Charging Voltage a little high in Absorb and Float stages

[Solar trucker]

Ok here we go!  The Absorb is set at 14.7 and Float 13.6 on the kid...and 14.8 and 13.7 on the Classic..
Absorb time is set at 3-1/4 hrs on both controllers....The actual measured voltage at the Bank with a Calibrated Fluke Meter is actually 15.1 at absorb and 13.9 in Float..the MDGP display also shows the Fluke meter Values.SP GRVTY of Batt bank was checked yesterday and values range from 1.265 being the lowest to 1.285 the highest...one cell only showed 1.260...
I have set the float at 13.7 because US Battery give the value of 13.08 for new batteries...from what I understand it's a good idea to increase the float charge about a tenth of a volt per year..the batteries are between 5 and 6 years old so I figured that 13.7 should be a safe float charge with out being too high.
When the classic went into float today, the SOC was still only 95%...there is only a fairly constant drain from the bank of about 4 amps...Also noticed the classic went into resting for quite awhile when SOC still showed 95%...SOC eventually does hit 100% during the day but then soon drops very slightly thereafter! (99% or 98%) and stays there till sun goes down....with 1650 watts of panels receiving ample sun, and virtually negligible draw (4-5 amps), should I not have 100% SOC at sundown?   I have EQ set for once a month...should I maybe try a manual EQ and see what happens the next day?
Both controllers are feeding the same bank, maybe I should try each one separately and see if the Anomaly
continues...Also wondering...can the weakest battery cell at 1.260 be causing the lower SOC values lately?

[Westbranch]

Looks like you have the WBjr on the Classic, what is your EA set at?

With a constant load you probably will not get to 100% SoC daily... 

Your Cl should go into float ~ 95% SoC unless the EA is 0.1 or 0.0A...  that is, it has to come out  at some time to finish the charge before the sun drops.

Is you KID also on a WBjr?

Did you measure the voltage at battery and Classic ?
Do you have a BTS on both controllers?
What is the ambient temp when charging?

Do you have any Voltage offsets in play?

Yes that weak battery may well be having an impact on the bank... can you isolate those 2 - 6V  from the bank?

hth

[Vic]

Hi Solar trucker,

We cannot know where you are located,  or the temperature of your batteries,   but  if the batteries are cool,  perhaps this is the reason that the Vabs and Vflt read a few tenths of a volt high,  and,  this is probably the reason that the SOC indicated when the Classic makes its own transition to Float.   This transition should reset the SOC to 100 %,  if the battery is at the temperature that is set as the reference temp.   This is normally 25 - 27 C ( 77 - 80 F) for almost all batteries that we use.

If the Temperature Compensation value for your batteries is --5 mV/cell/C,  then about 250 millivolts of increased Float voltage would imply that the batteries might be around 17 degrees C.   This is just an approximation,  as the Vflt is different between the Classic and the KID,  etc.  AND,  we do not know the factor you are using for the change in battery Capacity verses measured battery temperature,  and so on.

Also,  with Flooded batteries,  all of the charging occurs in Bulk and Absorb.   Float is designed to keep a fully-charged battery,  fully charged.   If a significant amount of time is spent if Float,  one could try to adjust Vflt to just maintain SGs at the fully-charged level.

Regarding the SG readings for your battery bank,  it is not the target SG for a fully-charged battery,  but for mature batteries,  this spread in SG readings is not excessive,  IMO.

SG measurements need a small Temperature Compensation,  but this is only about 3 points per 10 degrees F  from the reference temperature.

Usually,  EQs for Flooded batteries are done when  there appears to be an excessive variation in SG readings,  or about every three months,  or so.

All-in-all,  is seems that your batteries are doing well under your care.

My opinions,   FWIW,   Vic

[Solar trucker]

First of all...As always Thanks Westbranch and Vic for your prompt, informative replies!   To answer WB's questions first...

The Kid does not have a temp sensor attached or a WBJR...I'm only pumping at best 300 watts through it, and I have it set slightly lower than the classic in Vabs and vflt....It's really only there to pump in some extra charging during the day to help the bank somewhat when there are periods of unusually higher use! 
The Voltage readings were done right at the bank and right at the classic, although I must admit there is very little variance between measurements from the controller to the bank or at the MNGP display which is remotely setup 25 ft from the classic. The distance from the controllers to the bank is positive 2(0)cable is 4ft  and negative 2(0)cable is 7ft max.

