Adding more panels.. Is it possible.?

[deserthorizons]

I currently have 2 strings of (6) 100 watt panels tied into my Classic 150 on a 12V system..
***At the present time I have no desire to change to a 24V system.***
I have 1 string of 6 panels on an East facing roof (~about 40 degrees)
and another string of 6 panels on a West facing roof (~about 40 degrees)
I also have 4 panels facing south on a separate PWM controller..
Because of the angle and direction the panels face, I never get above 850 watts going
in at any one time through the Classic 150..
What I would like to do is add those 4 panels to the current strings so I would then
have 2 strings of 8 -100 watt panels going into the classic 150..

I know the sizing tool says that is a no-no,, but is it really a bad idea.?
Wouldn't the 150 limit the excess power going into my battery bank if it ever got that high.?
I am currently feeding 16 Trojan T-105 6V batteries hooked together into 12V..
***Again, at the present time I have no desire to change to a 24V system.***

I know I could do more strings to make this work however that requires combiner boxes..
I am trying to do this without having to purchase any more stuff or rewiring..

My complete system video rundown is available here> https://www.youtube.com/watch?v=JtlOPsKivlw

[ClassicCrazy]

Does the Midnite sizing tool say putting the extra PV on is bad because the voltage is too high ? If so you just can't do it.
You might be able to make the case if it is just too much current  and you have them east and west like you do so it won't exceed the current limits anyway.
I think you are correct that  the Classic would just limit the extra.
The biggest consideration for your design is if you put more in series you up the string voltage and even if it is not at limit of Classic you will be finding out your Classic fan runs a lot more because it has to do more work to drop the higher voltage way down to your 12v charging. The closer you are between the PV input and the battery charging the more efficient the Classic will be - it won't heat up so much. If it heats up too much it may keep working but will cut down the current output to keep it within it's safe zone ( circuit boards and components heat range ).
Why do you want to eliminate the second little controller you have ?

I won't talk about going to 24v since you don't want to .

I took a quick look at your video of you setup.
A couple of my comments ...
Do you have a Whizbang ? That really is the best way to know what is going on with the batteries - trying to guess their state of charge using the voltage is difficult.
While you can take the batteries down to 50% if you look at longevity charts you will see that the deeper you cycle the batteries the less deep cycles you get. They will last longest if you only take 20% out of them (80% SOC)
Concerning the way you have your batteries wired up - it is difficult to keep that many parallel batteries balanced.
Take a look at this link for best battery parallel wiring  options.
http://www.smartgauge.co.uk/batt_con.html
Vic who comments on here often and knows his flooded lead acid battery stuff would suggest to get a decent hydrometer , number each cell on each battery , and take the specific gravity readings on them on some schedule and log it in a book. That way you can spot if any of the cells are getting weaker over time by being unbalanced and you will be better able to take equalizing action to try and correct that to save the battery . Use only distilled water and rinse your hydrometer with it often while taking readings so it doesn't get sticky for the float.

Larry

[KyleM]

Might be helpful to link the results from the sizing tool?

-Kyle

[deserthorizons]

here is what it says when using 2 x 8 panels:
Rated PV Array Power:                   1600   Watts
Anticipated Array Power @   117F:   1440   Watts
Rated PV Array Current:                    11.5   Amps
Battery Charging Current @ 14.4 V:    111.1 Amps
VMP (Maximum Power Point Voltage) :   139.2 Volts
VOC (Open Circuit Voltage):           172.8 Volts
VMP @ 15 F°:                                   160.8 Volts
VOC @ 15 F°:                                   192.8 Volts
Max VOC                                            TOO HIGH   
Temperature The Classic Will
Enter HyperVOC                     ALWAYS  -9.4 F -166 F° (I am in southern AZ so I will never see temps like this)   
Array Power (Wattage)               EXCESSIVE      
Classics Required                          1.3   
(tried to do a pic of the sizing tool,, but I forgot how)
There are different Voltage numbers (vmp, voc), It only gets down to 15 F maybe once a decade if that..

No Whizbang Jr in my setup..
I always try to limit my battery usage to >75% SOC
I understand that the way I have the batteries hooked up is not the recommended way,, but it is what I have done..
I am very meticulous on battery maintenance and care.. My main concern is that I never see a "full" charge going into the batteries..
I have 1200 watts of panels so I would expect to see closer to 1000 going through the 150.. Yet it never gets above 850 and I assume that
is because of the directions I have the panels facing.. So I thought I would have "room" to put those other 4 panels with the current ones
with no problem.. That way it is going through the Classic, and then would allow me , if necessary, to put additional 200 watt or larger
panels going through the PWM ,, so  I am not planning on totally "eliminating" it,, just repurposing it..   

[Vic]

Hi desert,..

Thanks for the attached String Sizer output.

Strings of eight 12 V PVs  will simply NOT WORK,  with your Classic 150.

Strings of six of those PVs is probably pushing things,   a bit,   especially on a 12 V system.

Vic

[deserthorizons]

Hi desert,..
Thanks for the attached String Sizer output.
Strings of eight 12 V PVs  will simply NOT WORK,  with your Classic 150.
Strings of six of those PVs is probably pushing things,   a bit,   especially on a 12 V system.
Vic

Thanks, that is what I needed to know..

btw, the sizing tool says it is perfectly fine to run 2 x 6 w/ 12V setup so that is the info I
used when originally designing the system.. Which I have been using for ~3 yrs now and
it has been operating extremely well..

[Vic]

Hi Desert,

YES,  the Sizer did note that strings of 6 of those PVs  would work.   One of the systems here does run strings of 3, 24 V PVs,  which would be equal to strings of 6 of your PVs.   But this is on a 48 V system,   which will be "easier" on the Classic  --  a bit less heating of the Classic than on a 24,  or 12 V system.   And,  our mild climate,  with the lowest temps of about 24 F,  means that we have never been in HYPER Voc.

Classics are very capable,  tough and durable CCs.   Have been running a Classic 150 on this system for ten years,   and it is still going strong!

But,  in a warm/hot environment the Classic might need to reduce its current output to limit its heating.   WIth your PVs,  facing at different angles,  the maximum power produced will be averaged over more hours,  and a lower max CC output current,  so you are probably OK,  except for coldest days,  when the Classic may be in HYPER Voc,  for some of the day (usually around Sunrise-ish).

IMO,   Good Luck,  Vic