PV Voltage and Charging

[Vic]

Hi Robert,

Thanks for confirming that ARST is ON,  and NO Skip Days.

The main reason for asking those two questions,  was that you mentioned that on the "second" day after the deeper discharge,  that the Classic was not charging the battery (IIRC,  you said that it began in Float).   ARST being OFF can cause that.

Should have asked,  what version of Firmware are you running in the Classic,  and MNGP?

IMO,  try to keep in mind:

1.  Flooded batteries are rugged,  and quite tolerant of overcharging (much better than when they are chronically undercharged)

2.  Battery SOC monitoring devices,   really only give a rough approximation of actual SOC.

3.  The Gold Standard of actual SOC on Flooded batteries (FLAs)  is to use a good quality Hydrometer.

4.  As has been stated before,  EA is generally a very good way to terminate Absorb when the batteries have received a sufficient charge.   As you know,  the time required for Absorb varies relatively directly with the Depth Of Discharge of the battery,  in the previous discharge.

5.  Some water consumption is good for FLAs.   The difference between some and excessive,   is of course,   a grey area.

In summary,  you can choose several Pilot Cells (usually cells that have the lowest SG, compared to others in THAT string of batteries).   These cells will give a quick read on actual SGs,   and can be used to adjust charge parameters.  Each string of batteries needs at least one Pilot.   It will still be a good idea to measure the SGs of each cell in the bank every month or two,   after things stabilize with the bank.   Be certain to thoroughly RINSE the Hydrometer with Distilled Water three or more times after each measuring session.

You will want to mark each battery and cell with a number,  and letter (usually),   and enter in your Battery Logbook,  all the SG info,   charge parameters,   EQ date,   duration,   and  voltage,   date the bank was watered,   and,   at least the total quantity of Distilled Water that was added,   etc.

Just some opinions.   Vic

[RobertA]

Ok, all, I guess a setting is off, after all.

The reason I thought Classic ignored Whizbang was because I would consistently see SOC at 100% and the Classic still pushing absorb mode. That's what I'm seeing now too but if I look at (phone app) 'Messages', I have ending amps set at 3.0a, and the system is indicating "(currently at 8.1 A)". So I guess I've never had ending amps properly set?

SOC:  100%
Battery Current:  7.8 A
Consumption:  7A
Capacity:  700 total, 700 remaining

I keep looking at Messages, Ending Amps and it just sits between 7.8-8.1

So, what's up? Deca indicates my ending amps should be 1.5% of AH/20 rating, which is around 3.

[Vic]

Robert,

If your batteries are not being fully charged,   when using EA,  why not set EA to 0,  for now,  until you are able to fully charge the batteries.

You can set the Absorb time fairly long,   and watch the WBjr current into the batteries.   At some point,  that current will taper,   with a very low rate-of-change in the WB current.  It is in that region,  where the best EA resides.

The correct EA for those batteries will change as they cycle (as Westbranch noted),  and with the Absorb voltage (Vabs),   and as the batteries age.  But,  still,  it seems to be well worth the effort to get the EA dialed in.

Measuring SGs  will be your primary indicator of how well the batteries are being charged.

BTW,  here is a Link to Surrette Battery's article on measuring SGs.   This is a good  summary,  for most any Flooded batteries:
http://support.rollsbattery.com/support/solutions/articles/4347-measuring-specific-gravity

EDIT:   Also,  the EA settings for the FLAs here had been about 0.9% of 20-hour Capacity.  In the past several years,  the Vabs needed to be increased by about 0.4 V (on 48 V banks),  and this (probably among other things),  necessitated  increasing the EA up to about 1.5 % of C.

FWIW,   Vic

[RobertA]

Good question; why can't I set it to 0?
Answer: It would never get there.

UPDATE:
So I changed ending amps to 8, saved and restarted. On system start ending amps jumped to 11.7, which means it didn't read the Whizbang logs as SOC was still 100%. Because it started at 11.7 it went back into absorb mode (as it always does on restart). Over a period of 5-7 minutes it slowly worked itself back down to 7.8 again and did, in fact, change to Float mode. And you know what? that consistent 7.8-8.1 ending amps reading then dropped to 2.1.

Very bizarre stuff that begs the question: OK, what the heck is ending amps than? Because it dropped when Classic went into Float mode it must have to do with output amperage, but why did that output amperage never drop even though Whizbang indicated that SOC was at 100%?

