Upgrading RV solar, mismatched panels?

[Isaac-1]

I have an older (installed in 2015) 400 watt solar installation on my motorhome which uses 4 100Watt Grape Solar GS-STAR-100W (VOC 21.9, ISC 6.13), I have also recently acquired a number of very lightly used 305Watt LG NeON (VOC 40 ISC 10.1) panels from a hurricane damaged installation, that I would like to re-use along with Victron 100/50 MPPT solar controller for this upgrade. My issue is that I only have enough rooftop real estate to fit 3 of the LG NeON2 panels due to vent / skylight / antenna placement. I could however additionally fit 2 or possibly 3 more of the 100W Grape panels in smaller open spots around the roof.

Which leads to the mix and match potential options, and do you think it will work:

3 LG panels in parallel (VOC 40) along with 2 Grape panels in series so as to get a VOC of 43.8 on the Grape panels?

2 LG panels in series (VOC of 80), paralleled with 1LG and 2 Grape panels in series for a VOC of 83.8 combined for all 3 panels?

Will this not work at all, should I just live with only 3 LG panels, and only go from 400 to 615 watts of panels on my upgrade,...?

p.s. correction they are LG NeOn not NeOn2, ISC and VOC has been corrected above

 

[Isaac-1]

I have been playing with the mix match solar calculator here https://footprinthero.com/solar-panel-series-and-parallel-calculator and it seems to suggest my best bet may be keeping all 4 of the 100 watt panels wired in series then adding 2 of the 305 watt panels in parallel loosing only about 5% efficiency

 

[scrubjaysnest]

I would remove the grapes and use them as portables through a separate CC.

 

[Isaac-1]

That probably makes sense I spent several hours last night running through the variations on this while looking at overhead photos of the RV, and it seems I would need to have 2 Grape panels wired in series, and 2 of the LG panels wired in parallel for it to make sense to keep them, with 2.87% losses. However given available space on the roof, it makes more sense to just install 3 of the LG panels, and maybe keep one of the Grape panels wired to a separate controller to maintain the engine starting battery, it is overkill for that, but with the way the Grape panels are mounted 3 side b side, and 1 on its own in a space where an LG panel will not fit, it makes sense to just leave it in place and run a new wire for the LG panels. Of course with 3 LG panels on the roof, it means they will need to wired in parallel so as to not go over the 100V max of the Victron MPPT 100/50. 3 of the LG 305W panels mated to the Victron MPPT 100/50 will put the system oversized at 131%, which I don't think it is too bad considering these are flat mounted panels.

 

[RvNaut]

An expensive option is to build a rack to elevate all panels above the vents and AC. That is my long term goal. Right now I was able to squeeze 6 230w panels on my 32'

In your case I think I would consider a different controller for the new panels and mount as many as you can. g'luck.

 

[Isaac-1]

It would be tempting however right now I have less than 4 inches of clearance between the top of my air conditioner, and the roll up door in my storage shed.

 

[0truck0]

Put your newly aquired panels on a separate solar charge controller. You can feed multiple charging sources into one battery just fine.
I have two separate solar systems that used to feed into one battery via separate controllers. The controllers will not get confused and nothing bad happens, is all perfectly fine. I eventually got second batt, so now have two systems that are separate.

 

[RvNaut]

I have an older (installed in 2015) 400 watt solar installation on my motorhome

Is that you Ike?? Trek?

 

[Isaac-1]

Yes it is, how go your travels?

 

[RvNaut]

Yes it is, how go your travels?

If you look at my posts, you'll see what I ended up doing...

The Build - 48 volt 280Ah - RV Integration

Good Day Arm Chair Electricians I live in a 2004 Safari Trek 31SBD. It currently has no solar, a 12 battery bank made up of 4 6-volt golf cart batts ( buh bye none too soon) and Freedom 451 Inverter charge controller( also soon to go buh bye). My power needs are vaaaahst :D I run a full size...

diysolarforum.com

It has been running since March.

Travels have been largely uneventful...

 

[Rocketman]

You probably want the 100w panels on its own SCC. The three 305w panels in parallel will produce 915w. The Victron 100/50 can only send 700w to the battery.

You are already over paneled nicely. Which will help because of flat panels. So it probably doesn’t make sense to overpanel even more.

Putting 3 panels in parallel requires that you fuse each panel - so be sure and get three MC4 fuses. Also, your Imp (working amps) are close to 10 on each panel- Do you have 10awg (which will be maxed out) or better yet 8awg going from the parallel connectors to the mppt. Also make sure you have 6awg (or larger) going from the mppt to the batteries- you will get 50amps flowing in good sun.

Good Luck

 

[Isaac-1]

Thanks, I will be using 10AWG wiring between the panels with 20A MC4 fuses on each of the LG panels, and 8AWG or larger between the Victron 100/50 to the main power distribution blocks.

 

[Rocketman]

8awg between the mppt and the main power distribution blocks is too small.

8awg - can only handle 40amps - you will have 50amp.
6awg is rated at 50amps.
If the distance is longer you probably want to move up to 4awg.

Also, what is the Imp of your 305w panels. It will be around 10amp. 10amps *3 panels = 30amps - which is the max of 10awg wire. So if the Imp is above 10 - you need to move the wire from the combiner to the mppt up to a 8awg.

 

[Isaac-1]

Thanks for the catch there, I will be using something larger than 8awg, probably whatever I have on hand for the run, which is about 4 feet, maybe a bit less from the Victron 100/50 to the distribution block. Imp is 9.65 amps, so just under 30 amps combined for 3 panels.

 

[LeAnn]

I hope it's okay to tag on to this thread... uhm, I'm new. I used the awesome calculator @Isaac-1 listed. I have two 100w 19.23vVmp and 5.21aImp + two 220w 17.52Vmp and 12.6sImp. The calculator tells me to wire the identical in series and then the series strings in parallel. Ok. I get that. This results in 624w max output, 35.04vVmp and 17.81aImp. I have a MPPT 150v/35a. I then went to their calculator for MPPT sizing and filled in the open circuity voltage for the two sets of panels (22.12Voc and 20.52Voc respectively) and it recommended the 150v/35a MPPT. So, based on the calculator and my ability to follow directions, the MPPT I purchased is fine with this setup. Am I figuring this correctly? My return window for the MPPT is closing... . and thank you in advance for your help.

 

[Rocketman]

Leann,
it is best to start a new thread, rather than add-on - different conversations gets confusing.

So let’s me make sure I understand your plan - I think you typed it a bit incorrectly.

Your 2 100w panels need to be wired in parallel. In parallel amps add and you use the lowest volts - giving Vmp 19.23v and 5.21+5.21= 10.42a

Then you have the two 220w panels Vmp 17.52 Imp 12.6a.

Then wire all these in series v= 19.23 + 17.52 + 17.52 = 54.27v and use the lowest amps 10.42a

That will give you 565w of power.

Did I understand your plan???

FYI - your penalty for wiring non-identical panels is 220+220+100+100=640w possible
640 - 565 = 75w penalty.

You may just want to wire the two 220w panels to the 150/35 and then run another set of wires and run the two 100w panels into another 75/15 controller- Then you get the full 640w of possible power.

Definition on wiring:
Parallel- wire positive to positive and neg to neg.
Series - wire pos to neg then pos to neg then pos to neg.