Measuring the meter

S

Stumpy

Guest
I've got an old car that sees sporadic use from a new(learning) driver.
After sitting unused for ~3 weeks it had a low battery, but charged right up
overnight. I want to leave a 9-15v horizontal panel meter dangling from the
12v cigarette lighter outlet in order to monitor battery health. Problem is
that the outlet is unswitched, meter is deflected even when the ignition is
off.

Can anyone point me to a procedure for measuring or calculating the current
drain from the meter?

The meter says CK-250A, Taiwan and it is very small made from clear plastic.
Looks like it was manufactured for inclusion into a 12v battery charger. I
bought it at an old industrial liquidator outlet - now closed.

TIA
 
Stumpy used his keyboard to write :
I've got an old car that sees sporadic use from a new(learning) driver. After
sitting unused for ~3 weeks it had a low battery, but charged right up
overnight. I want to leave a 9-15v horizontal panel meter dangling from the
12v cigarette lighter outlet in order to monitor battery health. Problem is
that the outlet is unswitched, meter is deflected even when the ignition is
off.

Can anyone point me to a procedure for measuring or calculating the current
drain from the meter?

The meter says CK-250A, Taiwan and it is very small made from clear plastic.
Looks like it was manufactured for inclusion into a 12v battery charger. I
bought it at an old industrial liquidator outlet - now closed.

TIA
Click to expand...
How about putting a potentiometer in series with the meter +.
Adjust the potentiometer until the meter voltage reads half of what it
read without the potentiometer the remove the test circuit and measere
the potentiometer resistance. Calculate from there.
 
On Mon, 5 Dec 2011 15:48:22 -0800, "Stumpy" <perilmung@spamnet.corn>
wrote:

I've got an old car that sees sporadic use from a new(learning) driver.
After sitting unused for ~3 weeks it had a low battery, but charged right up
overnight. I want to leave a 9-15v horizontal panel meter dangling from the
12v cigarette lighter outlet in order to monitor battery health. Problem is
that the outlet is unswitched, meter is deflected even when the ignition is
off.

Can anyone point me to a procedure for measuring or calculating the current
drain from the meter?

The meter says CK-250A, Taiwan and it is very small made from clear plastic.
Looks like it was manufactured for inclusion into a 12v battery charger. I
bought it at an old industrial liquidator outlet - now closed.

TIA
Click to expand...
Check the meter with an ohmmeter.

John
 
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +.
Adjust the potentiometer until the meter voltage reads half of what it
read without the potentiometer the remove the test circuit and measere
the potentiometer resistance. Calculate from there.
Click to expand...
If you can read the resistance of a potentiometer, you most likely have a
multimeter which, being multi, has modes for measuring voltage and current.

Just put /that/ in series with the device, and flip it to current measuring
mode to obtain the current drain directly.
 
"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205165432.291@kylheku.com...
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +.
Adjust the potentiometer until the meter voltage reads half of what it
read without the potentiometer the remove the test circuit and measere
the potentiometer resistance. Calculate from there.

If you can read the resistance of a potentiometer, you most likely have a
multimeter which, being multi, has modes for measuring voltage and
current.

Just put /that/ in series with the device, and flip it to current
measuring
mode to obtain the current drain directly.
Click to expand...
I do have a multimeter but thought maybe that the multimeter itself would
change the circuit. The original meter may be "dynamic" and have varying
resistance as the needle is deflected.

I'll put a multimeter in during daylight hours.
 
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:63qqd7lc9vou578lfhvrt3gsv9sm2iau4v@4ax.com...
On Mon, 5 Dec 2011 15:48:22 -0800, "Stumpy" <perilmung@spamnet.corn
wrote:

I've got an old car that sees sporadic use from a new(learning) driver.
After sitting unused for ~3 weeks it had a low battery, but charged right
up
overnight. I want to leave a 9-15v horizontal panel meter dangling from
the
12v cigarette lighter outlet in order to monitor battery health. Problem
is
that the outlet is unswitched, meter is deflected even when the ignition
is
off.

