Using a handheld voltmeter, at the battery on my car, I get
a reading of around 12.5 volts. When I use the same
voltmeter at the cigarette lighter socket and at the
accessory outlet, I get a reading of only around 4.5 volts.
(The latter reading jumps about a volt if the engine is
running.) Why aren't the readings on the cigarette lighter
socket and the accessory outlet pretty much the same as at
the battery? (Both the cigarette lighter socket and the
accessory outlet work just fine to recharge my laptop
computer.)

Enlightenment appreciated.

--
----------
CWLee
Former slayer of dragons; practice now limited to sacred
cows. Believing we should hire for quality, not quotas, and
promote for performance, not preferences.

"CWLee" wrote in message
m...

Using a handheld voltmeter, at the battery on my car, I get a reading of
around 12.5 volts. When I use the same voltmeter at the cigarette lighter
socket and at the accessory outlet, I get a reading of only around 4.5
volts. (The latter reading jumps about a volt if the engine is running.)
Why aren't the readings on the cigarette lighter socket and the accessory
outlet pretty much the same as at the battery? (Both the cigarette
lighter socket and the accessory outlet work just fine to recharge my
laptop computer.)

Enlightenment appreciated.


Assuming the sockets work as you say, you may have a bad connection of your
voltmeter test probes at the point you are trying to measure. The voltage
should jump a volt or two with the motor running as it takes more voltage to
charge the battery than what it is normally.

I have also seen bad connections on the wiring that measured the normal
voltage, but under load the voltage would drop. That is not your case.

Ralph Mowery wrote:
"CWLee" wrote in message
m...
Using a handheld voltmeter, at the battery on my car, I get a reading of
around 12.5 volts. When I use the same voltmeter at the cigarette lighter
socket and at the accessory outlet, I get a reading of only around 4.5
volts. (The latter reading jumps about a volt if the engine is running.)
Why aren't the readings on the cigarette lighter socket and the accessory
outlet pretty much the same as at the battery? (Both the cigarette
lighter socket and the accessory outlet work just fine to recharge my
laptop computer.)

Enlightenment appreciated.


Assuming the sockets work as you say, you may have a bad connection of your
voltmeter test probes at the point you are trying to measure. The voltage
should jump a volt or two with the motor running as it takes more voltage to
charge the battery than what it is normally.

If it's the same with two jacks, it must be the ground. I'll bet if the
OP measured between the point he thought was ground and the negative
terminal of the battery, he would find approximately twice the
resistance of his meter.

When humidity is low, clothing rubbing against car seats can cause
static shocks when a person touches grounded metal. If the car
manufacturer puts some megohms between that metal and ground, touching
it will drain the charge painlessly.

"E Z Peaces" wrote in message
...
When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.

Actually the car metal does not have to be grounded. As the car is a large
mass of metal it will have a differance of potential from the person that
slides across the seat.
PUtting a resistor between the car and ground will do nothing for this
effect.

Years ago some gas trucks would drag a chain to ground the truck. This was
thought to drain off any static charge the truck would have so the gas would
not blow up when the hose was used to transfer the gas. A spark could jump
from the end of the hose to the storage tank.

"E Z Peaces" wrote in message
...


When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.



~10 years ago, when 3M still made the "touch me first" anti-static strips
for computer keyboards, I took one and stuck it to the armrest/door handle
of my car then ran the wire in behind the trim and attached the wire to some
point on the body. It worked great. Wish I could still get them!

On Sep 13, 2:05*pm, "CWLee" wrote:
Using a handheld voltmeter, at the battery on my car, I get
a reading of around 12.5 volts. *When I use the same
voltmeter at the cigarette lighter socket and at the
accessory outlet, I get a reading of only around 4.5 volts.
(The latter reading jumps about a volt if the engine is
running.) *Why aren't the readings on the cigarette lighter
socket and the accessory outlet pretty much the same as at
the battery? *(Both the cigarette lighter socket and the
accessory outlet work just fine to recharge my laptop
computer.)

Enlightenment appreciated.

--
----------
CWLee
Former slayer of dragons; practice now limited to sacred
cows. *Believing we should hire for quality, not quotas, and
promote for performance, not preferences.

You might try scratching the leads against the metal when you take a
reading.

You should be getting at 12 volts.

Ralph Mowery wrote:
"E Z Peaces" wrote in message
...
When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.

Actually the car metal does not have to be grounded. As the car is a large
mass of metal it will have a differance of potential from the person that
slides across the seat.
PUtting a resistor between the car and ground will do nothing for this
effect.

Years ago some gas trucks would drag a chain to ground the truck. This was
thought to drain off any static charge the truck would have so the gas would
not blow up when the hose was used to transfer the gas. A spark could jump
from the end of the hose to the storage tank.



