Not seeing the charge currents as expected

[ScottTENN]

I have 2000 watts of panels.  I have seen 1800w as a peak so I know I can reach at least 80+% of my theoretical output.  I have added a second pair of LiFePo4 batteries. 4 in total, 12v, 24v configuration.

Today my batteries were at about 50% charge and sunny.  I was expecting to hit some big numbers.  What I have seen today is 1200-1300w consistently (45-50 amps).  If I go out and turn on a high draw AC device I can see my solar jump to 1400+ but no more.  (Maybe there is more haze than I think.)  Why is the Classic not using all the power from the panels when I know there is more in reserve?  This was Bulk MTTP.  (I will double check that my 4 strings are all working.)

The Classic has been in float (27.2) for 2 hours with an absorb of 27.7 (15 minutes).  That would mean that I hit 27.7 for my duration before going to float. Float ends at 15amps (whizbang).  I have not hit this yet and the light is dying.  Total energy for the day is 8.1kwh.  My net hours are still -85 and the capacity has already reset to full.

Does battery wiring affect charging?  Serial then parallel or parallel then serial.  Batteries have a 200a BMS (both charge and discharge capable).  Manufacture indicates 4 in series max, 4 in parallel max.  I'm S then P.

I plan to add another 1000 or more watts soon but if the system isn't going to use it then it would be a waste.

Should I expect steady long charge times or wide open power until done?

[ClassicCrazy]

You have two things regulating your charge - the controller and your BMS.
Hard to know exactly what is going on unless you have the type of BMS that you can get data from and see what their status is and the voltage of each cell.
Regarding your PV - it isn't often you get the full rating of power from them. At least not where I live.  Except in winter time when the PV is cold , the sky is clear with not much humidity, and there is often reflection from snow then I can get full rated power or more . I also depends on time of year when the sun is at the perfect angle to my fixed PV arrays.
And yes battery wiring can effect charging - ideally you want all your battery wiring to be the same length so each string has the same resistance.
http://www.smartgauge.co.uk/batt_con.html
Larry

[ScottTENN]

I did get some information back from Amperetime.  They suggest parallel then series.  2P2S.  I'm the opposite.  I'll get that changed over this week.

I'm in South Carolina.  Yesterday was 60-65 and sunny.

The BMS is not bluetooth or anything.  I just would have expected a 50% battery to swallow up more power.  I'm still not discounting a bit of haze or maybe dirty panels.  Though they look good and yesterday was quite bright all day.  8.2kwh in total.  (I wanted to see double digits for the first time and I wanted to see 70+amps charging for a sustained period. (Wish in one hand,...))

1454w for a max input, 27.5v was the max on the batteries.  Still not at the absorb 27.7 so I'm not sure how it got to float not going through or to the absorb voltage.  Last Monday my high was 1741w and 27.8v.  Much closer to what I was expected.  Batteries were not as discharged then so I know that power was momentary, plus the graphs only show a spike.

Thanks for the conversation.

[Steve_S]

When reconnecting the batteries, do ensure the cable lengths are the SAME and of course same gauge right through from Battery to E-Panel & to Inverter.   (Assuming you are using an E-Panel).  From your description (too basic) but with the amount of Solar etc, I'd guess 2/0 Fine Wire Welding Cable would likely be best option.

Remember to Fuse the Bank 200/250A at least.

The AmperTime Batteries are actually pretty good !  They have made gradual improvements and now they are actually quite good and I believe they have just started offering batteries with Warming & Smart BMS with BlueTooth (I'm pretty sure but not 100%, so many new players getting in).  NOTE:  These do not have Active or Passive Balancing.  (Passive is pretty much useless with cells above 100AH)

Try setting ABSORB to 28.0V (3.500Vpc) and allow for 1 (One) hour Absorb Time.
EndAmps @ 15A is OK but remember that is seen by the WizBangJr as the Collective EndAmps of the 4 Packs in Bank.  You CAN take that up to 20A without worry.   Set FLOAT to 27.8V (3.475Vpc).  When Charging is Completed and the cells settle (normal & natural for LFP) they should settle to around 3.400Vpc which is the top of the Working Voltage Range which is 3.000-3.400 Vpc and outside of the knees.  (This is WHERE your AmpHours actually come from, a very flat curve indeed).

*NB-1* The GOTCHA pending on how you are wired, Batt-1 (that which get's the POSITIVE Wire) Will be the leader and will top-off first and reduce amps which are passed to the rest.   Best Way to balance this is to use a Common DC Bus with the Paired Batteries Attached to the Common DC Busbar and then to Switch to E-Panel & SCC/Inverter from there.   

*NB-2*  Calibration !   Be sure to Compensate (Classic Tweaks Menu) for the Voltage/Amperage drop from SCC (Solar Charge Controller) to Battery Pack "Terminals".  There is ALWAYS a couple of points dropped so use a Very Good Multimeter and test at the terminals of the SCC & Batts.  I have a 0.3V Drop during Charge and 0.0 Drop when no charge & only discharge is occuring, THIS IS NOT UNUSUAL !   ALSO remember to correct for the Voltage Drop at the Inverter because you want it to cut off at 22.0 Volts (2.750Vpc) and not lower and if it's off by even 0.5V you can have issues.   
Voltage Drop will appear one way when Charging from either Solar or External like an Inverter/Charger AND will be different when only Discharging is going on.  This is OBSERVABLE with careful monitoring & checking with a DMM/DVOM.

