Tying to Calculate my Solar Requirement for Small RV

[Murph]

Was wondering if folks could tell me if I am doing this correctly. I have a small Aframe RV Rockwood A122S that I am calculating my DC load to determine how many panels I need. Would like to stay with portable suitcase style for flexibility. I am currently using (2) AGM 100 AMP hour batteries. I calculated my summer vs cold weather needs separately. What would you say my wattage needs for solar would be. I am a little confused since I have seen many small RVs like mine using 100W or 200W total portable panels and they seem to doTT fine. I am just looking to trickle charge my batteries when boon docking. If I can get away with a 200W portable suitcase I will want to upgrade the controller to a MPPT.

Newbie here and thanks for any help.

Summer:

1. Refrigerator run on propane(does have minimal DC requirements)2 AMPS=24 watts x 24 hrs a day=576 watt hours
2. Water Pump 4 AMPS= 48 watts x 1 hrs a day= 48 watt hours
3. Radio 4 AMPS= 48 watts x 3 hours a day max = 144 watt hours
4. Dometic Ceiling Fan 4 AMPS=48 watts x 4 hours a day max = 144 watt hours
5. Interior LED LIghts 1 AMP x 2 = 2 AMPS = 24 watts x 3 hours a day = 72 watt hours
6. Outside Light 1 AMP x 1 = 12 watts x 2 hours a night = 24 watt hours
7. CO2 Detector 1 AMP = 12 watts x 24 hours a day= 288 watt hours
8. USB outlets (2) Cannot find the draw for these???
9. Gas Range - Cant see that there is a DC load here since it is all propane

Total Watt Hours = 1296 per day = 108 AMP Hours

Winter:

1. Furnace 12 AMPS? = 144 Watts x 8 hrs a day = 1152 Watt hours
2. Refrigerator run on propane(does have minimal DC requirements)2 AMPS=24 watts x 24 hrs a day=576 watt hours
3. Water Pump 4 AMPS= 48 watts x 1 hrs a day= 48 watt hours
4. Radio 4 AMPS= 48 watts x 3 hours a day max = 144 watt hours
5. Dometic Ceiling Fan 4 AMPS=48 watts x 4 hours a day max = 144 watt hours
6. Interior LED LIghts 1 AMP x 2 = 2 AMPS = 24 watts x 3 hours a day = 72 watt hours
7. Outside Light 1 AMP x 1 = 12 watts x 2 hours a night = 24 watt hours
8. CO2 Detector 1 AMP = 12 watts x 24 hours a day= 288 watt hours
9. USB outlets (2) Cannot find the draw for these???
10. Gas Range - Cant see that there is a DC load here since it is all propane

Total Watt Hours = 2,448 per day = 204 AMP Hours

 

[sunshine_eggo]

Fridge likely only uses about 1/3 of your estimate. Will actually use less in winter.
CO detector likely won't even register. Consider that you can buy battery powered units that run on a 9V battery for months.

USB typically pull 10W (5V/2A).

Gas range pulls zero.

Everything else looks pretty sane.

That would put summer at 592Wh (49Ah) and winter at 1744Wh (145Ah).

Since you're dealing with relatively low demand items, you could conceivably power the entire RV plugged into a kill-a-watt meter with 15A shore power. This would give you actual usage. Multiply result by 0.85 to eliminate converter inefficiency.

100W panels properly oriented and tilted with all-day exposure can harvest about 500Wh.

 

[jbird526]

You may want to check the amps on the furnace. I have seen them use only about 7 amps, so you may be high on the 12 amp estimate?

@Murph Is the furnace that you mention the 10k Cool Cat heat pump/ac unit?

 

[Murph]

Thank you both. I thought I may have been high on some of these. Some of these came from Forest River Forums and others from the owners manuals.

So I should be safe with a 200 watt panel and maybe even a 100 watt in ideal situations in summer?

I am in WI so not ideal for full sun at times

Thanks

 

[MisterSandals]

So I should be safe with a 200 watt panel and maybe even a 100 watt in ideal situations in summer?

Put as much solar as you reasonably can. You can never have too much.

