solar upgrade

[Starburst2]

On my RV roof I presently have 2 Kyocera 135 W panels, flat mounted, hooked in series, feeding to my Blue Sky Solar Boost 3024iL charge controller. I want to add more panels to my array. The simplest seemed to me to be to add a Kyocera 215 W panel or a 245 W panel but I do not want to owerpower my charge controller.
The two 135 W panels have the following specs: Vmp 17.7 , Imp 7.9 A, Voc 22.1, Isc 8.7A
The 215 W panel has the following specs: Vmp26.6, Imp 8.1A, Voc 33.2, Isc 8.8 A.
The 245 W panel has the following specs: Vmp 29.8, Imp 8.2 A, Voc 36.9, Isc 8.9 A.

The Charge Controller specs are: Output Current Rating 30A/40A, the Nominal Battery Voltage is 12/24 VDC, and the PV input max is 57VDC.

Since the two 135 Watt panels are hooked in series I am not sure how that affects the load on the charge controller.
Can someone who understands all this give me some guidance as to what maximum size panel I can add without exceeding the capacity of the controller?
Thanks for your feedback folks.
Regards,
Lloyd

[Starburst2]

SMKettner, see my response to 2oldman. Is the article that says partial shading on your array is a non issue with mppt controllers, valid or a pipe dream.?
Lloyd

[Starburst2]

2oldman, shade in moses lake should be a welcome topic. I am sitting in LaMesa's RV lot in Phoenix and you could fry eggs on the pavement so shade would be welcome here too. However, shade on the solar panels may be a horse of a different color. I read an artcle on the Nortern Arizona Wind and Sun forum which convinced me that partial shade is a non issue when you have an mppt controller. What say you?....as Bill O'Reilly always says.

[2oldman]

Interesting problem.

I was going to say you'd lose 1/2 your amperage on the larger panel if you go in series, but, I realized its amperage is about the same as the 135s, so, I'm thinking you could go all 3 in series and be ok.. panel wise.

Now, as for the controller, as the others have asked, we need to know what voltage you see with the 2 panels you have now. Adding the Voc goes over the 57, but, I don't know if one ever sees that in actual use.

Talking about shade gets to be a dangerous subject around here.

[time2roll]

Shade is always an issue. Since the second pair in series would need to be parallel with the first pair.... either pair with shade will pretty much drop out from supplying power.

Cut out some cardboard and see how well they can be placed. Consider elevating an extra 2" to 4" to minimize shading from vents etc.

If it saves space you can mount the two butted to each other on a rack and mount like a single panel.

A pic of the roof with carboard mock up would get best opinions.

[HiTech]

Does your controller find multiple power points? With those voltage specs it looks like the new panel would have to parallel to the other 2 that are in series to stay in spec for what the controller can handle.

The second panel you are looking at has a closer Vmpp to 2x your existing panels. Closer MPPs means the system will make better power across the different spec panels because each can run closer to its optimum voltage when run together.

Jim

[westend]

What voltage are you seeing for the existing series pair of modules? I see that the BS 3024 has a maximum input voltage of 57V. No problem if you parallel the next module but you could go over the controllers max input if everything was in series.
You may get the controller confused with two strings at different Vmp, it may be a better idea to go with two more 135w modules that are closer in output to the existing ones.

[Starburst2]

Thanks smkettner. I thought about 2 more 135's or 140' s but have not graphed out my roof to see if I can get that much area without running in to partial shading from the AC's or the vent covers.. Would you still recommend the two 140's if partial shading would detrimentally affect one of the two?
Lloyd
.

[time2roll]

Perfect choice for small and mid size systems up
to 540 watts PV for 12V systems

http://www.blueskyenergyinc.com/uploads/pdf/SB3024iL_datasheet.pdf

I would add the larger panel as Vmp is a closer match. Two more of the 135w would be even better IMO. And perfect 540w total.