Author Topic: End amp hours (w/WBJR) noob!!  (Read 195 times)

ricardo

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End amp hours (w/WBJR) noob!!
« on: July 09, 2018, 03:06:28 PM »
So -- i just wanted to post this so that someone else can find it in the future.

I am a total noob, but a quick learner. -- I added a WBJR to my small off grid setup so i can have a better feel for the state of the batteries and to use end-amps for entering FLOAT.

I used the provided instruction sheet from Midnite, and configured the KID to use the WBJR, entered all the info on the KID (size of the battery bank, etc, etc) ..

and then i left it alone -- batteries were charging, and i could see the SOC, and amps going in/out of the battery bank, so the WBJR is working fine..

-- it wasn't until a week later that i realized that end-amps are something you need to specify in the confguration of the battery on the KID.

This might be obvious to everyone, but being a noob, it wasn't to me.. i thought that the KID would choose some reasonable end-amps to use for charging if you enable a WBJR.

-- after some research i found that most people set end-amps between 1-3% of the battery capacity. -- so i went right down the middle and set it to 1.5% .. (around 3.4 amps). -- i left the absorb time alone.

And now i can clearly see that when we get to around 100W in the absorb cycle, we move right into FLOAT  ..

simple -- but not obvious to a noob.
« Last Edit: July 09, 2018, 06:07:15 PM by ricardo »

ClassicCrazy

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Re: End amp hours (w/WBJR) noob!!
« Reply #1 on: July 09, 2018, 09:25:41 PM »
Ricardo - I don't remember what kind of batteries you are using . But if they are flooded  you want to have the end amps set to just about the point where the whizbang amps ( those going in to the battery ) start to level off. This should coincide with around 100% SOC which you confirm with specific gravity reading of the battery electrolyte.

It takes a bit of trial and error to tweak it all right . Your Node-Red graphical interface should help because you can look at the whizbang amps ( hopefully that is one of the data points made available on the kid ? ) and watch for the point where the whizbang amps come down and start to level off.  You may need to set the Absorb time longer to see this so it doesn't go to float before completed.

Larry
« Last Edit: July 09, 2018, 09:29:32 PM by ClassicCrazy »
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

ricardo

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Re: End amp hours (w/WBJR) noob!!
« Reply #2 on: July 09, 2018, 10:23:44 PM »
I am using FLA .. (Trojan T105's) ..  i'm going to order a specific gravity meter to verify what is happening at the end of the cycle..  i think currently we're going into float a little early .

ClassicCrazy

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Re: End amp hours (w/WBJR) noob!!
« Reply #3 on: July 10, 2018, 12:04:57 AM »
Also consider a refractometer - they are more accurate .  Of course some people may not want to have the acid so close to their eyes but no problem with care - only a few drops used.

https://www.ebay.com/itm/Glycol-Refractometer-Auto-Car-Fluids-Antifreeze-Battery-Acid-Engine-Tester-1Pcs/372280230477?hash=item56ada1824d:g:gsYAAOSwew5a1afS

Otherwise I got an East Penn Deka sp gauge for not too much at local store in auto section - and it also had the thermometer in it for temp compensating . Vic will tell you to rinse and rinse again with distilled water every time you use it.

https://www.google.com/shopping/product/16362379241591596822?lsf=seller:6583990,store:11512167933450002260&prds=oid:10788622383360814260&q=east+penn+deka+hydrometer&hl=en&ei=1jBEW57nJI77jwSUrp3wCw&lsft=gclid:CjwKCAjwj4zaBRABEiwA0xwsP-fhgx9xsbRhCQPDMqt7KzCnkGRvrTJDx04NyHgtOm00VCAqROOAMxoCN3UQAvD_BwE

Larry

« Last Edit: July 10, 2018, 12:07:34 AM by ClassicCrazy »
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

ricardo

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Re: End amp hours (w/WBJR) noob!!
« Reply #4 on: July 10, 2018, 01:02:04 AM »
I was checking out the battery amps graph for today .. (this comes from the WBJR on the KID) ..

