Solar panels system, where to run wires down to battery?

[folivier]

2006 Monaco Monarch SE with single slide, V10. I ordered a 400 watt Renogy solar panel system (4 panels). Looking for the best way to run the 10 gauge wires down to the battery bay which is behind the passenger side rear wheels. The fridge is 2 compartments in front of the rear wheels so if I go down the fridge vent I'll have to go along the frame to get behind the wheels. Another option is through the rear cap. The rear inside wall ends about 8" before the rear cap so there should be plenty room to pass wires. Is there anything that would be in the rear cap?

There is no inverter so that'll be my next question on how and where to hook that into the 120 vac system. I'll install the inverter next to the solar controller to keep that cable run short. I'll be keeping the 2 6 vdc golf cart batteries and possibly adding 2 more. I've done LiFePO4 systems on other coaches but won't for this one. This is for an Alaska trip next summer. We went in 2019 in a 36' Foretravel where I had 300 amphours of LiFePO4 + 400 watts solar and it worked great.  I'm planning on a 2000 watt Renogy inverter with 4000 watt peak and using it for short microwave use, coffee pot, hair dryer, and tv. Thoughts on where to wire the inverter into the 120 vac system?  At the transfer switch?  At the breaker panel which is above the bed?  

[JohnC3]

The 2 places I saw when researching it were the roof refridge vent (if you have one) or the plumbing stack. I used the fridge vent and ran the wires down behind the fridge close to the exterior wall.

Hope it helps,

John

[folivier]

I looked up into the rear cap, there is a divider but it appears to be hollow. Good thing about it is any leaks will not get into inside of coach.

[tmw188]

Take the cover off your refrigerator vent cover on the roof (if your frig is not in the slide) look and see if there are some wires roughed in for solar under a cover like this.  

Edited September 3 by tmw188
Added photo

[Martinvz]

For my residential fridge I ran a wire from the fridge via the box next to the toilet. Then thru the wall into the bed room. I then drilled a hole from the battery box thru the floor and exited under the closet slide.  
The slide does not touch the cable and it is not visible unless you look for it. 
I am not sure of you layout and if you could do the same. 

[tmw188]

There should be all kinds of posts about this, it comes up now and then. Did you do a search?

[folivier]

Yes I did search but found nothing about using the rear cap or nothing about a Monarch 30'.

Also nothing about where and how to connect an inverter.

If you have some suggestions I'd be happy to see them.

[CAT Stephen]

@folivier,

 

I recommend that you consider taking an alternate approach to wiring your solar panels to obtain the maximum output.  Here is why you should not wire all of your solar panels in parallel:

- With 10 Gage wire, you will experience a significant voltage drop of 4.1% because this wire size is very inefficient for the load (athough it is safe), thus wasting 4.1% of your usable energy right out of the gate. 

- To achieve the same low voltage drop (0.7%) that I have (details later in this post), you would need to use 2 gage wire for your parallel installation which is expensive and hard to work with

• Voltage Drop Calculator (make sure that you double your enter double your wire length from your solar panel termination on your roof to your solar controller to accomodate the total length of both your positive and negative wires
  • https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html

- Your batteries can only charge when there is a minimum of ~16-17V available from your solar array (assuming that your house battery system is 12V nominal)

•  This means that you will not produce significant voltage on cloudy days and very little at the start and the end of the day, effectively reducing your usable energy by another ~25%

Please post what solar controller that you intend to install.  Just so that you know, wiring your four panels in series will minimize your wire size and will have a tremendous positive impact on performance except when one or more panels are partially shaded.  

Be aware that PWM solar controllers have terrible operating efficiency converting solar power to usable power and are also very inflexible in terms of voltage range, typically requiring all of your solar panels to be wired in parallel. Thus PWM controllers waste ~30-50% of your otherwise available solar energy.  For example, a PWM solar controller can only use ~16V of your solar panels 24.3V output.  Thus the difference is pure wasted energy.

MPPT solar controllers are iconic for their tremendous efficiency, typically producing 200-300% more usable energy than the cheapo PWM solar controllers.  Also, MPPT controllers accommodate high voltage solar arrays versus PWM controllers that can only accommodate 12VDC or in some cases 24 VDC if you have a 24VDC house bank.

I'm currently running the exact same solar panel that you have installed.  I have 12 Renogy 100W solar panels for a total of 1.2Kw.  I wired the first 6 panels in series for the forward half of the coach, and 6 panels in series for the back half of the coach.  I then parallelled the two series arrays with a combiner box.  Thus, output is 145.8 VDC max at 10.42 amps (short circuit) via 14 gage stranded marine rated copper boat wire. This 14 gage wire has some headroom to spare for more power while transmitting the full theoretical 1.2Kw.  Remember that amps (not volts) drives wire gage larger.  Thus, my voltage drop (solar energy loss) is only 0.7% which is 600% less usable power loss than your 10 gage wiring in parallel approach.

Also, most people installing solar are unaware of HyperVOC.  This occurs in low to very low temperature because solar panels produce much higher voltages than at nominal temperature (~70F) which can result in destruction of your charge controller.  

• https://midnitesolar.com/pdfs/whyHyperVOC.pdf

In summary, if you are willing to consider wiring your panels in series, you will gain a minimum of 200-300% more usable power versus parallel wiring, significantly decrease your wiring size / expense, nearly eliminate voltage drop.  But, you will need to use the appropriate MPPT solar controller as PWM controllers can't accommodate higher voltages.

 

 

[cbr046]

Along those lines I found this article on MPPT vs PWM solar controllers enlightening.

https://www.cleanenergyreviews.info/blog/mppt-solar-charge-controllers

- bob

[scottknight]

i used the rear cap dropped a plum bob thru hole ended up in rear passenger bin where i mounted controller next to inverter then on to batteries. My next solar addition will be folding remote I discovered that I like shade on rv as much as i like solar. I am not an expert just a user of solar. Wife runs sewing machine and quilting when boondocking. I did run # 2 Stran DC wire on roof to controller then to battery bank to mitigate voltage drop