Adding Panels changing connections

[gnoeld]

I currently have 6 250 watt panels wired 3 in series and then 2 in Parallel. I want to add 2 panels and I was thinking to rewire for 4 in series and 2 parallel. At 9 amps and 30 volts per panel I am thinking my 150V/60A Renogy charge controller could handle the 120 volts 18 amps. Input please.
Assuming this makes sense how do I run this thru a combiner box(s)?

 

[Dynoman]

Assuming the label on the back of of the solar panels list 250 watt at 30 VOC...

Looking at the specs of the Renogy Rover 60 (assuming that is the charge controller) It depends on the voltage of the system.

Renogy Rover 60 amp SCC specs are listed as (PV Input Power: 800W/12V; 1600W/24V; 2400W/36V; 3200W/48V Max).

(8panels x 250watt = 2000 watts)

Assuming a 24 volt system 2000 watts would be over-paneled. 48 volt system is OK.

The one consideration is temperature. Specs of Rover 60 are PV Input Voltage: 150 VDC (25°C)

If the location has cold temps in the winter then it is probably to close at -14 to -22F 4panels x 30VOC x 1.21 = 145.2V. See chart.

FilterGuy has a really good document on the subject of over-paneling. See attached document.

Don't use a combiner box so can't help there...

 

[gnoeld]

I should have added that the battery bank is 48 Volts 300A
Currently with 6 250 watt panels 3s2p I'm "Technically" producing just under 100 Volts and 18 amps on one Renogy 150/60 Charge Controller.
By adding 2 panels 4s2p i will be at or slightly above the 150 Volts limit on the CC.
Any ideas or comments are hlpfulThanks

 

[MichaelK]

My 30V panels have a Voc of 37.5, so four in series would reach 150V right at room temp. One cool morning, not even seeing frost, and the controller is fried.

You are better off getting three more panels and wiring together a third string, so 3S3P. (250W X 9 panels)/50V charging = 45A, so even without derating them, your controller can handle this amperage just fine.

With three strings in series though you MUST either fuse or breaker each string. I use a Midnight-6bay combiner for that.

 

[gnoeld]

A couple of questions
3 panels @ 37.5 VOC in series would be 112 volts and about 9 amps so 2S2P would be 112V and 18 amps
If I am correct so far if I did 3S3P I would be at 112 V and 18 amps?
Please correct as necessary

 

[BartHenry]

Series you add Voltage, Parallel you add Amps... so 3S3P would be 112v and 27 amps.

 

[MichaelK]

Series you add Voltage, Parallel you add Amps... so 3S3P would be 112v and 27 amps.

Keep in mind that's the voltage and amperage coming into the controller. Going out, it would be (112V X 27A)/50V charging = 60.5A, right at the limit of this controller. With reasonable derating (85-90%), the value you should see in the real world is most likely to be 51-54.4A. So, everything looks good.