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Other MidNite Electronics => WBjr => Topic started by: alyaz on February 13, 2019, 07:26:29 PM

Title: Dialling in the SOC reading...
Post by: alyaz on February 13, 2019, 07:26:29 PM
I read a few threads here and am wondering if you guys have any suggestions or if it is possible to get the SOC % reading a bit closer than what it is currently showing.

From reading the threads, I suspect this is going at it back asswards, but wondering if this way around is also possible...

Today my three Classics went into float (set for end amps) at the same time that the SOC% reading was toggling between 92-93%.

So would you adjust the battery efficiency parameter (currently set at 85%) or the capacity parameter which is currently set at 1075 a/hrs (1105 a/hr bank) or both?  Steve at Rolls suggests that the FLA’s are about 80% efficient, so in your opinions should I just lower that parameter?   

Thanks.
Title: Re: Dialling in the SOC reading...
Post by: ClassicCrazy on February 13, 2019, 08:25:39 PM
If you are using follow me they will all go to float at the same time - that is what it does.
Yeah - I would lower the efficiency .
Then I would monitor the specific gravity sometime when they are charging and if it hits full by SG when it is says at SOC ( and by ending amps)  you are okay.
Main thing is you want the batteries to be charged. 
Do you have the Absorb Voltage at the lower end of the range - if not I would lower that.
You may want to adjust your ending amps too if needed.

Larry
Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 13, 2019, 09:12:37 PM
Thanks Larry.

Yes I have the absorb amps set at the low end of the range.

Will try the 80% then...

Should have mentioned I did check a few of the cells and SG was between 1.260 and 1.275.
Title: Re: Dialling in the SOC reading...
Post by: ClassicCrazy on February 13, 2019, 11:31:37 PM
Sometimes I see my batteries go to end amps and float at around 92% .  Seems like it depends on how cold my batteries are, how deeply discharged they were the night before, and how many amps are flowing in . 
Do you have your Absorb time set long enough ? I ask because if your absorb time runs out before it gets to your end amps it will go to Float no matter  what the SOC is at.

Larry
Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 14, 2019, 12:23:53 AM
Yes.  I have my absorb time set at five hours and today I got to float after 3:15 hours in absorb. 
Title: Re: Dialling in the SOC reading...
Post by: ClassicCrazy on February 14, 2019, 01:29:41 AM
Actually now that I think about it - if your batteries filled up at 92% then you want to raise the efficiency not lower it.
Did you notice if all the amps taken out the night before had been filled back in and then some extra before it went to to Float ?
Mymidnite makes it easy to look back at the history because you can drag the line across the graph and see the negative amps  go up as it charges , and you can see the SOC at the same time . So if it fills 100% of what is taken out , and then keeps charging some more above that to make up for the efficiency - that is the point where you want to see the ending amps terminate the Absorb. On the graph you should able to see the system amps - battery charging amps start to level off for a bit - that should be your ending amps setting.

Larry
Title: Re: Dialling in the SOC reading...
Post by: boB on February 14, 2019, 02:03:13 PM

Amp-Hour efficiency should be in the around mid-90% area typically.

Maybe old  batteries might be less.  But shouldn't be 80 or 85% for pretty sure.

And for ending-amps, you might want to let them charge for many hours and watch to see where the current goes to a flat low spot and stops decreasing.   It can't be any lower than that and shouldn't be too much higher of course.
Title: Re: Dialling in the SOC reading...
Post by: Vic on February 14, 2019, 04:04:20 PM
Speaking as someone who is NO battery expert,   will make a few IMO-comments:

Yes,   there are many variables when trying to set battery parameters.

It seems that one important variable in choosing an Ah Charge Efficiency factor for a Flooded Lead Acid battery is  the rate at which it was discharged  --  the Peukert factor.   When  we count Ah into and out of the battery,   and cannot account for the Peukert factor,  that some significant variable is accounted for,  because the actual SOC at the end of the discharge really does depend on the Rate of the discharge.

Also,   most FLA battery manufacturers do note that the Charge efficiency of their batteries is 85%,   but this is almost certainly based on a discharge to 0% SOC (as this would make the efficiency appear to be its highest).

Battery Charge Efficiency is highest during the part of the charge that is at low SOC  --  very efficient  to about 80%  SOC,   much less so for batteries that cycle from 70,  or 80% SOC to a full-charge.

Again the following Link to some tests done at Sandia Labs on FLA Lead Antimony batteries:
https://xtronics.com/uploads/batpapsteve.pdf

The above tests were performed with C/30 discharge and charge Rates,   so will not necessarily be comparable to most of our off-grid,  Solar charged FLAs.

