BMPCC4K (6K) cheap battery option

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Justin Jackson

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BMPCC4K (6K) cheap battery option

PostThu Feb 13, 2020 10:45 pm

Hey all,

I have a nice vmount setup for my camera/monitor, but sometimes I want to just use the camera on a tripod for a couple hours. There seem to be some nice options here on the forums for using Canon or other batteries, including the large BMPCC grip option.

I have posted a while back on another thread about this, but thought i'd share again as I see various threads about powering the camera, etc.. and possibly a lot of new people here with the 4K and now 6K cameras being more readily available.

So, the hack is fairly simple. I bought this: https://www.amazon.com/gp/product/B06XS ... UTF8&psc=1

It is a pack of 4 18650 battery holders. Each is wired in series. Unlike my previous one which was NOT wired and had crappy clips, these have springs so are a bit nicer to get batteries in and out of. The better thing is it is already wired up in series.. but one concern would be are the leads between the pos and neg "thick enough" to handle more power draw. The clips that are connected are thicker than the wires I use on my barrel adapters, so I assumed they would be. In testing.. it worked great, so I don't believe for this particular use.. there is any concern with the power draw of the camera overheating the metal leads between the pos and neg posts. I felt them after over an hour of use and they were not warm at all, so again I don't think they are a problem. I say this because SOME options come with very thin leads that CAN heat up and melt/break and cause the battery pack to stop working.

NOW, having said that these units DO come with VERY thin pos/neg wires attached. These I fear could be a problem with too much power draw. What I did is I just ripped those off.. they are very weak. I then soldered quickly my barrel plug (female end with leads) to the pos/neg posts. The only issue I ran in to is the neg lead attaches to one with a coil on it.. and it was hard to heat up the post fast enough to solder the barrel plug neg lead before the cheap plastic started melting around the coil.. so in one of my packs the coil got loose a little bit and bent down so that I have to kind of hold it up when I put the battery in so it touches the battery plate. It isn't a big deal, and my second one I did worked fine. The pos lead was easy to solder in place.

I realize this isn't for everyone.. I wanted a simple cheap way to provide a couple hours of juice to my camera. These are not "pretty" by any means. I put some electrical tape around the soldering area to "seal it up".. not sure that is necessary but.. why not.

You can add some sort of velcro strap to the back of these, either with hot glue or some other method. The thing here is.. I can quickly replace 18650 batteries in the packs, and use really good 18650 cells. I bought 4 NCR/Panasonic 18650 cells (3400mah) for $28 shipped. The pack along with the battery in the camera gives me around 3 hours of use.

I built 4 packs.. with batteries.. for $130 (including barrel plugs). I also bought a barrel plug to DC input (https://www.bhphotovideo.com/c/product/ ... mm_dc.html).

So, I can hot swap each pack while the battery in the camera keeps things running in between quick hot swaps (love that BM has this working like this!!). Basically the 4 packs give me an all day recording capability for the camera.

I haven't yet looked at using these to power my monitor.. but I know it will work as well.

Anyway.. just wanted to share. It is NOT pro looking by any means, there are much nicer pro looking options out there.. but they do cost more than what it cost me to put 4 of these together with batteries. I suspect with a little bit of ingenuity one could make these look pretty good, hidden, etc and nobody would know.. or complain.
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youlikeny

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Re: BMPCC4K (6K) cheap battery option

PostFri Feb 14, 2020 1:56 pm

Out of curiosity, wouldn’t it be easier/cheaper/more convenient a simple NPF battery plate (15$) with a 25$ NPF battery? You can even get those NPF batteries with USB input so all you need to charge it is a phone charger.
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Michael_Andreas

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Re: BMPCC4K (6K) cheap battery option

PostFri Feb 14, 2020 2:39 pm

One problem you can encounter in your setup is the lack of battery cell monitoring and leveling. There are circuit boards that will monitor the cell voltages and warn or disconnect when one of them gets too high or too low. Battery cells have variability in their capacity, and the cell that has the least capacity may be overcharged and over-discharged. Here is a BMS board that might work. I say "might" because I haven't done this myself.

You might get by with this setup if you (1) charge the 18650 cells individually in a properly designed charger and (2) don't discharge the batteries too much. To determine when you've reached "too much" might require a DC voltmeter to monitor the individual battery voltages, or maybe you could get by with just limiting your operating time.
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Justin Jackson

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Re: BMPCC4K (6K) cheap battery option

PostFri Feb 14, 2020 11:00 pm

@youlikeny: Yes.. probably but they wont last as long. Also, they only put 7.2v out I believe. I don't know how low the BMPCC4K DC input can handle, but I assume once the NPF starts draining it will drop voltage as well? I know there is a 7.2 internal battery option, but I thought the DC required 8.4v to 20v input? Technically 3 18650's should work as well.

@Michael_Andreas. Yes, I have seen that and thought of something similar. I do charge my batteries correctly to 4.2v, and have tested all of them put same v output, but you are correct in that if one drops faster and too far, it could cause a problem.

The proper thing to do is do what you suggest.. add BMS on top of the cheap rig, which wouldn't be too expensive.
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youlikeny

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Re: BMPCC4K (6K) cheap battery option

PostSat Feb 15, 2020 2:25 am

Justin Jackson wrote:@youlikeny: Yes.. probably but they wont last as long. Also, they only put 7.2v out I believe. I don't know how low the BMPCC4K DC input can handle, but I assume once the NPF starts draining it will drop voltage as well? I know there is a 7.2 internal battery option, but I thought the DC required 8.4v to 20v input? Technically 3 18650's should work as well.


NPF plates output 12V, so you can plug it into the DC, and an average 58wh 20$ battery runs for 2.5/3 hours..
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Justin Jackson

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Re: BMPCC4K (6K) cheap battery option

PostSun Feb 16, 2020 1:26 am

Ah.. I was thinking a different plate I think. That sounds cool. Got an example of it being used, mounted, etc?
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dondidnod

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Re: BMPCC4K (6K) cheap battery option

PostSun Feb 16, 2020 2:41 am

Here's an example using two NPF-970s.

Re: Best battery for Pocket 4K?
viewtopic.php?f=2&t=87085&p=496297&hilit=Smallrig+Sony#p496297
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Justin Jackson

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Re: BMPCC4K (6K) cheap battery option

PostMon Feb 17, 2020 2:04 am

Meh.. it works.. and to each their own, but that looks a bit too gaudy to me. Not saying my rigged 4x18650 in it's present form is super nice either to be fair. :D. I do like the lighter weight and ability to easily just switch out my little packs though. But that works just as well.
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youlikeny

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Re: BMPCC4K (6K) cheap battery option

PostMon Feb 17, 2020 3:46 am

Justin Jackson wrote:Meh.. it works.. and to each their own, but that looks a bit too gaudy to me. Not saying my rigged 4x18650 in it's present form is super nice either to be fair. :D. I do like the lighter weight and ability to easily just switch out my little packs though. But that works just as well.


Here are a couple of examples...
Hard to go any lighter and cheaper than this for 3 hours of battery life...
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Justin Jackson

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Re: BMPCC4K (6K) cheap battery option

PostSat Feb 22, 2020 3:57 am

I get about the same with the 4x18650, but you are not wrong. I am trying to figure out how to rework a 2x2 bike light pack that is wired in a 7.2v configuration (2 parallel 2 series). If I can rework that to make it full series, it would provide a very nice more compact package with USB output as well as barrel output, and an enclosed but removable water sealed top. They didnt make it easy to access the one side of the posts though!
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