Renogy(Vmp 17.9v) vs. Newpowa (Vmp 17.0v)

[hovr]

Hi all,

I am deciding on what panels to use for my 16RB, my goal is to get > 200w panels. Due to roof top space limitation, My panel selection is limited to the 2 options below.

1. Renogy 100w + 50w + 50w (Voc: 21.6, Vmp: 17.9) total 200w

2. Newpowa 75w x 3 (Voc: 20.3, Vmp: 17.0) total 225w


I am leaning towards #2, as it offers more watts and having the same panels are always a plus.

But since I need to install them in parallel due to roof top A/C unit shading, I am concerned that the ~1v Vmp drop in Newpowa might not work well with my Victron SmartSolar 100/20 SCC and LiFePo4 battery bank (13.4v fully charged)



According to the SCC manual the

Voc needs to be 14.4+5 = 19.4v for SCC kickoff charging

Vmp needs to be 14.4+1 = 15.4v for SCC to staying in charging

here I am using 14.4v as a fully charged LiFePo4 bank.


This is very close to the spec of Newpowa panels (20.3v, 17v) and even more so consider the voltage drop(~0.1v) after 10 feet or so 8awg wiring. So I am wondering if it's a bad idea to use these panels - panels won't be able to supply high enough voltage for SCC on a less than perfect day? The Renogy panels would have a more comfortable margin(although not by much) and should be used instead?

I am wondering if anyone has experience with these 17v vmp panels?

BTW I am open to connect the 3 newpowa panels in series if someone had success in that configuration.

Thanks in advance!

[pjshier]

We find that keeping the coach out of direct sun helps interior environmental conditions immensely, even in relatively cool Alaska, so we opted for a 200w suitcase. The stock supplied cables permit placing the panel wherever the sunshine is best near the coach, while keeping the interior heat load reasonable. The suitcase is easy to tote, store, clean. Might consider that option #3. Of course, it does not work while underway to the next site.

[Mount'n Man]

Originally Posted by pjshier

.... The suitcase is easy to tote, store, clean.

Ha! We just got a Renogy 200w suitcase to expand our boondocking capabilities. It came in at 44lbs (8lbs heavier than specified) and I had to modify the hall closet in our 25'FB to accommodate the beast. It does pump out the juice, tho, and works great on a sunny day!

[hovr]

Thanks for the suggestion but portable panels won't work for us.
We do mostly weekend 2-3 days camping, during the day we most likely will be away from the trailer exploring or hiking and don't feel comfortable leave panels unattended

[pcskier]

Your situation is different than my flooded with your Lithiums but you might be surprised how quickly the voltage ramps up even before there is direct sunlight, or even if it's overcast, though the current is very low. Also keep in mind that when you apply a draw to the batteries (such as running the water pump a few moments) the batteries 'show' a decreased voltage while the draw is taking place, which can kick on the controller. I would not be concerned. Plus, in the morning the batteries are unlikely fully charged from overnight use. And if they *are* still fully charge...you don't need solar charging (yet) anyway.

If you decide to go series, then of course the potential issue goes away with the tripled voltage, but the shading issue rears its head.

[Mount'n Man]

I was boondocking with a friend last weekend who has a 100w fixed panel on his roof. We were both in full sun he was getting 2-3amps while I was getting up to 14amps with the well-positioned suitcase. Advantage for him was that he didn't have to babysit the panel and of course he could come and go as he pleased. Flip a coin?

[hovr]

Originally Posted by pcskier

Your situation is different than my flooded with your Lithiums but you might be surprised how quickly the voltage ramps up even before there is direct sunlight, or even if it's overcast, though the current is very low. Also keep in mind that when you apply a draw to the batteries (such as running the water pump a few moments) the batteries 'show' a decreased voltage while the draw is taking place, which can kick on the controller. I would not be concerned. Plus, in the morning the batteries are unlikely fully charged from overnight use. And if they *are* still fully charge...you don't need solar charging (yet) anyway.

If you decide to go series, then of course the potential issue goes away with the tripled voltage, but the shading issue rears its head.

Thanks and this is helpful. I am not too worried about Voc (open circuit voltage) that kicks off the SCC, I am more concerned that the panels with 17v Vmp will not be able to keep the SCC in charging state as well as the Rengoy 17.9 vmp panels.