gauge or use of an ohmeter

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gauge or use of an ohmeter

Postby gene so » Sun Feb 14, 2016 5:17 pm

Hello Teardroppers,

I have been aided so much with regard to the electrical challenges facing me in the construction of my camping trailer. Part of the problem is the simple fact I have not done any of this, from a camping standpoint; nor do I know anybody in this remote area of the Rockies who does this sort of thing. There will be a get-to-gether in August in NM and I shall be towing down my trailer in its present construction condition, and listen to others.

In the meantime I have been urged to get a special gauge that registers the remaining juice in my 12v battery. Discovered on the shelves of the garage on the property we have purchased is an ohmeter. Couldn't this device simply be used to test the battery, since it would be stored in the tool section of my storage box, where the battery itself would reside?

Since the digital gauge used for the testing is $200.00+, I must admit I would rather spend that same money for upgrading the interior of the trailer.

I am wide open for any insights in this matter.

Thank you in advance,

Gene So
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Re: gauge or use of an ohmeter

Postby GuitarPhotog » Sun Feb 14, 2016 6:09 pm

First a battery condition gauge should not cost more than $25 or so. Second, an ohmmeter is not the right instrument to measure voltage.

Either buy a battery condition monitor from an RV supply, or get a cheap Voltmeter from the local hardware/electrical supply store and use a battery condition chart to determine your battery condition.

Here's a nice digital meter for $20
http://www.powerwerx.com/batteries-char ... gQodvd0N5Q

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Re: gauge or use of an ohmeter

Postby halfdome, Danny » Sun Feb 14, 2016 6:44 pm

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I just plug in one of these in one of the 12 volt female plugs I install in the teardrop.
Cheap and easy solution.
Available at Walmart for under 15 bucks.
:D Danny
Last edited by halfdome, Danny on Mon Feb 15, 2016 2:01 pm, edited 1 time in total.
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Re: gauge or use of an ohmeter

Postby Shadow Catcher » Sun Feb 14, 2016 7:37 pm

A volt meter is only accurate after a period of inaction of no current going in or coming out, my memory is something like four hours. A battery monitor reads all the current going into the battery and coming out. Trimetric and Victron battery monitors will tell you accurately, I have my Victron set to read SOC (state of charge) most of the time. The reason I went with a battery monitor is to keep us above the 50% magic number on an expensive 150AH AGM battery.
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Re: gauge or use of an ohmeter

Postby Trevor57 » Sun Feb 14, 2016 9:41 pm

http://www.amazon.com/gp/product/B00MIF ... ge_o03_s00. I bought this one for my ct project coming up. I got decent reviews, and seems to be what I am looking for. I had one in my old trailer called "watts up?" Still available on amazon, but for more than twice the cost.
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Re: gauge or use of an ohmeter

Postby GuitarPhotog » Sun Feb 14, 2016 10:31 pm

Trevor57 wrote:http://www.amazon.com/gp/product/B00MIFF26W?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00. I bought this one for my ct project coming up. I got decent reviews, and seems to be what I am looking for. I had one in my old trailer called "watts up?" Still available on amazon, but for more than twice the cost.


Less than $20 is a deal. I would go for this one.

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Re: gauge or use of an ohmeter

Postby capnTelescope » Mon Feb 15, 2016 1:14 pm

Not to be a wet blanket, but ...

Based on this excerpt from the G.T. Power RC data sheet:
G.T. Power RC.jpg
G.T. Power RC.jpg (105.75 KiB) Viewed 1503 times

I don't think this monitor will give a continuous charge/discharge indication of battery state of charge. Look at the second example in the illustration. This shows the monitor hooked up for charging, with the battery as load. As shown, it will show the amount of charge added during charging. To show the amount of battery amp-hours used, see the other 3 illustrations, where the battery is connected to the source connection.

In other words, the power monitor can show how much power is used from or added to the battery since the last time the monitor was connected, but not both nor the net state of charge.

