powering a gps unit

I have a GPS device which runs on either it's own rechargeable battery, or by being wired into the car's power.  The problem is, the battery on the device runs out almost every day, so the only practical solution is to wire it into the car's power.  The device comes with a kit that consists of the adapter that connects to the device, a fuse to protect it, and the red and black wires.  The car's lighter port won't work because it only gets power when the ignition is on.  I have a Mitsubishi 2002 Galant.  Behind the glove compartment and below it are a lot of wires and harnesses / ports.  I have a multimeter.  I assume that the red wire should be attached to a stripped section of one of those wires, while the black wire should be attached as a ground to a bolt on the car's chassis. 
The main complication I have.. is finding an appropriate wire that is LIVE even when the power is off.  I'm guessing that a wire to the electric window, power locks, or lighting might work.

I need help finding the right wire to tap into and all the advice I can get. 

Normally a GPS is IGN power fed.

The GPS will probably sense power on & off and automatically power-on and (offer to) power off.

And the supplied PSU should be sufficient to both run the GPS and recharge its internal battery.


Though I have a constant power cig-socket for my cig-socket to USB-plug adaptor for my 5V GPS, I usually pull the adaptor from the socket whenever I turn off the IGN (for a reasonable time...).

Forgetting to turn it off can be a thief attractant. It could also flatten the battery over several hours (say 12hours to a few days).


I recommend you try the lighter socket for now.
Don't run on batteries (for long) if you don't have to.

If you do want extra time from the socket AND the GPS battery reserve isn't enough (and you can't switch to ACC) or the auto-off mode is not overrideable, then I'd suggest a "push to keep on" circuit with "push off" or low-voltage cut-out.
But more on that later - if needed.

This GPS is meant to operate 24/7, not just when the car is in motion.

For whatever reason, it lasts at MOST 5 days on a 4 hour charge, and it often doesn't last more than a day - sometimes as little as 18 hours.

The device determines its location via GPS, then uses up a lot of power transmitting that data like a cell phone would do.. so, it's not just a receiver, it is a transmitter also.

Also, the device is completely hidden.  Not unlike a LoJack device.   Using the cigarette lighter would reveal it's presence.

see, you're talking about a gps tracking device, we think you're talking about a navigation device. you should be more clear, although its very strange that something like that has an internal battery. i guess its for a failsafe incase your cars battery goes dead they will still know where it is but something tells me that its not supposed to be ran off of the battery all the time.

your gps needs to be hooked to the constant +12v wire from the ignition switch. it shouldn't be hard to find if you have a multi-meter. it will be one of the larger gauge wires under the dash but im not sure what color it will be but knowing mistubishi its probably a black wire with a colored stripe.

the black wire from the gps needs to be screwed to bare metal with a ring terminal.

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Thanks SnS!

Agreed - definitely not to be run off the battery - that is its fallback.


But I would have said some direct (fused) battery source - rather than involve the Ign switch.

Maybe internal/glove box lights (usually hot with ground switching; but be careful with hot internal dimmers which may always show as +12V).

well, just about any constant 12v source should hold something like a gps tracker. they dont usually suck much current. i say go to the ignition harness constant because i know exactly what it does, stay hot. you can never trust hooking something to a light because the source could just be on a delay.

and i wouldn't go to the battery simply because its more work than its worth. he would probably be extending wires and drilling holes and all that good stuff.

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oldspark wrote:

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Thanks SnS!

Agreed - definitely not to be run off the battery - that is its fallback.

Maybe internal/glove box lights (usually hot with ground switching; but be careful with hot internal dimmers which may always show as +12V).

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The device is meant to be hidden. It uses cell phone technology to transmit it's location.  The company that makes it says it will go 5 days on a charge - nonsense.  I can't understand how something with no moving parts, no lights, no sound, manages to consume all that power. 

Amazingly, that glove box does NOT have a light in it!  I would NEVER recommend a Mitsubishi car to anybody.  Of all the cars I've had, the best one by far was my Nissan Sentra.

soundnsecurity wrote:

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well, just about any constant 12v source should hold something like a gps tracker. they dont usually suck much current. i say go to the ignition harness constant because i know exactly what it does, stay hot. you can never trust hooking something to a light because the source could just be on a delay.

and i wouldn't go to the battery simply because its more work than its worth. he would probably be extending wires and drilling holes and all that good stuff.

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Although I know it will work with a 12v source, I'm sure that 5v is enough because it can also be powered by a usb port on a laptop computer, and those ports are all 5v.

My biggest frustration is getting the information on the wiring of the Mitsubishi Galant 2002.  I don't understand why, but they omit that information from the owner's manaul. 

Also annoying is that all the auto service places that I knew of that did electrical work on a car no longer do it!  All they want to do is sell you tires and batteries and that is about it!

By a fused battery source I meant existing wiring.
I didn't want it "attached" to the IgnSwitch in case that gets ripped out (as idiots do on older cars LOL!)

But the unit would not be intended to be run off batteries unless it had 2 batteries... but even that is stupid.

It's supposed to run off the car battery - its own battery is its reserve time after the main battery is disconnected.
(Isn't it funny when you car is stolen on the 4th day just as you were going to charge the GPS... you're tracking the car when suddenly the battery goes flat.)
Plus you'll be replacing the GPS battery far more often if you cycle it fully instead of using the car battery.


