Cell phone drains power plugged into truck's 12v?

[KidVermicious]

Ok, so this is a weird weird thing and I don't even know where to start. My cell phone (Evo 4G, if it matters) doesn't charge when I plug into 12v from the truck, and I think it actually drains.

I know it's not the battery, because I swapped the battery for a known good one I had in the garage - both of them read 12.5 volts with the truck off and 14.7 when it's running. I've got 14.4 volts at the 12v socket in the dash with the truck running. I know it's not the 12v USB adapter or USB/miniUSB cord, because I've swapped both of those. If I disconnect the battery from the truck and rig up a 12v socket straight to the battery, it charges. If I plug it into the 12v socket in the dash, it actually loses battery faster than when it's not plugged in. I know it's not the phone, because it charges fine in every truck I've plugged it into except my own.

I'm stumped. I don't have adequate electrical diagnostic skills, so I don't know where to go from here - what could cause this, and how can I isolate it with my little $5 Harbor Freight multimeter?

 

[KidVermicious]

I know the truck's electrical can pull power through the 12v socket, because I've seen "battery boosters" that plug into the 12v port and help start a car with a low battery. I think that's what's going on here, but I don't understand how or why or what to do about it.

 

[eddiebx]

When you rig it straight to the battery, are you using two pieces of wire straight from the battery and touching it to the adapter's terminals? or are you directly rigging the cigarette lighter socket to a battery and then plugging the adapter into the socket?

Have you tried poking your finger around in the socket (lol) and cleaning it out some? Maybe there's crud built up and causing conductivity issues...measuring it with a meter might not accurately reflect what voltage the adapter is getting when plugged in because the probe tips are usually a lot sharper and can "pierce" through all the surface crud, if any.

Also does the adapter have a light on it to show you it's on, and if so does it come on when you plug into the socket?

 

[KidVermicious]

When you rig it straight to the battery, are you using two pieces of wire straight from the battery and touching it to the adapter's terminals? or are you directly rigging the cigarette lighter socket to a battery and then plugging the adapter into the socket?

Alligator clips off the battery to the terminals on the back of a Blue Sea 12v/USB plug (http://www.amazon.com/Blue-Sea-Dual...d=1379015180&sr=8-2&keywords=blue+sea+12v+usb) which will eventually be installed in the truck, if I can verify that installing it will fix this trouble.

Have you tried poking your finger around in the socket (lol) and cleaning it out some? Maybe there's crud built up and causing conductivity issues...measuring it with a meter might not accurately reflect what voltage the adapter is getting when plugged in because the probe tips are usually a lot sharper and can "pierce" through all the surface crud, if any.

Yup. Swabbed it out with alcohol, and I don't see any corrosion in there either.

Also does the adapter have a light on it to show you it's on, and if so does it come on when you plug into the socket?

It does, and it does. And for what it's worth, the phone tells me that it's charging.

 

[eddiebx]

Alligator clips off the battery to the terminals on the back of a Blue Sea 12v/USB plug (Amazon.com: Blue Sea Dual USB Charger Socket - 2 USB Ports w/Watertight Cap: Sports & Outdoors) which will eventually be installed in the truck, if I can verify that installing it will fix this trouble.



Yup. Swabbed it out with alcohol, and I don't see any corrosion in there either.



It does, and it does. And for what it's worth, the phone tells me that it's charging.

You know this reminds me of something that happened to me once...I some how ended up with a bad USB cable, my phone would indicate that its charging, but power does not go in at all...this was driving me nuts until I figured out it was the f-in USB cable. I kept swapping chargers and it would work intermittently, I guess maybe when the cable was held in a certain position, it would be making contact?

But my point is it's very possible that a phone can indicate that it's charging, but not actually charge. I have no clue how that's possible though, lol.

Since you cleaned it out and checked all the connections on the OE socket, it sure sounds like you're getting a good connection, so swapping the socket might not do much for you. Just as an experiment, have you thought about diode protecting that cigarette lighter so voltage can only flow one way? This can tell you if there is something trying to "pull" the voltage out of your socket. Keep in mind most off the shelf diodes can't hand much current unless you run a gigantic one, so the socket would only be good for lower power devices such as a phone charger and such.

I am not sure if you understand how diodes work or not, so forgive me if I am stating the obvious, but they basically only allow current to flow in one direction, so you just place it inline in the direction you want the current to flow, and presto you're done.

