Bunch of Questions from Super Newbie

[TSher]

Hey Everybody! Hope you y'all are doing well! I'm struggling on a few things here and would appreciate any help as a newbie and math challenged individual.

1. SOLAR PANELS: If I have 3 x 375watt panels that have a 48v voc and 9.96amp output, it looks like I may not need all three panels for my 2200 watt hours per day 188ah requirements? With my calculations I would need 675watts of solar panels. Do you think I should mount all 3 of the 375 watt panels? The panels are big and mounting 2 on the RV roof is doable but the third would have to be mounted on a rack. My battery bank is 4 x 6v GC Trojan t105s at 450ah wiring for 12v.
2. MOUNTING: Being in Southern California do I need to mount them so they can be tilted to max the exposure?
3. WIRING SERIES OR PARALLEL OR? Which way to wire the panels series or parallel or series/parallel? Is it correct, series will increase the volts exponentially, which will increase the size required for the MPPT?
4. SHADE ISSUES? Should I consider shade for series vs parallel? Not sure how often one of the panels would be shaded. But I imagine if parking somewhere hot we would look for shade. I understand in series that the panel in the shade negatively effects all the panels output. Also wiring needs to be increased for parallel.
5. INVERTER; What size inverter? Does this go by the device that pulls the most watts on startup and then the top load of all the items being turned on at once?
6. CONTROLLER? I suppose the MPPT controller the way to go? If so what size? It depends on the panels being wired series or parallel?
7. Wiring fuses circuit breakers (haven't really researched this much yet) Any suggestions?
8. Any brand suggestions for the above?

We might spend up to 3 months out at one time in the RV. Unfortunately not retired yet.
Appreciate all the support comments and suggestions and help getting through this project! Still so much to learn and so little time. Thank you all!

 

[Hedges]

In Winter, 1000W total of panels may be ideal for 2kWh

Flat mounting won't self clean as well. Tilt to your latitude is typical. Tilt toward summer or winter if you need more power in a particular season.

MPPT is needed for that panel voltage and 12V battery.

I like series connection, good for having shade only cause one diode-bypassed section to be lost.
But for a battery system, putting panels in parallel and tilting the for for morning and for afternoon sun spreads production over the day, less cycling of battery.

5 kWh of batteries, 1 kW PV, charge rate is OK.

Consider also 24V setup, depending on inverter wattage.

Inverter needs to put out all power used at once. To start something like an A/C, it needs to surge (for seconds not milliseconds) 5x the label rating.

Wires and fuses ... after you pick the inverter.

Brands? How many $$ do you have? Prices range from $200 to $5000.
Some inverters include PV charge controller. Some work with a shore-power plug or a generator.

 

[snoobler]

1. output depends on available solar, panel orientation and tilt. Check yours in link #5 in my signature. 1125W of panels should produce more than 2200Wh of energy per day except in extreme conditions (Alaska). Flat panels can perform VERY poorly in winter conditions. Fit as much as you can. You are more likely to use more power than you have, especially if you encounter clouds/rain.
2. Generally, no, but it can be helpful. If you truly have a large surplus, it matters much less.
3. Parallel primarily to avoid shading issues. RV roof protrusions can shade panels, and it will impact all panels in series. You can always select a smaller charge controller to limit your total production but collect your peak power for more of the day. This is called over-paneling.
4. See #3. Most panels and PV wire are 10awg, and it can handle 30-40A, so no worries there.
5. Yes to both. Your decision.
6. Yes. MPPT is mandatory for high voltage panels to charge 12V. 1125W/14.4V = 78A, so you'll need an 80A controller to capture all of your potential solar. This will only be an issue in late June when the sun is nearly directly overhead. Will has links on his website.
7. Yes. Check out Will's Blueprints.

Have you truly conducted an energy audit to determine your needs? Link #1 in my signature.

Something else to consider - when you WANT shade for comfort - a deployable array with similar voltage characteristics to your roof panels. Since you have 48Voc, they are likely 24V panels. You could have 2 or 4 100W/12V panels in 2S or 2S2P configuration. You could deploy those out in the sun and wire them in parallel with your current panels to still get 200-400W of production while enjoying the shade. 100W panels can be transported pretty easily. It might be worth getting flexible panels for ease of transport and deployment. You can find a few examples of folks making cheap light and adjustable frames with 1/2" SCH 40 PVC pipes and zip ties. If you go flexible, make sure they're the ETFE type with a 5 year manufacturing warranty and 20+ year production warranty. The non-ETFE type don't last long at all.

