Yet another solar panel question

pessimist

pessimist

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sitting here on the boat surrounded by solar paraphernalia.

I have one 80watt panel fitted and working satisfactorily using a non mppt controller. I have two more 80watt panels and an mppt controller to fit. I propose to fit the new panels wired in serial to the mppt controller. It would be convenient to wire the existing panel into the mppt controller but this would put it in parallel with the new panels. Is this a particularly stupid idea? Should I leave the existing panel alone with its own controller and install the new panels and controller alongside?

Sorry if this is a stoopid question.

Apologies for any spooling or grammatical mistooks. I'm typing this on a tablet and have fumble fingers.

Cheers

Colin
 
pessimist said:
Out of curiosity why can't I do this?
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For the life of me I can't think why not, other than some vague idea in my own head about mixing 12 volt supplies with 24volts. But my instincts tell me that Nigel is right.

I'm trying to think of an analogy with two water tanks in parallel and one in series but that hasn't helped me. I'll be interested in the replies you get.:ambivalence:
 
Hi Colin

If you are using more than one solar controller, please make sure they "Talk" to each other, or the two controllers will not be very efficient as the more powerful controller will be putting a higher voltage into the Batteries and the other controller will be reading this voltage thinking that the batteries are nearly full, so it will not allow the third panels full charging potential. If you can afford it then look for a Victron product "BlueSolar MPPT 75/50" which will suit your 3 x 80w panels wired in series and as the input voltage of up to 75volts will do a fantastic job of charging the batteries when the sun is low or limited light.
Please do check that your panels are 32 cell and would be suitable for the controller before purchase. The manual can be downloaded from here:

http://www.victronenergy.com/upload...ontroller-MPPT-75-50-EN-NL-FR-DE-ES-SE_A6.pdf

Also on a quick note, if you are using all these panels for an extended cruise or are living aboard. I would recommend purchasing a wind charger as well, unfortunately we found this out the hard way and after 10 days of cloudy conditions in an ocean you do get a bit sick of running the motor to charge your battery's. Solar panels are brilliant but only work efficiently when the sun is out!

Good luck

Darren
 
Rigger Mortice said:
For the life of me I can't think why not, other than some vague idea in my own head about mixing 12 volt supplies with 24volts. But my instincts tell me that Nigel is right.
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It's fine to put two panels of the same voltage in parallel - that's what's inside each panel anyway. What you can't do is put two 12V system (~17V output) panels in series, and then put a single one in parallel with those two.
 
JumbleDuck said:
It's fine to put two panels of the same voltage in parallel - that's what's inside each panel anyway. What you can't do is put two 12V system (~17V output) panels in series, and then put a single one in parallel with those two.
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Yes, I understand that and, as I said, that's what my gut reaction is. What I haven't been able to work out is why not? What would happen if you did connect things like that? I suspect that any permutation of three panels would be a problem; except for all three either in series or in parallel.
 
Rigger Mortice said:
Yes, I understand that and, as I said, that's what my gut reaction is. What I haven't been able to work out is why not? What would happen if you did connect things like that?
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Without blocking diodes the 24V panel would send some of its output backwards through the 12V panel. With blocking diodes the 12V panel would never produce a high enough voltage to send any current out.
 
I would suggest you OP look at the MPPT controller you have. Look for max voltage input and max current or power input. This will dictate if 3 panels should be in series (most likely) or parallel. You could just leave your existing one panel with controller connected to the battery and then add the new panels and MPPT controller connected to the same battery. As battery charges near full the first set will probably go into the mode where it thinks the battery is full while the other keeps pumping in. But i don't think this will matter so much in practice. good luck olewill
 
Thanks everyone for the advice.

I went for the simple option and left the existing installation alone. I then installed the two new panels in series controlled by the new mppt controller.

13amps (according to the Link monior) at 4pm yesterda:) Bugger all today:( Where's my sunshine?

Thanks again.

Colin
 
Interested as to why you need 13 amps of power. I have a single 80 watt panels which keeps 6 x 110 amo batteries at 13.6 volts. Have you got air conditioning on board?
 
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