 

[KidVermicious]

I am not sure if you understand how diodes work or not, so forgive me if I am stating the obvious, but they basically only allow current to flow in one direction, so you just place it inline in the direction you want the current to flow, and presto you're done.

Nope, I appreciate the education. Is that the sort of thing I'd be likely to find at a Radio Shack?

 

[eddiebx]

Nope, I appreciate the education. Is that the sort of thing I'd be likely to find at a Radio Shack?

Check this link out, I think it will make sense once you see diagrams: Blocking Diodes, Isolating Door Triggers and Sensors

Yep you can find them at radio shack, but I am not sure what's the biggest size they carry...basically look for something like this: 3-Amp Diodes : Diodes | RadioShack.com

Or you can get like 10x the amount for a few bucks more here: Amazon.com: Install Bay Diodes 3 Amp 20 Pack- D3: Car Electronics

 

[fourwd1]

The USB adapter you plug into the lighter socket takes the vehicle 12V and converts it to 5V.
That circuitry only works in one direction.
12V--->5V
It can't do 12V<---5V

 

[KidVermicious]

The USB adapter you plug into the lighter socket takes the vehicle 12V and converts it to 5V.
That circuitry only works in one direction.
12V--->5V
It can't do 12V<---5V

Got it, thanks. So maybe it's just kicking up it's power consumption when it thinks it's charging, and that explains the faster drain. Or maybe I'm just making that part up.

 

[nevada]

Ok, so this is a weird weird thing and I don't even know where to start. My cell phone (Evo 4G, if it matters) doesn't charge when I plug into 12v from the truck, and I think it actually drains.

I know it's not the battery, because I swapped the battery for a known good one I had in the garage - both of them read 12.5 volts with the truck off and 14.7 when it's running. I've got 14.4 volts at the 12v socket in the dash with the truck running. I know it's not the 12v USB adapter or USB/miniUSB cord, because I've swapped both of those. If I disconnect the battery from the truck and rig up a 12v socket straight to the battery, it charges. If I plug it into the 12v socket in the dash, it actually loses battery faster than when it's not plugged in. I know it's not the phone, because it charges fine in every truck I've plugged it into except my own.

I'm stumped. I don't have adequate electrical diagnostic skills, so I don't know where to go from here - what could cause this, and how can I isolate it with my little $5 Harbor Freight multimeter?

so that socket is always hot?
the key doesnt have to be on?

 

[KidVermicious]

No, it's the stock wiring on the dash socket.

 

[nevada]

No, it's the stock wiring on the dash socket.

so....

wouldnt having the key on explain why the battery goes down?

 

[KidVermicious]

so....

wouldnt having the key on explain why the battery goes down?

*blink*

The phone battery goes down, when it's plugged into the trucks electrical and "charging". The truck battery is fine.

 

[nevada]

*blink*

The phone battery goes down, when it's plugged into the trucks electrical and "charging". The truck battery is fine.

ahhhh.
hahaha, totally misunderstood the original post.

 

[RAD4Runner]

It does, and it does. And for what it's worth, the phone tells me that it's charging.

KidV, This means ignition is on, of course...
Care to verify that you're getting full voltage at the cigarette lighter socket when USB adapter is plugged in?

Also, how about if you connected cigarette lighter plug to your known-good Blue Sea socket and plug it into the stock lighter socket?

...happened to me once...I some how ended up with a bad USB cable...my phone would indicate that its charging, but power does not go in at all...

IF voltage reading above is good, given the other facts mentioned, it could mean:

• USB adapter you are plugging into cigarette lighter socket is defective (barely putting out enough power), yet phone is not smart enough to know it (still indicates charging), OR
• When inside truck phone gets poor signal, it "searches" and uses more power doing so. This drains battery; reason why when one flies or goes to remote areas where signal is poor , it's best to turn phone off or activate "Airplane mode".

 

[KidVermicious]

Thanks for chiming in, Rad. I have 14.7v at the battery with the truck running, and 14.4v at the 12v socket with the truck running. I'm not sure how to test voltage output at the USB adapter, but it appears to work fine in my wife's truck so I've ruled that out.

Should be I be testing anything besides volts? Ohms Law is black magic to me, but I know that there's more to electricity than voltage.