UPDATE 2: I recorded it this time:  https://youtu.be/_ZdSnGBMtXY

[Vic]

Good question; why can't I set it to 0?
Answer: It would never get there   ...

...   Very bizarre stuff that begs the question: OK, what the heck is ending amps than? Because it dropped when Classic went into Float mode it must have to do with output amperage, but why did that output amperage never drop even though Whizbang indicated that SOC was at 100%?

UPDATE 2: I recorded it this time:  https://youtu.be/_ZdSnGBMtXY

Robert,   Do not know what you are saying when you mentioned,   "Good question; why can't I set it to 0?
Answer: It would never get there ..."

My Classic can be set to 0.   The reason that I suggested setting it to 0,  was,  so the full Absorb time that had been set would be used,   and the Classic would not use an EA,  because it was set to zero.

What is EA?   It is the Finishing Current (Ending Amps),  that is going into the batteries,   as measured by the WBjr on the Shunt.

If the voltage applied to the battery by the CC is reduced,   then this current into the battery is reduced.   This IS what happens on the transition to Float,   as Vflt is customarily set below the Vabs,  or Veq.

If one feels that a higher Vabs is needed,   then the Finishing Current will often need to be increased,   as this voltage increase will increase the current flowing into the battery.

####   What version of Classic and MNGP Firmware are you using?   ####

Thanks,    Vic

[RobertA]

Firmware:     
- Classic Rev: 2126
- Network Rev: 2097

[ClassicCrazy]

Good question; why can't I set it to 0?
Answer: It would never get there.

UPDATE:
So I changed ending amps to 8, saved and restarted. On system start ending amps jumped to 11.7, which means it didn't read the Whizbang logs as SOC was still 100%. Because it started at 11.7 it went back into absorb mode (as it always does on restart). Over a period of 5-7 minutes it slowly worked itself back down to 7.8 again and did, in fact, change to Float mode. And you know what? that consistent 7.8-8.1 ending amps reading then dropped to 2.1.

Very bizarre stuff that begs the question: OK, what the heck is ending amps than? Because it dropped when Classic went into Float mode it must have to do with output amperage, but why did that output amperage never drop even though Whizbang indicated that SOC was at 100%?

UPDATE 2: I recorded it this time:  https://youtu.be/_ZdSnGBMtXY

Robert ,
Maybe we are not all on the same page .
Here is what happens and happened in your video.

It starts out below the Absorb setpoint  and that is Bulk
When voltage climbs  to Absorb voltage  setpoint it changes to Absorb mode
It will stay in Absorb holding the Absorb voltage setpoint but decreasing the current.
How long will it stay in Absorb ?
Either for Absorb time
or
if you have these things done
Config / Tech/ Ending amps ( whatever number you have in there ) and check box for  Use WBJR for Ending amps

Just for example
You have Absorb voltage 28.8 v and Absorb time 2 hours
and Ending Amps is set for 0 ( on that config menu
Then you would see it go from Bulk to Absorb when voltage gets to 28.8
and it will stay in Absorb at 28.8v for 2 hours
The current ( system amps )  will decrease during that time but voltage stays the same
at end of 2 hours Then it will go to Float voltage and hold that voltage for the rest of the day as long as there is sunlight to do that

Second example
You have Absorb voltage 28.8 v and Absorb time 2 hours
and Ending Amps is set for 5 ( on that config menu )
Then you would see it go from Bulk to Absorb when voltage gets to 28.8
and it will stay in Absorb at 28.8v
The current will decrease during that time but voltage stays the same
When the current ( system amps)  gets to 5
it will go to Float
But only if it does that in less than 2 hours
So in this case if it never got to 5 amps in 2 hours that would mean the Absorb time of 2 hours was too short.

Does this make sense ?
Those were just made up numbers for examples. Like Vic said you need to find ending amps by setting ending amps  to zero ( set absorb time longer like 3 or 4 hours  )  then watching for the current - system amps - to level off and this should be about the same time you would see the specific gravity getting to 1.265 ( forget if that is the right number for 100% charge )
So when you find this system amps and specific gravity reading that will be your ending amps to put in
Config / Tech/ Ending amps ( whatever number you have in there ) and check Use WBJR for Ending amps

In your video I was hoping you would have gone through all your Config screens so we could see what everything is set for. In the video you mentioned 8 and I did not know what you were referring to .

