Positioning an Inverter

[Long & Winding road]

Yeah I was going to say "12 solar panels?" How big is your inverter and battery bank? How many watts are each panel? Do you plan on powering your Air Cond. for a few hours each day?

As a genral rule they say 100 watts of solar per 100 amh of batteries. So many RV'er have TWO 100 panels to charge TWO 12 volt (or TWO 6 volt) batteries.

You many already know this but I just thought I would point this out.

So if your putting up like 1200 watts of solar you to make it worth it (use up all your solar input juice) you need like 1200 amp hours of storage...... using the 50 % rule for LA batteries that like 2400 amh total which could be as many as 24 lead acid (@ 100 amh each) of batteries (or like 12 Litium 100 amh batteries).

Tell us more about your system.

[Long & Winding road]

Also will you be able to walk around your roof for general inpection and maintance not to mention to WASH the panels every week or two?

I guess if you went with flexable panels you can walk on them (I would not suggest to do so but I know some say its OK).

[Long & Winding road]

YOu know I walked away and "24 batteries" dont sound right... .LOL. I guess 12 of the 100 Amh Lead Acid batteries for 1200 Watts of solar would be correct? But you may only have 600 or 800 watts... hard to tell since some of your panels look like the 50 watt square ones.

[Judge]

Originally Posted by Long & Winding road

Also will you be able to walk around your roof for general inpection and maintance not to mention to WASH the panels every week or two?

I guess if you went with flexable panels you can walk on them (I would not suggest to do so but I know some say its OK).

If he lays down EternaBond tape over ever seam and opening before installing the panels, he won’t need to worry about roof maintenance other than cleaning the panels now and then.

I just put EternaBond Tape down on the roof of my 2020 Magntiude on ever place there is Dicor. I shouldn’t have to do much, if any roof maintenance any more. It will be a pain to remove if I need to replace a fan, Winegard ConnecT 2, etc. but it is worth it not to have to maintain the Dicor and worry about roof leaks.

[Long & Winding road]

This is true. I would still want to do an inspection once a year ..... but he will need to clean the panels every week / 2 weeks or so in order to maximize his input wattage.

[The_Breeze]

Sorry about this post.

Panels wired in series: double the volts, double the amps or both?

Answer:
When solar panels are wired in a series, voltage is additive, but the amperage stays the same.

[The_Breeze]

Originally Posted by Long & Winding road

Also will you be able to walk around your roof for general inpection and maintance not to mention to WASH the panels every week or two?

I guess if you went with flexable panels you can walk on them (I would not suggest to do so but I know some say its OK).

If you look close, I left a small walkway. It's not much but should let me move around where I need to. The front is a challenge. If I need to work on the fan or antenna, I'll have to be careful or get creative.

[The_Breeze]

Originally Posted by Judge

If he lays down EternaBond tape over ever seam and opening before installing the panels, he won’t need to worry about roof maintenance other than cleaning the panels now and then.

I just put EternaBond Tape down on the roof of my 2020 Magntiude on ever place there is Dicor. I shouldn’t have to do much, if any roof maintenance any more. It will be a pain to remove if I need to replace a fan, Winegard ConnecT 2, etc. but it is worth it not to have to maintain the Dicor and worry about roof leaks.

Thanks for the tip. Just changed the shopping list from Dicor to Eternabond

[The_Breeze]

Shoot holes in it. I'm learning.

[Judge]

Originally Posted by The_Breeze

Sorry about this post.

Panels wired in series: double the volts, double the amps or both?

Answer:
When solar panels are wired in a series, voltage is additive, but the amperage stays the same.

Correct!

But make sure to use an MPPT Controller to handle the extra voltage.

[The_Breeze]

Originally Posted by Judge

Correct!

But make sure to use an MPPT Controller to handle the extra voltage.

I believe I read somewhere that amps charge batteries and maximize amps, not volts. The out volts have to be compatible with the battery but volts are generally static, sufficient amps charge batteries. Still doing homework. Reading this:

"Because a battery is not totally efficient at converting electrical energy into chemical energy and vice-versa, re-charging a 100Ah battery requires about 120Ah to be put back into it, and this can be achieved by either
120 Amp-hours / 10 hours = 12 Amps for 10 hours
120 Amp-hours / 15 hours = 8 Amps for 15 hours
120 Amp-hours / 24 hours = 5 Amps for 24 hours etc."
(re:http://www.operatingtech.com/lib/pdf...20Charging.pdf)

Another reference: https://hespv.ca/blog/wire-solar-pan...lel-vs-series/

[Long & Winding road]

The Breeze, So how many watts of solar are you adding?

How many batteries?

I see the walkway on the edge of the RV (but it dont look very wide). I would not want to walk on the edge... I would fall off for sure. Can you make a walkway in the middle of the roof?

Cant wait to see the finish product.

[The_Breeze]

I'll only sacrifice the space already reserved for 4 batteries under the steps. Cavie level set me on 12 v. 120. I'll locate all the components in that void and use Romex to make the run to the control panel. I may install a 30A socket in the power cord compartment and use the existing technology to take care of the rest.

Testing boundaries. Trying not to get burned.