A Reminder...  ALL Lithium Based Batteries ARE Millivolt/Milliamp sensitive, they are NOT Brute Force like Lead Acid Batteries.

A Note of BMS' triggered cutoff.
In your setup, 1 Battery could cutoff and that would dump 24V+ to the second in series. AmperTime states the BMS can handle that but it too will cutoff as that is overvolt internally.  Ultimately that would cut One Pair of the Two Pairs.  The Classic will see the AMPS taken drop hard and then recover to continue pushing what it can (it happens fast) once this starts it will cycle like that faster & faster till both "pairs" start cutting off... That's NOT Good !  IF this happens, try reducing the BULK Charge Voltage by 0.2V to 27.8 from 28.0.   ***  WHEN LFP get's over 3.450Vpc (into the high curve) they can rapidly "run" to 3.650 which is the normal Cut-Off for LFP Chemistry causing the BMS to trip.  Stepping down by 0.1 Increments can help you find the "Sweet Spot", of course this is far easier with BMS' that have displays or output data to monitor their state.

WizBang & Other settings.
LFP is 99.0% Efficient !  Make sure you correct that in the settings.
Rebulk Voltage set to 24.0V
Min Volts to 22.0V
Max Volts to 28.2V

Hope it helps, Good Luck.

[ScottTENN]

Thanks for more information.
Currently my inter-battery connections are 2/0.  The bank to the bus bar is 4/0 and from the bus bar to inverter is 4/0.  Working on getting everything up to 4/0.  There is a 200a fuse on the bank to bus side.  Classic to bus is 4 I think.   I don't recall at the moment.  In the picture I have 2 long 2/0 wire connecting my strings in parallel.  It's what I had handy and need to be shortened.  Attached is also what AmpereTime recommended for a 2P2S connection.

Amperetime batteries, mine, seem to be very nice.  Yes they have out a warming version for low temp environments but they only warm when there is an inbound charge on them.

As I sit at my desk I have my phone connected to the app.  I went from bulk mppt to float and never hit absorb.  It would seem that when the amp capacity (600ah for this bank)  equaled my hours of recovery, it just moved to float.  Battery voltage is still at 27.5. 

There is still something odd about when it goes to float.  In my attachment you can see that I still have a negative ah, but the system seems to think I'm even again.  I'm pretty sure this is why I'm still at 27.5 in "float" when I would still expect it to be in bulk.

More to learn.

[Steve_S]

I assume that in the WizBang EndAmps you have "Use WBjr use EndAmps Checked ?

BTW, I run 5 24V LFP Packs in a Split Parallel Bank.  A Section has 3x24V/280AH and B Section has 2x 24V/175AH.
All of them now being switched over to One common BMS system. 

I have observed that the Classic will reach Bulk Voltage Target and resets Remaining SOC to 100% and continues for the 1 Hour (my setting) at which point the Voltage Differential between cells inside the packs will deviate quite a bit as I am over the 3.450V per cell point when runners take off.  After that hour has passed, it transitions to FLOAT and the amperage taken typically start decreasing from that point forward.  On a nice sunny day, I am typically in Float by Noon.

NOTE:  My Current System (pre-transition) used Chargery BMS' with Passive Balancing during "Charge Only" enabled and triggered to commence at 3.350Vpc.  Each pack also has a QNBBM-8S Active Balancer which takes care of balancing out all of the cells quite nicely, so within 30 minuters after charge, all cells are within 15mv in all packs.

My reconfiguration eliminates a LOT of stuff as I am changing All of my packs (Production & Utility) to JK-BMS with 2A Active Balancing, Blue-Tooth, RS485/Canbus and that is simplifying things out but means more tweaking in the powerhouse for optimal performance.

Wire Lengths can really create invisible issues which are hard to track down.  Also every single crimp, connection, fuse/breaker adds to Voltage & Amperage LOSS...   Yes Amperage Loss too getting to the batts.

I dunno what app you are using there...  I use the Windows Midnite Solar Status Panel, not the web based or other versions if they exist.

[ScottTENN]

The app is called "Classic Monitor" in the Google app store. It is by "graham22".  Free, read only software (can't make system setting changes).  He does take donations.  I found it worth wild enough to give a bit.  I use the Windows app too for config changes.

WizBang is checked.  I have my settings set for what AmpereTime recommended in the manual.  I have noticed that LFP manufacturers have started providing charge, absorb and float values.  I will experiment.

You said to use a bus bar for your parallel banks.  In the Ampere diagram they show the same.  Electrically there should be no difference between that and my setup where the pairs are connected at a battery lug.  The bus bar just adds another set of wire and crimps, to your power loss statement.

On a personal note, I hope you're felling well Steve_S.