# of panels for charge controller

[Kent0]

Yes, the Classic 150 is rated for lower input voltage but it handles more power. Take a look at the Classic power curves. Notice that for a 48-volt battery with a 120-volt PV array the current rating of the Classic 150 is 76 amps (or 4434 watts) and the rating of the Classic 200 is 70 amps (or 4080 watts).

[Jonah]

But aren't these both the same in real terms? 58.3 v Or are there more losses in the 200? I was also looking for the reason not to get the 200 over the 150 but couldn't come up with one but if tHis is right there is 6amp loss at 120v in.

[Halfcrazy]

Well it is not loss it is simply a factor of the differential between the input and the output voltage causing things to run warmer. This is a case with any MPPT controller. So as the spread in voltage widens we have to back the max power down a little to keep things cool. So you are not losing that 6 amps you just cant push that many amps through the controller.

Ryan

[Jonah]

Ok thanks, so is it best as said before that if you can use the 150 use it? I was of the thinking that the 200 is the one to get as it can handle more, I'm only having a 4kw system which are 20 200w voc 45.1 imp 5.5 vamp 36.4 isc 5.9 and they are only 1.4m to the closest panel run and 9.4 m to the furthest, combiner to cc is 0.5m and cc to battery is 0.375m...

What would you guys do?

Thanks

Marc

[boB]

Ok thanks, so is it best as said before that if you can use the 150 use it? I was of the thinking that the 200 is the one to get as it can handle more, I'm only having a 4kw system which are 20 200w voc 45.1 imp 5.5 vamp 36.4 isc 5.9 and they are only 1.4m to the closest panel run and 9.4 m to the furthest, combiner to cc is 0.5m and cc to battery is 0.375m...

What would you guys do?

Thanks

Marc

Jonah,
At that short distance, I would wire the array for lower voltage presented to the controller and use the 150.

But not REAL low...  If possible, run the input voltage higher than your nominal battery voltage by one or
2  12V multiples.   For example, 48V battery, wire for around 60V array or 72V array.  Higher voltages
are normally better for real long PV wire runs.  You got short runs so that's good.

boB

[Jonah]

Many thanks boB, so if I run 10 strings of 2 that'll have a voc of 90.2, vmp of 72.8 and 55 amps? Is that the best?

Thanks for your help.

Marc

[Vic]

Marc,

I would NOT run these 60-cell modules in strings of 2 in serise.  For a 48 volt bank the Vmp of 60.2 volts will be insufficient in hot weather,  doing an EQ (for FLA batts),  or,  at times perhaps even running an Asorb on a cold battery bank,  if you are using FLA batteries.

Strings of three are dandy.  This gives 90.3 Vmp string voltage,  and the Voc should be fine unless you are at the Notrh Pole.  The newest system here also uses 60-cell PV modules,  and run strings of three also,  for the reasons noted above.

Good Luck,  Vic

[Jonah]

Thanks Vic, unfortunately, I wired it all up before seeing your post... But...  Mine are 72 cell 72.8v vmp panels so hopefully this will give it the extra they need.

Thanks

Marc

[Vic]

Hi Marc,

OK on the number of cells in the PV modules that you actually have.  Was just going by the two references you posted previously .., "Cell Confi guration 60 in series"  and 30.1 Vmp (which also indicates 60 cells.

In your post #20,  you did indicate 72.8 would indicate 72 cells per module.  If you ARE running two 72 cell PV modules in series,  then you will be fine on a 48 volt bank.  72 cell PVs are real 24 volt modules.  Sorry that I missed this change.  Did note your ref to 90.2 Voc reference,  but thought that was a misquoted Vmp on the 60 cell jobs.

You should be fine with the specs you noted,   Good Luck swith the new system.   Vic