I don't get much more than a tenth of a volt variance from the controllers to the bank and anywhere inside the bank of six batteries!
Actually, I'm really somewhat pleased that my series parallel battery bank has performed this well up to date..guess because I stopped
at 3 series and 3 parallel strings, as per the general consensus out there in the solar community guidelines!
I'm probably going to go with 2v - 915AH AGM's next and get rid of some of that parallel wiring in the bank.

The ambient temp last few days has been coolish...here in southwest AZ...daytime highs of 60 deg F...nightime 32 deg F...battery bank
temp display showed 17 deg C ( VIC)...during the daytime..I have the T Comp set for -5mv/cell/C...WBJR end amps is set at .1
That load of 4 amps I mentioned is not constant...It's a 12 volt freezer that obviously cuts in and out to maintain -8 degF and it's sitting
outside always in the shade, so lately at night when it's 28 to 30 deg F...that freezer shouldn't be running much!
WB...I do have a Voltage Offset of +2 set on the MNGP...I found through measurements taken with my highly regarded and very reliable Fluke DMM that the MNGP was displaying 2 tenths of a volt higher than actual measured voltage..with that offset it brought the MNGP
more inline with actual battery bank measured Voltage...I also have a remote display for the Magnum Energy INV very close to the MNGP display and everything pretty much shows the same Voltages!

I could isolate the 2 batteries that are reading the Lowest SP Gravity with some work, and see if things go back to the way they were...

Just curious, what is the rule of thumb when adjusting End Amps?  Is there a specific formula that takes into account the battery type
or age or combination of other factors?
Do you guys think it really would be necessary to install a Batt Temp sensor and WBJR  on the Kid also??   Although...here's the caveat
The Kid and Classic had worked beautifully together in harmony for over a year now without the sensor and WBJR (on the kid)...
I sort of thought..If it aint broke...don't fix it...so when everything hummed along great for that length of time with no issues, I didn't
figure I'd have to spend the extra coin for the extra Batt temp and WBJR...BTW can 2 WBJR's be installed onto one shunt??

Vic...I tend to agree with you that the health of my batt bank is generally quite good..I never have been able to approach 6 or 7 years
on a set of batteries when I was previously using "Other Manufacturer's controllers- the "M" word...Dip switches alone cannot fine tune
charging parameters, which include generous voltage set points for both ABSORB and FLT including time as well...along with fine tuning
by the WBJR...I am very pleased with the classic and kid products thus far and endeavour to pass on my thoughts and views to newbies looking to get "into the game".

[Solar trucker]

Just Curious...forgot to ask this in my last reply!  What is the "Rule of Thumb" when designing an ideal "Solar" Input
to Battery Combination?

In other words, how many watts is too much for any given battery bank?  Obviously, the charge controller is going to cut off the charging once the set point values have been met regardless of whether there is one panel or 20 panels...When power demand is high, Bulk charging starts and all available watts gets routed via the controller to the bank...Ok so there must be a logarithmic equation for the ability of various battery types ...ie: standard flooded, AGM's, etc...to Recover back to a fully charged state!  I think I read somewhere that AGM's charged faster than standard flooded batteries by as much as 20-30%...

Where I'm going with this is that I now have 696 AH of Batt bank (6 x 6V) and 1600 watts (if I'm real lucky) up on my roof of the RV...
That scenario travels with me 24/7 because I'm on wheels and move around...but for a good 5 months of the winter I'm parked in one
spot and could easily add more panels!

I really cannot change the battery bank size (thats's pretty much a constant...except when I go to 2v batteries, I'm going to increase the capacity to at least 915 AH for the area they are presently in..and again that size of batt bank will be travelling 24/7 eventually....