And whilst those devices tend to consume very little power, it's when they transmit that consumption can be quite high. (I'm assuming it's a an on-line system with periodic check-ins rather than only transmitting after it's stolen?)

jdohe2002 wrote:

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soundnsecurity wrote:

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well, just about any constant 12v source should hold something like a gps tracker. they dont usually suck much current. i say go to the ignition harness constant because i know exactly what it does, stay hot. you can never trust hooking something to a light because the source could just be on a delay.

and i wouldn't go to the battery simply because its more work than its worth. he would probably be extending wires and drilling holes and all that good stuff.

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Although I know it will work with a 12v source, I'm sure that 5v is enough because it can also be powered by a usb port on a laptop computer, and those ports are all 5v.

My biggest frustration is getting the information on the wiring of the Mitsubishi Galant 2002.  I don't understand why, but they omit that information from the owner's manaul. 

Also annoying is that all the auto service places that I knew of that did electrical work on a car no longer do it!  All they want to do is sell you tires and batteries and that is about it!

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even though it might physically run on 5v, the red and black wires are there for a reason. if they are meant to be hooked to the car then they will need to see 12v on those lines. the GPS will internally convert it to 5v just like a lot of GPS accessories and sat radios, they have 5v converters built into the cigarette lighter adapter. some dont but most do. plus you will not find a constant 5v source in any car, if you do it is almost certainly low current and the car uses it for transmitting data or sensor status to the cars BCM. if you hook something to it that draws any current you can fry something.

the power wires from the GPS are already fused so it doesn't matter where you get 12v from as long as it can supply the 2amps or so of current.

the constant 12v wire is blue with a yellow stripe at the ignition harness. ground gets screwed to bare metal with a ring terminal.

if you connect to the ignition harness i would suggest soldering the connection. at the very least wrap the wires together and basically tie it onto your constant wire and wrap it generously with electrical tape and then put a zip tie around the tape so it cant loosen itself over time.

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Your reply below was brilliant!   The best reply I've gotten on this subject ever.  Yes, the device is 5v and 2.x amps, but I think it should be on a 12v line.

Preferably, I would like to splice into some wire under the glove box that is concealed by the removable plastic panel. 

I've done a bit of poking with the multimeter days ago, but didn't find anything live yet.   I'll give it another shot tonight. 

soundnsecurity wrote:

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even though it might physically run on 5v, the red and black wires are there for a reason. if they are meant to be hooked to the car then they will need to see 12v on those lines. the GPS will internally convert it to 5v just like a lot of GPS accessories and sat radios, they have 5v converters built into the cigarette lighter adapter. some dont but most do. plus you will not find a constant 5v source in any car, if you do it is almost certainly low current and the car uses it for transmitting data or sensor status to the cars BCM. if you hook something to it that draws any current you can fry something.

the power wires from the GPS are already fused so it doesn't matter where you get 12v from as long as it can supply the 2amps or so of current.

the constant 12v wire is blue with a yellow stripe at the ignition harness. ground gets screwed to bare metal with a ring terminal.

if you connect to the ignition harness i would suggest soldering the connection. at the very least wrap the wires together and basically tie it onto your constant wire and wrap it generously with electrical tape and then put a zip tie around the tape so it cant loosen itself over time.

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oldspark wrote:

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Plus you'll be replacing the GPS battery far more often if you cycle it fully instead of using the car battery.

And whilst those devices tend to consume very little power, it's when they transmit that consumption can be quite high. (I'm assuming it's a an on-line system with periodic check-ins rather than only transmitting after it's stolen?)

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The battery cannot be replaced, it is sealed into the device.  The purpose of the device is actually to track a vehicle that is going places it has no business going. 

I  wonder why car manufacturers still fiddle around with useless car alarms and transponder keys that cost a fortune.  Install these things and nobody would dare risk stealing a car.   However, my understanding is that pro car theives acquire the car - by towing or sticking it onto a flatbed truck, and stripping it of all it's goodies, then dumping the rest in a lake or in a junkyard, etc. 

jdohe2002 wrote:

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I wonder why car manufacturers still fiddle around with useless car alarms and transponder keys that cost a fortune

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Because some people prefer real-time first-hand alerts rather than being notified (if they can be).
Also GPS does not stop a vehicle being robbed - it is merely tracking.
Some have to pay for service subscriptions - or may eventually have to.
Some do no like being tracked.
It doesn't prevent, it merely aids recovery. (It helps them - not you; you get your money anyhow - and probably more or easier with total loss!)
And like most systems, is defeatable. And being wireless and GPS it is very easily defeated.
They are but a few reasons....


But it should definitely be connected. The power connections are not there to tell it it has been stolen. Being battery operated, it expects to be powered externally.
Consider it like a house alarm - external power with internal backup.

jdohe2002 wrote:

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Your reply below was brilliant!   The best reply I've gotten on this subject ever.  Yes, the device is 5v and 2.x amps, but I think it should be on a 12v line.

Preferably, I would like to splice into some wire under the glove box that is concealed by the removable plastic panel. 

I've done a bit of poking with the multimeter days ago, but didn't find anything live yet.   I'll give it another shot tonight. 

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thanks, i guess it helps that i install those things all the time for dealerships. still never had to install one with a battery though thats a new one for me. but they are very much like a home alarm which has small 12v batteries inside the alarm panel, i used to install those for a year or so too.

if you are hell bent on finding a constant 12v source behind the glove box you probably can find one at or near the A/C unit. or maybe in the passenger kick panel. if you have an interior fuse box on that side there should be there too.

remember to test any wire you tap onto first and test it with the key on in every position to make sure it never loses power. same goes if you end up tapping onto the A/C, test it with the a/c on and off.

any wire you tap should be around 14 to 16 gauge

STAY AWAY FROM BRIGHT YELLOW PLUGS. dont unplug them and dont test them.

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