Can anyone point me to a procedure for measuring or calculating the
current
drain from the meter?

The meter says CK-250A, Taiwan and it is very small made from clear
plastic.
Looks like it was manufactured for inclusion into a 12v battery charger.
I
bought it at an old industrial liquidator outlet - now closed.

TIA


Check the meter with an ohmmeter.

John
Click to expand...
Shows 4.43Meg ohms! But that is with the needle at zero/9v
 
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:63qqd7lc9vou578lfhvrt3gsv9sm2iau4v@4ax.com...
On Mon, 5 Dec 2011 15:48:22 -0800, "Stumpy" <perilmung@spamnet.corn
wrote:

I've got an old car that sees sporadic use from a new(learning) driver.
After sitting unused for ~3 weeks it had a low battery, but charged right
up
overnight. I want to leave a 9-15v horizontal panel meter dangling from
the
12v cigarette lighter outlet in order to monitor battery health. Problem
is
that the outlet is unswitched, meter is deflected even when the ignition
is
off.

Can anyone point me to a procedure for measuring or calculating the
current
drain from the meter?

The meter says CK-250A, Taiwan and it is very small made from clear
plastic.
Looks like it was manufactured for inclusion into a 12v battery charger.
I
bought it at an old industrial liquidator outlet - now closed.

TIA


Check the meter with an ohmmeter.

John
Click to expand...
Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with the
leads reversed it is "open" "O.L Mohms".
 
On Mon, 05 Dec 2011 18:01:26 -0800, Stumpy wrote:

"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205165432.291@kylheku.com...
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +. Adjust
the potentiometer until the meter voltage reads half of what it read
without the potentiometer the remove the test circuit and measere the
potentiometer resistance. Calculate from there.

If you can read the resistance of a potentiometer, you most likely have
a multimeter which, being multi, has modes for measuring voltage and
current.

Just put /that/ in series with the device, and flip it to current
measuring
mode to obtain the current drain directly.

I do have a multimeter but thought maybe that the multimeter itself
would change the circuit. The original meter may be "dynamic" and have
varying resistance as the needle is deflected.

I'll put a multimeter in during daylight hours.
Click to expand...
I don't think that a multimeter so profoundly cheap as to make the
measurement invalid exists.

Is the multimeter a light bulb, with a little card that equates filament
color with current? No? Then it's good enough.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
 
"Tim Wescott" <tim@seemywebsite.com> wrote in message
news:Moednf1ma5HX4EDTnZ2dnUVZ_qidnZ2d@web-ster.com...
On Mon, 05 Dec 2011 18:01:26 -0800, Stumpy wrote:

"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205165432.291@kylheku.com...
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +. Adjust
the potentiometer until the meter voltage reads half of what it read
without the potentiometer the remove the test circuit and measere the
potentiometer resistance. Calculate from there.

If you can read the resistance of a potentiometer, you most likely have
a multimeter which, being multi, has modes for measuring voltage and
current.

Just put /that/ in series with the device, and flip it to current
measuring
mode to obtain the current drain directly.

I do have a multimeter but thought maybe that the multimeter itself
would change the circuit. The original meter may be "dynamic" and have
varying resistance as the needle is deflected.

I'll put a multimeter in during daylight hours.

I don't think that a multimeter so profoundly cheap as to make the
measurement invalid exists.

Is the multimeter a light bulb, with a little card that equates filament
color with current? No? Then it's good enough.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Click to expand...
I did a test with an old battery in the garage. 6.8mA and the multimeter
didn't seem to effect the reading on the original meter.

So I guess that answers my question. Now I just need to decide if that is
too high a value to leave it connected to a battery that may only get
charged up once a week.
 
"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with the
leads reversed it is "open" "O.L Mohms".
Click to expand...
** The meter has a 9.1 volt zener diode inside it - that is how it reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



.... Phil
 
"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:9k5i16FotfU1@mid.individual.net...
"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with the
leads reversed it is "open" "O.L Mohms".