It looks like the amps were beginning to level off at the currentl setting of 1.5% . .(3.3A) .. but i think i'll try a slightly lower settings to verify what the amps graph looks like for a slightly longer time.  (amps are in yellow in the graph below)

right now the bank dod is fairly shallow (about 8 or 9% overnight) because i sized the system for winter .. when the battery's are going to be probably as cold as 40F .. and we get very little sun in Seattle in january.  -- anyone care to explain how DOD affects end amps?


ClassicCrazy

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Re: End amp hours (w/WBJR) noob!!
« Reply #5 on: July 10, 2018, 10:18:33 AM »
Without knowing the state of charge it was in  hard to tell if that ended Absorb on ending amps or when the Absorb timer ran out.

From my own graphs it usually seems like the 100% point would be a bit farther down the graph . So you need to set the ending amps lower and absorb time longer so you can see what it looks like over more time.  Do that when you can check with your hydrometer to confirm .

Seems like I used to have to tweak all the settings in the winter when it got cold here , but it gets real cold here in Wisconsin. Either raise the absorb voltage or lower the ending amps to get them full. The other consideration is if you don't have a big load and the batteries go to Float fairly early in the day then you may want to do some extended Absorb cycles to stir up the electrolyte so it does not stratify.  That can be done by setting Equalize to Absorb setpoint but for a longer time every 10 days or so . And it is good to Equalize the batteries once a month or so at Equalize voltage just to keep all the cells more balanced.

Vic always recommend that people chart the SG of the newer batteries for each cell and that way when you check them later on  you can see a history if one cell starts to not come up it may indicate some sulphation and then the batteries need a long Equalize to try and get the low cell up.   I think reality with the kind of batteries  you have is 5  years - maybe I would have gotten more out of them if I had done more attention and care like Vic recommends.  Of course the bigger factor is not going lower than 80% SOC  - only taking 20% out of them and then they will have  a longer life - that is something I never did when I had golf cart type batteries.

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

Vic

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Re: End amp hours (w/WBJR) noob!!
« Reply #6 on: July 10, 2018, 11:35:26 AM »
I was checking out the battery amps graph for today .. (this comes from the WBJR on the KID) ..

It looks like the amps were beginning to level off at the currentl setting of 1.5% . .(3.3A) .. but i think i'll try a slightly lower settings to verify what the amps graph looks like for a slightly longer time.  (amps are in yellow in the graph below)

right now the bank dod is fairly shallow (about 8 or 9% overnight) because i sized the system for winter .. when the battery's are going to be probably as cold as 40F .. and we get very little sun in Seattle in january.  -- anyone care to explain how DOD affects end amps?

Hi recardo,   another  nice looking graph from your system.

Have always used EA to end Absob.   13 years ago,   this current value came from the CC's (OB MX-60) current value,   so loads on the system were  included in  this value.

With the Whizbang Jr,  or course things have gotten better.

Agree,   that for the systems here,   we want an EA value that   has  essentially ceased diminishing  --  way out on the tail of the current reduction.

Using the Classics,   there are two additional variables that are involved:

  1.  Current Jitter  (probably really mostly Voltage Jitter,  causing  Wb current jitter),

  2.   And  voltage drops between the CC  and the battery which causes the A/C Opportunity load in the power room cycling to change the Wb current to change by about one Amp,  or so.   On this one system,  one finds that  an EA setting that works with the A/C always running,   will not ever end Absorb when the A/C is not running.

So,  one needs to guess on the Absorb timer setting.   But,  the required Absorb time  will vary,  depending on the DOD.   The DOD  really depends a lot,  on  how much A/C  was required from the batteries,  over-night.   Just too many variables,   too much uncertainty.   Just not possible to manage,  if the human manager is absent.

YES,   I should design an external computer gizmo,   that  manages the A/C opportunity load  --  when the battery bank is nearing the end of Absorb,   the A/C's target temperature is increased,   OR,  even,  the A/C  goes to Fan,  until EA is met ...

Later will say something on some observed effects of DOD,  on  ideal EA values on aged battery banks ...   back to work,  now.     Thanks,     Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!