 

[chrisski]

1. SOLAR PANELS: If I have 3 x 375watt panels that have a 48v voc and 9.96amp output, it looks like I may not need all three panels for my 2200 watt hours per day 188ah requirements? With my calculations I would need 675watts of solar panels. Do you think I should mount all 3 of the 375 watt panels? The panels are big and mounting 2 on the RV roof is doable but the third would have to be mounted on a rack. My battery bank is 4 x 6v GC Trojan t105s at 450ah wiring for 12v.

I like the idea of putting two on the roof on one MPPT, and for the third panel, put it on a separate MPPT as a portable panel.

1. MOUNTING: Being in Southern California do I need to mount them so they can be tilted to max the exposure?

I got 30% more production the day I tilted my RV panels on my roof, but going up and down the roof is not worth it. My portable ground panels are 2/3 the wattage of the roof panel, but output more because I move them to orient it the sun three times a day.

1. WIRING SERIES OR PARALLEL OR? Which way to wire the panels series or parallel or series/parallel? Is it correct, series will increase the volts exponentially, which will increase the size required for the MPPT?

Once you start looking at charge controllers, just look at the panel specs and figure out the coldest you’re operating and then in your panel spec sheet you can figure out how high the voltage would be. Two panels in series could exceed voltage output of a 100 volt controller and a cold day, so if that were the case paralllel woud be better.

1. INVERTER; What size inverter? Does this go by the device that pulls the most watts on startup and then the top load of all the items being turned on at once?

I like 1000 watts for 12 volt systems and 24 volts for 2000 watt systems. I have a 2000 watt inverter for my 12 volt system, but I will not be running 2000 watts constly, will never be above 1500 watts for 2 or 3 minutes, and I have it fused to go blow above 1500 watts.

1. CONTROLLER? I suppose the MPPT controller the way to go? If so what size? It depends on the panels being wired series or parallel?

I like the idea of 2 MPPT controllers to use 2 on the roof and one on the ground. I would not be surprised if you orient the ground panel, that it exceeds the output of your roof panel, but need a charge controller for this. I like Victron MPPT, but that is all I know.

1. Wiring fuses circuit breakers (haven't really researched this much yet) Any suggestions?

Really need to spend special attention to inverter and battery wiring. I am pretty conservative because I broke the 12 volt 1000watt rule and am using 4/0 wire, which is as thick as someone’s thumb. Solar Circuit breakers are different than Home Depot House Breakers, and have a higher DC voltage than most non-PV breakers, so be sure to get the correct one. Look at combiner boxes, pre-built for your parallel panels and circuit breakers.

1. Any brand suggestions for the above?

I suggest Midnite solar for Circuit Breakers and Combiner boxes.

===================

With parking in the shade and deploying an array, I have two cables for my portable panels one 10’ and one 40’. Voltage loss is for low voltage DC, and shorter cables have less. I did a bunch of calculations for these cables, but I’m not really seeing the loss on the longer cable than I expected. I think a portable array is better for an RV, but a couple issues is the amount of space it takes up, and also worrying about the panels “disappearing” when you’re not around. I finished building some locks for my potable panels today.

 

[TSher]

In Winter, 1000W total of panels may be ideal for 2kWh

Flat mounting won't self clean as well. Tilt to your latitude is typical. Tilt toward summer or winter if you need more power in a particular season.

MPPT is needed for that panel voltage and 12V battery.

I like series connection, good for having shade only cause one diode-bypassed section to be lost.
But for a battery system, putting panels in parallel and tilting the for for morning and for afternoon sun spreads production over the day, less cycling of battery.

5 kWh of batteries, 1 kW PV, charge rate is OK.

Consider also 24V setup, depending on inverter wattage.

Inverter needs to put out all power used at once. To start something like an A/C, it needs to surge (for seconds not milliseconds) 5x the label rating.

Wires and fuses ... after you pick the inverter.

Brands? How many $$ do you have? Prices range from $200 to $5000.
Some inverters include PV charge controller. Some work with a shore-power plug or a generator.

Thanks for the reply!
The teams in the world of solar that more panels

In Winter, 1000W total of panels may be ideal for 2kWh

Flat mounting won't self clean as well. Tilt to your latitude is typical. Tilt toward summer or winter if you need more power in a particular season.

MPPT is needed for that panel voltage and 12V battery.

I like series connection, good for having shade only cause one diode-bypassed section to be lost.
But for a battery system, putting panels in parallel and tilting the for for morning and for afternoon sun spreads production over the day, less cycling of battery.