** The meter has a 9.1 volt zener diode inside it - that is how it reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



... Phil
Click to expand...
Thanks, I agree. The original equipment battery was 80AH so
80AH/.0068A=11,765 hours=490days=13.6years

I'll leave the thing in forever.
 
On 2011-12-06, Stumpy <perilmung@spamnet.corn> wrote:
"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205165432.291@kylheku.com...
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +.
Adjust the potentiometer until the meter voltage reads half of what it
read without the potentiometer the remove the test circuit and measere
the potentiometer resistance. Calculate from there.

If you can read the resistance of a potentiometer, you most likely have a
multimeter which, being multi, has modes for measuring voltage and
current.

Just put /that/ in series with the device, and flip it to current
measuring
mode to obtain the current drain directly.

I do have a multimeter but thought maybe that the multimeter itself would
change the circuit. The original meter may be "dynamic" and have varying
resistance as the needle is deflected.
Click to expand...
For measuring current, a multimeter should have a low resistance. (We're
talking, some current sensing resistor having a small fraction of an ohm.)

Your battery meter is hopefully a voltage device with a reasonably high
resistance, against which that of the meter should be negligible.
 
On 12/5/2011 10:05 PM, Stumpy wrote:
"Phil Allison"<phil_a@tpg.com.au> wrote in message
news:9k5i16FotfU1@mid.individual.net...

"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with the
leads reversed it is "open" "O.L Mohms".

** The meter has a 9.1 volt zener diode inside it - that is how it reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



... Phil


Thanks, I agree. The original equipment battery was 80AH so
80AH/.0068A=11,765 hours=490days=13.6years

I'll leave the thing in forever.
Click to expand...
Now that you have a meter on the battery, how low do expect to let
the voltage get before you start the motor and let it run a while?

Why not just start the car once a week.

Mikek
 
"amdx" <amdx@knologynotthis.net> wrote in message
news:f3f12$4ede0efe$18ec6dd7$19983@KNOLOGY.NET...
On 12/5/2011 10:05 PM, Stumpy wrote:
"Phil Allison"<phil_a@tpg.com.au> wrote in message
news:9k5i16FotfU1@mid.individual.net...

"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with
the
leads reversed it is "open" "O.L Mohms".

** The meter has a 9.1 volt zener diode inside it - that is how it
reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



... Phil


Thanks, I agree. The original equipment battery was 80AH so
80AH/.0068A=11,765 hours=490days=13.6years

I'll leave the thing in forever.

Now that you have a meter on the battery, how low do expect to let
the voltage get before you start the motor and let it run a while?

Why not just start the car once a week.

Mikek
Click to expand...
Of course, but technically its not my car. I'm just the responsible adult.
 
On Tue, 6 Dec 2011 07:50:39 -0800, "Stumpy" <perilmung@spamnet.con>
wrote:

"amdx" <amdx@knologynotthis.net> wrote in message
news:f3f12$4ede0efe$18ec6dd7$19983@KNOLOGY.NET...
On 12/5/2011 10:05 PM, Stumpy wrote:
"Phil Allison"<phil_a@tpg.com.au> wrote in message
news:9k5i16FotfU1@mid.individual.net...

"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with
the
leads reversed it is "open" "O.L Mohms".

** The meter has a 9.1 volt zener diode inside it - that is how it
reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



... Phil


Thanks, I agree. The original equipment battery was 80AH so
80AH/.0068A=11,765 hours=490days=13.6years

I'll leave the thing in forever.

Now that you have a meter on the battery, how low do expect to let
the voltage get before you start the motor and let it run a while?

Why not just start the car once a week.

Mikek



Of course, but technically its not my car. I'm just the responsible adult.
Click to expand...
So be responsible and start the car.
BTW the battery can get quite low in starting capacity and still read
nearly 12 volts.
 
