Jay,
I do not think an analog voltmeter will be affected by the cold. I
would check the wires. How far from the battery? There could be a
voltage drop. What size are they? They may need to be bigger to
compensate for distance. Is there corrosion on the terminals? This will
affect the reading. Does the meter have a calibration screw on it? If
it does adjust it so it matches the reading of the digital at the
batteries.

Hope this helps.


Paul


wrote:
I have a situation that I am not sure if the two batteries are having
problem or the on-dashboard voltmeter doesn't work reliably in cold
weather. After I had fully charged the batteries (that were left on
the boat in cold winter like 32-degree), the needle in the on-dashboard
voltmeter would show exactly 12-volt. But after the batteries had sat
there doing nothing for a couple hours later, it showed at something
like 11.5-volt to 11-volt. I am sure that the batteries were not
supposed to have been used because I had turned the battery switch to
OFF. I recharged it anyway. Strangely, after I had recharged the
batteries for less than a minute, the recharger would stop recharging
and indicate that the batteries were fully recharged. I checked the
batteries with a portable mult-meter, and I found that both batteries
were fully charged (with 12.99 volt).

Seem like the batteries are really fully recharged and they are good
because of these facts (1) The recharger had stopped recharging the
batteries and indicated that the batteries were fully charged. (2)
Nothing was using the batteries. (3) The mult-meter also said that the
batteries were fully charged.

I am wondering may be the on-dashboard voltmeter doesn't work that well
in cold weather considering the fact that the on-dashboard is being
left in the cold for a long time. The multmeter still worked well when
I used it in the boat because I brought it out from room temperature,
and it was still warm when I used it to check the batteries.

Is my understanding correct? If my understanding is correct, I will
have to stop using the on-dashboard voltmeter to check the batteries
during winter, and I should use a multmeter instead. If my
understanding is not correct, does this mean that the on-dashboard
voltmeter is no good and it should be replaced?

Thanks for any info in advance.

Jay Chan

I do not think an analog voltmeter will be affected by the cold.

Great to hear this. This means I may not need to replace the voltmeter
on the dashboard, and can save some money. I thought the voltmeter
might be affected by cold temperature because the instruction manual of
the multmeter tells me not to use it when temperature is too cold.

I would check the wires. How far from the battery? There could be a
voltage drop. What size are they? They may need to be bigger to
compensate for distance. Is there corrosion on the terminals? This will
affect the reading.

Honestly, I didn't even think of checking the connection between the
battery and the on-dashboard voltmeter until you guys have pointed this
out. You guys are probably right in saying that the wiring may be
undersized because I recall that most of the wires inside the
batteries/wiring compartment are kind of thin like those light gauge
wires. I will document all the wiring inside the boat when the weather
becomes warm. For now, I will check the voltage in the voltmeter
terminals to see if the voltage is as low as what is being shown in the
voltmeter.

Does the meter have a calibration screw on it? If it does adjust
it so it matches the reading of the digital at the batteries.

Thanks for this tip. I didn't know that there is such a thing in a
voltmeter. I will find out when I get back home.

Jay Chan

Does the meter have a calibration screw on it? If it does adjust
it so it matches the reading of the digital at the batteries.

Thanks for this tip. I didn't know that there is such a thing in a
voltmeter. I will find out when I get back home.

I could not find anything looks like something for calibration in the
voltmeter. Thanks for the tip though.

Jay Chan

I could not find anything looks like something for calibration in the
voltmeter. Thanks for the tip though.

Jay Chan

Jay,
I do not know about the meter you have. But most analog meters
including analog multimeters have a screw at the pivot point of the
needle.

Look at the enlarged picture of the meter.

http://www.go2marine.com/g2m/action/...1&WT.mc_id=fr1

Paul

I could not find anything looks like something for calibration in the
voltmeter. Thanks for the tip though.

I do not know about the meter you have. But most analog meters
including analog multimeters have a screw at the pivot point of the
needle.

Look at the enlarged picture of the meter.

http://www.go2marine.com/g2m/action/...1&WT.mc_id=fr1

That looks like much more sophisticated than the simple analog
voltmeter on the dashboard of my boat. Mine is just a round thing with
a needle and a couple screws at the back with backlight. OK, I will go
looking for some thing similar to the voltmeter in my boat and see if I
can find an instruction manual and a wiring diagram for it.

Thanks for taking the time to find a sample marine voltmeter for me to
take a look.

Jay Chan