5 kWh of batteries, 1 kW PV, charge rate is OK.

Consider also 24V setup, depending on inverter wattage.

Inverter needs to put out all power used at once. To start something like an A/C, it needs to surge (for seconds not milliseconds) 5x the label rating.

Wires and fuses ... after you pick the inverter.

Brands? How many $$ do you have? Prices range from $200 to $5000.
Some inverters include PV charge controller. Some work with a shore-power plug or a generator.

Thanks for the reply!
More panels seem like the best way to go. also with them being tiltable is probably a big advantage especially since I could still get up on the roof.

How do you calculate the 5kwh on the battery system? That's one of my questions is to try and figure out how much I will be drawing and how much the solar panels will be putting back. I know a 24-hour. We will draw a total of approximately 2200 to 2400 watt hours. I found an online calculator that translated that into 186 amp hours.

If I decided to go 24 volt how would that change everything? Right now I have the 4 golf cart batteries that are 6 volt so I would need to put those all in series to get to the 24 volt.with the alternator from the motor still charge that correctly? Are any devices running off of 12 volt that would need some sort of conversion from 24 volt to 12volt?

I'd like to run the refrigerator from solar at least part-time to get off the propane. The microwave occasionally maybe 20 or 30 minutes a day. So I figure the size of the inverter would be around 3000 Watts. 3000 for the surge and probably about 1000 for maximum constant load guessing.

1. output depends on available solar, panel orientation and tilt. Check yours in link #5 in my signature. 1125W of panels should produce more than 2200Wh of energy per day except in extreme conditions (Alaska). Flat panels can perform VERY poorly in winter conditions. Fit as much as you can. You are more likely to use more power than you have, especially if you encounter clouds/rain.
2. Generally, no, but it can be helpful. If you truly have a large surplus, it matters much less.
3. Parallel primarily to avoid shading issues. RV roof protrusions can shade panels, and it will impact all panels in series. You can always select a smaller charge controller to limit your total production but collect your peak power for more of the day. This is called over-paneling.
4. See #3. Most panels and PV wire are 10awg, and it can handle 30-40A, so no worries there.
5. Yes to both. Your decision.
6. Yes. MPPT is mandatory for high voltage panels to charge 12V. 1125W/14.4V = 78A, so you'll need an 80A controller to capture all of your potential solar. This will only be an issue in late June when the sun is nearly directly overhead. Will has links on his website.
7. Yes. Check out Will's Blueprints.

Have you truly conducted an energy audit to determine your needs? Link #1 in my signature.

Something else to consider - when you WANT shade for comfort - a deployable array with similar voltage characteristics to your roof panels. Since you have 48Voc, they are likely 24V panels. You could have 2 or 4 100W/12V panels in 2S or 2S2P configuration. You could deploy those out in the sun and wire them in parallel with your current panels to still get 200-400W of production while enjoying the shade. 100W panels can be transported pretty easily. It might be worth getting flexible panels for ease of transport and deployment. You can find a few examples of folks making cheap light and adjustable frames with 1/2" SCH 40 PVC pipes and zip ties. If you go flexible, make sure they're the ETFE type with a 5 year manufacturing warranty and 20+ year production warranty. The non-ETFE type don't last long at all.

Super info. Will follow your lead. TY!

 

[TSher]

Thanks for the reply!
The teams in the world of solar that more panels

Thanks for the reply!
More panels seem like the best way to go. also with them being tiltable is probably a big advantage especially since I could still get up on the roof.

How do you calculate the 5kwh on the battery system? That's one of my questions is to try and figure out how much I will be drawing and how much the solar panels will be putting back. I know a 24-hour. We will draw a total of approximately 2200 to 2400 watt hours. I found an online calculator that translated that into 186 amp hours.

If I decided to go 24 volt how would that change everything? Right now I have the 4 golf cart batteries that are 6 volt so I would need to put those all in series to get to the 24 volt.with the alternator from the motor still charge that correctly? Are any devices running off of 12 volt that would need some sort of conversion from 24 volt to 12volt?

I'd like to run the refrigerator from solar at least part-time to get off the propane. The microwave occasionally maybe 20 or 30 minutes a day. So I figure the size of the inverter would be around 3000 Watts. 3000 for the surge and probably about 1000 for maximum constant load guessing.

Super info. Will follow your lead. TY!

Thanks to all who replied here! I have a lot to digest and learn. Will take some time to consider all your valuable input and suggestions. TY again! Great forum!!!

 

[TSher]

Thanks to all who replied here! I have a lot to digest and learn. Will take some time to consider all your valuable input and suggestions. TY again! Great forum!!!

