24v at the cigarette lighter?

[cyborg7]

Hey all. After doing a search on here, I'm assuming that's not how it's meant to be? I used the same setting directly across the battery to check I didn't have it on the wrong setting and got a more normal 13.8v.
I've recently put the centre console back together again so almost certainly something I've cocked up, but I can't fathom how it would make such a high reading.

*just thinking about it now I probably should isolate the trickle charger and retest it, but can't think it's that. Anyone got any clue please?

[djape1977]

that would be one very fast lighter!
disconnect charger, check again, buti don't see how that's even possible

[DieselSpider]

The only thing I can think of, if a trickle charger is hard wired into the system, is that it is in series with the battery instead of parallel to it.

[spider2081]

I agree disconnect the trickle charger and test the voltage with just the cars battery connected.

I believe some trickle chargers out put are pulses of voltage. The pulse width changes so the trickle chargers output current does not exceed the chargers current rating. So the peak pulse value could be 24 volts but for a very short period of time. A digital meter could display that value. The cars battery should filter these pluses to a constant value which would explain why when you measure at the battery you see 13.8 volts. And I would expect you to see about 13 volts anywhere you measure voltage in the cars circuits. With just the battery connected in the car I don't think you will measure more than battery voltage. Course the, God of electrons, is forever reminding me how small my mind is.

Let us know what you find.

[DieselSpider]

I have also seen some boosted voltage to ground when certain balasted lighting devices short internally but that would be a rare comedy of events in an automobile.

[cyborg7]

I've got just got home from work and 1st thing I did was take the trickle charger off and retest it. This time the multimeter gave the same reading as the battery now 13.4v so I guess it's somehow freaking the meter out when it's on. Quite why I didn't think of this at the time I don't know Apologies to all and thanks for the replies!

Just to be safe I've isolated the battery so that when the trickle chargers on it's not sending any power to the car's wiring. Otherwise like you said that would be one turbo-charged cigarette lighter.

[76was124]

Something still confuses me about this ... If the trickle charger was directly in parallel with the battery (at the battery posts) vs. through the cigarette lighter socket), and you read 13.8 volts at the battery, there is no way anywhere else in the electrical system you could read above the 13.8 volts. If this indead is what you see is happening, you might have had a floating connection, meaning the voltmeter leads are intermittent and the display will drift to some full range setting, but the reading would be jumpy, not a stable reading of 24 volts.

If the trickle charger was plugged into the cigaret lighter, then you likely have a bad (higher than normal resistance) ground wire or + wire from the cigarette lighter socket back to the electrical/battery system. Does the cigarette lighter socket work? If not, and you are using that for charging, you probably aren't charging and may want to check for a blown fuse, bad wire etc.

[cyborg7]

OK this is embarrassing... I tried to replicate what I found previously, reconnected the trickle charger in exactly the same way (directly to the battery), went through the same steps, meter in the cigarette lighter, +ive in the socket, -ive on the door hinge, but couldn't get anything other than c.12.8v on the meter.

The only way I was getting anything near the 24v that I was getting before is by having it on the wrong setting as per below:




I think I better get my coat....

[spider2081]

The meter should have a manual explaining the proper settings.

I think the the setting you have it on is for checking small batteries like flashlight and emergency light fixtures. 1.5, 9 & 12 volt sealed batteries.

To measure the voltage in your car you would be in the upper left area of the meter 200mv, 20, 600 settings. So You would select the 20 position to measure voltages greater that 0.2 volts and less than 20 volts.

[DieselSpider]

OK this is embarrassing... I tried to replicate what I found previously, reconnected the trickle charger in exactly the same way (directly to the battery), went through the same steps, meter in the cigarette lighter, +ive in the socket, -ive on the door hinge, but couldn't get anything other than c.12.8v on the meter.

The only way I was getting anything near the 24v that I was getting before is by having it on the wrong setting as per below:




I think I better get my coat....

That is the setting for testing 12 volt batteries with a reading of over 14ma being Ok.

7-10 Measuring Battery
Load resistance 1.5V range: 36Ω 9V range: 360Ω 12V range: 450Ω
7-10-1 1.5V batteries will measure 33mA or more if they are well charged.
7-10-2 9V batteries will measure 18mA or more if they are well charged.
7-10-3 12V batteries will measure 14mA or more if they are well charged.


Here is a link to the users manual:
http://r.search.yahoo.com/_ylt=A0LEV1EY ... NpNasH4eU-

[nalle]

Just for the meters.
Non professional multimeters are sometimes a little bit tricy.
is it a rms or a peak value meter?
Sometimes when battery (in meter) goes bad, it can show any values.

I quite often recommed analog meters for cars, they usually are easier to use and are more reliable.
And they have internal basic load, so you won't get the cat skin/fur (or how you say it in english) electricty so easily.

[76was124]

That's actually a very nice meter you have there from a features standpoint! Proper setting would be the 20V setting, lime green color around the 10-11 o'clock position on the dial selector. The flat dotted/ dashed lines indicates DC voltage ( Vs AC or verses electronic type battery testing that you have selected in your photo)

[cyborg7]

Thanks guys - and particularly for the link to the manual. I long since lost the original, so this is v. useful.

It dawned on me that I'd had it on the wrong setting when I came back to retest it - hence my cringing embarrassment. The meter was less than £10 so seemed a bargain (or it would be if I knew how to use it properly! ). Live and learn and all that.

At least I can now sleep peacefully without dreaming about frying my electrics. Cheers all. Chris