Thread: Weipu polarity

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  1. #1 Weipu polarity 
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    I am contemplating making up some power leads for my BMPCC 4k. Does the 2 pin weipu socket have any particular polarity?
    The Blackmagic Design Cinema Camera - what it says on the box!
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  2. #2  
    good question. The answer is yes, there is a tiny little duct on the Weipu plug so that it can be inserted only one way, and DC has to have polarity. But, and that's the real question, which polarity? It is a bit difficult to measure with a voltmeter because the plug is female. That's one of the reasons why - despite the high cost - I ordered the cable set, I'm sure it's indicated on the bare wired cable. Unfortunately I'm still waiting for the cable set (among other rather important accessories), so I can't tell right now.

    Edit: alright, soon later a DHL truck paid a visit to my humble place and delivered the cable set. It's just a plastic bag with 3 cables. The bare wire cable has a black lead and a red lead. I guess the red lead is hot (+) and the black one is ground/shield (-). But measuring is better than guessing. This will keep me busy for a while, will edit this post when done.

    Edit2: when viewed from the top, the Weipu plug has two markings that can be seen using a loupe. Left is labeled 1 and is hot (+), right is labeled 2 and is ground/shield (-). And it's correct that the bare wire cable is as described above, red hot, black shield.

    At last I have my custom cable. The Pocket 4k display shows the AC sign in the top right corner. I'm using my 'Mega24000' power packs from my solar system. They provide 88Wh, for a good 2 1/2 hours capturing time (calculated) for the Pocket 4k camera. I got them from Sistech.ch, but I've seen this model in other places too, with other markings and different colour.

    mega24000.jpg
    https://www.sistech.com/pages-0/PowerTankXXL (german language)

    Edit3: the Weipu's plug polarity is printed on the PSU, but it is so small to read you need a loupe and good light. Ha! I could have saved some time and not do the measurement with the voltmeter. But I would have done the measurement anyway, for final QC, before plugging things together.
    Last edited by Phil999; 08-12-2019 at 10:28 AM.
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  3. #3  
    I believe it is safe to leave the internal battery inserted while connected to external batteries when three conditions are met:

    1. the camera must indicate AC power input.
    2. one has to be sure that this won't change for the entire time the external battery is connected, that it has enough voltage and current for the entire session.
    3. the power indicator must behave exactly the same way as observed when connected to the PSU. When the internal battery is charging there is a lightning bolt sign next to the AC letters. As soon as the internal battery is full, the lightning bolt disappears. This lightning bold must never reappear again during that session. If it does, only for a moment, the internal battery should be removed while operating with external battery, in my opinion. The lightning bolt indicates the state between active charge (bolt visible) and trickle charge (bolt invisible).

    ---

    The 'Mega24000' has a switchable output voltage of 9/12/16/19/20 Volts and can deliver 4 Ampère. In case of the Pocket 4k I choose 12V, which results in 48W max output. I think that's more than sufficient for the camera, even while recording 4k at maximum quality, and connected XLR microphone with phantom power. As a comparison, the P4k power supply has 30W output (12V @ 2.5A). I could go further and select 16V, which results in 64W max output, or even more when selecting 20V. But I don't think this will be necessary.

    I'm pretty sure 12V/48W will suffice. I don't know the camera well, I got it for just a few days, but I know the 'Mega24000's very well. They are very reliable and powerful. They can provide their rated voltage and current for hours without interruption and without getting too hot. Of course they should always be kept in the shade while connected, never in direct sunlight.

    One reason to remove the internal battery while connected to external power with low voltage (below 12v) and/or low current (below 2.5A) might be conflicts in the camera circuitry (switching between charging and trickle charging states). Another factor is temperature, if the external battery gets hot and doesn't provide its rated output anymore, which is something that can change during a shoot, and which is something one may not be aware of all the time. Numbers and calculations are always theoretical values, one cannot really be sure until one has made extensive tests. One has to 'know' the system (relation between power source or sources, and the devices' demands).

    Another reason to remove the internal battery, also when the device is connected to mains power, is to maintain the battery's longevity. But this is a bit a difficult and also controversial topic. Some companies (Apple, Sensel) advice to let batteries drain to zero (total discharge), some say the exact opposite (Sistech, GoalZero). Experts at Sistech say that lithium-based batteries like to be charged as often as possible to keep their capacity. And each total discharge reduces capacity and longevity. Personally I have followed the latter advice. I use the internal battery when off the grid, and as soon as I have access to mains power or solar power, I charge every single device to 100% and leave it connected (sometimes for months). If a battery goes below 50%, I generally exchange it with a full one, or if the battery is built in, I change the device. If possible, of course. This could explain why all my Li battery driven devices and batteries are still fresh and in good shape concerning capacity. They are to me like Tamagotchi's, little electrical things that have to be nurtured and cared about regularly. I admit it's also a bit of an obsession, and I'm still not entirely sure if my strategy is the best. What I can say is that it is not bad. My 2011 iPads are still fresh and with good battery life.

    A general consensus however is to charge a lithium-based battery at least every 3-6 months.

    Advices for total discharge may have some reasons, probably for smaller devices and batteries, and for years long storage. But I suspect there are also some marketing strategies behind. A total discharge helps the circuitry/software to readjust its battery percentage indicator, makes it more precise again. And for many customers longevity is not a sales argument because they got used to buy new every couple of years.

    A note to my new cable: I now have the Pocket 4k hooked to one Mega24000 for over three hours. The camera was switched on all the time, without capturing, without microphone. It still shows the AC symbol, the lighning bolt has not reappeared as far as I can tell. The Mega24000 is at 43%, which is a bit more what I expected. I would say the first 'dry' test at home has passed.
    Last edited by Phil999; 08-12-2019 at 10:09 AM.
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  4. #4  
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    Above and beyond the call of duty sir. Thanks from me and the community.
    The Blackmagic Design Cinema Camera - what it says on the box!
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