Calibrating two Classic 150s to read the same battery voltage

[Powerplay]

My system has been charging all summer fine with two Classic 150s in 'follow me' mode and the Classic with the BTS will always measure battery voltage about .05V lower than the other Classic.  This has worked out fine and the second classic seems to be driven to resting (0W) first during the absorb phase on days when loads are lower. 

But yesterday I was  looking at the Local App and the battey needle was reading .2V different between the two Classics and I've never seen that before.  I thought next chance I get I'll recalibrate the Batt V reading for the two.  The Classic with the BTS is reading lower by .2V now.

Just monkeying with the Local App I saw an interesting thing.  When on the Configuration panel I can change the offset for one of them to -.1V and the reading on that screen reads, Batt: 50.6V, but the graphic on the front of the same panel reads Battery Volts 50.8.  Then if I go to the other Classic and change its offset to +.1 it reads , Batt: 50.9V on that screen but on the front page for that Classic it also still reads Battery Volts 50.8.  Given they were .2V off from each other and I raised the lower by .1 and lower the higher reading by -.1 shouldn't all the readings now match and be 50.8V?

I'm doing this at night, by the way, so no power input from the sun.  I'm very curious why I can't cause the readings all from the same battery bank to match up all around.   

[ClassicCrazy]

The battery is going to read higher if it is colder  because that is the battery temperature offset .
That is if your batteries are colder now then they were in the summer.
But I don't have anything in follow me so don't know if the temperature offset would only show on one and perhaps not the other ?
I see you said the one with the temp sensor is reading lower so not sure if that is what is causing the difference in volt readings.

Try going to your Local Status App Config Advanced screen and see what the temperature compensation reading at the right says - and compare that to what you have the Absorb voltage set for . Then check the other Classic for same thing and see how they compare.

Larry

[Powerplay]

Thank you for the reply.

See the attached png.

I had to change the offset on the Classic with the BTS back to 0 and change the offset on the one without BTS to -.2 and then reboot both so they will get along again.  They're happily charging away today with both reading the same or within .1V on battery voltage.  They've always calculated (and agreed) the correct T-comp set points but seem to charge about .1 to .2 volts lower than the calculated absorb set point.  I'm got some study time now that we've shut down a couple pumps and I can isolate loads better.

[WizBandit]

I think there is a bug in the Local App.  Seems the programmer may be reading the raw uncorrected battery voltage and displaying it on the dial when he should be using the register that holds the corrected value.  The attached picture tells it all.
The dial is reading 49.3v and the offset is -0.6v but the corrected value is displayed on the offset page as 48.6v and not on the dial.  Simple programming mistake. The Classic has a voltage resolution of only +- 0.1 volts.

Your pictures confirm this as well...

[ClassicCrazy]

I just tried it with battery reading 23.6  and then I put in offset by  -.6 and the display voltage on the local status dropped to 23.0 when I wrote it ( using the little arrow to right of offset )   Seems to work correctly here .

Larry