started powering off over and over, i didnt know what was happening. Then finally after i got home it stopped turning on all together, no matter what battery, what plug, anything. its fried. DO NOT put the 7.2 Volt into the DC. Learn from my mistakes

Using a dummy battery in place of the Canon LP-E6 with 7.2 VDC NP battery works fine. Connecting this low voltage to the 13-18VDC input on the side of the camera, no, will not work correctly and may damage the camera’s DC-DC power board which is looking for a minimum of 12VDC.
Cheers

It isnt rocket science.
I use these innexpensive 12 volt packs with a proper Weipu cable. Very effective and more practical than expensive batteries.
Decent run time.
https://www.amazon.com/dp/B01M7Z9Z1N?re ... b_ap_share

Hey everyone!

I was wondering if I could use this battery with my Pocket 4K:
Dorr CVL-65 Compact V-Mount Li-Ion Battery


I have the following cable
PTAP Power Cable for BMPCC 4K/6K by Tilta


I appreciate any help. I could get that battery + charger for next to nothing.