Industry Standard 1/4 Brick

Thread Starter

SNEW

Joined Jun 28, 2020
10
Apologies, very newbie question - How can I make a circuit with an 'Industry Standard 1/4 Brick'? I'm assuming these types of components usually get soldered into a PCB but is there something off-the-shelf I can buy and hand solder this into myself?

This is the component in question - https://www.xppower.com/portals/0/pdfs/SF_QSC150.pdf

It's for 12V conversion project I'm attempting for two network devices I want to mount inside an enclosure with all circuitry conversion circuitry.
 

Irving

Joined Jan 30, 2016
402
That brick is 150w of power, do you really need that much? There are lots of off the shelf power supply options, with various connection options. Be more specific about your project and you'll get more specific answers.
 

Thread Starter

SNEW

Joined Jun 28, 2020
10
That brick is 150w of power, do you really need that much? There are lots of off the shelf power supply options, with various connection options. Be more specific about your project and you'll get more specific answers.
the device I'm converting to 12V is a POE injector which draws 120W, this is the closest rated DC-DC converter I could find.

the question is more about how to use it to build a proper circuit. most beginners circuit building tutorials I see talk of temporary bread board setups however I want to create something a bit more permanent and robust. the final product will be deployed and redeployed several times a week so I want to build it as best as I can.
 

Irving

Joined Jan 30, 2016
402
OK, and the Poe users will draw 120W? If they only want 50w then this is overkill... Not saying you're wrong, I'm just testing your thinking.

Is your Poe injector a hub that upconverts to 48v from 12v or are you injecting 12v into a passive injector?

And your input voltage to the dc-dc converter?

If you search for open-frame dc-dc converters you'll find more suitable options with proper screw terminals rather than solder pins.

But you need to think about your overall power budget, and system losses - there will be some heat generated .

So what's going to power all of this? How are you sizing that?
 

Thread Starter

SNEW

Joined Jun 28, 2020
10
thanks Irving, i appreciate the feedback, this is my first real electronics project so it's very likely i'll need correcting along the way!

the POE injector is a 4 port device, each port is rated for 30W max. The APs that I'm using with it are max draw 17W but I want some overhead as I may swap them out for more powerful APs in the future. is it not better to over spec slightly? my thinking was not to run the converter close to max performance as it could shorten it's life span or not run as efficiently?

the injector accepts 44-57VDC, i went with 48V as it seemed much easier to find DC-DC converters for that voltage.

my input is a 11-16.8V battery, 14A max.

perhaps this would be more suitable? - https://www.cui.com/product/resource/vhk150w.pdf
 

Irving

Joined Jan 30, 2016
402
OK. Can you increase your input voltage? Higher voltage lower current will reduce losses. and those dc-dc converters don't come cheap!

Sticking with 12v input for now, that's 120W out of the dc-dc converter which will run at 85% efficiency typically. So input will be 120/.85 = 141W @ 12v = 12A approx.

You say your battery is 14A. Do you mean 14Ah capacity? If not what is its capacity and what chemistry, eg lead-acid, li-ion, etc.?
 

Thread Starter

SNEW

Joined Jun 28, 2020
10
increasing the input voltage isn't really an option, I work in the film industry and most of the equipment I use is 12V so i can use a common set of batteries.

The batteries are li-ion. 14A is the max discharge. the capacity is 191Wh (14.4V, 13.2Ah)
 

Thread Starter

SNEW

Joined Jun 28, 2020
10
yes that's enough, most of the time it will only be used with 2 APs and so roughly half it's full performance.
 

Thread Starter

SNEW

Joined Jun 28, 2020
10
that's great Irving, thanks for running through this with me!

I'm building the main circuit and devices into an enclosure. the battery will connect to quick-release plate on the outside of the enclosure
 

Irving

Joined Jan 30, 2016
402
Sounds good. Can I suggest you put 2 plates in parallel, then you can drop another battery in and pull the dying one off without shutting down. Or fit 2 at start to give a longer run time. A small panel voltmeter would be useful too. These packs have a BMS in which will shut them down when the voltage drops below 11.5v or so, the voltmeter will give you some early warning of that.

Use at least 18awg, ideally 16awg, wiring between batteries and dc-dc converter. You can use the same on the 48v side though it's a bit of overkill. I'd go for the higher stranded silicon sheathed cable, it's less likely to fracture from vibration. Solder or crimp ring terminals for connection to & from the dc-dc converter and batteries.
 

Irving

Joined Jan 30, 2016
402
I was just about to say "No, never use single core for portable stuff, it'll fracture" when I realised this supplier was confusingly using 'single core' to mean a single stranded cable. That'll do fine, its a bit larger and less flexible than my preference here which they sell as a red/black pair at £1.17/m for 10m (I buy a lot from these guys, good pricing and fast shipping). I prefer the high-temperature silicone sheath as it doesn't shrivel back when soldering to large connectors which need a lot of heat.
 

ThePanMan

Joined Mar 13, 2020
26
16.8V? Is that 5S 18650's? Are you paralleling them? How are you controlling their discharge and minimum voltage as well as recharging rates? How are you balancing their charge?
 

Thread Starter

SNEW

Joined Jun 28, 2020
10
16.8V? Is that 5S 18650's? Are you paralleling them? How are you controlling their discharge and minimum voltage as well as recharging rates? How are you balancing their charge?
it's an IDX battery. To parallel I was going to join both battery's positives in a terminal block and in a different block for the negatives - is that right? this is the terminal block https://www.12voltplanet.co.uk/bluesea-systems-20a-terminal-block-4-way.html

Do I need to control the discharge and minimum voltage? the battery shuts off at 11V and both it's upper and lower voltage is within range of the DC-DC converter.
 

Irving

Joined Jan 30, 2016
402
No, the BMS in the pack handles cutoff and over-current discharge for you, and you use the normal charger separately.

ThePanMan was rightly asking if you were planning to use individual Li-ion cells, which can be dangerous if you don't get it right.
 
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