55 replies to this topic

[Vic Harder]

Mark,

 

The MPPT controllers pull out way more power from the panels than a PWM controller can.  And to do that, you need to wire the panels in series, to pump the voltage up and give the controller room to play in.

 

The advertizing/review on the 100/50 is flashy... and the same applies to all the Victron controllers.  They are all very quick.  So don't let that disuade you from getting any other Victron controller!  

 

The series/parallel connection thing is even more important for those remote/portable panels, because instead of a 10' of wire, you now have 5 to 10x that.  I have 100' of cable for mine, so I can get them into the sun easily if I am in the shade. That's why I have TWO Victron controllers.  One for the roof array and another for my portables.

 

LiFePo4 batteries discharge about 3-4x slower than regular chemistry batteries.  If you are not parking for months, it won't be an issue.  Otherwise, I second Craig's recommendation of a NOCO Genius 7200.  I use one too.

 

I have bluetooth on my battery monitor, and at the time I didn't include bluetooth for my controllers.  I don't miss that feature much, as I ALSO have the remote displays and can change settings from those.  That said, there is little need to adjust the controllers.  I love having BT for my batteries, as I can monitor them from the house or cab of the truck.

 

 

Sorry about the upside down gauges!

Edited by Vic Harder, 08 March 2018 - 01:03 AM.

[Stokeme]

Ok, looking at a wire sizing calculator, I can see the relationship between volts, amperage, wire gauge & distance. So questions are:

Does a portable, if plugged into the rear wall outlet, combine with the amperage total of the panels, run in parallel, on the roof? Also, would you have to combine the roof to battery wire length with the portable to battery wire length in calculating power loss? Would the power loss at least be separated between by the two different plug in points, roof vs portable?

Say I do run the roof in series, 2 panels x 12v=24v. If I had originally planned on buying only one portable, at 12v, would I then be forced to buy 2 portables, to be able to match the 24v on the roof, if I wanted to use the same controller? Or be resigned to using two, one for each site?

Bottom line summary? If all the truck panels are run in parallel, you have to limit the # of panels & the wire length, or suffer measurable power loss ... or use real heavy gauge wire. The wiring from the roof to the house battery would be unpleasant to modify.
Running all the truck panels in series, roof & portable, almost requires two separate controllers. But, the increased voltage affords enhanced power efficiency & travel length, using much lighter gauge wire.

Could someone use a red pen & make corrections to my summary? Mid term exam, I’ll study a bit more for the final. I never wanted to deal with electricity.
FWC is using 10 gauge wire. I checked today.

Thanks again Vic & Craig

Edited by Stokeme, 08 March 2018 - 07:52 AM.

[rando]

As an armchair theoretician it pains me to say this - but we are all over thinking this.   The loss to thinner wires is a very minor effect, that you don't really need to worry about.    The difference between two parallel or 2 series 120W panels is ~3% under the absolute worst case scenario and usually much less than this. 

 

If you want to use a single controller with roof and portable panels, but them all in parallel and use the same type on panels for all your panels.   Your thought process should be:

 

1. Decide how many panels you want (2 x 120W on the roof and 1 x 120W portable seems to work well for most folks). 

2. Add up the short circuit current of all the panels (with the solar Cynergy 120W panels this would be 6.6A * 3 = 20A.

3. Pick the next biggest size charge controller (the 100V/30A either with or without built in blue tooth, probably worth the extra $30 to get bluetooth). 

4. Wire it all up and be happy!

[Vic Harder]

As usual, rando is being very real, and helpful.

 

To answer your question "Does a portable, if plugged into the rear wall outlet, combine with the amperage total of the panels, run in parallel, on the roof?"  Yes, to keep it simple, that external plug would usually be in parallel.

 

And to your question "Say I do run the roof in series, 2 panels x 12v=24v. If I had originally planned on buying only one portable, at 12v, would I then be forced to buy 2 portables, to be able to match the 24v on the roof, if I wanted to use the same controller?"  Yes, you need to feed more voltage than what you would get from one panel to really see the advantage of an MPPT controller.

 

And no, you never really need to upgrade the wiring already in the camper from the roof to battery box.  That run is too short to care about at the current levels and losses we are talking about.

 

Now to rando... are you suggesting that Mark run all the panels in parallel and use a Victron MPPT controller?  I'm not sure I see the advantage of MPPT in this case.

