Gauge of solar prep wires on 2021 22RBE?

[alias100]

We have two 200 watt 12 volt/9.5 charging amp solar panels on our 2021 22RBE feeding into a Victron MPPT 100/50 solar charge controller, then to two 206 amp hour SOK batteries. The panels claim to be 12 volt, but using a meter they measured at about 18 volt. We are adding two more of the same panels. The two we have are wired in parallel.

Not sure if I can add two more panels with all four wired in parallel or if I need to go to parallel/series wiring so I don't overload the wires from the roof. I would have to do some disassembly of the system in the pass through to see if the gauge is printed on the wiring so I am hoping someone knows what Grand Design would have used.

I am hoping I won't have to replace either the solar charge controller or the wiring from the roof, but I am an amateur at this solar stuff so any suggestions would be appreciated.

I have attached a screenshot showing the panel specs.


Thanks for reading, and I hope everyone had a great Thanksgiving!

[BoredWeasel]

I would switch your panels to run in series, Higher voltage means lower current and less loss. this means you will be running 72 volts at about 8-10 amps verse 14 volt at 32 amps. your victron is rated for 100 volts solar input.

Lower amperage means you will be good with the stock wiring

Edit: I assumed 100 amp solar panels, looking at the spec sheets they are 200 watts so roughly double the amps. so you would have 800 watts with the 4 panels

that means roughly 60 amps at 14 volts

or

16 amps at 80 volts

my choice would still be in series

[Riverbug]

To my knowledge all of the OEM solar is wired with 10 gauge. I'd go series/parallel so that when you have partial shade you still get as much solar coming in as possible. Once you decide how you want to configure them, then you can determine whether the wiring will accommodate. I wouldn't limit your configuration to the wire at hand, but that's my $.02. Use a calculator to determine the appropriate wire, fuses, etc., like these...of course you need to estimate the length of the wire as well.
https://explorist.life/category/blog/calculators/

[alias100]

@BoredWeasel and @Riverbug
Thanks for the very helpful info.
I am thinking series/parallel should work best as we sometimes camp in tree shaded locations.
Each of the pairs wired in series should put out 36 volts and 18-20 amps.
Then the 2 sets wired in parallel should up that to 36 volts and 36-40 amps.
Plugging 36 volts, 40 amps and 30 feet (I know from dropping the coroplast that the wire from the solar jack on the roof takes a circuitous route to the driver's side of the pass through where the solar controller is located, but it can't believe that it is longer than 30') into the wire sizing calculator gives 12 AWG as recommended wire size.
The 2 new panels are due Saturday and I have until our trip to Texas in April for the eclipse to get them installed so I think I can meet that deadline.
Thanks again and let me know if I have misunderstood any of this.

[Redapple63]

@BoredWeasel and @Riverbug
Thanks for the very helpful info.
I am thinking series/parallel should work best as we sometimes camp in tree shaded locations.
Each of the pairs wired in series should put out 36 volts and 18-20 amps.
Then the 2 sets wired in parallel should up that to 36 volts and 36-40 amps.
Plugging 36 volts, 40 amps and 30 feet (I know from dropping the coroplast that the wire from the solar jack on the roof takes a circuitous route to the driver's side of the pass through where the solar controller is located, but it can't believe that it is longer than 30') into the wire sizing calculator gives 12 AWG as recommended wire size.
The 2 new panels are due Saturday and I have until our trip to Texas in April for the eclipse to get them installed so I think I can meet that deadline.
Thanks again and let me know if I have misunderstood any of this.

Series/parallel is the way to go. I have 800 watts in the same configuration as you (well as you will have).

I have two each in series and each string in parallel.

Series doubles the voltage, parallel doubles the amperage.

I have Newpowa Solar 200 watt panels.

The voltage goes off the VOC or Voltage open circuit. Double the voc of each panel for two panels in a string, triple for three etc.

ISC is Short Circuit Current and that is max amps the panels can deliver without damage.

With two in each string you get the VOC of two panels and the amps of two panels. Easy peasy for 10 gauge.For my Newpowa the VOC is 21.8 volts and the ISC is 11.47 amps.
Therefore my operating voltage and amperage is 43.6 volts and 23.4 amps.

Your system should not be that much different. Easy peasy for 10 gauge. Good copper wire with get you 30 amps all day long. You have more than a 25 percent margin.

I hope this helps.

I up the VOC and ISC of your panels and give you the numbers.

On edit:
Here are the numbers for your panels:
VOC: 24.335
ISC: 9.87 amps

Do your system with 4 panels in series/parallel configuration would net you
48.77 volts and 19.74 dc amps.

You good.

Bill

[Conner58]

Series/parallel is the way to go. I have 800 watts in the same configuration as you (well as you will have).

I have two each in series and each string in parallel.

Series doubles the voltage, parallel doubles the amperage.

I have Newpowa Solar 200 watt panels.

The voltage goes off the VOC or Voltage open circuit. Double the voc of each panel for two panels in a string, triple for three etc.

ISC is Short Circuit Current and that is max amps the panels can deliver without damage.

With two in each string you get the VOC of two panels and the amps of two panels. Easy peasy for 10 gauge.For my Newpowa the VOC is 21.8 volts and the ISC is 11.47 amps.
Therefore my operating voltage and amperage is 43.6 volts and 23.4 amps.

Your system should not be that much different. Easy peasy for 10 gauge. Good copper wire with get you 30 amps all day long. You have more than a 25 percent margin.

I hope this helps.

I up the VOC and ISC of your panels and give you the numbers.

On edit:
Here are the numbers for your panels:
VOC: 24.335
ISC: 9.87 amps

Do your system with 4 panels in series/parallel configuration would net you
48.77 volts and 19.74 dc amps.

You good.

Bill

I have the same setup and working great ��

[BoredWeasel]

my system is a bit odd but it works for me allowing me to competely charge my battery bank in a couple of hours.

I have 2 roof mounted series panels one is the stock furron 165 watt panel and another hqst 190 watt panel I picked up on some sort of sale on amazon. the voltages were close enough to work. I can easily harvest 20 amps at noon in the summer on the east coast with a peak voltage from the panel from 34-38 volts. controlled by a victron smart solar 100 | 30 charge controller

I have 1kw in a series ground array I can move 30-50 foot from the trailer as needed it is made up of 10 100 watt panels hooked up in series. Peak voltage is 190-200 volts dc at a current of 10 amps max, I regularly see currents on the 12 volt side of 60 amps.
I have a victron mppt250 | 70 mc4 to do the solar to control it.

A bit of messing around with the ground array, but we don't take it on every trip and when we are on the outer banks it is more than enough to power the ac and recharge my battery bank.


There really is no 100 percent right or wrong answer to the great debate, just what ever works out best for you