Absorb set to 55.2v. Classic goes from Bulk to absorb at 54.8v

[5 Minutes 2 Midnite]

While whittling away at the topic of verifying End Amps (http://midniteftp.com/forum/index.php?topic=3779.0) this question popped up... so starting a separate thread.

Absorb is set to 55.2
Float is set to 55.1
End Amps set to "1" (WbJr in installed)

Any good reason the controller would change state from Bulk MPPT to Absorb at .4 volts lower than what is programmed?

[Westbranch]

check the OFFSET values.

[5 Minutes 2 Midnite]

Should have mentioned that I haven't touched the offsets. They are still at 0.

[ClassicCrazy]

Yes if the batteries are warm and temp compensation is set it would lower the setpoint .
What is temperature compensation value ?
You can go to temp compensation screen and it will show you the temperature compensated setpoint for whatever mode it is in at the time.

Larry

[5 Minutes 2 Midnite]

That's another thing I should have mentioned! :> These are LiFePO4 cells. Not using a temp sensor and I have not set a temp compensation. Just checked to be sure.

EDIT: In the last few minutes I rebooted the classic. Both Absorb and Float still lagging by a few 10ths of a volt. Also just raised the absorb absorb and float set point a few 10ths and rebooted. Still the same lag.

I realize that I can compensate for this discrepancy, but I'm still learning about this controller, and interested in seeing how close its tolerances are. My expectations are that it should believe its own readings and stick to them exactly.

[Westbranch]

Have you re-torqued all the connections recently? removed any connection, etc? Checked for any loose crimped fittings?

[ClassicCrazy]

How many amps were charging when it changed from Bulk to Absorb ?
Did you put a meter on the battery when it was doing this and see if the voltage was rising rapidly ?
Larry

[boB]

You might want to try changing the ending amps to  0.0

Where were you measuring the voltage being different ?  If on the Classic itself and
your battery temp comp is not used (as I had read), then the EA might be it.

boB

[5 Minutes 2 Midnite]

Have you re-torqued all the connections recently? removed any connection, etc? Checked for any loose crimped fittings?

The system's only a few days old. One thing I did do around this time is bypass low voltage disconnect. The LVD is a contactor inline with the positive cable between the battery and the inverter. I just placed each crimped cable end on the same terminal of the contact and torqued the bolt down.

I also checked and re-torqued everything. The battery terminals of the LiFePo4 cells were all good for a slight turn with the torque wrench.

How many amps were charging when it changed from Bulk to Absorb ?
Did you put a meter on the battery when it was doing this and see if the voltage was rising rapidly ?
Larry

Unknown, and no.

You might want to try changing the ending amps to  0.0

Where were you measuring the voltage being different ?  If on the Classic itself and
your battery temp comp is not used (as I had read), then the EA might be it.

boB

Thank you for replying.

I was in another building reading from the local application. I caught it shortly after the state had switched to absorb. But I dumped the log later to confirm (attached). It definitely shows bulk to absorb at 54.8, even though the absorb setting on the classic is 55.2.

Set EA to 0.0? Interesting. I was under the impression that setting effected the state change from absorb to float.

In any case, I am just going to watch how things behave over a couple of days and see if this discrepancy continues.

/jim

[5 Minutes 2 Midnite]

Some screenshots and log file excerpt to back up what I'm saying.

(EDIT: Just checked yesterday's log (7-13-17) and again bulk transitioned to absorb .4 of a volt early.)

[boB]

First, I wasn't thinking....   Ending Amps has nothing to do with what you are seeing.
EA only has an effect when the Classic goes from Absorb to Float.  Duh...

What is the voltage that the Classic regulates to in Absorb ?  Does it always stay below your
Absorb set-point voltage ?   It should be running withing a tenth or so of a volt of
your absorb voltage setting.  It can go slightly below that setting briefly (around 0.3V ?)
but usually only if the sun goes behind a cloud or something like that and is usually
very brief until the Classic can regulate back up to your setting.

What does the Classic display say the battery voltage is at this time ?  I would think it
would agree with the Local-App

boB

[5 Minutes 2 Midnite]

What is the voltage that the Classic regulates to in Absorb ?  Does it always stay below your
Absorb set-point voltage ?   It should be running withing a tenth or so of a volt of
your absorb voltage setting.  It can go slightly below that setting briefly (around 0.3V ?)
but usually only if the sun goes behind a cloud or something like that and is usually
very brief until the Classic can regulate back up to your setting.

Voltage does rise after the change from bulk to absorb. Here's some log excerpts to give an idea what happens:
Absorb setting = 55.2

12:51:58 - 54.8v - state changes from 4 to 3 (bulk to absorb)
12:52:18 - 54.9v
12:54:26 - 55v
12:55:24 - 55.1v (and holds here until next event)
13:19:22 - 55.1v - state changes from 3 to 5 (absorb to float) (Float is indeed set at 55.1)
13:19:24 - 55

voltage then stays at 55, never going higher, and late in the day starts to drop as sun goes down. THIS IS NOT SURPRISING THOUGH, AS THIS TIE OF DAY LOAD CURRENT STARTS TO MATCH INPUT CURRENT

What does the Classic display say the battery voltage is at this time ?  I would think it
would agree with the Local-App

I will have to verify at the next opportunity. Maybe today, but it's foggy.

/jim

[5 Minutes 2 Midnite]

SIDEBAR: I've been experiencing a few other anomalies with this cc but did not want to complicate things. But they are being persistent and maybe worth mentioning:

1) Checking for updates on the local app always fails even though the internet connection appears good. (I'm a network engineer so pretty sure about the static IP settings)

2) If the classic is turned OFF for more than a minute or two the time setting gets lost

3) At least 3 times now the checkbox to use the WBjr for end amps (Tech menu on local app) has become unchecked on its own. This is not due to reboots, because the checkbox stays ticked if the classic is remote booted from the app. I checked before/after

I took delivery on the classic in Dec of 2015. It sat in the sealed box for over a year before being fired up. I see in the manual they are using a 1216 coin battery (really?) so guessing the battery is kaput.

I'll pick up a battery and see what gets remedied with a new one installed. Maybe I'll get lucky and all anomalies will evaporate. ;>

[Vic]

Hi jim,

Regarding the time setting being lost,   that 1216 battery,  which is in the MNGP on Standard Classics.  Did you remove the paper insulator that keeps the battery from being connected before the Classic is commissioned?

You should be able to carefully probe the battery while it is still installed in the MNGP.

Fairly early in the evolution of the Classic,  there could be a bit of adhesive residue that could remain on the coin cell contacts that could keep the battery from doing its job when the CC battery breaker was OFF.   Also at times some have said that retensioning the battery holder contacts might help

Regarding the LA check boxes,   there often is a button toward the right of that checked function that needs to be clicked,   to send that data to the Classic (IIRC).   Believe that hovering the mouse cursor over this button says something to that effect.

Vic

[Westbranch]

Vic beat me to it ...  about the battery and the adhesive, use some denatured alcohol if you have it, it doesn't add anything to the adhesive...also that second button needs to to be clicked each time any value is changed...  you will see, via the app, that some sections have only 1 value to be saved, others have several, to many, to change and save.

hth