dual batteries for bag bds - 1x battery and 1x battery eliminator?

[osa]

Is it possible to use a dual battery cup in this configuration and more importantly is this a setup that someone currently uses - if even possible? In my research my gut tells me these are not designed for this purpose and this is where my skills are lacking. I am wanting to duplicate the features of cart power supplies in a smaller footprint but also do it safely, if this is possible. otherwise, I may just stick with dual batteries for this purpose. my hope was to have safe auto-switching power to my bag bds with #1 priority shore power in studio situations and #2 pick up and go on battery instead without powering down, and also having battery take over if someone unplugs me etc.

 

[rich]

Hi Osa.

I have made a power distro box for my cart which has two inputs. one has a battery connected, and the second has a mains power supply.
both inputs go through diodes to prevent each input seeing the other. 
current is drawn from the input with the highest voltage. so i have gotten myself a 15v mains supply as my Life battery only gets to 13.2.

its a seamless swap between the two. so if i lose mains, there is no interruption.

 

 

if you are using LiPo batterys - NP1s and the like, you will need an 18v power supply, otherwise your NP1s will discharge until they get to the voltage of the mains supply and stop there.

in my bag rig, i have a Hawkwoods NPD-8s which i bought because it had two inputs. though i tend to use two batteries on that for the run time, as if im using the bag rig, i need to be mobile, so mains isnt really an option.

https://www.hawkwoods.co.uk/Sound/P/NPD-8S

if you are planning on making something yourself, send me a message and i'll let you know how i made my power distro.

[Derek H]

Hey Rich, I did a similar thing by modifying a remote audio hot strip so that the two DC inputs are isolated by Schottky diodes. In my case I set the voltage of the mains PSU to about 16 volts and an NP1 goes into the other input. I assumed that once the voltage of the np 1 dropped below 15V this system would then only draw from the 16V PSU but in fact it still draws from both but not equally. It draws mostly from the PSU but not entirely. I never figured out at what point it stops drawing from the NP1 entirely. The setup works well regardless, providing a seamless battery backup. 
 

Do you notice a similar behavior with your setup?

[rich]

Hi Derek. i did notice whilst testing that when the voltages were similar, there was indeed still some current draw from both inputs. i wasnt able to adjust the voltage on either input to see what difference there needed to be to get no current draw on one input. but that is why i have gone for a power supply about 2v higher than the max voltage of my battery. with the 15v power supply, and my battery fully charged, there is no load on my battery.

i first built my box with Schottky diodes as well, though have now switched to an ideal diode board, which generate a lot less heat, and have less of a voltage drop. i got some 15A ones for solar panels which are working well.

[Derek H]

PS, OSA I think the PSC triple play distro is designed to do what you’re trying to do but check with them on specifics. 

[osa]

Thanks for the input! Currently i own a blackbird hi-q battery eliminator power supply that is 15.1volts and I manually switch powering down in between when needed. On a studio shoot recently someone unplugged me during downtime without realizing I was still pulling power so that’s what sparked this idea for me. Sounds like my 15 V power supply might work against me slightly. But I could be OK with partial battery drain for this type of set up in trade for battery back up security.  There is so much gray area around this subject and the manufacturers seem to strictly refer to dual batteries in any text that I read. They are not saying yes this will work nor are they saying don’t do this you will blow up. If someone owns this PSC power play 2 which I see is the most current version I would love to know if this set up works in a similar fashion. I read the PSC manual and as it states below it refers to using dual batteries, or a power supply, at least the way I read it – but not a battery and a power supply simultaneously and how that would work in terms of switching and voltage:

 

POWER INPUTS:
The PSC PowerStar Mini uses three (3) Switchcraft mini 4 pin male chassis XLR for power input. This connector is wired as follows: Pins 1 and 2 are negative (-) ground and pins 3 and 4 are positive (+). These pins are doubled up for redundancy and to lower connection impedance. You can use one, two or all three input connectors at any given time. Each input connector is rated for up to 5 amps of input current and is both polarity and Polyfuse protected. By combining inputs, you can support larger current loads. Most NP-1 batteries are internal protected (limited) to a maximum output current of about 4.7 amps. By using two NP-1 batteries, you can now safely power up an equipment package that draws up to 9.4 amps. Or

you can power smaller setups for longer battery run times by using multiple NP-1 batteries on the inputs. In addition PSC offers an AC Power Supply that is equipped with a TA4F connector that will allow AC powering of the PowerStar Mini Triple Play when AC power is available. This is convenient when you are doing long sit down interviews, etc

 

http://professionalsound.com/specs/pwrStarMiniTriple.htm

[Derek H]

I highly recommend just calling PSC or email if you prefer. The owner of the company, Ron Meyer, is incredibly helpful and will tell you everything you want to know about it. 

[osa]

3 hours ago, Derek H said:

I highly recommend just calling PSC or email if you prefer. The owner of the company, Ron Meyer, is incredibly helpful and will tell you everything you want to know about it. 

I was already on that hoping to hear back soon!

[Fish]

maybe？

[osa]

3 hours ago, Fish said:

maybe？

dual battery in general is great BUT do you use this rig with one battery and shore power simultaneously? That is what I am ultimately trying to find out. it sounds like the general consensus is the power is pulled equally from both sources when designed for this type of use (proper separation at bds with no accidental charging etc). Really looking for feedback from people operating this way to see if it might be different across different brands of bds for bag setups

[Fish]

8 hours ago, osa said:

dual battery in general is great BUT do you use this rig with one battery and shore power simultaneously? That is what I am ultimately trying to find out. it sounds like the general consensus is the power is pulled equally from both sources when designed for this type of use (proper separation at bds with no accidental charging etc). Really looking for feedback from people operating this way to see if it might be different across different brands of bds for bag setups

there are 3 input =====2TA4+ 1usb type-C（12V pd）。 so you can try

[osa]

Been using the psc and it is working great. I sill plan to build something similar for the cart with 4pin xlrs. The triple play is larger than i expected but great to have extra power jacks and 3x usb jacks. Just as described here - it will pull power from a fully charged battery first until it dips below 15v and then shore power takes over without further draining the battery in my experience so far. Only complaint if any on the triple play is the power switch. Its not deep set below the panel like remote audio bds and has a soft throw. Can be easily bumped off running around or bumped on in storage. I am working on a plastic cover for it or maybe 3-D printing some thing to protect it. But I do highly recommend it as a good solution for this type of setup