How to tweak absorb

Freewilley

Another thread dealt with my new battery set up with 2 brand new S550.
Finally my system will run an absorb cycle.
Now, I need to work with that, I guess.
I have only run these through 3 cycles or so, bringing them back to 100% each time and the other day purposefully taking them to 50% and back.
Today's absorb cycle shows some issues possibly. It was a pretty good solar day with some daytime heating clouds in the afternoon. Very little power use in the house, and what there was I ran the genny for.... a couple of hours first thing for the laundry and coffee.
Here is the history...
930 am had run genny for over an hour and sgs were 1.230 and 1.245 in pilots, current 24 amps and FM and MX were on ABS
1 pm absorb had run 3.5 hours and 1.245 and 1.250, current was 4.5 amps
2:45 absorb had run 4:15 hours and fm said Charged 1.235 and 1.250 current reading 2.8 amps
My settings were
MX abs 15.2v 4.5 hours
FM abs 15.0v 4 hours
I started an EQ cycle as they say that is not a bad idea when just starting (one battery has sat here for almost 3 months fully charged)
So even though I have a high voltage setting and long absorb cycle, they are not coming up like I would expect.
Tweaks or comments?

Vic

Hi Freewilley,

OK,   IIRC,  you have no way to read the actual battery charge current ...   think your Trimetric is dead   ...   forget.
But,  probably the currents that you note are CC output currents ?

And,   kinna asked before about just that type of Hydrometer you have ...   is it an all glass one,  or  was an earlier guess that it was the MidNite Hydrovolt ...  ?? ?

Those currents seem low enough for the SGs to be somewhat higher than your readings.  However,  coming from being about 200 Ah removed from the batteries plus inefficiencies,   you might need a second day or so of Absorption,  depending upon further nighttime discharge.

Assume that the batteries are a bit cool,   but not cold (?),   and you are using RTSes on both CCs for the S-550s (?).

Thanks for any added detail,    Vic

westbranch

Can you be more specific as to what you expected.... it can take up to 50 cycles for those batteries to get 'broken in'

Freewilley

westbranch said:

Can you be more specific as to what you expected.... it can take up to 50 cycles for those batteries to get 'broken in'

I am not sure....I know that they are about 80% capacity until broken in, but the battery has to be 1.26 or higher to be fully charged. I expect them to get up to at least that....even though the amp hours may be 80% of what they will be.
Am I wrong?

Vic
I have rts covered.
I have a glass hydrometer with the thermometer inset.
The acid temp is perfect, no adjustment up or down.
The current I am reading is on the cable going into the string...positive of course.
I am using my new Sears clampmeter, which I am very new to....never ever had one.

Will I always need that much absorb time or is that just starting out?

With my alternate "bad string" I can switch off these and start them off in the morning at 80% charged....

Vic

Freewilley,

OK on the glass Hydrometer with Thermo.   Good.   Just make certain to RINSE,  RINSE,   ...   RINSE it after every measuring session,  using Distilled Water.   This is essential for repeated accuracy.

Thanks,  too for the reminder that you do have a DC Clampon Ammeter,   just watch the zeroing carefully.   Clamp DC ammeters can be influenced by external currents,   etc,   so it can be fairly easy to get misleading readings,  IMO.

Did you not have a Trimetric/Shunt that may be broken, somehow ??   If it can still read the current going into/out of the battery using a Shunt,   this would be very beneficial.

The Absorption time depends directly on the DOD that the battery has experienced in the past discharge,   so this will be a variable.

It is probably a good idea to try to get a full recharge into the 550s,   soon.   You might need to limit the DOD,  in order to accomplish it ...   know that you are trying for a full charge.   Cycling to about 60%  SOC  on occasion is good,   but as a part of initial cycling  getting to full-charge several times per week would be good.   Full cycling  now  should also be a good thing.

Let me say,  that you DO seem to be very focused on getting things as good as you possibly can on these new 550s.   This is a very good thing!   Keep at it,   and they should settle in,   soon.

Vic

Estragon

I agree with Vic on the rinse thing. Also, it sometimes is a good idea to take multiple readings on each of the pilot cells so you can disregard a sticky one.

I had consistently low readings on my glass hydrometer. When I got a new one, the readings are consistently higher, so I wouldn't be all that concerned about getting to above 1.26. What would concern me though is having a cell that went from 1.245 to 1.235 with charging current over a couple of hours. Could be a bad reading, but could be a problem with the cell or wiring.