Being the power monitor is for RC models, it's probably not intended for on-board use. I'd go for a simple volt meter.
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Re: gauge or use of an ohmeter

Postby Trevor57 » Mon Feb 15, 2016 10:23 pm

capnTelescope wrote:Not to be a wet blanket, but ...

Based on this excerpt from the G.T. Power RC data sheet:
G.T. Power RC.jpg

I don't think this monitor will give a continuous charge/discharge indication of battery state of charge. Look at the second example in the illustration. This shows the monitor hooked up for charging, with the battery as load. As shown, it will show the amount of charge added during charging. To show the amount of battery amp-hours used, see the other 3 illustrations, where the battery is connected to the source connection.

In other words, the power monitor can show how much power is used from or added to the battery since the last time the monitor was connected, but not both nor the net state of charge.

Being the power monitor is for RC models, it's probably not intended for on-board use. I'd go for a simple volt meter.


This unit IS a volt meter.
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Re: gauge or use of an ohmeter

Postby tony.latham » Tue Feb 16, 2016 12:39 am

I use the G.T. Powermeter and think it's great. If I recall, it'll handle 60 amps, way more than I need. (But don't quote me on the amps.)

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Yes, it doesn't tell how much power my solar panels have produced, but it tells me how many amps I've used on any given trip. (You need to wire in a switch to reset it.) Plus it tells me the condition based on volts. (Yes, I let it "settle" before I look at the volts.)



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Re: gauge or use of an ohmeter

Postby noseoil » Tue Feb 16, 2016 11:33 pm

I use the small DC voltmeters from online stores like ebay or amazon. They cost $5-$6 & work just fine. All you really need is a voltmeter & a chart showing what voltage is the level of charge you have.
http://www.ebay.com/itm/like/1314895250 ... ps&lpid=82

Scroll down on this page & look at Don's list of stuff on state of charge. He has more information than you need, but a simple gauge will tell you what you need to know.
http://countryplans.com/smf/index.php?topic=11469.0
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Re: gauge or use of an ohmeter

Postby Socal Tom » Tue Feb 23, 2016 8:44 am

So the question to ask is what is the value to you for the fancy tool?
If the voltage is low, you will charge the battery,whether a voltmeter says so,or a Fancy gauge. The voltmeter may read a little low under a load, but as long as it isn't a big load, it probably won't change your decision ( a good contact with the battery ( larger wires) helps here. If the voltmeter says voltage is above what the charts say (12.2v for me), then you sleep happy. How does the fancy gauge change your decisions?
Tom
Ps. I use he same thing as Danny
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Re: gauge or use of an ohmeter

Postby daveesl77 » Tue Feb 23, 2016 9:16 am

HF gives away their cheap VOM several times a year with the free coupon thing. I originally used one of those that I modified in my truck camper. Has an on/off switch and is pretty accurate. However, I have found it much easier just to use the cheap plug in device that Danny uses. It is accurate, portable and just works.

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Re: gauge or use of an ohmeter

Postby Redneck Teepee » Tue Feb 23, 2016 11:00 am

http://thumbs.ebaystatic.com/images/g/Q ... s-l225.jpg

Like Danny I just use the plug in type. Mine has two USB charging ports built into it. :D

Amazon has these for about $10 bucks or so........very inexpensive.
I fear the day that technology will surpass our human interaction, the world will have a generation of idiot's.
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Re: gauge or use of an ohmeter

Postby noseoil » Tue Feb 23, 2016 11:07 pm

There's a 12 volt gauge in the cabin near the entertainment center (with a switch if I don't want the light on at night) & one in the galley. As cheap and small as they are, it's easy to put one where you need it for convenience.

Here's the cabin at the footboard, mounted in the electrical chase.

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This is in the galley.

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This past weekend we "camped out" in the back yard on Saturday night, listened to the stereo, watched a movie & ran the fan at the 10% setting all night for sleeping. This took the battery from 12.7 volts to 12.6 volts.

As soon as the sun came up Sunday morning, the system started charging again & we had full charge back in very little time. Nice to be able to see what's going on inside & outside if we want. The gauges are left running all the time, but there's no appreciable drain.
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