[blw2]

I thought this attachment might be of some little help to you.
Done back when I was playing around with ideas.
the panel rectangles are scale based on this panel kit
https://www.renogy.com/renogy-100w-12v/starter-kit/

A suggestion, call Thor and get the roof drawings based on your vin in case it's different than mine. Without "cad" or a decent pdf editor, an option would be to print it out, then to scale make some cuttouts of the panel size you're considering, then you can move them around on the roof drawing to play with ideas.

I used the drawing for "brainstorming"
I got up on the roof with my stud finder to verify location of the metal frame and marked it with pencil
Then I could be more certain of landing the screws into structure.
and for waht it's worth I ended up with a single panel on center line, between the AC and the front roof vent. I'm very happy with that part. Plenty of room all around for cleaning and roof maintenance and seems like a good position. I was going to include a photo but I cannot believe I don't have a picture!

The only thing I'm not happy with is my controller and breaker location. I mounted the controller under the bed, and added breakers on both sides so I could turn off the panel to the controller and turn off the controller to battery. As is, I have to put out the slide to raise the bed to get at it. Your location will be tons better.

[The_Breeze]

Originally Posted by blw2

I thought this attachment might be of some little help to you.
Done back when I was playing around with ideas.
the panel rectangles are scale based on this panel kit
https://www.renogy.com/renogy-100w-12v/starter-kit/

cut...

Thank you for this. It reminded me of the Title block and your suggestions welcome. This is what I have so far. Will get it to scale another day. Right now, it only shows everything should fit where planned. It's still a WIP. I'm messing around with ideas as you did.

[Judge]

Originally Posted by The_Breeze

I believe I read somewhere that amps charge batteries and maximize amps, not volts. The out volts have to be compatible with the battery but volts are generally static, sufficient amps charge batteries. Still doing homework. Reading this:

"Because a battery is not totally efficient at converting electrical energy into chemical energy and vice-versa, re-charging a 100Ah battery requires about 120Ah to be put back into it, and this can be achieved by either
120 Amp-hours / 10 hours = 12 Amps for 10 hours
120 Amp-hours / 15 hours = 8 Amps for 15 hours
120 Amp-hours / 24 hours = 5 Amps for 24 hours etc."
(re:http://www.operatingtech.com/lib/pdf...20Charging.pdf)

Another reference: https://hespv.ca/blog/wire-solar-pan...lel-vs-series/

As I understand it, a PWM controller can’t handle the voltages of panels in series whereas the MPPT controller can besides the other benefits it provides for larger and more complex systems.

[The_Breeze]

Originally Posted by Judge

As I understand it, a PWM controller can’t handle the voltages of panels in series whereas the MPPT controller can besides the other benefits it provides for larger and more complex systems.

Thank you. Just made the shopping list.

[RVGeek]

Power loss is inversely porportional to resistance and porportional to current squared (P= I^2 * R). One does not normally use the same wire gauge on both sides, as the current is 10X larger in the 12VDC circuit, as has already been stated. You reduce the 12VDC losses by increasing the wire gauge, but at much more cost.

Conclusion: Put the inverter as close to the battery bank as possible, and put circuit protection near the positive battery post. I use an inexpensive fusible link from an auto parts store.

Also, if the inverter has remote panel, remember that it produces a parasitic drain on the battery, so the inverter should be turned off when in storage.

Originally Posted by The_Breeze

I'm planning out a solar install. In my research, I have not come across anyone who explains where they placed things and why.

For instance, I read you should place the inverter close to the batteries to reduce line loss. My batteries are under the steps in the front of the coach and I have a nice void to place the inverter that's no more than 2-3ft away from the batteries. My fuse/breaker panel is in the rear under the bed. What about the run from the inverter to power panel? It plays into wire size. I found a calculator to help with voltage loss. My initial thought is locate everything up front in that void and run the inverter's 120v output back to the power panel. It's large enough to hold all the components and I have enough wall space to mount the monitoring and control panels. My concern is most all the outlets I use are located up front so, now I make that run all the way to the back to reach the power panel and send it all right back up front to use the outlets.

Is it best to locate the inverter somewhere in between to "split the loss", place it closer to one end or the other other to 'balance' the loss? Or just get it as close to the batteries as possible? See my dilemma?

If you have something I can read, I'd appreciate it. I'm not adverse to reading something for myself. I just need to find it.

[16ACE27]

Originally Posted by RVGeek

Power loss is inversely porportional to resistance and porportional to current squared (P= I^2 * R).

No, power LOSS is proportional to resistance and proportional to current squared as demonstrated by your equation. Remember, the resistance causing the loss is not controlling the current drawn from the power source, the actual load is controlling the current.

[telcoman]

Generally speaking you are best to put it close to the convertor. Your battery leads go there anyways, so should be of sufficient gauge. That also allow you to pick what circuits you want to go to the inverter which allows you to use the style which auto switches when the power is off without feeding items with too much current draw to run off an inverter like an A/c, or items you don't want to run off like a fridge which you want to auto switch to gas if no power. Generally speaking you only want small appliances, TV's etc to run off an inverter.