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Old 07-21-2017, 02:43 PM   #1
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2015 25' FB Flying Cloud
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Measuring battery discharge

I killed my first set of batteries and I don't want to do it again. I now have two AGM batteries and an upgraded charger/converter. I also know that you shouldn't discharge a battery below 40 -50% (12.2 - 12.06v.). I'm told that the meter in the camper really is useless in indicating how much the batteries have discharged.
Is there any way to tell where they are at without some additional test equipment? Are there any rules of thumb for monitoring batteries? Thanks
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Old 07-21-2017, 02:49 PM   #2
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I do not know of any way to check the actual status of the batteries without additional teat equipment of some sort.

I bought an inexpensive (less than $20) volt meter at Sears and it is an easy check and very accurate. Just lift the battery compartment lid and touch the probes to the posts and you know the status!
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Old 07-21-2017, 04:30 PM   #3
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I think most folks are using battery monitors. They measure the energy delivered (among other things).

There are lots of discussions about what to use.

I operate on the assumption that it isn't too difficult to measure the voltage across a calibrated resister and provide a running value of the energy. In my case I look at the battery voltage to guess at the state of charge and compare the energy delivered to my battery specs.

Such as 1.3kW would equate to about 100AH of battery usage, what should I see as the battery voltage. Again I am not using that sophisticated solution, I am sure others will share what they have.
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Old 07-21-2017, 04:42 PM   #4
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This may not be the best, but it works for me
http://www.bogartengineering.com/products/trimetrics/
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Old 07-21-2017, 04:44 PM   #5
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Most AS OEM battery voltage monitors are accurate enough to let us have an approximate reading very easily. It also permits all family members to become part of the team that is aware of the various functions and levels to watch including the water and holding tanks.

After disconnecting from shore power, waiting an hour, and turning off as many 12-volt loads as possible, any reading under 12.5 volts is noted by other family members. Any readings closer to 12.2 volts are further noted as needing follow-up with charging or some other solution.

An aftermarket voltage meter is fine to have for more accuracy, but it does not replace the direct and convenient observation by everyone of the important data, whenever they want.

Keep It Simple Stu . . .

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Old 07-21-2017, 06:33 PM   #6
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I would highly recommend a battery monitor. They continuously monitor the current into and out of your battery. You can see at a moment's glance how much battery capacity is remaining and the state-of-charge of the batteries. Battery voltage is affected by load, temperature and time. Am Solar sells a couple of models such as the Trimetric.
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Old 07-21-2017, 07:03 PM   #7
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Quote:
Originally Posted by WayneG View Post
This may not be the best, but it works for me
http://www.bogartengineering.com/products/trimetrics/
Been using the same one for the past 3 years. All the info you need.
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Old 07-21-2017, 08:13 PM   #8
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Hi

Borrow a multimeter and use it to check your internal measuring device(s). If there is an offset with no load current, write it down. Use that offset for the monitoring you do. For added fun make up a card that says " meter reads 0.3 V high". Stick it next to the monitor.

Bob
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Old 07-21-2017, 09:32 PM   #9
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Thanks for the suggestions. Does anyone have experience with the MidNite Solar MNBCM battery monitor?

http://www.thesolarbiz.com/battery-m...y-monitor.html

What kinds of places could install a monitor? Can any reputable RV dealer? I'm out of my wheelhouse on this one.
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Old 07-21-2017, 09:41 PM   #10
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Measuring battery discharge

This is essentially a voltmeter. A true battery monitor will use a shunt resistor to measure current. You won't find a proper battery monitor for $50.
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Old 07-22-2017, 07:18 AM   #11
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Hi

Paying a dealer $300 to instal a cheap monitor does not make a lot of sense.

Bob
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Old 07-22-2017, 11:02 AM   #12
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http://www.pbase.com/mainecruising/battery_monitor Good information and best instructions I have found. Also check Smartgauge on his site.
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