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Old 08-28-2015, 04:19 PM   #29
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Originally Posted by KYAirstream View Post
Does the Trimetric also show the status of the batteries while plugged in? For example, I have an analog meter that reads 12+ volts for my batteries when I'm plugged in. However, my batteries where shot and as soon as I would get off shore power the meter would drop to nothing. Would the Trimetric give an accurate read regardless of shore power status?
No, as long as batteries are connected and charging, the system voltage is whatever the converter is putting out. No meter can read the battery state unless it is not being charged.
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Old 08-28-2015, 05:01 PM   #30
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The Tri Metric and other use meters which are similar work like this:

When you set them up, you put the Amp hour capacity of your batteries into the set up process. In my case with two 6 volt golf cart batteries in series I used 220 amp hours as my original battery capacity. The batteries are fully charged, and then you are set to go.

As you use battery power, the meter counts down in either % of original capacity or Amp hours (your choice, I use %). So, if you are not plugged in, or your system is not charging it counts down the amount of power you have used. So, say you have the 220 amp hours of capacity I have. With it set in % display, it will slowly decrease the reading on the meter, 99%, 98%, 97 ... 55, 54, 53%. So that tells you the % of power remaining in your batteries. If you have solar, as I do, it adds the amount of charge input, so if you are using less than your solar is putting out, the meter will show an increase in % capacity. If you tow, and a charge is put into your batteries, that will also show as a % increase. If you stop and plug in, the converter/charger will put power into the system, and it will go (over the time needed to charge) to 100%. If you remain plugged into line power, the meter will stay at 100% as the converter/charger is supplying all the power, not the batteries.

Once it gets to 100%, it will reset itself (saying the batteries are fully charged, determined by their reaching float voltage) and only decrease if you start taking power from the batteries.

As an example, I am out camping right now (wildfires have driven me from my home) and have been in a Forest Service campground for 8 days. My Tri Metric shows that my batteries are at 87% of capacity. This is because I have solar recharge. It is a poor slow recharge, because of all the smoke, but still I have used only 13% of my battery capacity which has not been recharged by the solar panels. This morning it was 82% of capacity, so I have recharged 5% today, so far. No sun, only smoke, or it would be up to 100% I am sure. BTW, the meter adds a "fudge factor" for partial recharge, of about 10 to 15% as you must put more power into a battery to recharge it than you can take out. That is compensated for.

Now, if your batteries are shot, the original capacity number you put in when you program it is no longer accurate, and the Tri Metric cannot determine that. So, it would assume all is well and NOT produce an accurate number. So, once your batteries lose capacity due to end of life aging, the meter will no longer be accurate. However it does have a voltage function on it, and an amp readout, so if you find the voltage is rapidly decreasing with a moderate current drain, you could safely assume your batteries have reached the end of their life and replace them. I like to start with a fresh set of batteries when setting up a Tri Metric, but if your batteries are in reasonably good condition, it is not necessary to replace them.

You can think of the Tri Metric as similar to your checking account. You put money into it, you take money out of it, the meter watches the in and out and tells you the % of what you have at any specific time point. The difference between the meter and your checking account is that you program a ceiling into the meter, with a checking account there is no ceiling so no % of money can be determined.

But the meter also is great to tell you when your batteries are fully charged after driving, or when they are only partly charged when you come back home and thus need to be recharged so they don't sit discharged which will cause damage over time.

You can watch the meter and see if you are running less than 50% charge and how often it happens, which will give you a clue as to your degree of battery "abuse". You can look at the meter on a cold evening and see if you may have a problem getting through the night if you run your furnace (with some experience that is). If it says you only are running 30% capacity, and you know it is going to be 35 F and the furnace will run a lot, you may wake up to a cold trailer.

Battery use meters such as the Tri Metric are one of the only ways to really know what is going on in your 12 volt electrical/battery/solar/tow vehicle charge system. I recommend them highly.
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Old 08-28-2015, 05:19 PM   #31
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idroba has it right. The short version is: by voltage you cannot tell the state of charge of the batteries while charging, by whatever source....but by the programmed amp rating plugged into the TriMetric, one can tell the state of charge by %, as idroba says, or by the amp/hour reading of rate of charge, or by watts.

After you have a good monitoring system for awhile, you learn what is a normal charge progression and can note a suspect battery(ies) by a deviation from a normal charge sequence.

Of course, then pulling a batt and performing proper diagnostics is in order.
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Old 08-29-2015, 08:29 AM   #32
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Thank you both for the replies. The Trimetric is something I'm definitely adding to my list. It really does sound like a great way to monitor with a good deal of precision. Solar someday too, but that will have to wait for now. With your setups you guys can really be self sufficient and camp just about anywhere you want. I guess the only limiting factor may be water...
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Old 08-29-2015, 09:20 AM   #33
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The overhead compartment above the kitchen that houses the control panel in my 1979 seems like a logical place to put the meter. When installing the Trimetric and the shunt, would there be any issue with using the positive and negative leads that feed into the control panel, or do I need to go directly to the batteries?
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Old 08-29-2015, 09:38 AM   #34
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After looking at some pics online, it appears the shunt is typically installed close to the battery with a pretty heavy gauge wire. Looks like I have to figure out a way to fish the wires if I want to put the meter in the overhead compartment above the kitchen counter.
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Old 08-29-2015, 09:48 AM   #35
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The wire from the shunt to the meter is much smaller and fairly easy to fish.


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Old 08-29-2015, 09:59 AM   #36
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Electrical usage

Difficult to fish from one side of the ceiling to the other? I'm assuming ribs are in the way.

Another thought I have is running alongside the bottom of the opposite wall and tapping into the wires for the blank tank sensors, which are unused and lead back to the control panel.
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Old 08-29-2015, 12:38 PM   #37
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Look at the bottom photo in post #18 of this thread:

http://www.airforums.com/forums/f449...-124829-2.html


If you look at the very most bottom part of the bottom photo you will see the shunt for my Tri Metric meter. It must be in the negative line and at the batteries. All the power from the negative side of the batteries must go through the shunt.

The wire to the Tri Metric meter itself is a very small three wire set starting at the shunt and running to the meter itself.
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Old 08-29-2015, 03:07 PM   #38
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Thanks for the pic. That's a nice looking battery box as well. I like how it's outside on the tongue.
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