 

[TSher]

1. output depends on available solar, panel orientation and tilt. Check yours in link #5 in my signature. 1125W of panels should produce more than 2200Wh of energy per day except in extreme conditions (Alaska). Flat panels can perform VERY poorly in winter conditions. Fit as much as you can. You are more likely to use more power than you have, especially if you encounter clouds/rain.
2. Generally, no, but it can be helpful. If you truly have a large surplus, it matters much less.
3. Parallel primarily to avoid shading issues. RV roof protrusions can shade panels, and it will impact all panels in series. You can always select a smaller charge controller to limit your total production but collect your peak power for more of the day. This is called over-paneling.
4. See #3. Most panels and PV wire are 10awg, and it can handle 30-40A, so no worries there.
5. Yes to both. Your decision.
6. Yes. MPPT is mandatory for high voltage panels to charge 12V. 1125W/14.4V = 78A, so you'll need an 80A controller to capture all of your potential solar. This will only be an issue in late June when the sun is nearly directly overhead. Will has links on his website.
7. Yes. Check out Will's Blueprints.

Have you truly conducted an energy audit to determine your needs? Link #1 in my signature.

Something else to consider - when you WANT shade for comfort - a deployable array with similar voltage characteristics to your roof panels. Since you have 48Voc, they are likely 24V panels. You could have 2 or 4 100W/12V panels in 2S or 2S2P configuration. You could deploy those out in the sun and wire them in parallel with your current panels to still get 200-400W of production while enjoying the shade. 100W panels can be transported pretty easily. It might be worth getting flexible panels for ease of transport and deployment. You can find a few examples of folks making cheap light and adjustable frames with 1/2" SCH 40 PVC pipes and zip ties. If you go flexible, make sure they're the ETFE type with a 5 year manufacturing warranty and 20+ year production warranty. The non-ETFE type don't last long at all.

Great information! Thanks for the expertise and help!

 

[Hedges]

Thanks for the reply!
The teams in the world of solar that more panels

Thanks for the reply!
More panels seem like the best way to go. also with them being tiltable is probably a big advantage especially since I could still get up on the roof.

How do you calculate the 5kwh on the battery system? That's one of my questions is to try and figure out how much I will be drawing and how much the solar panels will be putting back. I know a 24-hour. We will draw a total of approximately 2200 to 2400 watt hours. I found an online calculator that translated that into 186 amp hours.

If I decided to go 24 volt how would that change everything? Right now I have the 4 golf cart batteries that are 6 volt so I would need to put those all in series to get to the 24 volt.with the alternator from the motor still charge that correctly? Are any devices running off of 12 volt that would need some sort of conversion from 24 volt to 12volt?

I'd like to run the refrigerator from solar at least part-time to get off the propane. The microwave occasionally maybe 20 or 30 minutes a day. So I figure the size of the inverter would be around 3000 Watts. 3000 for the surge and probably about 1000 for maximum constant load guessing.

Super info. Will follow your lead. TY!

"How do you calculate the 5kwh on the battery system?"

"My battery bank is 4 x 6v GC Trojan t105s at 450ah wiring for 12v."

Data sheet says 225 Ah at 20 hour rate:

https://www.trojanbattery.com/pdf/datasheets/T105_Trojan_Data_Sheets.pdf

6V, 225 Ah is 1350 Wh. Wired series/parallel for 12V 450 Ah. Four batteries is 5400 Wh no matter how they're wired.
Best to plan for up to 50% usage most of the time, so try not to use more than 2.7 kWh per night.
Your 2400 Wh should be ideal, considering mostly daytime so much less draw from battery.

Given perhaps 85% efficiency charge controller and inverter, 70% efficiency battery (processing 50% of power), you may need 3400Wh from PV panels, not 2200Wh. Of course, winter loads may be more or less than summer - more lighting, less refrigeration if you don't keep the place as warm. You may or may not get 3400Wh from 1000W of PV panels, depending on location, shading, panel angle. Good to have a backup charging method and monitor on battery.

You could get a DC-DC converter to charge 24V from alternator.

A propane/electric fridge will probably use too much electricity. Only if you have excess PV would that work. Either a DC compressor fridge or AC running off inverter; they are more efficient. I hear home AC refrigerators don't last as long in an RV as one designed for an RV, probably banging or sloshing around.

I suggest running most loads including refrigerator only when the sun shines, coast overnight on ice. Maybe set up a second thermostat to turn back on and run off batteries only if too warm.