How to run small devices on DC?

[metalheaddoc]

I am trying to figure out how to run small devices on DC off of a 12v battery instead of going through an inverter and AC plug that will convert back to DC anyways. I am talking about things like WiFi routers (Google Nest) or a network splitter box or my Google Fiber fiber jack. Often times, the manuals don't include information about the specific DC connector or the voltage needed to power the device. How does someone go about figuring out these specifications and how to power these off a 12v system?

 

[Bud Martin]

The device should at least show the Voltage and current rating at the DC input jack, or the sticker, or on the power supply that come with device.

 

[Leeds]

The input voltage of most modern (low power) appliances is actually quite variable. If I'm trying to see if something like a router will work on a different voltage I can go up but I never go down. If it takes a 9v wall wort I suspect I can power it with a 12v supply, etc.

Keep in mind even a laptop charger can accept 110vac-230vac and not even hiccup.

All this said- there can be danger in this sort of endeavor. I would never leave such an experiment unattended unless I made sure nothing was heating up.

 

[time2roll]

Measure the voltage of the brick output. Get a DC-DC converter to match the voltage.

 

[metalheaddoc]

Thanks for the ideas on determining voltage. How do I determine what kind of connector it is? A lot of these devices use barrel connectors. Do I measure the width of the barrel connector? Do these things come in standard sizes?

 

[billvon]

Thanks for the ideas on determining voltage. How do I determine what kind of connector it is? A lot of these devices use barrel connectors. Do I measure the width of the barrel connector? Do these things come in standard sizes?

Measure it with a caliper. There are about a dozen standard sizes. 5.5/2.1 and 5.5/2.5mm are two of the most common.

 

[time2roll]

I would find it very difficult by sight. Could get an adapter kit and test fit what works. Then use or order what is needed.

Example: (scroll down for specs)

https://www.amazon.com/aceyoon-Adapter-Universal-Connector-Thinkpad/dp/B0722J415P

 

[Bud Martin]

The popular barrel connectors are 5521 and 5525.
The barrel is 5.5mm, the center pin is 2.1mm or 2.5mm.

Measuring Power Supply Barrel Plug ID 2.1mm vs 2.5mm

One common question that is asked of Techs at Digi-Key is to trying to verify the correct replacement wall mount AC to DC power supply. The difficult specification to find on many of these power supplies is what size if the inner diameter of the plug / connector. This is made more difficult by...

forum.digikey.com

You can use this adapter so you do not have to buy the barrel and do any soldering works.

https://www.amazon.com/Power-Connector-Female-Adapter-Camera/dp/B07C61434H/ref=sr_1_3?

 

[time2roll]

I like my HF digital caliper for similar stuff.

https://www.harborfreight.com/4-in-digital-caliper-63710.html

 

[ianganderton]

USB-C PD (power delivery) is a useful standard for a wide range of devices from phones to laptops up to 200W

A 12V cigarette lighter type accessory socket is easy to install and there are a wide range of adaptors.

Here is a 160W usb-c pd adaptor

Limited-time deal: 160W USB C Car Charger, Baseus Type C Car Charger, QC5.0 PD3.0 PPS 3 Ports Super Fast Charging Car Phone Charger Adapter for iPhone 14 13 12 Pro, Samsung S22 S21 iPad MacBook Pro Air Laptop Steam Deck https://a.co/d/8d40t24

The adaptor solution allows changing/updating to newer technologies as they evolve

 

[metalheaddoc]

Thanks for everyone for your ideas.

 

[12VoltInstalls]

Measure the voltage of the brick output. Get a DC-DC converter to match the voltage.

My cell booster is a 12VDC brick. So it connects to a fused battery circuit. My water heater ignitor is supposed to run on two D batteries. I bought a 12V to 3V transformer ($4) and wired it behind the timer switch- no batteries. My phone charger is USB of course. I bought a 1.0625” automotive accessory USB charger with a power-off switch and wired it in. 11 of 12 of my lighting fixtures are 12VDC LED. I wired those through the BlueSea fuse box and switched accordingly. I haven’t had my TV on since 2019, and I’ve looked it up and read where that model is internally rectified and converted to 12VDC primaries (someone said the remote switches 120VAC but I don’t believe that). At some point I’ll open it and verify 12VDC, and probably wire that to the DC fuse box, too. The laptop requires 19VDC and my 20V cordless tools purportedly have bms circuitry in the charger base so those two things need 120VAC along with the fridge, coffeemaker, shopvac, and iron.

