Jump to content


Photo

Max PV Short Circuit Question


  • Please log in to reply
8 replies to this topic

#1 RallyRock

RallyRock

    Advanced Member

  • Members
  • PipPipPip
  • 45 posts

Posted 29 October 2022 - 04:43 PM

Ok I’m new to this so I’ve tried reading through threads but I can’t seem to get an answer on this. I have a 2022 FWC Hawk equipped with the following:

 

1 x 160W I believe overland Solar panel although I can’t find any docs from FWC to be 100%. Plus my foot is in a cast for a couple weeks so getting on the roof is a challenge. https://www.overland...nt-junction-box

 

an Overland Solar MPPT 100w/15A Controller

 

Zamp Portable Solar Plug

 

2x6volt batteries 224 AH

 

Here’s my question.  I found a 100w Massimo Portable Solar Panel on sale at Costco for 50 bucks so I snatched up 2 of them. Specs are near the bottom of this link. https://massimoelect...m/solar-panels/.

Aside from wiring, polarity, 5525 to SAE connectors etc, I was wondering if I can attach both panels via a Y splitter to the Zamp Solar Plug.  If not I’ll give the other to a friend but thought I’d give it a shot.  
 

My concern is that the MPPT controller (which I believe is a rebranded Victron) says it’s got a max PV Short Circuit power of 15A. If I add up the specs for the portable panels and roof panel I come out to about 17-18A. Voltage I am well under 100 max volts. Does anyone have any real world thoughts on whether 18A would damage my 15A controller?  Just seems odd to be so far under the voltage req but be past the current max.  Is my math or understanding of how this works accurate?

 

Portable Solar Short Circuit Amps = 5.68A x 2 = 11.2A

Overland Solar Panel Roof = 6.27A I think

Total about 18 to be conservative.

 

MPPT controller doc states 15A max PV Short Circuit. https://www.victrone...0-20_48V-EN.pdf

 

 

Any experience with this?


  • 0

#2 RallyRock

RallyRock

    Advanced Member

  • Members
  • PipPipPip
  • 45 posts

Posted 29 October 2022 - 04:57 PM

For the record, I was able to find that it is in fact an Overland Solar Panel on the roof. Had a nice little pillar I was able to climb on to be sure. 


  • 0

#3 ckent323

ckent323

    Senior Member

  • Members
  • 1,216 posts
  • LocationSolvang, CA

Posted 29 October 2022 - 05:15 PM

Typically, in the field, our solar panels rarely get illuminated in a way that produces the max power.   The Sun angle, small out of plane tilts, dust, etc all conspire to crate less illumination on the cells in the panel.  The Victron devices are pretty robust (but can be damaged so be carefully when connecting and disconnecting and make sure the panel is not producing energy (cover it).

Yes, you can connect panels together in series or parallel using Y cables.   Be certain you keep track of the polarity.  The SAE style connector polarity is (or may be) reversed as compared to the MCA type connectors, 

Even if you do achieve full power the Victron controller can only output 15 A.  So you simply do not get the additional power, it is lost.  But as I wrote above that is probably a rare situation.  It is best not too exceed the 15 A limit by much.  I am confident a couple of amps is OK.

Do not however exceed the input voltage limit.

Renogy has a reasonable explanation of all this at the following link about half way down the page in the section entitled "MPPT Charge Controller Sizing"

 

I know you have already spent your money so the following is not for you but others reading. 

I strongly recommend installing the largest wattage panel you can fit on the roof of your camper (typically in the range of 300 - 400 W).   The additional cost is marginal and it will be lighter than any combination of smaller panels over 100 W.


P.S.  Vmp is where your pv panel spends much of it's day,

I hope this is helpful.

 

 

Craig


Edited by ckent323, 29 October 2022 - 05:19 PM.

  • 0

1993 Dodge Cummins W-250 Club Cab long bed, 2007 FWC Keystone


#4 pvstoy

pvstoy

    Senior Member

  • Members
  • 2,760 posts
  • LocationCarson City, NV

Posted 29 October 2022 - 05:29 PM

You might have a issue with input voltage,  others here might know.

 

The Overland working about 28v and VOC around 32v  Your panel specs show working 18v and VOC 22.4v.  It would be best to match working voltages as the Overland panel might be reduced to the joining panel.

 

Some have just added a separate controller for the aux panels.

 

Others that know more can chime in.  Cheers,  Patrick


  • 0

Patrick

2015 FWC Hawk Flatbed


#5 RallyRock

RallyRock

    Advanced Member

  • Members
  • PipPipPip
  • 45 posts

Posted 29 October 2022 - 05:47 PM

Thanks Craig!  I will def be careful on the polarity and connections in general.  Just didn’t know how to make sense on input power to the controller and didn’t want to cause damage in the rare event everything is firing on all cylinders. I don’t have enough experience to know how variable it all can be. 

 

Besides the portable panel everything is stock because I just didn’t feel comfortable doing it on my own. Knowing what I know now I would probably design my own system.  One day I’ll do that, but probably not unless something breaks or tech like solid state batteries penetrate the market, in which case I’ll optimize the build. 

 

These two small portables though looked like a perfect way to learn this stuff at minimal cost per watt. Couldn’t resist;)

 

thanks again. 


  • 0

#6 RallyRock

RallyRock

    Advanced Member

  • Members
  • PipPipPip
  • 45 posts

Posted 29 October 2022 - 05:49 PM

You might have a issue with input voltage,  others here might know.

 

The Overland working about 28v and VOC around 32v  Your panel specs show working 18v and VOC 22.4v.  It would be best to match working voltages as the Overland panel might be reduced to the joining panel.

 

Some have just added a separate controller for the aux panels.

 

Others that know more can chime in.  Cheers,  Patrick

Hmmmm, well that would def suck. I do have a backup plan and that is just return it all lol. 


  • 0

#7 ckent323

ckent323

    Senior Member

  • Members
  • 1,216 posts
  • LocationSolvang, CA

Posted 29 October 2022 - 05:54 PM

I noted the following at the bottom of the page at the Victron link you posted

1a) If more PV power is connected, the controller will limit input power.

 

1b) The PV voltage must exceed Vbat + 5 V for the controller to start. Thereafter the minimum PV voltage is Vbat + 1 V

 

2) A PV array with a higher short circuit current may damage the controller.


here is a link to the manual for more details

https://www.victrone...FR-DE-ES-SE.pdf


I hope this is helpful

Craig


  • 1

1993 Dodge Cummins W-250 Club Cab long bed, 2007 FWC Keystone


#8 pvstoy

pvstoy

    Senior Member

  • Members
  • 2,760 posts
  • LocationCarson City, NV

Posted 29 October 2022 - 08:30 PM

Hmmmm, well that would def suck. I do have a backup plan and that is just return it all lol.


https://solarpanelsv...g-solar-panels/

https://www.google.c...mobile&ie=UTF-8
  • 1

Patrick

2015 FWC Hawk Flatbed


#9 RallyRock

RallyRock

    Advanced Member

  • Members
  • PipPipPip
  • 45 posts

Posted 29 October 2022 - 08:50 PM

Thank you pvstoy. I’m reading through these carefully. Will let you all know what I find out!


  • 0




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users