AGM  batteries have much higher Ah Charge Efficiencies,  due to their relatively high SG electrolyte,   which raises Gassing Voltage.  Resulting in considerably less time spent in the least efficient part of a LA battery charge stage  --  Gassing.

IMO,  for off grid FLA,  Solar-charged batteries,   the Charge Efficiency factor could vary considerably  from day-to-day based upon DOD,  discharge/charge Rates,   and a number of other variables.

Bottom line to me,   is that the WBjr  is a valuable,   inexpensive tool to help us monitor the charge and discharge of our batteries.   Am very pleased with the  performance of the WBs in use here.   But any Battery Monitoring device  will have limitations in its ability to show actual SOC,   and similar data.    A  great arrow to have in the battery-management quiver.

Just some personal opinions.   FWIW,   etc,   Vic
Title: Re: Dialling in the SOC reading...
Post by: boB on February 14, 2019, 04:53:35 PM
I'm definitely not opposed to changing % efficiency to 80 or 85%

One can do a lot of charging and measuring specific gravity and voltages after waiting a while as well to tell what the proper efficiency is.

I was going on the recommendations of Ralph from Bogart Engineering's SOC calculations in his manuals.

He had a lot of years of experience doing this.

But then again, it will not really hurt anything to lower the efficiency a lot lower.  It will just take longer to say 100% and possibly use water faster.



Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 14, 2019, 07:44:06 PM
Thanks gang.  I will play around a bit with it and report back.  I couldn’t make sense if I should be upping or lowering the efficiency %.  :)
Title: Re: Dialling in the SOC reading...
Post by: ClassicCrazy on February 14, 2019, 10:07:48 PM
Quote from: alyaz on February 14, 2019, 07:44:06 PM
Thanks gang.  I will play around a bit with it and report back.  I couldn’t make sense if I should be upping or lowering the efficiency %.  :)

Like Vic said above - it may be a bit different every day and SOC is just an estimate to make the invisible visable . 
There are probably more accurate ways to guess what is going on in a battery cell like monitoring individual cell voltages and temperatures and comparing them in relation to the charge they are getting at the time and in relation to each other.
But most people just seem to settle in for the good enough rough estimate.  Flooded lead acid cells can take a lot of abuse and still give pretty good performance so giving them better care than that is probably good enough .

Larry
Title: Re: Dialling in the SOC reading...
Post by: Westbranch on February 16, 2019, 09:24:28 PM
Uh, er....AL aren't these the new batteries ?

If so have they been through the 50 or so cycles that most battery makers recommend before worrying about the SoC etc?

I agree with a raise in the efficiency value especially if you are through the break in period.
have fun...
Title: Re: Dialling in the SOC reading...
Post by: Vic on February 17, 2019, 01:25:01 PM
Quote from: Westbranch on February 16, 2019, 09:24:28 PM
Uh, er....AL aren't these the new batteries ?

If so have they been through the 50 or so cycles that most battery makers recommend before worrying about the SoC etc?

I agree with a raise in the efficiency value especially if you are through the break in period.
have fun...

Wb,   am NOT Al,   but,   ...

These batteries have been in off-grid use for about four months.  See Reply #39:

http://midniteftp.com/forum/index.php?topic=4158.30

SO,   they should be sufficiently broken-in,   IMO.

FWIW,   Vic
Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 17, 2019, 08:52:09 PM
Yes, they are in full-time use so well over 50 cycles.

I didn’t get a chance to watch when it went into float today so will wait for another sunny day.  If nothing else, it’s all good information and experience for me to get to know the workings of the ‘system’ better.

Here’s another question (yes, yet another question).

While using end amps...

So, the absorb voltage used is the voltage that we set into the controllers.  The absorb time is the default time should the end amp setting not be reached.

What is the correlation between the absorb voltage and reaching the end amp setting.  For example, is there any difference using an upper parameter absorb voltage setting versus a lower parameter absorb voltage setting when using end amps?  Or as long as I am in the ballpark (in my case between 29.4 - 30v) will the batteries accept and react to the end amps the same?  Hope that makes sense.
Title: Re: Dialling in the SOC reading...
Post by: ClassicCrazy on February 17, 2019, 10:27:23 PM
With new batteries I would use the lower end of the absorb voltage range . You can raise it as your batteries age and may need it. They don't need it now so all you do with a higher voltage is theoretically heat them up more which shortens their life.