My question is:  I have a bunch more of these 327watt panels in my shed here at my winter location...I have plenty of real estate available to set them up...would I benefit greatly from adding say 3 or 4 more panels (up to 1.2kw) and another classic to the existing
equation just for the winter months?  The Sun shines here perpetually and it seems a shame to waste a drop of that glorious fuel when
I already have the panels sitting around...I could make temporary mounts that would break down and setup in no time...
I even have lots of spare 10 ga PV Cable and oodles of great quality 4 ga to tie in another classic...

Or is 1600 watts on the roof now...ample to charge a battery bank up to the anticipated 915 AH?  My general usage is fairly conservative now....SOC over the past 2 years has never been below 87% daily...think it was 85% once if I can remember..Saying all
that our usage is based on not going below that figure...so if I added another 219 AH of battery capacity and more panels, obviously
we could use more power in the daytime and slightly more at night and still stay in the 85 to 90 % SOC area...

[Westbranch]

ST, I'll start this and I am sure there will be lots of comments.... 

The recommended standard is to have between 5% and 13% of the Ahr rating of your bank available from  the array.  You can go down to 3% if your loads are not heavy.

Sounds simple but when you dig into it a bit you have  losses in the sytem which can be a bear to figure out... so 10% is often what gets used...

Then as you pointed out you have extra panels you want to use and that you don't always get a full charge (85 - 90% SoC).

I would start with the 90A target (10% of 915Ahr) and see just what the Calculator says for your panels   http://www.midnitesolar.com/sizingTool/displaySizing.php

or check out the KID too.  http://www.midnitesolar.com/sizingTool_kid/index.php

I know that 1680 nameplate Watts,  94.2A ( =~1250W & 50A max) to my 900Ahr battery for 3 hrs/day is just not enough in winter but more than adequate in summer when I see ~ 10 charging hours, it reaches Float every day.

Have fun..

[Vic]

Solar trucker,

First,  regarding a good EA setting;  For Flooded batteries (FLAs),  this is normally between about 3% to about 1% of 20-hour Capacity,  when one is using Vabs values in the range,  as recommended by the battery manufacturer.   When one changes the Vabs,  the ideal EA will change,  at least a bit.

You might start with EA about 2% of Capacity,  and use SG measurements to help zero in on that.   You will generally need to set the Absorb time to a value longer than you would expect the Absorb stage to take.

AND,  the EA value should be for the charge current going into the battery,  as read by the WBjr.  THe WB will measure the total charge current into the battery  --  from both the Classic and the KID.

Your system might be  a bit more predictable,  if you used a separate BTS,  connected to the KID,  near the other BTS,  on the same battery.

QUESTION:  What is the SG for a fully-charged battery,  as stated by US Battery?  OR,  what is the model number for your batteries ??

In general,     the recommended charge current INTO Flooded batteries is about 10 % of C,  with about 13% maximum charge rate.  However,  in the first 60 or 70 percent of Bulk,  this current could probably approach about 20% of C for FLAs.
EDIT: Although,  with parallel battery strings,  running much above 10% of C could be a bit risky is one battery string is hogging an excessive share of charge current.<

Some AGM batteries can Accept high,  or very high charge rates,  but this des not apply to all AGMs.

And,  generally,   AGM batteries cost about twice as much and last about half as long as FLAs,  that are well tended.

For some  the extra cost,  and the difficulty in determining when AGMs are actually fully-charged makes them difficult to manage.

Some folks actually feel that AGM batteries are maintenance-free,  which is not the case  --  they just need a different kind of attention and maintenance ...  IMO.

Later,   Vic

[Solar trucker]

WB...Thanks for the input Re: Array versus Battery Capacity...It's a good place for me to start

Vic...US Battery give the figure of 1.270 as the SP GRVTY for a fully charged US Battery XC 2200 - 6v (232AH)

I think that installing a BTS on the kid would also be a good plan, as you say to make things "A little more predictable"...
I was interested in reading your comments re: AGM's...I thought it was the reverse!  Maybe the sales literature
on them had swayed my thinking...I knew that they are much more expensive than the FLA's...but thought that
with that extra premium, one got no maintenance in regards to adding water, AND properly charged and discharged AGM's would give more cycles than FLA's at respective SOC values...
Actually, you've given me food for thought...I'm not adverse to adding water a couple of times per year...I must admit that cleaning some of the battery connectors from time to time with Baking Soda (again usually only twice a year also) is a little more of a pain in the Butt...BUT I could live with that if the general consensus
is that FLA's are still easier to charge and maintain that way!  and actually the cost is much more attractive!

