Need help - batteries not reaching full charge - adding more

[Resthome]

There are some good pictorials in the Kid owners manual on how to wire panels in series  / parallel configuration .
http://www.midnitesolar.com/pdfs/Kid_24V_4p_Series+Par_REV_B.pdf

Larry

Perfect Larry & WB. Much better that my long diatribe on the topic. Just wasn't sure how Robert was discribing his connections from the Combiner.  Thanks for the links that should let him verify his connections for us.

[robbertwilliams]

Thanks Vic, Larry, John, and WB.

I believe I've got it wired correctly and the schematic did confirm that. 

I think the confusion came with the use of the word "out" instead of "in"...but if you're familiar with any of Midnites MNPV Combiner boxes that are setup with MC4 "in's", then you've seen what I have before.  I know they don't make an MNPV3 with MC4 but I retrofitted this one to fit the bill.

I'll get LMAX turned off and hopefully we will be in good shape. 

Love the help. Priceless

[Vic]

Hi robbertwilliams,

Good work on getting your PVs wired 2S 2P,   this should make a large difference in PV production,   and,  thanks for adding the Signature with your system details.

Getting PV string voltage in  an efficient operating range for MPPT CCs is a common difficulty,  particularly with 60-cell PVs,  that are primarily designed for Grid-connected systems.   Those with experience with PWM CCs,  or replacing a PWM with an MPPT CC,  can run into this issue ...  you are not alone in this situation.

Given that the original string of batteries may well have been undercharged for some time,   doing an EQ on that string,  perhaps by itself might be in order,   and then do an EQ with both strings connected.   This could be done over a one week,  or so period - IMO.

Believe that you mentioned that you have a clamp-on DC Ammeter,   which will be a large help in monitoring the current balance twix the strings during charge and discharge of the battery.

Water consumption can be a fairly good gauge of how well your batteries are being charged.

You are certainly welcome for the advice.   If we are lucky,  we ALL are learning,   and all have benefited from all of the help and experience that so many folks bring to this (and other)  Forums.

Thanks to all contributors!   Vic

[robbertwilliams]

Thanks Vic.

Well...I know you live by the trusted Freas Hydrometer...I just picked up a refractometer and am loving the ease of use and clear readings.  However, I haven't calibrated out of the box.  I need to perform the SG test of Glycerin, or some other readily available chemical with an SG above 1.1.  Also, does anyone have a good routine habit of using the refractometer, especially in terms of cleaning the acid off after each cell test?  Currently, I'm wiping with wet paper towel, and then with a dry one (I'm not feeling like this is the best method). 

So, out of the box, and judging by the spacing of the SG scale in the optics, distilled water does appear to read 1.0 on the imaginary scale.  With that said, the readings yesterday on the new bank were quite different than that of the hydrometers.  The new bank lowest cell reading was 1.265 and the highest was 1.3.  The old bank had a low reading of 1.28 and a high of 1.3.  I did not do any individual cell voltage tests.

The charge went quite well with the new series/parallel setup.  However, the watts never exceeded 115, and the amps never over 4.  So, question, does the CC kind of have a clue as to what the batteries will take while its going through a charge?  It seems that if I had the bank drawn down much more, like to an SOC of 85, I remember the wattage hitting higher numbers.  So, that is where the confusion lies.  I'm still trying to wrap my head around how the CC works, what numbers/readings to look for as normalcy/irregularity, and when those numbers should or shouldn't occur. 

BTW, either since I rewired the PV or changed the shade setting to ON, my SPD300 at the PV's have LEDs on well into the dark evening. 

EDIT:  I just found a site with the identical scale and description of calibration with distilled water.  http://www.planetextech.com/profiles/blogs/calibration-and-operation-of-the-rf40-c-battery-coolant

The refractometer is calibrated correctly.  The SG's read yesterday are correct.

Since I'm getting readings higher than 1.265 (full charge SG according to DEKA), should I lower my charge settings?  Suggestions?  (Currently set at -- EQ 30.2, ABSORB 29.2, FLOAT 27.5)

The SG's taken yesterday are in the excel chart attached.

[Vic]

Hi robbertwilliams,

Good that you have a Refractometer,  I have never used one, but,  when calibrated it should be accurate and repeatable.