[Stokeme]

Rando, thank you, that is what I was hoping to hear. Vic, thank you for the replies & answering my questions. Craig, thank you for your patient PM & posting replies.
This Forum & it’s members are awesome ! I now have basic understanding, not to make harmful decisions about $ spent on a Solar System. Electricity was the one thing I never wanted to be involved with around the house or the yard.
I need & want to stay light with my build. Wish I could share a cold one with everyone ...

[rando]

Yup, I am saying run them all in parallel and use an MPPT controller.   This makes using a portable panel dead easy. 

 

You get the same advantages from an MPPT controller whether the panels are in parallel or series.   The only difference is that you get slightly less resistive loss in the wiring with the panels in series, but as pointed out before, this difference is small. 

 

Using the 120W solar cynergy panels as an example - they produce maximum power at 20V and 6A (thus the 120W rating).   An MPPT controller will run the panel at this point and under ideal conditions could provide the full 120W.   A PWM controller may pull slightly more current from the panel (but not more than the short circuit current of 6.65A) but only at the battery charging voltage of ~13.7V .   Therefore the PWM charge will provide a maximum of 13.7*6.65 = 91W under ideal conditions, so 25% less power from a PWM charger.   Realistically you will be in less than ideal conditions and get less power from either charge controller, but the MPPT will always provide more power. 

 

To be truly pedantic (which we all excel at) you also get a slight advantage from series panels in the voltage is higher and so the charger will switch on slightly earlier in the morning - but this has to be a third order affect. 

 

For someone who is not an electron enthusiast - go the simplest route possible: all the panels in parallel and all the same type of panels. 

 

 

As usual, rando is being very real, and helpful.

 

To answer your question "Does a portable, if plugged into the rear wall outlet, combine with the amperage total of the panels, run in parallel, on the roof?"  Yes, to keep it simple, that external plug would usually be in parallel.

 

And to your question "Say I do run the roof in series, 2 panels x 12v=24v. If I had originally planned on buying only one portable, at 12v, would I then be forced to buy 2 portables, to be able to match the 24v on the roof, if I wanted to use the same controller?"  Yes, you need to feed more voltage than what you would get from one panel to really see the advantage of an MPPT controller.

 

And no, you never really need to upgrade the wiring already in the camper from the roof to battery box.  That run is too short to care about at the current levels and losses we are talking about.

 

Now to rando... are you suggesting that Mark run all the panels in parallel and use a Victron MPPT controller?  I'm not sure I see the advantage of MPPT in this case.

[Vic Harder]

Thanks for adding to my understanding rando and Craig, and for asking all these great questions Mark!

 

I am now wondering about how to wire/switch my external panel connection to wire that in series with the roof panels when I plug it in....  hmmm.   

[Stokeme]

I initially gleamed parallel which I was happy to read. Thanks for a further & more detailed addition. I am highly into “dead easy”.
I purchased two flex 120w solar cynergy panels last night. I would like three but not sure how that might work yet with a kayak, & hopefully a canoe, on the roof too. Looking at a 80 or 100w (weighing best value) folding flex portable, from Lensun, very light weight. Going to buy a Victron SmartSolar 100/30 & Noco G7200 charger. I will initially rely on the inherent Bluetooth monitoring function in my battery instead of buying a battery monitor. - Any further thoughts are welcome - Putting my stamp on this Camper is fun.
I am initially abandoning my engine to house battery connection. If I need to initiate that later, I hope not, I would probably purchase this, as it was recommended by StarkPower, but yikes on the price ... It seems almost necessary to keep my LiFePo4 Battery healthy ...
http://www.sterling-...erycharger.aspx

[rando]

To reiterate, if you are going to combine panels into one controller, they really should be the same.   So putting an 80W lensun portable panel in parallel with the 120W solar cynergy panels on the roof may not be optimal depending on what their I-V curves look like.  When you put them in parallel, you are forcing them all to be at the same voltage which may mean the some of the panels are operating pretty far from their maximum power point.

[Stokeme]

So, I need a 120v portable panel? By the same, do you mean overall voltage, not manufacturer, correct? Or can you suggest I try to match (which particular?) provided numerical criteria, V or A, documented on the panel?

Edited by Stokeme, 08 March 2018 - 09:26 PM.