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fwunder View Drop Down
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Posts: 1676 		Direct Link To This Post Topic: Voltmeter Install
    Posted: 02 Jan 2014 at 4:09pm
This is a good bench project cuz it's looking pretty nasty outside!

I'm going to install a 12v. voltmeter (and maybe amp-meter and 120v. meter). I have a couple of questions you electrical gurus might advise on. The meter(s) will mount in the 4-inch space to the left or right of the Jensen head unit.

Rummaging around the basement I found a nice suitable piece of plastic from a storage box to make a mounting plate for the meter(s). I don't think she'll notice the hole I left. ;) I want to be able to remove the plate and meter(s) as a unit for adjustment and/or replacement. The voltmeter I bought (pictured below) has a potentiometer to fine tune voltage readout if needed.

I haven't mounted the switch (shown) because I haven't decided to use it or just wire it full time. The meter uses a negligible amount of current.  Would you switch it?

Exploring a bit, I found I could run wire pretty easily behind the Jensen head unit down to the panel/converter. Would you run it down or would you simply tap a 12v. line on the Jensen? Intuition tells me it would be better to attach (fused) hot lead to battery side of WFCO panel. Just talking 12v. voltmeter right now, not amp meter (shunt) or 120v.

If you RV'd with meters which did you find the most helpful? I'm thinking the 12v. meter. I carry a multimeter (not a Fluke!) if I want to check shore power and an amp meter would probably not be good for my obsessive compulsive behavior.

Thanks for any feedback. I promise not to be shocked by any response!

fred
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techntrek View Drop Down
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Posts: 9059 		Direct Link To This Post Posted: 02 Jan 2014 at 5:34pm

I would replace the switch with a normally-open push button.  It might not use that much but over time it is a lot.  The example I always give is a standard 4 watt night light.  In just a month it will use almost 3000 watts.  In a year it will use 35,000 watts.

Make the hookup directly to the source.  Use 12 gauge wire, not 16, to prevent a voltage drop.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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fwunder View Drop Down
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Posts: 1676 		Direct Link To This Post Posted: 02 Jan 2014 at 6:28pm
Thanks techntrek. Yeah, the soft switch (not momentary) is what I think I'll use. And going right to the source does make perfect sense. Not sure I understand the need for 12 gauge wire to the gauge though. We're only talking a 17 ma draw @ 14+ volts. How much drop could there be? According to this that's like a 0.0013 volt drop over 6 feet with 18 gauge wire. Just learning here.

fred
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CharlieM View Drop Down
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Posts: 1797 		Direct Link To This Post Posted: 02 Jan 2014 at 7:51pm
I would agree with most of what Techntrek said with the exception of the wire size. Connecting close to the battery is highly advisable, but anywhere in the converter panel is OK. An option is one of the unused 12V fuse positions. Comes with a built in fuse and indicatior. The voltmeter draws very little current to the wire drop is negligible so 18 GA wire is acceptible, but you should install a smaller fuse to protect the wire.  A 5A fuse should be fine.

The voltmeter would be my first addition ahead of the ammeter. With it you can get a good guess at the battery condition. It gives a lot better indication than the 4 bulb OEM status panel. Later, the ammeter can tell you how the battery is charging or discharging, but you will always need the voltmeter.

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Posts: 9059 		Direct Link To This Post Posted: 03 Jan 2014 at 12:48pm
ok, 12 is overkill with that draw.
 
I thought of another reason you won't want to keep the voltmeter on all the time - the blue glow at night will fill the pod.  We cover the display on the tv/dvd player for that reason.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Posts: 3990 		Direct Link To This Post Posted: 03 Jan 2014 at 12:50pm
I never noticed the Blue Glow from the Radio/TV, but then maybe I need to plug it in. :)   
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Posts: 9059 		Direct Link To This Post Posted: 03 Jan 2014 at 4:52pm
That would solve it too!
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Posts: 231 		Direct Link To This Post Posted: 03 Jan 2014 at 10:56pm
Why would you install one? Or better, what is the benefit of installing one? Sorry for sounding naive, but I was just wondering. Thanks!!
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fwunder View Drop Down
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Posts: 1676 		Direct Link To This Post Posted: 04 Jan 2014 at 8:36am
To know when to add more Dilithium Crystals! Sorry, Trekkie humor.

Short answer: To monitor health of 12v. battery system and charging system.

Longer answer...

Lead acid batteries like the one's commonly used on our pods actually have a very narrow (voltage) range of health often referred to as State of Charge.

A resting battery (not hooked up to shore power) would be considered at a State of Charge of 100% with a voltage of 12.7v or above. Often 13.2v is a 100% resting charge of many batteries. A battery showing 10.5v or below is considered at a State of Charge of 0%. It's dead, kaputt, out of juice and may not come back to life (unless you have a decalcifying charger like a Battery Minder).

It is a widely accepted practice to *not* drain lead acid batteries beyond a 50% SOC or 12.06v. I've attached a chart which I am using to refer to. The voltmeter and chart help me determine when I need to recharge the batteries and it will show that the converter/charger is pumping volts into the batteries.

And....it simply gives me a sense of power! Wink

That's a bit of an oversimplification, but I hope it helps.

-fred
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CharlieM View Drop Down
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Posts: 1797 		Direct Link To This Post Posted: 04 Jan 2014 at 8:54am
Exactly correct. The voltmeter is far better than the factory supplied system monitor. It is only good for telling you the battery is still there, maybe. To accurately assess the battery condition, short of a hydrometer, you need a digital voltmeter. I use a meter plugged into one of my added 12 volt outlets, which connect directly to the power converter.

http://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=sr_1_1?s=automotive&ie=UTF8&qid=1352484368&sr=1-1&keywords=battery+monitor+12v

Charlie
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