Briefly,  the Classic CC should begin every day trying to fully recharge the batteries,   unless Skip Days have been set to some value other than zero,  in the Advanced menu.

The Classic should begin the day in Bulk MPPT when there is some sun (even filtered sun).   Bulk is a stage that supplies the maximum available charge current to the batteries.   As Bulk progresses,  the battery voltage will rise,   and generally,  the current will also rise,  because the amount of PV power available increases as the sun rises higher in the sky.  Of course clouds and any shading will have a large effect on the amount of PV power available.

With your PVs rewired for 2S 2P,   you should see the input voltage to the Classic in the 65 - 80 volt range,  depending on the amount of sun,   and temperature of the PVs,   shading,  etc.

When the CC is in Bulk,   and Absorb,  what input voltage to the Classic are you seeing?   This is very important information.

When the batteries have not been discharged very deeply,  the Bulk stage will be short.   Depending on how you have set the Classic,  the Absorb stage may end by time,  or EA,   as you know.

The batteries control the amount of current that the CC supplies as charge current into the batteries,   this is called Acceptance.   Of course any loads on the inverter will add to the amount of current that the CC delivers,   up to the ability of the PVs to supply that amount of power ...   you know this.

If you have a situation where there are passing clouds,   then,  you might want to try a different Mode for the Classic  --  Legacy P&O,  in the Mode menu.    This Mode can help the Classic deliver maximum power with widely varying PV power conditions.   Legacy P&O sweeps for the Maximum Power Point much more slowly than does Solar Mode,   and can be helpful at times.

Are you seeing the Classic display "Shading"  on the MNGP display at times?

More Later,   Vic

[robbertwilliams]

I'm getting around 66-68v coming in.  And yes, such as seen last night, no light (FLOAT - PV SHADING). 

[ClassicCrazy]

"Since I'm getting readings higher than 1.265 (full charge SG according to DEKA), should I lower my charge settings?  Suggestions?  (Currently set at -- EQ 30.2, ABSORB 29.2, FLOAT 27.5)"

Robert ,
If the SG readings are where they are supposed to be I would lower the Absorb and Float voltages. The East Penn Deka gives a range so go to the lower part of the range and see if those do the job. If so stay lower and raise the voltage to the higher parts of the range as your batteries get older and may need it .

I have a refractometer and  pretty much do what you described , rinse with distilled water and then dry with a cloth. That is where the bulb type hydrometer has the advantage because you just squirt it out and go on to the next cell so it is much faster and easier to make sure you have gotten a good mix of the electrolyte for a sample each time. So it is possible to use both  devices to check SG use one to confirm the other . I usually used the bulb of one to take the samples for the other anyway because that way I knew I was stirring up the electrolyte well to get the couple drops that the refractometer needs. It is a bit messy though.

Larry

[robbertwilliams]

Today, around noon, the CC was in Bulk mode and was not charging (no watts and SOC at 97% where it was a day ago).  So, I shut it off and started it back up.  It went into absorb and started charging (voltage both times, before and after restart, were in the 60's).

Now, about 3:30 it is back in bulk mode, the absorb timer shows it never finished (1:38 left).  Any idea what is going on here?  It's been clear and sunny all day.

[Resthome]

Today, around noon, the CC was in Bulk mode and was not charging (no watts and SOC at 97% where it was a day ago).  So, I shut it off and started it back up.  It went into absorb and started charging (voltage both times, before and after restart, were in the 60's).

Now, about 3:30 it is back in bulk mode, the absorb timer shows it never finished (1:38 left).  Any idea what is going on here?  It's been clear and sunny all day.

If you see this again can you take a snap shot of the various MNGP status screens and post them here, even if it takes multiple posts because of size limits. Although I think the limit is now 4000KB  not the previous 400KB. Make sure to include the WBjr status pages showing systems amps going into the battery.

Bulk mode and 0 watts sure isn't correct. Resting okay but not Bulk with full sun light on the panels. Do your panels get any shading during the day from surrounding objects? What kind of angle are the panels and what direction are they facing? Are they all the same angle and direction?

BTW don't think I have seen you post the firmware versions of your Classic. Can you also do that.

