Sizing my Victron charge controllers - Help!

[Famtraveler24]

Hi all. Still new to the community.

I am installing a total of 8 385w Jinko panels. Originally, I had planned 2 strings, each in a series-parallel connection. I had planned on using 2 250/60 controllers.

Then, someone told me I could go with a 150/85 for each string if I wired each string in parallel.

My panels:

Vmp - 40.8v

Imp - 9.45a

Voc - 49.1v

Isc - 9.92a

Device rating- 20a

I have a 24v system.


Any suggestions?

 

[RickP]

The first number in a Victron SCC is the incoming voltage limit, the second is the outgoing max charge current. Depending on your scenario, you can go multiple ways. Consider:

1. Battery capacity for charging, which can be limited in the SCC
2. Your available wire size for PV
3. Your length of PV cable run
4. Any future expansion you have in mind

Personally, I over-spec’ed mine and went with the 250 | 100, as it gave me the most options down the line and a $200 premium up front was worth not having to re-buy later for me. Your situation, needs, and intention might be different.

By the way, #s 2 and 3 above play into reasons you might consider series vs parallel wiring. There are pros and cons to each method.

 

[Famtraveler24]

Pv wire size is 10 awg. From Combiner to scc is 6 awg.

 

[RickP]

Pv wire size is 10 awg. From Combiner to scc is 6 awg.

What are the approximate distances of these runs? It plays into whether you’d be best served by wiring for volts or amps, as a part of your system design. If you panels are relatively close, it won’t matter, but if the run to the array is a long one, you might need to opt for higher volts rather than amps.

 

[Famtraveler24]

It's a 42' fifth wheel with panels running from front to back, with the two strings to be combined and 2 pairs of wires run down to the 2 controllers. So good bit of length.

 

[rmaddy]

Use Victron’s MPPT calculator

MPPT Calculator - Victron Energy

MPPT Calculator - Victron Energy

www.victronenergy.com

You can enter your custom panel info and play around with various series/parallel combos and see which controller they recommend.

With the 150 you can only put 2 in series. 3 would get over 150V below STC. With the 250 you can do 4. 5 would likely be too much Voc at colder temps.

 

[Famtraveler24]

I think I'll stick with the 250/60s and series parallel. Thx.

 

[rmaddy]

I think I'll stick with the 250/60s and series parallel. Thx.

You can do series parallel with the 150. You are just limited to 2S. It would need to be 2S4P. The 250 would allow 4S2P for your 8 panels.

In either case just make sure the total wattage is in range.

 

[Famtraveler24]

Total wattage will be 3000. If I go 4s2p, I was thinking I needed 2 controllers, given the high open cir voltage. No?

 

[rmaddy]

Total wattage will be 3000. If I go 4s2p, I was thinking I needed 2 controllers, given the high open cir voltage. No?

Those panels at 4S will be a bit under 200V. Higher in the cold. The 250/?? Can easily handle the input Voc. Use the calculator I linked. It will tell which controller will work for those panels in 4S2P. But you should only need one controller.

 

[rmaddy]

I just realized most of my replies were based on Vmp, not Voc. I was looking at the wrong value. I fixed my last reply. I’ll go back and edit my others.

ok, I’ve fixed all of my replies to use the 49.1Voc instead of the 40.8.