Solar questions for small RV roof
The last stage of my project is getting near, I have doubled my battery capacity and wired in my inverter the next step is solar. The problem I'm facing is the small roof of my 25' fifth wheel. Bet...
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charging batteries in the same for solar and converter in the amount of time it takes. If your added solar panel could keep up with the discharge rate of your batteries for the day/night battery run it would be great but we both know that ain't going to happen with three or four panels installed on the roof.
To charge a battery up to its 90% charge state in a three hour time period it still takes 14.4VDC at 17-20AMPS of DC CURRENT per battery. You would need a pretty large solar system to accomplish this as a typical 120WATT SOLAR PANEL will only produce 5-6AMPS when in full high sun... The fact that the solar panels will produce high current for around 5-6 hours in the high sun solar day you will be able to get to high percent of charge before the high sun goes away.
I am also in the thinking state of what to go with on my even smaller size roof on my OFF-ROAD POPUP trailer.
I have been looking at what MELLO MIKEs has done with his truck camper solar setup and will use this as a good guide. I plan on putting two 120WATT Panels on either side of the Fantastic vent fan on the tongue end and then hopefully a 240 WATT panel across the roof between the Air Conditioner and rear end of the trailer... This should give me a good 20 AMPS of DC current to charge my four batteries with. I am planning on replacing my current battery 255AH capacity bank with two groups of 300AH capacity batteries with one group on the trailer tongue area and the other group in the back of my truck bed. I have two reason for battery banks being my Emergency radio operations from my truck alone at time as well as camping. I will be able to combine both battery banks when camping to give me a good 550-600AMPS of battery capacity. I will not have enough solar power to get to the 90% charge state in three hours but should do alot of charging in the average 6 hours of full sun each day.
My back-up plan will be my 2KW Generator which I may have to run for an hour or so each day to get past the high current part of the charge cycle then allow the remaining time of the high sun day to get the batteries back up close to full charge.
You will need to have the generator anyway and you can't rely on having full high sun everyday. Might be raining or cloudy so the generator is must have item for me.
I have been camping off the power grid now for over five years using around 255AHs of battery capacity so I am already in the know of what I can run appliance wise using an Inverter for the 120VAC items and 12VDC items direct connected to the battery system. I run until 8AM each morning and still have at least 12.9VDC showing on my batteries. This allows me to use the generator to power up my trailer so that the on-board smart mode converter/charger will re-charge me back to the 90% charge state in a three hour generator run time when allowed to the run the generator so I can do this all over again for the next day/night run off the batteries. Its all second nature for us now...
The bottom line is to never allow your battery bank to get below the 12.0VDC level (Approximately 50% charge state) without re-charging back up to at least 90% charge state each day.
My POPUP roof requires to be raised for setup and the added weight of the panels may force me to mount them after the roof is raised. I am planning on going with the lightweight aluminum uni strut mounting frame work. This also allows me to use the edge of the trailer roof to bolt to. This also will allow me to keep two of the panels on the ground and position for best results if the need arises...
These are some of the things I will be thinking about doing for my solar install.
Just passing all of this along to show my idea of planning and some of it may be useful for your thinking. Its all in the planning...
This will be a first for me SOLAR PANEL wise as well...
Roy Ken
To charge a battery up to its 90% charge state in a three hour time period it still takes 14.4VDC at 17-20AMPS of DC CURRENT per battery. You would need a pretty large solar system to accomplish this as a typical 120WATT SOLAR PANEL will only produce 5-6AMPS when in full high sun... The fact that the solar panels will produce high current for around 5-6 hours in the high sun solar day you will be able to get to high percent of charge before the high sun goes away.
I am also in the thinking state of what to go with on my even smaller size roof on my OFF-ROAD POPUP trailer.
I have been looking at what MELLO MIKEs has done with his truck camper solar setup and will use this as a good guide. I plan on putting two 120WATT Panels on either side of the Fantastic vent fan on the tongue end and then hopefully a 240 WATT panel across the roof between the Air Conditioner and rear end of the trailer... This should give me a good 20 AMPS of DC current to charge my four batteries with. I am planning on replacing my current battery 255AH capacity bank with two groups of 300AH capacity batteries with one group on the trailer tongue area and the other group in the back of my truck bed. I have two reason for battery banks being my Emergency radio operations from my truck alone at time as well as camping. I will be able to combine both battery banks when camping to give me a good 550-600AMPS of battery capacity. I will not have enough solar power to get to the 90% charge state in three hours but should do alot of charging in the average 6 hours of full sun each day.
My back-up plan will be my 2KW Generator which I may have to run for an hour or so each day to get past the high current part of the charge cycle then allow the remaining time of the high sun day to get the batteries back up close to full charge.
You will need to have the generator anyway and you can't rely on having full high sun everyday. Might be raining or cloudy so the generator is must have item for me.
I have been camping off the power grid now for over five years using around 255AHs of battery capacity so I am already in the know of what I can run appliance wise using an Inverter for the 120VAC items and 12VDC items direct connected to the battery system. I run until 8AM each morning and still have at least 12.9VDC showing on my batteries. This allows me to use the generator to power up my trailer so that the on-board smart mode converter/charger will re-charge me back to the 90% charge state in a three hour generator run time when allowed to the run the generator so I can do this all over again for the next day/night run off the batteries. Its all second nature for us now...
The bottom line is to never allow your battery bank to get below the 12.0VDC level (Approximately 50% charge state) without re-charging back up to at least 90% charge state each day.
My POPUP roof requires to be raised for setup and the added weight of the panels may force me to mount them after the roof is raised. I am planning on going with the lightweight aluminum uni strut mounting frame work. This also allows me to use the edge of the trailer roof to bolt to. This also will allow me to keep two of the panels on the ground and position for best results if the need arises...
These are some of the things I will be thinking about doing for my solar install.
Just passing all of this along to show my idea of planning and some of it may be useful for your thinking. Its all in the planning...
This will be a first for me SOLAR PANEL wise as well...
Roy Ken
