Power Conversion - 12v Lighter Plug to USB

I was quite the happy camper having added a 12V (cigarette lighter) socket to my handlebars to power my GPS while in transit.

Imagine my surprise a few days ago when I discovered that the cable was degraded, splitting open at various points, and the conductors peering out for the world to see. In a jiffy I cut out the bad section and spliced in some new cable. That bought me some time while I explored my options for converting the 12V plug to USB...


I took a USB-->RJ45 cable from a Computer Battery Backup/UPS, snipped off the RJ45 connector and metered out the pins to determine what colors went where. The important stuff in this case was, +5v and ground... Pin1=RED and shield did it for me!


So then I used a caliper to measure the OD and ID of the connector that went into the GPS.
I was looking for something meeting the following dims... 3.2mm x 0.9mm x 10mm. Turned Radio Shack upside down, scoured the web, but no joy.


Then I discovered "coaxial power connector" on wikipedia. What a treasure trove of info!? I was overjoyed to learn that CUI Inc is a supplier, so I wasted no time placing my order...

Today, the stuff arrived...


Then I set about getting my connections soldered in...
With the cable now complete, I plugged in my GPS, and it came alive! I'm excited to now have flexibility in powering/charging this gizmo at a traditional power outlet as well as via USB. What took me so long? I guess necessity was the mother of re-invention!

First: Cool!

Second: I have no idea what you said, but cool!


Lol, ok so I get the general drift, but am confuzzled a bit, hee hee.


You have a 12V socket.

You made a USB-to-coaxial plug cable.

Now you can power your GPS via either a 12V plug end cable into the 12V socket, or a USB plug end cable to a...(USB adapter in the 12V socket? Or a dedicated USB power socket in addition to the 12V accessory socket?)

Where I'm confused- (please bear with me, I'm an electrical and math 'tard of the worst kind) USB ports are 5V right? With my Nuvi 765T I can't use it as a GPS unless it's on it's internal battery, or plugged in through it's 12V clip style connection. If I plug into it's 5V USB port, it goes into "computer and/or charging" mode, and I can't use it for navigation.

How can you plug into a 5V USB power source, but still go into a (presumably) 12V-requiring coaxial port on the device, too? I can picture a USB plug and USB port, and a 12V plug and 12V port(coaxial), but a mix of the two?

I'm soooooo lost, lol.

Is not that coaxial power connector the same than Nokia phones used?

Anyway, as L.B.S. said... Cool! LOL, I have no idea how that 12V versus 5V is working!

Edit: just realized your previous power connector was converting from 12V to 5V so now I understand!

L.B.S. said:

First: Cool!

You made a USB-to-coaxial plug cable.

Now you can power your GPS via either a 12V plug end cable into the 12V socket, or a USB plug end cable to a...(USB adapter in the 12V socket? Or a dedicated USB power socket in addition to the 12V accessory socket?)

Where I'm confused- (please bear with me, I'm an electrical and math 'tard of the worst kind) USB ports are 5V right? With my Nuvi 765T I can't use it as a GPS unless it's on it's internal battery, or plugged in through it's 12V clip style connection. If I plug into it's 5V USB port, it goes into "computer and/or charging" mode, and I can't use it for navigation.


How can you plug into a 5V USB power source, but still go into a (presumably) 12V-requiring coaxial port on the device, too? I can picture a USB plug and USB port, and a 12V plug and 12V port(coaxial), but a mix of the two?

I'm soooooo lost, lol.

Click to expand...

L.B.S., here's how [Picture below]. I guess I should have mentioned that I have one of those lighter socket to USB adapters (green arrow), mine is from "Trackside" (they're pretty cheap). My GPS is a Magellan Maestro 3140, and the only 'USB' looking port is the one with the MiniType B port that has the 'Devils Fork' icon/imprint (see blue arrow). Yes, when I plug in there, it believes I'm in the "transferring data" or "updating software mode" and no navigation is possible. However, the information sticker on the underside of the GPS stated "Input 5V--1A". So all I needed to do was get the coaxial power plug and wire it to a USB cable, and voila!



If you want to go with USB on your device, measure the OD and ID of your connector, then go shopping. I've noticed that some 'Android' devices have a similar coax power plug, and will juice (power) your device, however, they're about a 1mm too small on the OD and will fall out of the "foreign" device. The Wikipedia link may help if you cannot pick one up at your fave supplier...

TechiePilot said:

L.B.S., here's how [Picture below]. I guess I should have mentioned that I have one of those lighter socket to USB adapters (green arrow), mine is from "Trackside" (they're pretty cheap). My GPS is a Magellan Maestro 3140, and the only 'USB' looking port is the one with the MiniType B port that has the 'Devils Fork' icon/imprint (see blue arrow). Yes, when I plug in there, it believes I'm in the "transferring data" or "updating software mode" and no navigation is possible. However, the information sticker on the underside of the GPS stated "Input 5V--1A". So all I needed to do was get the coaxial power plug and wire it to a USB cable, and voila!

View attachment 764

Click to expand...

Ah, Brilliant!

Even with pictures 'n everything! I follow completely now

Thank you lol

:nosy LBS:

L.B.S. not nosy at all. I appreciated you bringing this oversight to my attention. I neglected to include a piece of info that would have made this crystal clear. If you were befuzzled, then others might also have been... If I can help anyone feel comfortable enough to attempt this conversion they might not have considered, then that's a good thing. I've learned much from my fellow forum buddies...

For the curious, the hole on the GPS without arrows is the audio port for the standard 3.5mm phono plug, but I always have the GPS on mute, so that was moot.