I have a 2011 Rav4, a couple of months ago I noticed I had a hard time getting one of my chargers to work. I thought it was the charger itself, so I bought a new one, that did the same thing, so I thought that maybe it was the weight of two usb cords plugged into the dual charger, then the single started doing it. Then one day I noticed a burning smell and realized it was coming from the outlet, I thought it was the charger, but when I put another charger in the next day it did the same thing. Now I can only get either of my chargers to work for a few minutes. It’s still under warranty, so I’m sure I could take it in, and will do before the next long trip, but I’m just not sure what’s going on, any ideas?
You may want to measure the voltage coming out of the outlet. Get a cheap multimeter from Harbor Freight, learn how to read DC volts using its instructions and measure across the car’s battery. It really shouldn’t be appreciably higher than 14.4 volts or so.
For things to heat up, that voltage must be a lot higher than normal. That could do damage to other things in that car. I’d get that checked soon, just in case.
Current (amps) causes things to heat up. Not voltage. So you want to check the current draw on that circuit.
Tester
On those USB devices, it is the voltage drop from 14 to 5V that will heat them up as USB is 5 volts. Internally those bricks they use a regulator that basically has to dissipate 9 volts at whatever current that’s drawn - that’s under normal conditions. They will heat up some. If a device draws 0.5 amps, you have to dissipate that drop (9V)x current (0.5A) =4.5W which basically shows itself in heat. One would assume they can deal with that kind of dissipation by design.
If that input voltage is a lot higher, it would need to dissipate a lot more power - something they may not be designed to deal with as cars are usually 14.5V or so. Those little bricks can only dump so much heat. Any more, they can thermally run away and get hot like a two dollar pistol.
One would assume the phone (or whatever device) that’s plugged in works elsewhere without heating up the charger so the device is likely okay.
Assuming the chargers are operating by design, I’d first check the input voltage.
or maybe try those chargers in another car to get a feeling for what is normal.
The center contact of the socket may be corroded. If the charger’s plug didn’t make good contact, there could have been an arcing that damaged the contact. After pulling the fuse for the circuit which powers the socket, you may be able to spray it with some contact cleaner and then with a small blade of a pen knife, scrape the corrosion off the center contact.
@RemcoW - just curious, have you opened one up and verified they are using a linear supply? USB devices typically negotiate with the hub (master) for current. IIRC, you can stub out this feature for “dumb” supplies and draw the max. But USB devices can draw many amps where available. Using a linear supply would be wasteful and problematic dealing with waste heat. Switching supplies are more common and don’t have the heat dissipation issue as I am sure you are familiar with. Just was curious if you have ever had occassion to pry one open and see.
I agree with your diagnosis approach- the first thing to check is the bus voltage at the socket, especially if multiple chargers are doing the same thing…
@TwinTurbo – The generic ones I have are simple linear supplies - well, the two that broke on me. They are the cheap $3 ebay type that look like a power plug with a female USB connector on it. You can basically just plug your USB cable into it.
It seemed to have a simple dropping resistor and something that looked like an LM317. The two data lines weren’t hooked up to anything and those lines are normally used to negotiate power, per the USB spec.
The generic ones absolutely refuse to work with one of our droids so it must require some sort of smarts to be present, like you said. They are not all created equal, that’s for sure.
The ‘wall wart’ variety seem to be switching supplies, just judging by the 80-240VAC range and the small size. Not sure whether they have smarts in them, tho: they are more robust so haven’t broken on me yet to crack them open. 
Offhand, it sounds like the outlet is being overloaded. An automobile warranty is for factory defects in material or workmanship so if problems have developed because of devices you’ve added on then the warranty is not valid on that.
The power outlet should be protected by a fuse. Overloading to the extent of causing smoke should have caused the fuse to pop.
I think the first thing I’d do is open up the console and check the wiring and connections for evidence of heat damage. Consider the power outlet to be unsafe until you do this. I’d then want to verify that the fuse is correct and in good shape. I’d also want to search for any TSBs on the issue. An overheating power port is a serious hazard, and others may have experienced the same problem.
Testing the voltage at the port as well as the current draw from the converter are both okay, however I’m inclined to still want to know why the circuit allowed enough current to cause smoke.
Could be that someone spilled some kind of liquid into the power port. almost anything plugged into the port is going to generate some heat, maybe enough to cause whatever is in there to start smoking.
Best way to clean it is with a #2 pencil eraser. Use a brand new pencil. The eraser is just the right diameter. center it on the center conductor and twist to clean the center contact. You can wipe the side of the outlet barrel with a moist paper towel. You don’t nave to clean all the way to the bottom as the contacts make about half way down.
Hoping the warranty covers it, there may be dome kind of short in the power point itself.
Your trouble may be due to excessive AC ripple voltage coming from the alternator which has some bad diodes inside it. Check the DC voltage across the battery while the engine is running around 1,500 RPM. You should see no more than 15 volts DC. Also check the AC voltage which should be no more than 0.1 volt. If it exceeds that then there are some bad diodes inside the alternator. Make sure that your meter blocks DC while in the AC voltage position so you won’t be confused with the reading. Measure a battery while in the AC function and the reading should show zero volts if it blocks DC voltage.
My answer is going to be a lot more “shade tree layman” than the others.
Start with something simple, like the wire connection to the outlet. Make sure the connection isn’t loose and that it is properly grounded. If everything checks out, then I’d start worrying about things like the alternator, voltage, and amps.
Identify and check the fuse for the power outlet. Is the fuse the proper one (amps)?
These guys may have gotten way too technical without considering it might be something simple. If it gets much more complicated than what I’ve proposed, you might want to farm this out to an electrician.
You might consider having an additional power outlet or two installed so you don’t have multiple devices running from a single outlet.