Ideally you would want SOC to be at 100% at the exact that ending amps is reached.  You want the end amps to be when the batteries are 100% charged according to SG test. The end amps at that point should be leveling out and not changing too fast - if you looked at it on the graph  you would see it start to plateau and smooth out.

Hard to get it all perfect because of real world variables and the batteries are not precision devices but they last a long time if a minimal effort is taken to get them set up right and check them seasonally to ensure they are happy.

Larry
Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 18, 2019, 12:19:49 AM
Thanks Larry. 
Title: Re: Dialling in the SOC reading...
Post by: Vic on February 18, 2019, 01:28:04 PM
Quote from: alyaz on February 17, 2019, 08:52:09 PM

   ...   Here’s another question (yes, yet another question).

What is the correlation between the absorb voltage and reaching the end amp setting.  For example, is there any difference using an upper parameter absorb voltage setting versus a lower parameter absorb voltage setting when using end amps?  Or as long as I am in the ballpark (in my case between 29.4 - 30v) will the batteries accept and react to the end amps the same?  Hope that makes sense.

Hi Al,

If the Absorb voltage is changed on your FLA batteries,   it WILL affect the current that is charging the battery.   This will have some effect on the desired EA value,  and you would need to watch the WbJr current into the battery to find how the Vabs change affects this current.

Raising Vabs will increase the battery charging current (and should dictate some increase in the EA value) to terminate the Absorb at the appropriate time,   and lowering Vabs  will decrease this current,   and could easily require some reduction  in EA value.

Our choice of an appropriate EA value,   is in the area of the WB battery current where (it)  has STOPPED decreasing   Often there is a reasonable Jitter in the WB current value. This Jitter can make it difficult to really see when the current has stopped decreasing,  especially when viewed on the MNGP (at least on the systems here,   that use EA).

Am sure that you have significant changes in the amount of Solar production from one day,   to the next,   this time of  year. Short Solar days and inclement WX often dictate somewhat higher Vabs under these conditions.  Generally use the lowest Vabs that will allow your batteries to be fully charged (as noted by Larry).

FWIW,   Vic
Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 18, 2019, 02:07:39 PM
Thanks Vic. 

I’ve got my numbers working now.  Guess we will see if and how quickly the % falls off as time passes.

One thing I find amazing though is how on top of things a person really needs (needed) to be before the Whizbang Jr.  Everyone around this area is absorbing the heck out of their batteries everyday, based on absorb time.
Title: Re: Dialling in the SOC reading...
Post by: alyaz on February 22, 2019, 09:42:53 AM
I know you guys have explained a lot of this to me already, so sorry for that.  Seems I need the explanations framed in my situation to make sense for me... 

So in a perfect world, do you guys try to set your end amps as low as possible so that your controllers move into float fairly seamlessly?  In other words, I lowered my end amps from 12 to 11 and when I have had time to watch the amps ramp down, they move pretty continuously lower until the end amps are below 11 and the controllers go into float.  Wondering if I should try 10.5 or is this ‘end amp number’ best predicated on SG readings?  Or is the battery bank not really fully charged till the amps level off (which I am having a tough time deciphering from the Wzb Jr graph).  Before I set up the Wzb Jr, I was watching the amps fall as low as about 9 before levelling out.  And am I slicing hairs here, in other words, is the difference between 11 a and 10.5 a or 10 a so minute that it’s not worth worrying about.  Thanks.
Title: Re: Dialling in the SOC reading...
Post by: ClassicCrazy on February 22, 2019, 12:53:36 PM
I think it is easier to spot the leveling off using Mymidnite graphs . Use full scale option . When you have the graph ( or past days graphs) on the screen you can select which parameters you want displayed  - so use SOC, whizbang amps, net amps , etc  - you can choose which ones you want to display.  The good thing is that once the graph is up you can drag the mouse along the graph and the data on the left will change to the point of the day where indicated.  So start out and night 0 amps coming in , then as the sun comes up  you see the amps go up, the negative net amps get charged, the SOC percentage climbs, and you can see the spot where it goes from Absorb to Float.
If you look back a week or so you can get an idea of what your system is doing - ideally you want to see SOC get to 100% when it goes from Absorb to Float and that should be the point where the amps on the graph start to level off.

Larry
Title: Re: Dialling in the SOC reading...
Post by: Westbranch on February 25, 2019, 12:41:44 PM
I use Grahams Android App on my tablet , as it gives me a better , larger, view than a smart phone.
I set the EA to 5 amps and then watch at the end of the day, in winter we lose the sun behind the mountain ~ 2 PM, so have to wait for it to get up over the ridge before I can get a real EA estimate...  about the  end of March.
As Larry said you look at the 'tail end' of the graph and look for the flattening of the curve, which should be visible to the eye...
Now use the visually determined value and reset the EA setting, next day see wheat your vales are and do your SG readings and if you don't like it work from that point.

