Xantrex C40 PV input voltage

76 Posts

May 20, 2008 09:39 am

I would like to add more solar soon to my existing array. To keep current safely under 40A, I'd like to up the voltage, putting my 12v PV modules in series strings of three instead of two, as they are now. The page on the C40 says the max input voltage for all output voltage selections is 125v. I just wanted to make sure that I can have a different input (36v, for example) for my 24v battery array, and I'm not going to damage anything. Not only would it lower current for the watts, but it would also keep the wiring a little simpler.

(+ = series, & = parallel, each "12" is a 12v PV module)

So, in short, here's what I have.
(12+12) & (12+12) & (12+12) & (12+12)

What I'd like to do is
(12+12+12) & (12+12+12) & (12+12+12)

Thanks!

James Cormican

578 Posts

May 20, 2008 10:50 am

Re: Xantrex C40 PV input voltage

i wouldnt do that, but you can if you wanted to.

the c40 can handle that voltage, but is not maximum power point tracking.

coming in at a higher nominal voltage than your battery bank will not wreck the controller, but will not be the most efficient. the c40 is not down convertering like an mppt controller, it is just chopping excess voltage as far as i know.

i would keep it at 24v, and if you want to go at a higher voltage input than output, look into an mppt controller. remember you must have the same make, model and string size for mppt.

james
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Travis M

76 Posts

May 20, 2008 11:23 am

Re: Xantrex C40 PV input voltage

Thanks for the input.

Once I can afford it, I'd like to finish the roof with solar panels. To do that (and take advantage of the controller type you're talking about) I'd need to get all the same model PV module, and that's plunking down a lot of dough at once. Right now I have 125w Mitus and 130w Kyoceras. This is plenty to keep my garage running (tools, freezer, etc.), but I'll need the additional power to charge my electric truck (which is FINALLY running and almost done!). I'll probably take all the modules I have now and mount them elsewhere (maybe on the south facing wall to get maximum sunrise and sunset power) on their own controller like the C40, then get a MPPT controller and a nice big bundle of PV modules to throw on the roof. Then I could wire the roof-mounted modules for much higher voltage and still go down to 24v for my inverter.

Thanks again. Looks like I'll keep it at 24v nom. for now.

Any idea which 12v >120w modules won't be discontinued in the near future? It'd be nice to order a few now and be able to order more in a few months, but I don't want to be stuck with discontinued items again.

James Cormican

578 Posts

May 20, 2008 12:11 pm

Re: Xantrex C40 PV input voltage

the kyocera 130 are slated for discontinuation, but the date has been softened. we know it is coming, we just dont know when the well will run dry. we think that when a j-box equivalent in the kd series comes, that will be the end of the 130tm.

as for the mitsu, i dont know what their policy is. things seem to come in from japan and that is what is available. i dont have info on future of those mods. currently the 110 and the 120 are available in the thousands. i am not sure if the 120 is the brother of the 125, and therefore close enough for mppt. you can look at the stats to compare.

a two controller setup is not the end of the world. with newer inexpensive mppt controllers like the morningstar sunsaver mppt, you have the option to isolate existing same module groups, and usuing your c40 for the rest. if you have the dough, you can get an mx60, and put up to 1600w on it for a 24v system. then you are just tied into getting one or the other, the kyo or mitsu, just not both.

there are still kyo130tm available, and we have another shipment expected.

james
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Xantrex C40 PV input voltage

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