Larry

[RobertA]

Makes perfect sense, i don't doubt for a second that that's what it's doing.

What I'm saying though is that if Classic followed the Whizbang, it would boot up, recognize SOC is at 100%, and then immediately go into float mode. That should be the case in every other scenario too. If SOC is at 100% Classic should not be boiling my battery with amps, regardless if some here think that's perfectly fine.

[ClassicCrazy]

Makes perfect sense, i don't doubt for a second that that's what it's doing.

What I'm saying though is that if Classic followed the Whizbang, it would boot up, recognize SOC is at 100%, and then immediately go into float mode. That should be the case in every other scenario too. If SOC is at 100% Classic should not be boiling my battery with amps, regardless if some here think that's perfectly fine.

Bubbling electrolyte is a natural function of lead acid battery charging - it is going to happen every day.
As Vic and others have said - the SOC is just an estimate so the Classic can not use that to control charging.
If you have the ending amps set correctly it will terminate the Absorb charging cycle and go to Float sooner than if you have it set to just use Absorb time - ( unless the batteries are really low ) .

The Classic does follow the Whizbang when in Ending Amps mode - it is monitoring the system amps ( what is going into the batteries).

I think that is the extent to how I can explain how it works !

Larry

[Vic]

   ...   What I'm saying though is that if Classic followed the Whizbang, it would boot up, recognize SOC is at 100%, and then immediately go into float mode   ...

Hi Robert,

Again,   the SOC reading from any Battery Monitoring device is not particularly accurate.   If we have the Vabs,  EA and Vflt set accurately for our batteries,   the most accurate SOC reading from the WB will be when the Classic makes its own transition from Absorb to Float (this is when the WB/Classic reset the SOC to 100%).

There are  many reason for the inaccuracies in SOC monitoring devices.  One of the largest of them is the Remaining Capacity of Flooded batteries depends to a large extent upon the Rate at which AH are removed from the battery (discharge current).   Most battery monitors do not account for this variable rate,  AND attempting to create a good model of this variable,   for any particular battery is quite involved,   and affected by other variables.

There is a (IMO) much better approach to determine when to end battery charging  --  setting a nominally correct Vabs,   and using EA to terminate Absorb (and having the Absorb time set long enough for almost any recharge scenario).

The above is not exactly what you appear to want to have happen.

I have not ever seen you state just what is the reason that you have this power system.   Is it a Backup to Grid power,   is it 100% off-grid,  etc ?? ?   Seems that you expect that there will be a reasonable chance that your batteries will begin days at 100% SOC.   If there were NO loads on the batteries during the night,   there will be some amount of self-discharge during the night.  In some number of days,   this self discharge will need to be accommodated by a battery charge cycle.  Certainly,  with only an inverter running during the night hours,   this idle current consumption will need cause the batteries to need recharging every day or so ...

If your system has little or no loads on it,  you might wish to consider Skipping Days of battery charging.

Have not looked at the first Video that you posted,   but,  it would be very convenient for those trying to help you,  if you created a Signature that details the type of system you have (Grid Backup,   Off-Grid,  etc),  the system hardware and the battery Capacity,  manufacturer and model number,   etc.   This will allow more effective advice,  without you being asked time and time again for the details of the system.

Many of us would like to see functions added to the Classic and WBjr,   but having perfect SOC readings are simply not close to being a reality,  due primarily to the nature and behavior of Flooded batteries in varying discharge and charge conditions.

My opinions,    Vic

[RobertA]

Good post, Vic (you too CC), especially about amperage draw rate.

My system is a hybrid. I can be fully off-grid, as I have been for months now, or, as long as I'm at a location with grid power, I can connect to that instead. With AC becoming mandatory soon, I suspect I'll be using the latter more than I'd wish. We'll see though. It's an RV https://www.youtube.com/watch?v=G6gXr-GAuBs

Boiling batteries aside, I'm going to take a few suggestions from this thread and see if they help. I have new Deca voltages to consider and an understanding that Classic will jump into float automatically (which I didn't see evidence of before). The first thing I've done adjusted battery voltages and set ending amps at 1A, and I have absorb timer at 8 hours. I will monitor SG throughout day and try to determine correlation with ending amps.

[ClassicCrazy]

Good post, Vic (you too CC), especially about amperage draw rate.

