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boxx shorting my batteries


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#1 Ramon Engle

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Posted 24 July 2012 - 09:29 AM

I placed a Boxx transmitter on my sleds battery bracket then piggy backed an AB battery to fly a 24v millennium XL. everything powered up fine until I tried to connect a BNC signal (SD) into the composite input on the boxx. It tripped my batteries. Shut them down as in an electrical short. Once I placed the boxx on an AB mount and DID NOT piggyback a battery and powered the boxx via cable to the video out port all was well. This scenario occurred on both my MK-V and PRO sleds.


Thoughts?
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#2 Brant S. Fagan SOC

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Posted 24 July 2012 - 10:30 AM

Sure, you are attempting to route your power through the Boxx unit to make 24vdc (series circuit) and it won't accept that voltage. Boxx TXs like and must have only 12vdc (nominal).
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#3 Benjamin Treplin

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Posted 24 July 2012 - 11:35 AM

Which battery mount (in the series connection) did you use for the Boxx? The first (0-12V), which also powers video acc. or the second (12-24V).
Sounds like you connected video GND over the Boxx to GND of the second batt.
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#4 Ramon Engle

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Posted 24 July 2012 - 11:40 AM

Benjamin it seems you may be on to something. Brant the only power the boxx was receiving was through the piggybacked dionic 90. So 14.4 volts only.
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#5 Alec Jarnagin SOC

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Posted 24 July 2012 - 02:07 PM

Ramon,

You're lucky you only tripped the battery's breaker. A friend borrowed a monitor from me a few days ago because he shorted out his Cinetronic doing the exact same thing (he had run a BNC to the HDSDI in on his monitor which was now carrying 24 Volts!!). BY having the sled in 24 Volt mode you are placing the two batteries in series so in theory you should still be getting 12 Volts into the Boxx, but there is something odd about the way the Boxx handles this pass through power (or so it seems). This is of course assuming that you had the Boxx piggy-backed to either the Camera or the AUX battery and not the Monitor battery (in which case it really makes no sense). Seems the moral of the story is DO NOT PIGGY BACK A BATTERY ON THE BOXX AND USE IT IN 24 VOLT MODE ON THE CAMERA OR AUX BATTERY PORT. Power it from a cable or piggy back it to the monitor battery only.
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#6 Alec Jarnagin SOC

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Posted 24 July 2012 - 02:09 PM

Just re-read Benjamin's post. Yes, I think you're on to something, but on the PRO with a there battery block, the video AKS are powered from the monitor battery.
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#7 Benjamin Treplin

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Posted 24 July 2012 - 04:15 PM

Even with a three battery setup like on a PRO you can run into this problem. When the camera connects video GND and power GND (and most do) you have the same potential difference issue as in a two battery setup.
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#8 Brant S. Fagan SOC

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Posted 24 July 2012 - 04:15 PM

Regardless of how the unit was mounted, clearly there is a problem with the power flow, either from stacking or a new wiring path not intended for that voltage.
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#9 Alan Mehlbrech

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Posted 27 July 2012 - 11:27 AM

I am not clear.

Is the BNC acting as a ground or is it carrying power (12v/24v) power from the Boxx?
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#10 Ramon Engle

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Posted 27 July 2012 - 03:56 PM

I will need to set up the scenario and employ a volt meter to determine exactly what's going on. I do think the video ground is the culprit. I think the Video grnd is carrying current.

Ramon
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#11 Aaron Medick SOC

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Posted 27 July 2012 - 07:28 PM

Hi all, I'm the one Alec refers to.

Alan, I believe both is the answer to your question. The Bnc is becoming a live ground, to the monitor in my case frying my HDSdi bored because there is no breaker. This causes the bored to be receiving more then twelve volt. I can't say for certain but I would guess it's getting 12 addition volts. The batteries also go down because of the back feeding of voltaging into the battery through the bnc.
To avoid this, you have to be in 12 volt mode or be running the BNC into something using the same power source.

Anyway, that's my understanding. If someone know different. please chime in.

Oh and it diesn't matter that is was a Boxx. I was using a wevi. I think this will happen with any accessory that pass power through it at 12 volt, then is run in series.

Aaron
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#12 Brant S. Fagan SOC

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Posted 27 July 2012 - 08:50 PM

Gents--Now we're all saying the same thing! The grounds are shared and thus backfeeding and over-volting the device. Vote for Pedro!!!! Which Olympic team has brought Pedro to London?
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#13 Jess Haas SOC

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Posted 27 July 2012 - 11:11 PM

When you run two batteries in series and then run a twelve volt accessory off of the "top battery" you end up with different devices running with grounds at different potentials(if you connect a meter to both grounds it will read the voltage of one of your batteries when you want it to read 0). So if you connect the grounds bad things can happen such as shorting one of your batteries and your accessory getting 24volts instead of 12. Connecting the BNC is connecting the grounds together.

~Jess
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#14 Alan Mehlbrech

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Posted 28 July 2012 - 01:46 AM

So, right now I am powering the Boxx with a IDX Powercube inline on the bottom of the sled and feeding it HD from my Transvideo HD monitor WITHOUT issue. I have the MK-V V4 electronics, Alexa, 24v.



Is this a Pro/Boxx issue or is this a ticking time bomb for my monitor?
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#15 Jess Haas SOC

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Posted 28 July 2012 - 02:25 AM

It isn't specifically a Pro issue. Not sure exactly how the MK-V is wired but the reason it works for you is probably because only one of the two battery plates involved in running 2 batteries in series for 24v will show this exact problem. There are other concerns when doing this though. For instance when you remove the battery from the back of the boxx and still have a battery on the other plate the boxx may be getting reverse polarity power while the Alexa gets the 12ish volts from your other battery but with all of the current running through the boxx. Weather this hurts anything depends on the design of the Alexa and the Boxx.

If running in a 3 battery configuration putting the Boxx on the 12v accessory power battery should be perfectly safe.

~Jess
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