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Old 02-11-2020, 10:50 PM   #15
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I am thinking the idea is: The RV has solar panels for boondocking, extended off piste - whatever. The RV isn't owned by full timers. So, if the RV is used X months of the year...what value are the solar panels when the RV isn't being used?

So, if the solar investment has been made...how can it be leveraged 12 months of the year? Providing some energy is better than no energy. Especially if the equipment and installation cost is already sunk.

Once a technical implementation plan exists (use RV solar for house daily use or also sell back unused energy) then it's easier to figure out the economics. I have a suspicion that no RV solar system creates enough energy to exceed the house use so there will likely be no selling back to the utility.
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Old 02-11-2020, 11:06 PM   #16
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Quote:
Originally Posted by Dav L View Post
I am thinking the idea is: The RV has solar panels for boondocking, extended of piste - whatever. The RV isn't owned by full timers. So, if the RV is used X months of the year...what value are the solar panels when the RV isn't being used?

So, if the solar investment has been made...how can it be leveraged 12 months of the year? Providing some energy is better than no energy. Especially if the equipment and installation cost is already sunk.

Once a technical implementation plan exists (use RV solar for house daily use or also sell back unused energy) then it's easier to figure out the economics. I have a suspicion that no RV solar system creates enough energy to exceed the house use so there will likely be no selling back to the utility.
Agree. Am in South Texas, have a Tesla so checked out Solar with them. Appears I will need about 8000 watts of solar on the roof with a payback of 21 years to break even. My 1455 watts on the motorhome will not make much of a difference. But do have 5200 watts solar on the S&B that will recharge my car and run 2 refrigerators. This is a homemade system with no grid tie.
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Old 02-12-2020, 07:25 AM   #17
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Agree. Am in South Texas, have a Tesla so checked out Solar with them. Appears I will need about 8000 watts of solar on the roof with a payback of 21 years to break even. My 1455 watts on the motorhome will not make much of a difference. But do have 5200 watts solar on the S&B that will recharge my car and run 2 refrigerators. This is a homemade system with no grid tie.
You sound to be in a best case situation. You have already bought two solar systems and have good use of the derived energy and where to put it (Tesla).

Your RV is 28% of your total system. Where does that energy go when you aren't boondocking in the RV? Just float charge the RV batteries? If so, then 25% of the RV system isn't being utilized.

And, being in Texas where the sun shines bright, you have the capability to use most of the available sun power. Maybe utilizing the RV solar 12 months of the year will decrease the payback a few years for the total system.

So, what's the magical "box" that uses solar derived power when it's available to meet the current demand and not pull from the utility company meter...is that the "relay"? so:

Solar panels > charge controller > batteries > inverter > relay > circuit panel > outlets and appliances

and if solar not enough for demand:

Utility company > pay meter > relay > circuit panel > outlets and appliances

If that's the case then:

RV solar system > battery > inverter > new 110 volt line to house > magical relay > house solar relay? Or circuit panel directly?

Or should the RV charge the house solar battery (if you have a house solar system):
RV solar > battery > inverter > new 110 volt line > charger > house solar batteries

I assume we don't want to feed battery voltage to the house (large battery cables, long lengths, incompatible voltage with house batteries etc)

And if one only has RV solar an not house solar:

RV solar new 110 volt line to house > magical relay > circuit panel feed?


This week we are writing a software driver for a solar energy consumption meter. (Modbus RS485). One step towards managing these "complicated" systems. A charge controller monitoring driver would be next.
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Old 02-12-2020, 08:41 AM   #18
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Yes lots of complications. RV is 12 volt with 120 volt only inverter. House is 48 volt with 120/240 volt inverter. To utilize grid tie, must use 240 volt inverters etc, plus transfer switches, permits, electrician installed meters, etc. For the 4 or 5 kwh on a good day, I can get off the coach, not worth it to me. If I lose the grid, and house solar and batteries cannot handle the essentials, can always run an extension cord from the coach.
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Old 02-12-2020, 09:24 AM   #19
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For my "future" system, I think the power prioritization looks like:

Use solar power from the future house solar system when demand doesn't exceed capacity.

If the RV is "docked" with it's solar...add that to the solar capacity (this is where the "miracle relay" might help)

If solar capacity is exhausted, then switch over the overneed to utility (is this "all or nothing" or is solar mixing in on as available basis. Or is grid used and any solar goes to recharging batteries that will switch over when need doesn't exceed inverter?)

If house demand exceeds battery AND utility (power lines are down), then start up the whole house generator, flip the transfer switch, and use that in place of utility.

RV solar charges RV batteries and any overage shifts over to house need. (turn on inverter when batteries are full).

I am thinking I need to learn more about the "transfer relay" and how they work to understand how the above can be pulled off. Do they "mix" the available energy sources, or just flip from one to the other...and if they flip, do the downstream devices see a blip of energy unavailable (PCs reboot if not on a UPS, clocks reset)? If the relay "flips", then if on solar and the air conditioning compressor kicks in...does the relay flip immediately over to utility for the surge needed? Or does one wire the house so air conditioning never is run off of the inverter?

Any comments to the above? It will help my understanding.
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