input amps

[robertd]

my classic 2oo does not deliver capable amps from panels
suntec 280  8 banks two per bank
some how I never can get over 50 amps down  max should be 64 amps
   when compared to my brother who lives next door with same setup
except he is using an outback charge controller  he is always 8-10 amps higher than
I am
is there a way to adjust input amps
does bat-temp sensor play a role in this
I connected a pair of panels direct to battery and amp draw was 30 % more than going trough
charge controller

[Vic]

Hi robertd,

One issue could be that on battery based systems,  the power from the PV array needs somewhere to go -- a load.

During the Bulk stage,  comparisons are more meaningful,  as the CC is delivering the maximum current from the array that it can.

In comparing two different systems,  the exact direction that each set of PV modules face,  and the exact tilt will also matter at a certain time of day.

Another thing to remember is that PVs are rated for output at 77 degree F (25 C) cell temperature,  and at exactly 1,000 watts per square meter of light input.  The cells get warm/hot when in the sun which reduces output,  and many times there is not 1 kW of solar input.  PV output is usually about 77 - 80 percent of STC rated output.

This may not cover all of the things that are affecting the output of your system.   Vic

[robertd]

set up is the same on both systems to include tilt angle and positioning
am in bulk stage now battery volts now at 55.23 v and amps reading at 31amps
compared to outback based system 53.9 v and 37amp

[Vic]

Hi robertd,

Thanks for the reply.

Should have mentioned before that normally,  the Input Current would default to 99 A (IIRC),  and there is no reason to lower it.

The RTS should have no meaningful effect on the amount of power /current that the Classic will deliver.

OK,  so we will start guessing some ...

So,  you have a 48 V battery,  with,  as  I read as 16 ea PVs in eight strings of two modules.  I will guess that these PV modules have a Vmp of about 31 V @ about 9.0 Amps (??).

So  where are you located,  and what is the temperature in the room/area where the Classic is located?

What size wire is used to connect the PVs to the Combiner box?  What size wire is used to connect the combiner to the input of the Classic?

What is the total one-way distance between the PVs (on average) and the Combiner?  What is the one-way distance between the Combiner and the Classic input.

Also,  what size wire and what is the distance between the Classic and the battery connections.

It can be challenging to compare two different systems in similar but different locations,  as there are very many variables.

Thanks.  Vic

[Vic]

AND,  if the guesses about the approximate output voltage of the PVs,  that would mean that there is a bit too low an input voltage for the CC to have enough headroom for efficient operation.

Perhaps those PVs are in the 36 Vmp range.
What is the exact model number and manufacturer,  OR what are the exact specs on those PVs -- Vmp,  Imp of those PVs,  in particular?

Thanks  Vic

[robertd]

sorry but I made a strange discovery  I have much cloud cover now and input amps is
now 4.3 amps    output  3.1 amps    it would appear as mppt function not working
will answer other questions in a bit because it has started to rain

[robertd]

suntec 280 w
ov   44v
operating v   36
8amp output
distance between pv and cc   25 feet
wire size 4ag
battery bank 950 amh
cc  classic 200
battery volt 48v

[robertd]

location   montego bay  Jamaica
room temp of cc about 27-28 deg average

[Westbranch]

another factor may be a difference in daily consumption by the 2 different systems, or the age of the batteries.

If you use less power overnight than your brother, you will recharge quicker and have less power input, per day, to your batteries than he does. 
Similarly the older the battery (and longer used) the more power it takes to recharge it fully.

[Vic]

Hi robertd,

Thanks for the added info.

Some CCs are a bit optimistic in reporting output currents,  this could be some of the differences twix the FM and the Classic.  boB mentions that the Classis's Output Shunt is very accurate.  The input Shunt is a little bit less accurate (which should not be a problem,  as most of us are looking at power delivered).

Regarding input Current Limits,  go to the Charge screen,  and scroll over to Limits.  There should be Input and Output limits numbers shown there.  Believe that the Default number for Input is 99 A,  it is fine to have 99 for this value.  On a Cl 200 the Default is probably 74 or 76,  (forget).

You might try a different MPPT Mode,  like Legacy P&O.  This should not make a large difference,  but something to try.

Since the differences in power between the two systems was reported in Bulk stage,  the batteries themselves should not be a factor in looking for power differences,  in my opinion.

And from the data you provided, robert,  looks like you have short distances and stout wire.  Others will have additional ideas ...  for now.  Off for Brunch,  Thanks,   Vic

[Vic]

One more question;  What is the Vin on each system?

These measurements from each system really need to be done within seconds of each other,  in cloud-free conditions.  If one system is sweeping and the other not,  this can make a large difference.

What version of FW are you running in your Classic 200?   Thanks again,   Vic

[boB]

Robert, the main numbers to look at are output to the battery and not input current from the PV itself.
The input current can be deceiving for one because it is power you are interested in and not curren which
will depend on input voltage TO the controller.

Also, the PV input current as read on the Classic is not always as accurate as the battery output current reading and
the WATTS reading on that main MNGP display.  The WATTS display is battery output watts also.

The other numbers to look at is PV input Voltage.  Can you tell us what the Voc (PV open circuit voltage) is and
also the PV input voltage while the Classic is showing MPPT and has been stable for a few seconds at least ?

With an MPPT system, you will almost always measure more PV current when it is connected directly to the battery
compared to when it is going through an MPPT charge controller because the PV input voltage is usually  higher
than the battery voltage in normal conditions but the power in watts should be better than direct if the PV
array has a higher MPP voltage than the battery.  This is how MPPT works.  Depending on the wiring of the
PV array, on hot days the PV max power point voltage (MPP V) can be at or below the battery voltage
which is not very good.

What were you using to measure the direct connected PV current ?
The Outback FM controller does not measure the PV input current by the way.  It only calculates it
and may be farther off of a measurement than the Classic's input current is showing.

You can "play" with the PV input voltage too from the main status menu by pressing the soft-left (upper left) key
to bring the input voltage down and bring up the PV input voltage with the soft-right key (upper right key)

This is handy for checking the tracking of the charge controller.

If the MPPT input PV VOLTAGE is about 75% to 81% or so of the PV Voc voltage, the controller is
most likely tracking correctly unless you have partial PV shading on your PV array.

The charge stage must also be MPPT and not Absorb or Float to get maximum output power and battery current
but it sounds like you are  good to go there.

Identical arrays are close but not always exactly the same for power especially when there is partial shading
and/or the measurements are taken at a different time.

You may also want to try the Legacy P&O mode instead of the SOLAR mode to see if it works better.
Some times Legacy will work better when the PV input voltage is very near the battery voltage.

boB

[robertd]

thanks all  will try in the morning again and post an update
8.03 pm Jamaica time now

[robertd]

hello all  I am smiling ear to ear today
I did all the checks and all was ok
switched to legacy and problem solved
amps went up 12 points   now am 2 amps higher than outback
thanks all so very much   did not feel happy having an outback whip me

[Vic]

OK robert,  great news.  Glad that the Classic is whipping the FM!    Vic