On Tue, 6 Dec 2011 07:50:39 -0800 "Stumpy" <perilmung@spamnet.con> wrote
in Message id: <46OdnbHV-dFRpEPTnZ2dnUVZ_sGdnZ2d@earthlink.com>:

"amdx" <amdx@knologynotthis.net> wrote in message
news:f3f12$4ede0efe$18ec6dd7$19983@KNOLOGY.NET...
On 12/5/2011 10:05 PM, Stumpy wrote:
"Phil Allison"<phil_a@tpg.com.au> wrote in message
news:9k5i16FotfU1@mid.individual.net...

"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with
the
leads reversed it is "open" "O.L Mohms".

** The meter has a 9.1 volt zener diode inside it - that is how it
reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



... Phil


Thanks, I agree. The original equipment battery was 80AH so
80AH/.0068A=11,765 hours=490days=13.6years

I'll leave the thing in forever.

Now that you have a meter on the battery, how low do expect to let
the voltage get before you start the motor and let it run a while?

Why not just start the car once a week.

Mikek



Of course, but technically its not my car. I'm just the responsible adult.
Click to expand...
IIRC they do make a cutoff switch that will mount under a hood that
connects to the + terminal of the battery. Haven't seen one in ages, but
I'm almost sure you can still buy them.
 
"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205211858.963@kylheku.com...
On 2011-12-06, Stumpy <perilmung@spamnet.corn> wrote:

"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205165432.291@kylheku.com...
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +.
Adjust the potentiometer until the meter voltage reads half of what it
read without the potentiometer the remove the test circuit and measere
the potentiometer resistance. Calculate from there.

If you can read the resistance of a potentiometer, you most likely have
a
multimeter which, being multi, has modes for measuring voltage and
current.

Just put /that/ in series with the device, and flip it to current
measuring
mode to obtain the current drain directly.

I do have a multimeter but thought maybe that the multimeter itself would
change the circuit. The original meter may be "dynamic" and have varying
resistance as the needle is deflected.

For measuring current, a multimeter should have a low resistance. (We're
talking, some current sensing resistor having a small fraction of an ohm.)

Your battery meter is hopefully a voltage device with a reasonably high
resistance, against which that of the meter should be negligible.
Click to expand...
I'm pretty much done worrying about this, but, it occurred to me that my
numbers don't add up.

I = E/R = 12v/4,430,000ohms = 2.7mA

vs. a measured 6.8mA

I can live with such a minor discrepancy. Also negligible.
 
"JW" wrote in message news:jvgsd7hu95dahl8gmr2hk5olqs68j8opc8@4ax.com...

IIRC they do make a cutoff switch that will mount under a hood that
connects to the + terminal of the battery. Haven't seen one in ages,
but I'm almost sure you can still buy them.
Click to expand...
http://www.harborfreight.com/battery-disconnect-switch-97853.html

http://www.harborfreight.com/15-watt-solar-battery-charger-44768.html

I have an old lawn tractor and a few years ago I replaced the original
lead-acid battery with a SLA battery I bought cheap at a HamFest, probably
10 years ago. I think it has a 2000 date code. About a year ago I decided to
see if it still held a charge, and it had enough to light the ignition lamp.
Then I forgot about it until a few days ago, and I was sure it must be dead,
but it still lit the lamp, after more than two years sitting outside. It's
probably too weak to turn the starter, though.

OTOH, I have a 1989 Toyota pickup truck that I use only occasionally, and
after a few months the battery has gone flat. I have been able to start it
by using a booster. In August I tried to start it, and using the booster it
started to run, but would not maintain an idle. I used the diagnostic code
to find it was a problem with the throttle position sensor, but it checked
OK with an ohmmeter. I slapped it a few times with a screwdriver and then it
was OK.

But I put the battery on charge for a couple of months, and when I went to
start the truck, it was dead. So I had to use the booster.

A year ago I had driven my car to Harrisburg, parked it for a few hours, and
when I returned the battery was totally dead. I got a jump start and it ran
for a while, but as soon as I touched the brake, the brake light load was
enough to kill the engine. The battery had been working fine up until then,
with no sign of a problem. So batteries are really difficult to evaluate.
Maybe a load test would work, but the ultimate load test is starting the
car, which I did, and six hours later it was dead.