Estragon

Have to disagree with Vic on the absorb time being variable with DOD though. Bulk will vary, but absorb time depends on what the battery needs - it's however long it takes for the battery to take minimal (~1%C) current at Vabs.

Freewilley

Well, mea culpa. 
I do not rinse my hydrometer. Certainly not for many years....I think I knew, and did, that at the start 8 years ago.
 I have a new hydrometer (two as of reading this post) on order. 

And I may have cured a problem that affected absorb times.
Last night the system went down a couple of times when there was a heavy draw (my sewage pump). I went back to my old string and was very perplexed because the voltage was higher on the old string than the new...even though the SG readings were higher (and good) on the new string. All 6 cells were 1.240 on the new....
So I wiggled all the cables etc and all seemed good. Ran the Dishwasher with the genny on for an hour and voltages came right up on the new string...bedtime they were reading 12.5 on the Mate.
So upon investigation and thought....I said must be dirty connections. I pulled the cables off the new string and cleaned up the lugs and terminals...they were not BAD, but I got the lugs nice and shiny etc and reconnected.

I am thinking there was just enough of a bad spot that I was having a weak connection. I would not have thought so looking at the cables, but I am sure I have good connections now.
Vic, nothing to do with the shunt as it was not ever installed here. I tried it on my RV a dozen years ago. The parts are in a box....

The experiment continues.....and thanks for your thoughts!

BB.

Using a volt meter set to 2 volts (or even 0.2 volts) full scale and measuring voltage drop on each cable and connection while there is heavy current flowing (charging or discharging) can quickly identify poor or bad connections (or even cables that got electrolyte up inside and are corroding).

Generally, you are looking for differences (i.e., everything is 0.01 volts or less, and one point is 0.5 volts drop).

-Bill

Vic

Freewilley,

Ok on the Trimetric from years past.

It is a very good idea to gently clean the battery terminals and lugs as necessary.   Tin plated lugs  often fare well without very much burnishing at all,   just do what is necessary to make them generally shiny.  The Tin plating is thin so gentleness is usually good,  and all that is needed.

IMO,  once the battery terminals and lugs are clean and fairly shiny,   coat all of the mating surfaces and all of the battery terminals and cable lugs with petroleum jelly.   This is inexpensive and tenacious.   There seems to be no compromise in conductivity between the batt terminals and the cable lugs ...   this,   too,   may be a bit controversial.

There is the following formula for calculating the time for Absorption of a LA battery,   then,  one would see,  that there is NO variable for SOC,  or DOD of the battery:

t = 0.42 x (C/I)
 Where:

t = Absorption Charge Time (Hours)

C = 20 hr Rated Capacity (AH)                [ex: 2 strings x S-550 models (428 AH)  = 856 AH rated capacity]

I = Charging Current (Amps)                  [charger output min 5% up to max 10% of 20 hr rate] 
(above formula stolen from Surrette Battery Ltd possible Copyright applies)

BUT,  to me,   the above is for Constant Current charging (IUI).

For most of us that are using RE charge sources,   we really cannot use Constant Current chargers.

SO,  we  use Constant Voltage for Absorb.

All of the battery banks here  have Absorb times that require a wide variation in Abosrb times,  that does depend upon the DOD of the battery in the previous discharge.

Otherwise,  using the EA functions in the good solar CCs  would be of no use,   and also,  why would there need to be a Max Absorb time setting in many CCs,  if the Tabs was NOT a variable in battery charging?

The above,  just mo read on things,   not to argue too much,  FWIW,   Vic

Freewilley

Thanks Vic. 
Oh, you are supposed to keep the tin on???? I light sanded them to the copper. Is that a problem?

Given the 2 CCs and the fact they do not time absorb the same (one takes over and one sleeps often) or at the same setting and are not synced, I decided since the new batts were 80% charged and a great solar day that I would only use one CC and  see what happens. I was leaving for 5.5 hours and I left the MX on, with ABS set to 15.2 and 3.5 hours. Float was set to 14.7 (yes, should have taken that down to 13.2)
I just came back and the SGs show 1.245 to 1.255 with 4 being 1.240. The MX had run its ABS cycle and was floating. It had taken in 1.2 kwh. There was only the fridge on in the house, which uses about 1kwh per day, so lets say the batteries took in about .8kwh in the time I left and got back. The voltage shows 13.2 after the string was disconnected from charging for about 15 minutes.
So I am not happy.  Why not 1.260 or better?
Next step...I shut down the MX and am running the FM from start with a new absorb cycle. Trying 14.8 and 1.7 hours (the time remaining until the Good Wife starts cooking supper). The current read .8 to 1.2 with a median of 1 amp. That is measured at the positive lead at the new string (hope I am doing that right).
Will let you know...