Thanks

[robbertwilliams]

I'll be there all day tomorrow keeping an eye on things.

No shading near noon hour.  The panels are all on a DPW top of pole mount.  I have them tilted to the second to last hole (approx 60 degrees).  The panels are facing true south.  The firmware is 2096 (3/23/16).

[Resthome]

I'll be there all day tomorrow keeping an eye on things.

No shading near noon hour.  The panels are all on a DPW top of pole mount.  I have them tilted to the second to last hole (approx 60 degrees).  The panels are facing true south.  The firmware is 2096 (3/23/16).

Do you know what the MNGP firmware is at?

There are actually three Classic, MNGP, and Network.  The Network version can only be seen on the LA IIRC.

[Resthome]

Today, around noon, the CC was in Bulk mode and was not charging (no watts and SOC at 97% where it was a day ago).  So, I shut it off and started it back up.  It went into absorb and started charging (voltage both times, before and after restart, were in the 60's).

Now, about 3:30 it is back in bulk mode, the absorb timer shows it never finished (1:38 left).  Any idea what is going on here?  It's been clear and sunny all day.

Yeah there is just a lot of questions about this. Had it gone into Absorb and then back to Bulk or did it only go to Absorb after you cycled power? Did you see the 0 watts in the Main Status screen? Did you see exactly when it went to 0 watts? Were you using the MNGP at the time? 

See what I mean about a lot of questions?  This is where all the recorded data from the LA could help in troubleshooting the issue. Sorry I'm not being helpful as I've never seen this before. Seen it resting during the day but not charging in Bulk, no.

This maybe one for boB to comment on.

[Vic]

Agree with John ...   Have never seen the Classic stay in Bulk  and make 00.00 watts.   To be in Bulk,   the Buck Converter needs to be running.   The Classic will shut off the Converter and go to Resting below about 14 watts of output.   Guess that for an instant,  perhaps the Classic's output could be 00.00 watts and show bulk,  but would be that if that could be the case,  it would exist for a second or less.

So,

1.  Why not try that other Mode suggested previously  --  Legacy P&O?

2.  If you happen to see the Classic Resting,  in full sun,   check the Reason For Resting,   RFR,  as noted in this Thread:
http://kb1uas.com/mnsforum/index.php?topic=2034.0

3.  So,  before you added the second string of batteries,  how well was that string of batts being charged ...   did you measure SGs?

4. Since you did your own conversion of an MNPV3 to MC4 inputs,  kind of wonder if there might be some kind of poor connection,  or even miswiring that might cause you to have more reasonable PV string voltage than before,   but perhaps the PVs cannot supply very much current (due to a poor connection),  so the Classic spends much time Resting.

5.  Previously,  you mentioned some concerns about Shading.  You do realize that really ANY shading at all whatsoever,   can easily essentially kill ALL PV power production  --  a shadow from a cable,  a pipe,  vent,  etc is a real killer.  Also any snow,  ice etc will do the same.

I had hung my hat on the concern about parallel strings of 60-cell PVs being the culprit.

Did you say that you had a clamp-on DC ammeter?   This could allow you to test the Short Circuit current (Isc) of your PVs,   which could be quite telling regarding any poor connection issues.

Realize that it might be quite a task to get access to the PVs themselves with your probable weather,  but you could do such a test near the input to the Classic,  if you DO have a clamp DC ammeter  --  a very useful tool,  especially when one has multiple strings of batteries.

Have you ever Updated the Firmware on the Classic/MNGP?.

More later ...   thinking about this.   Vic

[ClassicCrazy]

Robert ,
If you have an Android - get Grahams Classic App - it is easy to take screenshots and post them .
Or easy to take screen shots of Local Status App too and post those.

It would be good to see some actual photo's of your systems wiring.

Larry

[robbertwilliams]

I'll get a bunch of photos today.  I'll put them in a Flickr account. 

When testing D.C. Amps at the panels, I am getting the same per string as the combined CC reading (2.5/string to 5/CC).

I'm still onlycharging one single string of batteries until this mess of unknowns is cleared up.  I'd hate to make it any more complicated.

I'll be running the local app all day today (however, as it has done in the past, it often closes the connection).