It's really best to start a car once every week or two, and let it run long
enough to get up to temperature. And it's also good to actually drive it. My
truck's brakes froze up after a long time of sitting.

Paul
 
"JW" <none@dev.null> wrote in message
news:jvgsd7hu95dahl8gmr2hk5olqs68j8opc8@4ax.com...
On Tue, 6 Dec 2011 07:50:39 -0800 "Stumpy" <perilmung@spamnet.con> wrote
in Message id: <46OdnbHV-dFRpEPTnZ2dnUVZ_sGdnZ2d@earthlink.com>:


"amdx" <amdx@knologynotthis.net> wrote in message
news:f3f12$4ede0efe$18ec6dd7$19983@KNOLOGY.NET...
On 12/5/2011 10:05 PM, Stumpy wrote:
"Phil Allison"<phil_a@tpg.com.au> wrote in message
news:9k5i16FotfU1@mid.individual.net...

"Stumpy"

Oddly, with the black lead of the multimeter on the + terminal of the
original meter(and red on negative terminal) it is 4.4Mohms but with
the
leads reversed it is "open" "O.L Mohms".

** The meter has a 9.1 volt zener diode inside it - that is how it
reads
only from 9 volts and up.

The current draw is gonna be tiny and nothing to be concerned about.



... Phil


Thanks, I agree. The original equipment battery was 80AH so
80AH/.0068A=11,765 hours=490days=13.6years

I'll leave the thing in forever.

Now that you have a meter on the battery, how low do expect to let
the voltage get before you start the motor and let it run a while?

Why not just start the car once a week.

Mikek



Of course, but technically its not my car. I'm just the responsible
adult.


IIRC they do make a cutoff switch that will mount under a hood that
connects to the + terminal of the battery. Haven't seen one in ages, but
I'm almost sure you can still buy them.
Click to expand...
A good idea, but, It's a Ford Focus - has some computer generated "tuning"
type settings so they don't recommend leaving the battery disconnected.
Would have the car relearn settings every time its reactivated. This
problem will probably go away as soon as the learning permit becomes a
license.
 
On Mon, 05 Dec 2011 18:39:28 -0800, Stumpy wrote:

"Tim Wescott" <tim@seemywebsite.com> wrote in message
news:Moednf1ma5HX4EDTnZ2dnUVZ_qidnZ2d@web-ster.com...
On Mon, 05 Dec 2011 18:01:26 -0800, Stumpy wrote:

"Kaz Kylheku" <kaz@kylheku.com> wrote in message
news:20111205165432.291@kylheku.com...
On 2011-12-06, BeeJ <nospam@spamnot.com> wrote:
How about putting a potentiometer in series with the meter +. Adjust
the potentiometer until the meter voltage reads half of what it read
without the potentiometer the remove the test circuit and measere
the potentiometer resistance. Calculate from there.

If you can read the resistance of a potentiometer, you most likely
have a multimeter which, being multi, has modes for measuring voltage
and current.

Just put /that/ in series with the device, and flip it to current
measuring
mode to obtain the current drain directly.

I do have a multimeter but thought maybe that the multimeter itself
would change the circuit. The original meter may be "dynamic" and
have varying resistance as the needle is deflected.

I'll put a multimeter in during daylight hours.

I don't think that a multimeter so profoundly cheap as to make the
measurement invalid exists.

Is the multimeter a light bulb, with a little card that equates
filament color with current? No? Then it's good enough.

--
My liberal friends think I'm a conservative kook. My conservative
friends think I'm a liberal kook. Why am I not happy that they have
found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

I did a test with an old battery in the garage. 6.8mA and the
multimeter didn't seem to effect the reading on the original meter.

So I guess that answers my question. Now I just need to decide if that
is too high a value to leave it connected to a battery that may only get
charged up once a week.
Click to expand...
I don't know what the capacity of a car battery is in amp-hours, other
than "lots". 10mA for a week is less than two amp-hours. Unless my head
is screwed on backwards your battery capacity is way more than that.

Why not just unplug it when you're not looking at it?

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
 
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