Freewilley

Also, given that I see my two CC not in sync often, I am thinking that I should have bought the bullet and added a Hub when I realized I needed 2 more RTS...but I am contemplating the Hub now.
Not much info on the forum, some saying no need for them to talk to each other. 
In my case I have 2 different controllers with very different PV arrays. I think I need to buy into this...just for my sanity.
I am not sure if the Hub will work correctly with my Mate, which is gray and is 9 years old or so...
I just spent 30 minutes on hold to ask Outback but never got through. I left my number and will see if they call back.

Freewilley

The second absorb cycle did not raise the SG. After resting a couple of hours they are still 1.250
I will start them off at that level tomorrow and absorb them again.
Any advice on the settings for absorb for the 2 S550s?

Vic

Hi Freewilley.

Your low-ish SG readings might be due to a Hydrometer that has some air bubbles causing low readings.   Hope that your new Hydrometers arrive there soon ...

Regarding the Tin plating being sanded through on some of the battery terminal lugs,    if those lugs and terminals are clean,  you should be able to just goop them up with petroleum jelly,  which should protect them from acid attack.

Could you please remind us  what are the PV array sizes on the FM,   and the MX CCs?

It is THE customary issue when one has multiple CCs on a single battery bank,   that it can be a real handful trying to find settings for each CC that allows them to share Absorb stage sharing,  when not coordinated by some other device.

Suggest that you wait to buy any more equipment (Hubs,  Mates,   FNDC,   etc).   Please let others who are much more familiar with all of the ins,  and outs of OB gear than I help you develop a plan before spending more ca$h.

Later, running late.  Please keep us informed,    Thanks,    Vic

mike95490

Freewilley said:

Thanks Vic. 
Oh, you are supposed to keep the tin on???? I light sanded them to the copper. Is that a problem?

Whoops.  The copper corrodes pretty quickly, and copper oxide is not a good electrical conductor.  The tin was there to protect the copper

Freewilley

I have coated the lugs and terminals with jelly.
This hydrometer is very bad for bubbles but after many years I know how to get a stable reading, just tap on the side and the bubbles pop up.. I have seen readings of 1.260 on these batteries, so it is not consistently low.
My pv is (actual, not nominal) 700 watts on the MX and 550 on the FM. 

That second absorb cycle was only showing a current of 1 amp. So methinks that even though it was the first absorb cycle of the day for the FM, the cycle does not really start again if the batteries are 90% charged??? This is all new to me.

I am wondering what kind of absorb setting to use on the new string when it is starting out at 1.250 today? How high a voltage and for how long? 

mcgivor

Read the manual it states all the information, don't baby the battery, they are large tall cells, which need to gas once in a while, to stir the electrolyte, if it were me, I would fully charge, then EQ until the SG is where it is supposed to be, gassing freely, no loads between EQ'S. This may take several days with solar. My opinions, others may differ.

Freewilley

Read the manual....lol
I have spent months working with Steve Higgins at Rolls and he OFTEN advises different settings than in the manual. And we have great folks who in the last week have advised new Rolls need higher absorb rates and longer times than the manual.

Anyway, I keep reading that I should use my new Clampmeter and when the current remains static then that is the end of my absorb cycle. I have set end amps to 0, as suggested.
So I ran the absorb for an hour and SGs now are 1.255 to 1.260 and the current is fluctuating between .7 and 2 amps. So that is the end of absorb, I guess?
As Rolls does talk about an EQ to commision the bank I have started one for 3 hours and 16 volts.

What the heck is an FNDC?

Estragon

FNDC = FlexNetDc, presumably.

It's a box to monitor shunt(s) and displays stuff on the mate.

BB.

What is the actual (measured with a DMM) charging voltage (absorb voltage) at a the battery bank terminals and battery bank temperature when you are at the end of the charging cycle?

-Bill

Freewilley

Well I have checked the voltages at the terminals and the CC with a meter and they are the same...so it reads the absorb voltage which I had set to 15.2 ...is that what you are asking?
Temperature is not high. My thermometer only reads the SG adjustment number up or down from 80. It is about plus 3-4 SG adjustment so they are not  very warm.