Have fun
Title: Re: Dialling in the SOC reading...
Post by: alyaz on May 12, 2019, 09:52:26 AM
So got everything set up nicely but what I have noticed as of late (has been sunny every day) is that with ‘end amps’ set up, the batteries are only in ‘absorb’ for about an hour or so before the ‘end amps’ setting is reached (and SG readings show full charge). 

I clued into this as my Midnite Solar Battery Monitor has the lights on it that shows a yellow light if the bank hasn’t theoretically been fully charged within the last week.  The criteria for the monitor yellow light, as I am sure you know, is that the batteries must be at 29.4v for a least two hours, for the monitor to reset to green.

So yesterday I watched the timer before it got to the EA setting (and reset) and figured out that this is what must be happening.  It seems much of my charging is occuring in Bulk and not much absorb time (at least with this much sun) is needed to reach the EA setting.

So... if the bank is reaching EA and not absorbing much, should I be ‘zeroing’ out the EA maybe once a week and just letting the timer take it through a longer absorb cycle?

If I do that, I get the batteries to absorb longer, but my SG readings climb too.  Currently the EA settings, even with the short absorb time, are currently getting the batteries up to the 1.275 / 1.280 SG limit.

Fwiw, I already have my absorb charge voltage at the low end (29.4v) and my EA at 12a.  (Steve at Rolls suggested 12a to 14a).  I have played around with EA’s, setting it lower than 12a, but my SG readings climb a bit too high.

Does sulfation occur under these conditions?  Thoughts?  Thanks.
Title: Re: Dialling in the SOC reading...
Post by: Westbranch on May 12, 2019, 01:41:55 PM
What happens when you add 0.1V to the Max /voltage for Absorb? How many minutes longer does the Absorb last?sorb?
How many days will the experiment  take till you get a full Ab?
:)
Title: Re: Dialling in the SOC reading...
Post by: boB on May 12, 2019, 01:53:44 PM
Quote from: alyaz on May 12, 2019, 09:52:26 AM

So... if the bank is reaching EA and not absorbing much, should I be ‘zeroing’ out the EA maybe once a week and just letting the timer take it through a longer absorb cycle?

If I do that, I get the batteries to absorb longer, but my SG readings climb too.  Currently the EA settings, even with the short absorb time, are currently getting the batteries up to the 1.275 / 1.280 SG limit.

Fwiw, I already have my absorb charge voltage at the low end (29.4v) and my EA at 12a.  (Steve at Rolls suggested 12a to 14a).  I have played around with EA’s, setting it lower than 12a, but my SG readings climb a bit too high.

Does sulfation occur under these conditions?  Thoughts?  Thanks.

Sulfation may very well  occur when you don't Absorb once in a while at least.  This is typical.

Other than that, I think you have it right.

Skip Bulk Days was made for your scenario.   A combination of skip days and EA usage would have been even better though.

Sulfation should not happen as long as a good long absorb cycle happens at least once every few days at least or maybe once per week ?

I'm not sure what too high of a specific gravity is though ?  A higher value just means that the electrolyte has more sulfuric acid in its solution which in my mind means there is less of it on the battery plates ?  What I mean is that if you can see a higher SG, then there is more on the plates ? So if too much is left on the plates, wouldn't that mean eventual partial sulfation ?

I'm not an expert on that theory though so you will want to ask your doctor  :)   (i.e. the battery manufacturer, someone who knows this)

boB
Title: Re: Dialling in the SOC reading...
Post by: mike90045 on May 13, 2019, 12:46:51 AM
If Specific Gravity is still rising,  the batteries are still charging. 

Once the SG stops climbing, you are needlessly gassing the batteries and causing + plate corrosion.

You cannot raise the SG too high, you can only raise it to the set-point of the factory fill.

You can slightly extend the battery life by only charging to 95% full daily, but you still need to get to 100% to drive the sulfur off the plates and back into solution.    The longer the sulfur sits on the plates, the tighter it sticks, and once bonded, you have lost that portion of battery capacity.  The plates have started to sulfate and special measures are required to reverse it.
Title: Re: Dialling in the SOC reading...
Post by: boB on May 13, 2019, 01:18:38 AM
I think you hit the nail right on the head, Mike !