Solar Upgrade

[Winf]

Hi All
I have been going over numerous threads on solar and am still confused on a couple of points. If someone could provide me with some answers (or even point me to their previous responses to the same questions) it would be appreciated.

Current electrical system is as follows:
420W AGM house bank.
2x50W BP250/1 panels - age unknown
Solar controller BP Solar GRR1000M (think this is 10amp)
Energy budget calculated estimate 205ah/day

We are in a marina at present and on shore power but will be heading off in June for extended cruising with most time spent at anchor.

Looking at upgrading solar as follows:
2xKyocera 245W panels
Outback Flexmax 60 MPPT controller

My questions are as follows:

What to do with my existing panels and controller and can they be integrated into the upgrade? If so, how? I can relocate the existing panels to the roof of the pilot house where they will receive some shading but I need the space over the stern for the two new 245w panels.

If the existing panels can be incorporated into the system, do I integrate them with the other panels (series or parallel configuration) or can I just run them as a completely separate system on their existing controller?

Specs for the old panels:
Pmax 50W
Vmp 17V
Imp 2.94A
Isc 3.22A
Voc 21.2V

Specs for the new panels:
Pmax 245W
Vmp 29.8V
Imp 8.23A
Isc 8.91A
Voc 36.9V

Any assistance appreciated.

Thx
Winf

[djmarchand]

Your new panels are approximately double the voltage of the old ones, so you need the MPPT controller to reduce the voltage to the battery charging voltage of about 13-14V. So one way is to wire them in parallel with your old system all the way to the batteries, in other words don't wire the panels in parallel before the controller, wire them after.

But there is another way if you want to try it. You can wire the old panels in series and then wire them in parallel to the new panels before the new controller. The two series wired old panels will match the voltage of the new ones (close enough) and the controller will convert the voltage down to the battery voltage.

Your controller needs to have enough current carrying capacity to do this. Your two new panels will produce approximately double the current spec after the controller (due to the MPPT electronics) or maybe 18 amps each. Add to that the current from the existing panels of about 3 amps each and you get a total of about 42 amps. That is within the specs of the Outback controller so you should be ok.

So either way should work. It would be easier I suspect to parallel the old with the new.

David

[sailorboy1]

If it was me I would sell your old system, which should give you enough money to just buy another 245W panel for your new system (check the Outback cals to be sure you are still in the capacity).

[Winf]

Originally Posted by djmarchand

Your new panels are approximately double the voltage of the old ones, so you need the MPPT controller to reduce the voltage to the battery charging voltage of about 13-14V. So one way is to wire them in parallel with your old system all the way to the batteries, in other words don't wire the panels in parallel before the controller, wire them after.


David

Thanks for the response David. I get what you mean in the second part of your post however my concern with that is that as the old panels need to be relocated to a less favorable location regards shading, they may drag down the new panels.

Not sure I am 100% clear on what you mean by the red bit in the first part of response above though.

Do you mean simply leave the old panels connected with each other and their controller as is (ie bp panels---->bp controller---->battery bank) and have that system running in parallel with the new panels and controller (ie kyocera panels ----------->MPPT -------> battery bank)

I may not be understanding how these controllers work but will that configuration "confuse" the controllers as to what is the actual battery bank voltage that they see and therefore what charge mode they operate under?

Also considered selling the old to help fund another new one but it comes down to available real estate. I could probably squeeze a third panel in across the stern but will then begin to resemble Skylab a bit. If I can get something beneficial out of the old ones that is my preference. They are in good physical condition and the amps out of them still looks fine.

Thanks
Winf

[djmarchand]

Yes, your interpretation of my statement is correct.

Two charging sources won't confuse each other. They will coexist fine and will find a common voltage to supply the batteries at.

David

[roetter]

I have two Outback FX 60 feeding my battery bank. They do no confuse each other, nor do they get confused by the alternator or shore power charger. Each FX 60 is connected to 3x300W solar for a total of 1800W. No problem for the FX60.