Vic

Freewilley,

YES,   Estragon is correct,  the FNDC IS the FlexNetDC accessory from Outback (OB),   sorry for the oblique reference.

It is reported that the FNDC can coordinate multiple CCs going to Float at the same time,   BUT,  it may not work well in doing this unless (as mentioned on the OB Forum) that will ONLY do this with an MX-60 that has the latest Firmware (FW)  --  version 5.11.   I have none of the needed OB giblets other than the MX-60,   so cannot test it.

Regarding a Hub,  the Hub should allow sharing a single Remote Temperature Sensor (RTS) among most/all OB hardware devices ...   but,  you really need two RTS sets --  one on each battery string,   so,   to me,   it seems that you need to switch between two RTSes,  depending upon which string is getting charged.   And,  since there are  two CCs and two switchable batteries,  it becomes more complex...   I do not know enough about Hubs,  which Mate a Hub might require,   and just how one might be able to manage switching RTSes between the two CCs,   etc.   Manual switching may be the most direct/inexpensive way to do this.

If your battery temperatures do not vary much,   at this time of year,  perhaps running the RTS only on the new 550s,   and manually managing the charge settings when charging the older bank (for now).

Your Hydrometer readings are still probably suspect (IMO).   And so are the Clamp DC ammeter readings,   if they vary that much,  WHILE BEING STILL IN ABSORB.   2 A in Absorb,  especially at your elevated Vabs  seems almost impossible to attain on new,  healthy Flooded batteries  ...   is it possible that at that time,   the CC had dropped out of Absorb,  due to insufficient  PV power  (clouds or too late in the day)?   Guess that with very young batteries,  not really broken in,   that an elevated Vabs might possibly show about 0.5% or Capacity as a Return Current ...   but,  to me this would mean that the battery really is really about fully-charged.

Yea,   too  much conjecture.   Hope that the new Hydrometers arrive soon,   as this should remove at least one of the unknowns with your system.

FWIW.   Will later add something about one CC resting in Absorb (?) ...   thanks for noting the PV array sizes.   Back to work,   Vic

Freewilley

I think I am satisfied with my hydrometer readings...I EQd for 2 hours, now the new batts have rested offline for 3 hours and are reading 1.260 to 1.265 and 12.8 volts.
So I think the H is not reading low....also glad to see these up to 100%. 
I will keep cycling them....

Freewilley

Still having concerns over absorb cycles....have not got any ideas on tweaking on this thread yet...but learned many other things, so thanks, especially to Vic who must have given me 100 pieces of advice over the last few years.

So at 1.5 hours into my absorb cycle today, the FM is absorbing, the MX is floating and the SG pilot cell is 1.245. The current is 9 amps (since end amps is set at 12 on the CC, I guess that is so low to be insignificant?).
So it is still weird that my absorb cycles do not take the battery to 100% but in truth this has actually been the problem for my batteries for at least 4 years. The only way I get them up to 100% is running an EQ cycle.
I started with these 2 new batteries isolated and pampered thinking that would change. It does not seem to be...
So that is why I think I need some tweaking on absorb. Or I need to splurge for that hub and coordinate the charging. and one other confusion....if one CC is running an absorb cycle so is reducing current over time, what effect does the other CC have when it is set to a float of 14.7 or so? Is it cancelling out the reducing current because it is not running an absorb cycle and keeping current high?

Estragon

The current drops because the battery takes less to hold at Vabs, not because the CC is "turning it down". The current will taper on a curve that approaches but never quite stays at zero, which is why we end absorb with a time and/or end-amps value. Absent this termination, the CC would basically float at Vabs until the sun went down.

If one CC is floating (with Vfloat set lower than the Vabs set on the other), it will be sending no current to the bank. It will (should) only send current when it sees voltage at or below its float setting.

Freewilley

Thanks! Very helpful explanation.

Vic

It is a bit curious that one CC is Absorbing, and the other is Floating ...   unless the Vflt on the one Floating is set close the Vabs of the other,  would expect that the CC not Absorbing would be Sleeping ...

YES,   the situation with only one CC carrying ALL of the Absorption and the other contributing nothing  is perfectly fine,   as the lazy CC has nothing to contribute,  and the other has enough power available to do the Absorb job.