So it’s all doable in some fashion.

 

[J.P.]

I am trying to figure out how to run small devices on DC off of a 12v battery instead of going through an inverter and AC plug that will convert back to DC anyways. I am talking about things like WiFi routers (Google Nest) or a network splitter box or my Google Fiber fiber jack. Often times, the manuals don't include information about the specific DC connector or the voltage needed to power the device. How does someone go about figuring out these specifications and how to power these off a 12v system?

Some electronics run off of lower voltage than you might think. When looking into my water heater controller, I actually found out that the 120VAC wall wart was reduced to 12VAC at the plug. Then just after the connection on the circuit board, it was further reduced and transformed into 5VDC (via a full bridge rectifier and a 7805 IC) which the entire rest of the board ran off of.

At that point I just purchased a cheap 12V down to 5V buck board and ran bypass wires just past the rectifier and 7805 to directly power the controller that way. Then I realized that the full bridge rectifier did not care whether is was getting AC or DC voltage so I took out the buck board and just fed straight 12VDC into the plug and let the 7805 IC reduce the voltage to 5V and everything is as happy as it can be. This has been running continuously for a few years now.

I have yet to have need to look at other devices but would not be surprised if many of them also run off of 5VDC.

 

[Rednecktek]

Limited-time deal: 160W USB C Car Charger, Baseus Type C Car Charger, QC5.0 PD3.0 PPS 3 Ports Super Fast Charging Car Phone Charger Adapter for iPhone 14 13 12 Pro, Samsung S22 S21 iPad MacBook Pro Air Laptop Steam Deck https://a.co/d/8d40t24

Am I the only one concerned about a USB device asking for 13+ amps through the lighter port? No car I've ever owned can top 5a. Either they're using "New Math" or they're making a killing selling replacement fuses.

 

[ianganderton]

Am I the only one concerned about a USB device asking for 13+ amps through the lighter port? No car I've ever owned can top 5a. Either they're using "New Math" or they're making a killing selling replacement fuses.

Most of my vehicles have been 10A as standard

I’ve just purchased 20A rated sockets for this purpose

Narva 12/24V Accessory Socket - Heavy Duty, 20 Amp

Narva 12/24V Accessory Socket - Heavy Duty, 20 Amp

www.supercheapauto.co.nz

FWIW I’m pretty confident no one has ever got rich selling replacement fuses for poor circuits ?

 

[pollenface]

Cut the power supply brick from the end of the cord, plug it in, test the voltage with multimeter to determine positive and negative, then identify those wires on the rest of the cable and attach them to the battery.

I did that with my cctv system, going up to 14.6v at times didn't seem to have any ill-effect, if concerned you could use a little step-down module to output exactly 12v

 

[drocanyd]

I just started a few projects converting things from 110 power bricks to various voltages using DC to DC buck transformers. They can be bought off ebay very cheap, and some of them will take an input from various DC volts (depending on what you buy) and convert them down to various specific voltages or use a small potentiometer to adjust. I always cut the trace and use specific voltages if at all possible to avoid drift from temperature shifts or even a dirty pot after time. The ones I got recently are about the 3/4 the size of my thumbnail. The transformer on it does get a bit warm, I might fabricate a small heat sink for it. These specific ones rated at 3 amps, but are probably most reliable to about 1.5 amps, though bigger ones can be had I'm sure. they are cheap enough and small enough to build into most devices and allow them to plug directly into the DC systems of most campers I would think. This particular one I have setup to convert an older airport express with the audio out for airplay to run off 12v so I can have that. It will also allow me to route a small local network using an external wifi bridge. Only one thing to change at a campground (the external bridge adapter), then all the devices inside the camper always connect to the airport.

just look up "DC to DC buck" on ebay and you'll find lots of variations.