12V Cooler

[Russ]

Hey Sum... yea we got electricity here. T-Storms in the West can be intense. The forecast is for some serious snow tonight and possible thunder SNOW storms. Yuck!
I installed the solar panel this weekend and will be wiring my new voltmeter/ammeter in a few days when this junk melts. I guess the solar panel won't be working tomorrow.

I got this combo unit on e-Bay. The guy was very professional with his wiring of the thing and it switches between volts and amps with a toggle. One meter, two functions, pretty cool. This also hooks up to the negative side, but I think that was because of the way it was wired. It's no problem because my Mac has all the negative wires going to a central bus so it should be easy to install.

With no load it read .2 amps which I assume is a calibration problem. Still, the Edgestar wasn't pulling much. That's encouraging. The insulation on the cooler is very good and I'm going to add some foam/tray on top to help even more. Looking forward to "dry" food and no ice.


--Russ

[Hamin' X]

What you folks really need, is somethimg like this:



Measures DC power usage over time.

DOC Wattson model R102 digital panel meter

~Rich

[Sumner]

What you folks really need, is somethimg like this:



Measures DC power usage over time.

DOC Wattson model R102 digital panel meter

~Rich

Now why didn't you post that before . That looks like a lot for the money. I'll keep it in mind if my stuff decides to quit working. Are you actually using one? Can you reset the Amp-Hours and kilo Watt-hours or how does that work?

Thanks for posting the link,

Sum

[Russ]

Now why didn't you post that before . That looks like a lot for the money. I'll keep it in mind if my stuff decides to quit working.

+1


--Russ

[Inquisitor]

What you folks really need, is somethimg like this:



Measures DC power usage over time.

DOC Wattson model R102 digital panel meter

~Rich

Sounds perfect...

But I have one question. I assuming that to measure the amps, all the current has to run through it like it does through my volt/amp meter. Is that right? I just read the web site... it handles 100 amps (good enough), but it seems to be running that 100 amps through 14 gage wires! Does that make sense or what am I missing?

[Sumner]

What you folks really need, is somethimg like this:



Measures DC power usage over time.

DOC Wattson model R102 digital panel meter

~Rich

Sounds perfect...

But I have one question. I assuming that to measure the amps, all the current has to run through it like it does through my volt/amp meter. Is that right? I just read the web site... it handles 100 amps (good enough), but it seems to be running that 100 amps through 14 gage wires! Does that make sense or what am I missing?

I'll bet it is like the one I have that has a shunt that hooks to the negative side like Russ mentioned and the current goes through the shunt and not the meter and the meter reads the shunt,

Sum

[Inquisitor]

I just read the Wikipedia definition of shunt. Reading that didn't really help and what I don't understand about electronics is far larger than what I do know. If it was AC and using inductance, I could understand how it could "sense" without actually handling the load. So I'll take it that its a FM, black box that can measure current without actually having to handle that current.

I'm good with that.

[Hamin' X]

No, I do not have one of these meters. I only posted it as an example and I am sure that there are more out there, since this was just a quick google on "DC kwh meter". As far as a shunt goes, it allows most of the power to bypass a meter, but sends a known percentage through the meter.(Not really the way it works, but is representative of the outcome.) Most DC amp meters are made this way. Also remember, that current carrying ability of wire is not only a function of size, but length and composition. This means that 14 gauge wire will handle 100 Amps, if short enough.

A similar device, called a Kill-A-Watt, is made for use at home with AC.



~Rich

[waternwaves]

Shunt in this case is a wire in parallel with the circuit you wish to measure. This smaller line iis in a circuit with known resistance at most operating temps. an extremely sensitive measurement of the change in voltage across this smaller circuit corresponds to a similar change in the larger circuit.

[Russ]

Sounds perfect...

But I have one question. I assuming that to measure the amps, all the current has to run through it like it does through my volt/amp meter. Is that right? I just read the web site... it handles 100 amps (good enough), but it seems to be running that 100 amps through 14 gage wires! Does that make sense or what am I missing?

Interesting because based on the picture I thought the same thing. 14 gauge wire, no way.
Then I found the manual online and it does not mention the use of an external shunt (like my ammeter uses). It mentions "Built-in 0.001 Ohm current shunt." The fine print also says 50 amp continuous which is more reasonable than 100 amps.

So, back to your question: 50 amps over 14 gauge wire? Even as Rich stated, 14 gauge is fine for short runs, I still wouldn't feel comfortable pulling 50 amps continuous over even a short 14 gauge wire.
Now realistically, on our boats there isn't much that's gonna pull 50 amps except maybe a big honkin' inverter so this would probably work fine, but I'd run heavier wire into it.

According to this thread, the Xantrex is the one to use. However at $300 bucks I'm not sure I can justify it.





--Russ

[DaveB]

Hamin,
I use only a digital 12 voltage meter that plugs into a cigerate plug ( $15 or less any RV store) or a cheap $5 Amp and Voltage digital meter.
I don't want anything on all the time that relates to monitor devices, regardless of how low their current may be.
I even use 60 -75 watt inverters that plug into a Cigerate lighter plug as they don't have fans to drain batteries. I do have a larger 300 watt inverter but never use it as the smaller ones run Laptop and all our other needs.
I ck the the battery voltage, morning and night by pluging in the Volt meter into the Cigerate lighter plug, have 4 on board so one can ck another if you see a large voltage change.
I like to keep things simple but practical.
Dave

No, I do not have one of these meters. I only posted it as an example and I am sure that there are more out there, since this was just a quick google on "DC kwh meter". As far as a shunt goes, it allows most of the power to bypass a meter, but sends a known percentage through the meter.(Not really the way it works, but is representative of the outcome.) Most DC amp meters are made this way. Also remember, that current carrying ability of wire is not only a function of size, but length and composition. This means that 14 gauge wire will handle 100 Amps, if short enough.

A similar device, called a Kill-A-Watt, is made for use at home with AC.



~Rich

[Hamin' X]

The point of using a KWH meter is to monitor power usage over time. I would use it on individual devices, such as your cooler, to get a definitive answer of what the actual power consumption will be. Anything else is just WAGing. There would be no need to leave it in line permanently in your case.

~Rich

[DaveB]

Rich,
I agree for testing draw from your battery bank for diffrent times of year and equipment demanding that power. To test for a one unit such as a Refig. one has to do it direct .
This is a interesting subject and I have had a lot of expereance building wind Generators for the Air cooled Adler Barber system than to water cooled in the Carribean.
Back than the Adler Barber system (1982) only had the air system and drawing 3.5 amps running over a hour usage in the Carribean (usually cycled 50 % time as we were in and out Temps always 82-86 degrees, Night 70-72).
I built a Wind Generator on stearn of my Alberg 35 to generate 8 amps DC in 14 knots of wind with a 6 ft. redwood blade in St. Thomas , It powered all elect. needs but Batteries at that time were crap.
How things have changed, wish I was 20 years younger.
Dave

The point of using a KWH meter is to monitor power usage over time. I would use it on individual devices, such as your cooler, to get a definitive answer of what the actual power consumption will be. Anything else is just WAGing. There would be no need to leave it in line permanently in your case.

~Rich

[Hamin' X]

Yeah, I'd like to roll the calendar back about 35 years and still know what I know now. I'll tick over the 60 mark this year, But still having fun.

~Rich

[DaveB]

Rich will do the 60 in October, until than I am over the hill at 50's. Retirement shortly and thats good! more sailing time!
Dave

Yeah, I'd like to roll the calendar back about 35 years and still know what I know now. I'll tick over the 60 mark this year, But still having fun.

~Rich