My system is a hybrid. I can be fully off-grid, as I have been for months now, or, as long as I'm at a location with grid power, I can connect to that instead. With AC becoming mandatory soon, I suspect I'll be using the latter more than I'd wish. We'll see though. It's an RV https://www.youtube.com/watch?v=G6gXr-GAuBs

Boiling batteries aside, I'm going to take a few suggestions from this thread and see if they help. I have new Deca voltages to consider and an understanding that Classic will jump into float automatically (which I didn't see evidence of before). The first thing I've done adjusted battery voltages and set ending amps at 1A, and I have absorb timer at 8 hours. I will monitor SG throughout day and try to determine correlation with ending amps.

What you are looking for is watch when it goes into Absorb - note the system amps and keep watching the amps when the SG starts to get up to full charge . The system amps at first will keep dropping but around when the specific gravity is showing full charge you should notice the system amps is not dropping so fast - it will be sort of holding steady for longer period of time . This is the number that your Ending Amps would be.

But you should run a good load on the batteries the night before so that it will make it easier to spot this transition.

Do you have ability to use MyMidnite - needs internet connection  ?  I find that is a good way to look back at the day of charging because it graphs the curves and state of charge so it makes it easier to spot that system amps leveling off .

If you are good with  data you can also use the Local Status app data collection and download it to Excel and make a graph . But you will have to look up in past forums how to do that - I have messed with it but am not well versed enough with Excel to tell you how to do it ( or myself for that matter) . But if you don't know how maybe you can hire a local geek kid who does to chart out the data for you!

Larry

[Vic]

Hi Robert,

First,  great work on modifying the RV to accommodate your power system!

As CC Larry mentioned,  watching the WB Current (battery charge current).  As the batteries become more fully charged,  the WB current will taper. The rate-of-change in this current will become very small,   as the proper EA value (at least for the Vabs that has been set).   You will find that at the very end of the of this,   the rate of change will become essentially zero.   The WB current at this time will be a very good value for the EA setting in the Classic.   There is some small variation in the WB current readings (jitter),  but just watching the WB current on the MNGP will allow you to average the WB readings.

You can measure the SGs when the WB current approaches zero rate of change.   As mentioned before,  the amount of WB current that represents this zero rate of change will vary,  depending upon the Vabs.   If the Vabs is increased,   this (essentially) zero change current change will occur at a higher current value.

Wb mentioned that new FLAs will need a number of cycles before they build Capacity to its final value.   This cycling is good,   and you will probably notice that some of the charge parameters,  and the proper EA value may well change,  as well as the AH Efficiency setting (probably).

CC Larry noted that boiling (gassing)  of batteries is normal if one wants to fully charge FLAs.   Gassing mixes the acid in the electrolyte,   and this mixing reduces or eliminates Stratification (EQing does an even better job of mixing).   Stratification is where the heavier acid sinks to the bottom of the batteries,   and needs gassing to reverse this.

Recharging FLAs must involve raising the charge voltage above the Gassing voltage.   This is a must.   Gassing consumes water,   and causes some plate erosion,   but this is far better than not gassing enough,  resulting in undercharge.  Chronic undercharging will cause hard sulfates to build up on the plates,  which is difficult or impossible to remove.  Chronic undercharging of FLAs is usually the most common reason for battery failures.

There is little that is absolute about Lead Acid batteries.  Many variables exist,   and not all of these are always evident.

BUT,   FLA batteries are quite forgiving,   can take a considerable amount of overcharging.  Just watch electrolyte levels,  and NEVER  allow the electrolyte level to go below the tops of any battery plates.   This will surely ruin batteries.

Larry also mentioned the battery AH Efficiency setting for Flooded batteries.  You could probably start with a setting of about 85%.   Opinions differ on this.   As your batteries cycle  this value will probably need to change.   Aging of batteries will also usually mean a change to this setting (in WBjr Setup).

Good Luck,   and please let us know how you are doing.
Vic

[dgd]

...
With AC becoming mandatory soon, I suspect I'll be using the latter more than I'd wish. We'll see though. It's an RV https://www.youtube.com/watch?v=G6gXr-GAuBs

AC becoming mandatory for what?

[Vic]

Hi dgd,

Think that that AC = A/C=Air Conditioning (probably).

Alternating Current IS always mandatory!

FWIW,   73   Vic