Fuel trucks still use static dissipation devices.
Instead of chains there are conductive straps
that are less likely to cause a spark when dragged
across metal. The straps are used on cars, trucks
and motor cycles. Sometimes the chains you may see
under a truck could be automatic snow chains. It's
some interesting stuff.

http://www.mizter.com/index.htm

http://www.onspot.com/

Check out #9

http://www.wilsonantenna.com/tsswrt.htm

TDD

On Sun, 13 Sep 2009 18:29:02 -0400, "Ralph Mowery"
wrote:


"E Z Peaces" wrote in message
...
When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.

Actually the car metal does not have to be grounded. As the car is a large
mass of metal it will have a differance of potential from the person that
slides across the seat.
PUtting a resistor between the car and ground will do nothing for this
effect.

Not what the guy said. Put a resistor between the metal part you might
touch and the VEHICLE ground, and the likelihood of getting a static
shock can be reduced dramatically.

Years ago some gas trucks would drag a chain to ground the truck. This was
thought to drain off any static charge the truck would have so the gas would
not blow up when the hose was used to transfer the gas. A spark could jump
from the end of the hose to the storage tank.

When fueling aircraft the fuel tug (truck) MUST be grounded to the
plane before the fuel hose gets CLOSE to the plane.

CWLee wrote:

Using a handheld voltmeter, at the battery on my car, I get a reading of
around 12.5 volts. When I use the same voltmeter at the cigarette
lighter socket and at the accessory outlet, I get a reading of only
around 4.5 volts. (The latter reading jumps about a volt if the engine
is running.) Why aren't the readings on the cigarette lighter socket
and the accessory outlet pretty much the same as at the battery? (Both
the cigarette lighter socket and the accessory outlet work just fine to
recharge my laptop computer.)

Enlightenment appreciated.

Hi,
Picked a good grounding spot and pushed center connector inside the
jack? If it is truly 4.5V Nothing plugged in there would work.

In article ,
"Bob M." wrote:

"E Z Peaces" wrote in message
...


When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.



~10 years ago, when 3M still made the "touch me first" anti-static strips
for computer keyboards, I took one and stuck it to the armrest/door handle
of my car then ran the wire in behind the trim and attached the wire to some
point on the body. It worked great. Wish I could still get them!

I don't remember those, but maybe you could make your own personal
discharge device with a piece of self-adhesive copper foil and a
resistor. Or look into the ESD gizmos (wrist straps, etc.) used by
electronic assemblers.

Ralph Mowery wrote:
"E Z Peaces" wrote in message
...
When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.

Actually the car metal does not have to be grounded. As the car is a large
mass of metal it will have a differance of potential from the person that
slides across the seat.
PUtting a resistor between the car and ground will do nothing for this
effect.

Years ago some gas trucks would drag a chain to ground the truck. This was
thought to drain off any static charge the truck would have so the gas would
not blow up when the hose was used to transfer the gas. A spark could jump
from the end of the hose to the storage tank.

Not exactly my field, but I have read that modern car tires have enough
carbon in them to be a ground path. Might be high resistance?


I agree with other that the OP probably does not have a good connection.

--
bud--

On Sep 13, 8:51*pm, The Daring Dufas
wrote:
Ralph Mowery wrote:
"E Z Peaces" wrote in message
...
When humidity is low, clothing rubbing against car seats can cause static
shocks when a person touches grounded metal. *If the car manufacturer puts
some megohms between that metal and ground, touching it will drain the
charge painlessly.

Actually the car metal does not have to be grounded. *As the car is a large
mass of metal it will have a differance of potential from the person that
slides across the seat.
PUtting a resistor between the car and ground will do nothing for this
effect.

Years ago some gas trucks would drag a chain to ground the truck. *This was
thought to drain off any static charge the truck would have so the gas would
not *blow up when the hose was used to transfer the gas. *A spark could jump
from the end of the hose to the storage tank.

Fuel trucks still use static dissipation devices.
Instead of chains there are conductive straps
that are less likely to cause a spark when dragged
across metal. The straps are used on cars, trucks
and motor cycles. Sometimes the chains you may see
under a truck could be automatic snow chains. It's
some interesting stuff.

http://www.mizter.com/index.htm

http://www.onspot.com/

Check out #9

http://www.wilsonantenna.com/tsswrt.htm

TDD

Looking at that automatic tire chain sitting so close to the ground
got me to wondering.

If he ran over a piece of tire debris and knocked it loose, that could
cause some serious damage to his truck.

Andy

The cigarette lighter should be about the same as the battery. This would be
measuring DC volts with the multimeter.

1. Does the ignition switch need to be on for this to work? Also be sure you
are measuring directly to the socket itself and not through any plug-in
device (which could change the voltage).

2. The problem could be with the +12 volts which would be the center of the
socket, or the ground which would be the round metal. Get a long wire or
jumper cable and connect it to the + of the battery, then measure from that
to the ground of the lighter socket (this tests the ground). Then switch the
cable to the ground on the battery and measure from that to the +12 center
connection on the socket (this tests the +12).

If the ground is bad, check the ground connection to the socket.

