Battery monitor panel 400

pthomas745

And, I realized: I have all this stuff that will show what I mean, instead of rambling along.

From my Victron.  The trailer was fully charged about four hours before this, and I ran the fan on the lowest setting for an hour or so.  (I have one of the rheostat control fan mods).

Picture 1.  What the Victron says while the fan is running on low.  Note the "Voltage" is reading 12.09, which would be 50 percent according to the chart.  That is a "false reading." Note the "Consumed AH".  The trailer uses about 4 amps a day, and the fan is using about a half amp per hour.  If I didn't have the monitor, I might guess I had used 3 or 4 amps so far in the day. 

Picture 2.  I turned the fan off, and then the battery switch off.  Now the battery has nothing to do. After three minutes, the Victron says 12.42.

After 7 minutes, the Victron moved up to 12.46.  After about an hour, it was up to 12.48. (I skipped those pictures).

Picture 3.  I turned the trailer back on, and waited 5 minutes.  With just the parasitic drain, the battery shows 12.37.

I hope this shows the value of even a slight "rest" of the battery.  You will get a much clearer picture of your state of charge. 

PS:  let me know if these pictures need to be resized...I used 600x800 pixels........

JEB

ScottG said:

To address your second question. The requirement for a battery to "rest" applies when it has just been charged. In that circumstance, the battery voltage will read high until the surface charge has dissipated. However, applying a load (such as your refrigerator) to the battery will dissipate the surface charge much more rapidly. After that, you really only need to flip your fridge off just long enough for the battery voltage to stabilize--probably no more than a minute or so.

Exactly.  I boondocked for 7 nights earlier this month and I was able to get a reasonably accurate measurement by checking my batteries in the morning before the sun hit the solar panels or in the evening after sundown.  I’d wait for the fridge to cycle off, then I’d plug my Innova meter into the cigarette lighter and wait for the voltage to stabilize. It would always peak well before the fridge cycled back on. Not as accurate as a Victron, but good enough for a $12 meter. 

jpi68

Got home from our Arizona adventure. Last two nights on shore power and about 700 miles charging on truck. INNOVA volt meter came in the day after we got home. So the battery rested for about 24 hours. INNOVA volt meter read 12.67 volts, from what I have read here that is fully charged. We turned off the cut off switch, trailer is in storage lot until our next adventure, Rocky Mountain fall leaf tour next weekend. Thanks to everyone here for all your support. Next project is to set up a suitcase solar system...

Verna

@jpi68, I hope you left the leading “1” off of your voltage reading, as a reading of 2.67V would indicate a very dead battery!

jpi68

 My bad 12.67 volts

Verna

@jpi68, that is great!  You had me worried 😉