Still suspect (somewhat)  the SG readings,   hope the new Hydros get there soon.  Air bubbles inside Hydros can create false high,   and false low SG readings ...   it just depends.

Cycling the batteries should bring some stability/repeatability,  predictability to their behavior.

How much water is the new bank consuming,  on average?

Also,   as before,  unless your MX-60  is running 5.11 Firmware (or perhaps 5.10 or 5.11),  from what I read on the OB Forum,   the MX will not be able to coordinate the transition to Float (or, even might coordinate other stages, too).   Additionally,   a later model Mate might be required for this.

Furthermore,  as before,   since your system has two battery BANKs and a switch to select,   seems that you would also need to switch the RTSes between the battery being charged,   and the CCs   ...   doubt that any of the OB hardware would handle this automatically.

Driving by,   but keep at it Freewilley,   you ARE paying attention,   and like people,   batteries like to be attended to.

I am NO expert on OB stuff,   at all.   Or most anything else,   Keep at it,   Vic

Freewilley

Not worried about moving the RTS. Just leaving them on the new string.
The old string is decrepit and I only bring it up by running EQ cycles on it. Not thinking the RTS will make much of a difference.

Well, got a new hydrometer but the float broke during the unpacking. So have to wait until Tuesday to replace that one.

In the meantime, what effect would raising, the ABS volt setting have? I am already at 15, but how high should I experiement with? Should I just got up in .1 volt increments until I see a higher SG rate?

BB.

Look in the battery and see how much bubbling is going on... As far as I know (I am no battery expert)--Small bubbles and fizzing like a soft drink is good (and approaching full charge/good for equalization). If you approach anything with rolling large bubbles--That is way too much current (note, you can get a big bubble once in a while as the gas goes from being trapped below the plates and burbles up the sides).

I am sure that others with more experience than I can clarify/correct my suggestions.

-Bill

BB.

I should also add--Monitor battery temperature. Warming battery is OK (by a handful of degrees). Getting a battery up towards 110-120F+ -- running series chances of battery damage/shortening life.

Batteries will get warm/hot if you are charging them with high EQ voltage and current (5% nominal, ~2.5% of 20 Hour battery capacity minimum) where almost all of the charging energy goes into gassing and heating. If they get towards upper temperature limits when equalizing, stop equalization, let bank cool, and continue EQ (after normal charging) the next day. This (multi day EQ) has been known to go on for days (week+?) when trying to bring back these big Rolls/Surrette batteries to proper full charge/equalization.

-Bill

Vic

Freewilley said:

Not worried about moving the RTS. Just leaving them on the new string.
The old string is decrepit and I only bring it up by running EQ cycles on it. Not thinking the RTS will make much of a difference.

Well, got a new hydrometer but the float broke during the unpacking. So have to wait until Tuesday to replace that one.

In the meantime, what effect would raising, the ABS volt setting have? I am already at 15, but how high should I experiement with? Should I just got up in .1 volt increments until I see a higher SG rate?

OK,   probably an OK idea to only run RTSes on the new batteries.

SORRY to hear of the Hydro breakage   ...   a few of us believe in having about three Hydrometers  --  check them all for agreement,   choose the two that are closest in agreement,   and one will be your primary Hydro.   Mark the other two as to how much difference there is twix the primary,  reserve them in a safe place in a small box or similar.

If hydros are rinsed just after every use,  perhaps not letting them sit,  unrinsed for more than about an hour,  you should bet more than ten years of use from one ...  just be careful with them.

If your Vabs is still 15.2,   why not just leave it there.  With your new Hydro/es,   you should be able to actually see how well the batteries are getting charged,  based on fresh SG readings.

In response to your earlier wonderment about a CC EA setting of 12 A,   and measuring 9 A  with the Clamp meter,  personally would NOT use EA at this point.   Just set a long Absorb time,   and remove the uncertainty of the effects of inverter loads on the system keeping EA from being very useful.

IMO,   when the new batteries are broken in,   then it the time to try to find a CC EA setting that will work with your system.

No part of battery charging is exact or perfect.   BUT, with Flooded batteries,   things really do not need to be perfect very often,  just good enough   ...  again  paying attention to what you can measure,   and trying to get a sense of what the batteries are telling you  is a good thing.   FLAs are very forgiving,   unless they sit at a very low SOC for long,   without a recharge,   or,  if the plates get exposed from too little added Distilled Water ...   IMO.

FWIW,  Good Luck,    Vic