If the +12 is bad, check the fuse and measure for +12 at the fuse. If +12
good at fuse, but not at socket, then problem with the wire or connectors
between the two.

If the +12 is not good at the fuse (you would probably be having problems
with starting your car in this case), check all main electrical connections
and wires.

How to test automotive fuses...
http://www.dinosaurelectronics.com/Test_Fuse.htm



"CWLee" wrote in message

Using a handheld voltmeter, at the battery on my car, I get a reading of
around 12.5 volts. When I use the same voltmeter at the cigarette lighter
socket and at the accessory outlet, I get a reading of only around 4.5
volts. (The latter reading jumps about a volt if the engine is running.)
Why aren't the readings on the cigarette lighter socket and the accessory
outlet pretty much the same as at the battery? (Both the cigarette
lighter socket and the accessory outlet work just fine to recharge my
laptop computer.)

Enlightenment appreciated.

--
----------
CWLee
Former slayer of dragons; practice now limited to sacred
cows. Believing we should hire for quality, not quotas, and
promote for performance, not preferences.

In article ,
"Bill" wrote:

The cigarette lighter should be about the same as the battery. This would be
measuring DC volts with the multimeter.

1. Does the ignition switch need to be on for this to work? Also be sure you
are measuring directly to the socket itself and not through any plug-in
device (which could change the voltage).

2. The problem could be with the +12 volts which would be the center of the
socket, or the ground which would be the round metal. Get a long wire or
jumper cable and connect it to the + of the battery, then measure from that
to the ground of the lighter socket (this tests the ground). Then switch the
cable to the ground on the battery and measure from that to the +12 center
connection on the socket (this tests the +12).

If the ground is bad, check the ground connection to the socket.

If the +12 is bad, check the fuse and measure for +12 at the fuse. If +12
good at fuse, but not at socket, then problem with the wire or connectors
between the two.

If the +12 is not good at the fuse (you would probably be having problems
with starting your car in this case), check all main electrical connections
and wires.


Yeah, all good ideas to troubleshoot a lighter socket that isn't
working. The OP's lighter sockets are working.

"Smitty Two" wrote

Yeah, all good ideas to troubleshoot a lighter socket that
isn't
working. The OP's lighter sockets are working.

Further update from the OP: I've concluded I was not
pressing the probes from the voltmeter hard enough against
the proper places on the sockets to get a good connection.

I have two vehicles, and the same thing happens on both -
meaning my laptop recharges from both, yet I get readings of
around 4-5 volts at the sockets on both. Both cars start
easily, and readings at the batteries on each are 12-13
volts.

Thanks for all the replied.

Bob M. wrote:
"E Z Peaces" wrote in message
...


When humidity is low, clothing rubbing against car seats can cause
static shocks when a person touches grounded metal. If the car
manufacturer puts some megohms between that metal and ground, touching
it will drain the charge painlessly.



~10 years ago, when 3M still made the "touch me first" anti-static
strips for computer keyboards, I took one and stuck it to the
armrest/door handle of my car then ran the wire in behind the trim and
attached the wire to some point on the body. It worked great. Wish I
could still get them!

Window glass typically has the right amount of resistance to drain
static safely. If you could pick up static at the arm rest and carry it
to a conductor that brushed against the glass, that should work.

Another trick is to wipe an insulating surface, such upholstery or an
arm rest, with a soapy wash cloth. The soap film will allow static to
bleed across the surface to a ground.

Polyurethane soles, which are very common these days, insulate so well
that static can build. If I start getting shocks, I use a soapy cloth
to wipe the edges of my soles. I wish I knew something that wouldn't
wash off the first time I walked on wet grass!

On Tue, 15 Sep 2009 16:49:13 -0400, E Z Peaces
wrote:

Bob M. wrote:
"E Z Peaces" wrote in message
...


When humidity is low, clothing rubbing against car seats can cause
static shocks when a person touches grounded metal. If the car
manufacturer puts some megohms between that metal and ground, touching
it will drain the charge painlessly.



~10 years ago, when 3M still made the "touch me first" anti-static
strips for computer keyboards, I took one and stuck it to the
armrest/door handle of my car then ran the wire in behind the trim and
attached the wire to some point on the body. It worked great. Wish I
could still get them!

Window glass typically has the right amount of resistance to drain
static safely. If you could pick up static at the arm rest and carry it
to a conductor that brushed against the glass, that should work.

Another trick is to wipe an insulating surface, such upholstery or an
arm rest, with a soapy wash cloth. The soap film will allow static to
bleed across the surface to a ground.

Polyurethane soles, which are very common these days, insulate so well
that static can build. If I start getting shocks, I use a soapy cloth
to wipe the edges of my soles. I wish I knew something that wouldn't
wash off the first time I walked on wet grass!


Just hang on to something conductive and grounded to the chassis as
you get out of the car, until your feet are firmly on the ground and
you will never get a static shock getting out.