Cigarette Lighter output

I have blown up many cell phone chargers and now 2 brand new cell phones using the charger in the cigarette lighter of my XJ. Some time ago I took the Jeep to Sears to hve the battery replaced. In doing their "check" they plugged a black box into the lighter and said that their was no power their. That is not true as the lighter does work. Any thoughts? While I don't smoke, I'd like to be able to use my lighter as a reliable source of power. TIA

Pickup one of those cig lighter adapters from radio shack, the kind with two connectors on it and stick a dvm on it and see what it says..

Hmmm. I wonder if the leads could be reversed and you're getting positive out of the negative side and negative out of the positive side. Like RichP said, a voltmeter should tell you what's going on. If you don't have one you can get a simple, cheap one at Sears or most any hardware store for less than $15. Well worth the investment.

dmillion said:

Hmmm. I wonder if the leads could be reversed and you're getting positive out of the negative side and negative out of the positive side. Like RichP said, a voltmeter should tell you what's going on. If you don't have one you can get a simple, cheap one at Sears or most any hardware store for less than $15. Well worth the investment.

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I had thought of that reversal but was hesitant to mention it, as that could cause a whole bunch of other problems but for the 15 seconds the lighter normally takes might not be obvious. The lighter would could not care less which way the electrons are going and would work either -12v or +12v, I just looked at mine and it's in a plastic housing so it would not ground to the vehicle ground directly. But I image it would play havoc with a cell phone charger not to mention the cell phone and it's smart connector thats for sure after it hosed the charger, man theres audio in and out plus the serial data pins in that plug depending on the phone, not a good thing at all..
I remember a friend of mine back in late 69 that had a triumph TR3, he went thru 3 or 4 Craig am/fm/8 track radios in quick order because the TR was backwards british lucas.

The cigarette lighter should not put out anything more than the alternator is supplying. Generally that's 12 to 14 volts while the engine is running. The center of the cigarette lighter is the positive terminal and the outer part is the negative. There should be an inline fuse to protect the cell charger, as well as a voltage regulator. Most cell phones run on around 3.5 to 5 volts. There is a chance that the polarity is reversed on the cigarette lighter but I would imagine there are diodes in the charger that prevent a reversal of polarity and it simply wouldn't work. You could rig up another cigarette lighter wired directly to the fuse block. I don't know if that would help. I think it would be getting the same voltage as the other providing all the grounds were good.