One of the main reasons, I was looking at AGM's was the fact, that they are made in various AH ratings in the 2V style as compared to FLA style 2V batteries seem to only start at 1150 AH...which also means (!25 lbs)
per battery...that puts the total weight of a 1150AH bank at 750 lbs....A 915AH AGM Bank is 570 lbs ...with
both banks using 2V batteries!  That's almost 200 lbs difference...If I shored up the battery bank platform
with extra underneath struts, could accommodate the extra weight...I must admit the extra 200 AH from the
FLA- 2V version would be welcomed...

Just Curious, can only one WBJR be installed per shunt?

Walter

[Resthome]

Walter

You might want to refer to the Wizbang Jr â€" Installation Instructions manual. There are a number of settings that can effect what you see for SOC% on the MNGP. While it is close it is not 100% in accuracy. You can view the NET A-HRS to see if you are in the positive territory. If you have it set in the Tweaks menu when you go to Float the NET AMPS should get reset to zero.

You also want to verify the Battery SOC setup shows the correct AMP Capacity for your battery bank (700 A-H) and the Efficiency of you bank should probably be around 90% or slightly lower for your older batteries.

And there is the Battery Capacity Temp Compensation which should be set to your battery reference temp (usually 25C) and percent of Capacity change per degree C of battery temp (default is 1%). Mine is set to 0.6% per manufacture data chart.

If you battery are colder than 25C then you will have less AH Capacity available from your battery bank.
If you are using Auto Equalize on old firmware there were issues with it not working correctly. You need the latest firmware or use EQ in manual mode until you get the firmware updated.

You have Absorb set to 3.25 hrs and End Amps set to 0.1 A if I read your comments correctly. You want to make sure the Classic is set in the Charge â€" Advance menu to show “SHUNT”.  I think your End Amps is set too low. So you are most likely ending Absorb at the 3.25 hr setting. You want End Amp set to the value at which your WB Jr amps into the battery bank roll off to a flat reading when looking at the WB Jr amps graph on the Local App. Not sure if this can be plotted on MYMidnite web site as I have no internet connection at the lake so use the LA on my laptop. You should initially set the Absorb timer higher until you determine the end amps then it can be determined how long it takes to get to End amps and set the Absorb timer slightly higher.

See sample of graph. Might want to read this thread also.

http://kb1uas.com/mnsforum/index.php?topic=2364.msg22539#msg22539

[Solar trucker]

Good points John...I am using auto equalize...I will do a manual EQ tomorrow early in the day so I can fully do a proper 2hr one and because I'm on mac, have neglected updating the firmware!  I have been meaning to borrow a windows laptop to try and do an update...

Also, my bank charge eff is set at 94% which is obviously the recommended  setting for new batteries, so good
point I should be lowering that figure to reflect the older batteries!

Also will look at my settings re: WBJR setup...you are right about EA being set too low also...

Thanks,
Walter

[Resthome]

Here's another one of my graphs to determine end amps. I also plotted the MNGP SOC on the right axis. The left axis shows the WB Jr Amps into the battery bank. The end amps would be set around 12.5-13 Amps. You can see where the WB Jr Amps start to flatten out. Note the SOC reaches 100% well before this point.

[Westbranch]

Walter, check back here when you borrow a Winderz machine you want to make sure you get the right version of the update program AND corresponding instructions for W7, W8, W10 or?Ther are a few tricks you need to follow

[Solar trucker]

John...that's a great little graph depiction of the charging status!  Thanks for the tips on the
other stuff as well...I will look at the battery temp comp and efficiency settings tomorrow.
I know that the WBJR setup in the MNGP is set for shunt for sure...

WB....I agree that I definitely need to get my hands on a Windows machine and update to the latest
Firmware and then see what's going on...Also then I can approach the settings with the proper
Firmware....
Thanks for the suggestion...

[CDN-VT]

Just Curious, can only one WBJR be installed per shunt?

Walter

Yes it can be done . I'll post pix

I did a post of just that & explained the setup of the spacers

VT