Can someone show me some math?

Registered Users Posts: 26 ✭✭
edited August 2017 #1
I was thinking of getting a 4th panel for my little setup I have but I run into a problem with my controller I think.

I understand series and parallel when it comes to V and amp...I get lost when it comes to watts?

my controller has 260 watts max ( rover 20amp mppt )  change the configuration  I get from 12v to 24 etc..

amps change too but what to watts do?

John

I found W = amp x V  so are my current 3 100 watt panels not pushing 300? generally I see 17v and 10ish amp based on sun

so maybe thats only 170 watts and another panel should be fine ( 3 panel 12v parallel  abut 15 feet of cable)

• Solar Expert Posts: 1,518 ✭✭✭✭
Your controller should take 520 watts into a 24 volt battery bank if it does in fact do 12/24 volts.

2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

• Registered Users Posts: 26 ✭✭
what I have a problem with as setup now, is when it clouds over, ill still have 13.5+ volts at the CC but amps may drop to less than 1

12v 5a + 12v 5a + 12v 5a parallel  W = 12v x 1a

if I add a panel to 4 total and change to 24v 5a + 24v 5amp = 24v 10a at CC (2 series to parallel ) would I really see much difference in

the charge to the batteries?  Ive increased to 24v to the CC but if it clouds and the amps drop would that extra voltage add much to

correct my charge issue since W = 24v x 1a

sorry for rambling, understand enough to do math but not finer details like will 12 extra V when cloudy help at all
• Solar Expert Posts: 1,518 ✭✭✭✭
Clouds obscuring the sun will severely affect your array's current output, nothing you can do about that. Any shadowing will affect its output. Manmade or natural shadows (trees), on the other hand can be mitigated by locating your array where there will be no shadows.

As far as changing over to a 24 volt system this will allow double the wattage through your controller because that doubled wattage is flowing at half the amperage it would be at 12 volts. Watts are watts regardless of the voltage and amperage they are arriving at so don't worry that you are only seeing 10 amps at 24 volts because it is the same amount wattage wise as 20 amps at 12 volts.

2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

• Registered Users Posts: 26 ✭✭
ok if i get another panel Ill get it a try

thanks