Volt meter useful?

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Volt meter useful?

Postby TimC » Fri Sep 25, 2015 10:39 am

I am finishing up plans for electrical design and I'm wondering if a volt meter is really that useful. How many of you have installed one and refer to it for battery condition? Does the volt meter trickle much juice from the battery? Is there any reason to consider an amp meter?

I'm looking at just one U1 35Ahr battery to power a limited amount of lights and fans. Other than putting a multimeter on my battery every now and then is there another way to check battery condition? I kind of like the volt meters than have just a series of LEDs to show battery condition. Are they of any use?
Tim
Niagara, WI
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Re: Volt meter useful?

Postby tony.latham » Fri Sep 25, 2015 10:58 am

I think it's imperative to have ––at the minimum–– a volt meter. Otherwise, you could easily cross the line to where you're damaging your battery.

Something like this will work and not measureably draining your battery.

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I use one of these:

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They're cheap!

http://www.amazon.com/Amps-Power-Analyz ... watt+meter

It goes well beyond how many volts. It shows my current amp draw and how many amps I've used on the trip (it needs a disconnect switch). Along with other data I don't pay much attention to.

On the last teardrop I built––which was a gift––I put the combo volt meter/dual USB port in the galley and the G.T. meter on the battery that's in the tongue box. That may be a bit on the ADD side, but I like to know what's going on.

Tony

the volt meters than have just a series of LEDs to show battery condition. Are they of any use?
I think the RV makers use those because they can get them for $8 and they don't scare the "I don't understand what 12.3 volts means," crowd.
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Re: Volt meter useful?

Postby Shadow Catcher » Fri Sep 25, 2015 8:02 pm

A voltage reading is some what valid only after some hours of no input and no output, One of the best sources for a basic understanding is http://www.solar-electric.com/deep-cycle-battery-faq.html The only accurate way of knowing the state of charge of you battery(s) is by using a battery monitor, the most common choices are Bogart engineering and Victron.
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Re: Volt meter useful?

Postby MtnDon » Fri Sep 25, 2015 8:13 pm

Shadow Catcher wrote:The only accurate way of knowing the state of charge of you battery(s) is by using a battery monitor, the most common choices are Bogart engineering and Victron.


And those are only as good as the information programmed into them. As batteries age the data entered must be updated.

Don't take that the wrong way. I have a meter myself on the cabin setup. But like a lot of things, garbage in = garbage out. Also, IIRC the Trimetric does NOT have temperature compensation which is too bad if your batteries are in a cold location. The meter us handy but still does not get down to the cell level. Only a hydrometer can tell if individual cells are having issues. More important as batteries age and cell differences develop.
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Re: Volt meter useful?

Postby TimC » Fri Sep 25, 2015 10:18 pm

Thanks for all the info everybody. I'm going to go the low tech method and incorporate a simple switched volt meter to monitor the battery.

So back to basics... Fully charged should read 12.6ish volts after rest. 12.1 volts after rest is approximately half charged, or at least the voltage to never allow the battery to go under.

I understand that if I discharge my battery below 12.1ish volts (after an extended rest) too many times it will considerably shorten its life. The short answer to extend my battery is to be sure to not discharge below 12.1ish volts, ever. I'm assuming keeping a battery at full charge is the best condition to extend its life. So, my plan is to keep it hooked up as much as is practical to a 15w, .9a max solar panel and a charge controller. When camping I will change out to a trip panel of 50-100watts.

I am unlikely to measure my ahr usage either electronically or otherwise. So, I'm thinking that with a volt meter I can check my pre-trip voltage (assuming it has rested the required amount of time) and decide if I need to recharge before draining it further.
Tim
Niagara, WI
My First Benroy Teardrop Build Thread - A 5x8 Woodie - http://www.tnttt.com/viewtopic.php?f=50&t=63575
My Second Teardrop (partial) Build Thread - Started August '16 - http://www.tnttt.com/viewtopic.php?f=50&t=66939
#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

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Re: Volt meter useful?

Postby dales133 » Sat Sep 26, 2015 2:23 pm

Ive installed the same volt meter inside the cabin as tony pictured.
From testing circuts ect it seems to work well and is nice and clear,they can be had pretty cheap on ebay from Hong Kong as with the cig outlets and usbs.
The bonus is too that you can easily swap it over for a cig outlet at any stage later.
I plan on installing another analog volt an amp meter also
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Re: Volt meter useful?

Postby Shadow Catcher » Sat Sep 26, 2015 4:26 pm

MtnDon I have a 150AH AGM and the VIctron can be calibrated with fair ease. I have never had the battery below 64% SOC so not a huge concern.
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Re: Volt meter useful?

Postby capnTelescope » Sat Sep 26, 2015 9:27 pm

I use a cheapo panel voltmeter. I just want to know about what my SOC is. Approximately. Roughly approximately.
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BTW, the ammeter on this puppy ain't worth a hoot. Poor resolution on the low end. Go for the straight volt meter.
I'll burn that bridge when I come to it.

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Re: Volt meter useful?

Postby TimC » Sun Sep 27, 2015 9:52 am

capnTelescope wrote:I use a cheapo panel voltmeter. I just want to know about what my SOC is. Approximately. Roughly approximately.


Yup, I'm into approximately too!
Tim
Niagara, WI
My First Benroy Teardrop Build Thread - A 5x8 Woodie - http://www.tnttt.com/viewtopic.php?f=50&t=63575
My Second Teardrop (partial) Build Thread - Started August '16 - http://www.tnttt.com/viewtopic.php?f=50&t=66939
#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

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Re: Volt meter useful?

Postby Gettin Started » Sun Sep 27, 2015 10:53 am

I like the use of a switch for the volt meter so it isn't permanently on. I'm about to mount mine on my build, and plan to use a push button momentary-on switch to apply power to the volt meter. Push and hold button in-see voltage, release button-display goes dark.
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Re: Volt meter useful?

Postby tony.latham » Sun Sep 27, 2015 11:34 am

Gettin Started wrote:I like the use of a switch for the volt meter so it isn't permanently on. I'm about to mount mine on my build, and plan to use a push button momentary-on switch to apply power to the volt meter. Push and hold button in-see voltage, release button-display goes dark.


I put a toggle switch on my first build thinking the same. It's on the circuit to my voltmeter and my USB plug that has an LED light when it's powered. But after I installed my G.T. meter on the battery --it measures down to a tenth of an amp–– and it couldn't detect when my voltmeter/USB was on, I passed on the switch for build number three.

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Here's the solution to worrying about your battery when the 'drop is sitting unused. I didn't have this for my first two years and this has been a real plus. Solar Blvd has these 20W panels on sale right now for $32. I already had the controller in the box for my folding 60 watters.... so no more setting those panels up unless I'm in the boonies for a few days.

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No more checking the battery between trips. It's under constant maintenance.

Tony
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Re: Volt meter useful?

Postby Graniterich » Sun Sep 27, 2015 8:56 pm

I have experienced the same thing with the combo ammeter /volt meter with out side shunt
Then I found these with built-in shunt, 20 amp rating. Have tested three very accurate at low resolution. 50 milliamps no problem, reading measures 48 on real ammeter. Scales nicely amps go up
http://www.ebay.com/itm/271845603042?_t ... EBIDX%3AIT
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