 

[Murph]

You may want to check the amps on the furnace. I have seen them use only about 7 amps, so you may be high on the 12 amp estimate?

@Murph Is the furnace that you mention the 10k Cool Cat heat pump/ac unit?

@jbird526 I think the cool cat is the AC. The furnace is either the NT-16SEQ or the NT-20SEQ

 

[jbird526]

So I should be safe with a 200 watt panel and maybe even a 100 watt in ideal situations in summer?

You camper for solar is either the best possible or worst possible roof you could have. Since the roof is not flat, in ideal conditions the camper/panel could be angled and pointing south to pick up all the wondrous rays. You could also be facing north and not get any sun at all. If you had one on one side of the peak and another on the other you may pick up an east/west sunrise to sunset and may work.

A flat roof is a compromise but generally always picking up a fair percentage.

A portable array that you build out, perhaps 4 100watt panels would allow you to align most optimally.

 

[jbird526]

The furnace is either the NT-16SEQ or the NT-20SEQ

Based on the following: 2.8 x 8 hours = 22.4 amps or 268.8 watts

• SUBURBAN MODEL # NT-20SEQ (QUIET MODEL)
• Electronic Ignition
• WHITE GRILLE
• HEIGHT 9 1/2"
• WIDTH 9 3/8"
• DEEP 21-27 3/4"
• Does Not Include Outside Vent or Thermostat
• 19,000 BTUH
• Propane Gas Fired
• Direct Discharge
• 12 volt DC Blower
• Amp Draw 2.8

Not sure if the above Electronic Ignition is AC or DC and could surge during that phase, but that draw would be intermittent.

 

[Murph]

You camper for solar is either the best possible or worst possible roof you could have. Since the roof is not flat, in ideal conditions the camper/panel could be angled and pointing south to pick up all the wondrous rays. You could also be facing north and not get any sun at all. If you had one on one side of the peak and another on the other you may pick up an east/west sunrise to sunset and may work.

A flat roof is a compromise but generally always picking up a fair percentage.

A portable array that you build out, perhaps 4 100watt panels would allow you to align most optimally.

I am not looking for a roof mount. Going to purchase a portable suit case so I can position it where I need. It is solar ready with an SA connector in the rear of the camper.

 

[sunshine_eggo]

I am not looking for a roof mount. Going to purchase a portable suit case so I can position it where I need. It is solar ready with an SA connector in the rear of the camper.

IMHO, most solar suitcases are way overpriced. Here's a DIY option:

Cheap Dual Flex Panel Mobile/Tilting Stand

Here’s a super lightweight and cheap adjustable stand design that I use for 100w flex panel pairs. Each unit costs

diysolarforum.com

 

[jbird526]

I am not looking for a roof mount. Going to purchase a portable suit case so I can position it where I need. It is solar ready with an SA connector in the rear of the camper.

Now that I think about it... you could add some panels, hinged at the top and prop them up to be flat when you are in position. Just a thought to add some permanently installed additional power.

 

[Bobert]

I live in northern NY about the same distance north as upper peninsula border. The problem I have here is that I cannot get enough hours of sun in order to properly charge lead acid batteries. If the batteries are in the cold the problem becomes much worse. Think about it in late fall I could have my batteries at %80 by 10:00 in the morning and have an easy 5 hours to get them full by sundown. By thanksgiving the batteries would not reach %80 till noon and I only have a few hours of good sun left. I could almost never get the batteries to full charge. I had a ground mount array of 2100 watts. I seriously doubt you will be able to deploy enough portable solar to keep from ruining your batteries in the winter. I would suggest a generator of some sort for backup.

 

[time2roll]

Portable? For the effort I would go 200 watts. Better to have a little extra than not enough. I have better things to do than monitor the battery.

My small RV idles at about 500 milliamps running the fridge etc. Assuming the lights are LED there will not be much to worry about until the furnace comes on in the cooler months.

 

[Bobert]

Portable? For the effort I would go 200 watts. Better to have a little extra than not enough. I have better things to do than monitor the battery.

My small RV idles at about 500 milliamps running the fridge etc. Assuming the lights are LED there will not be much to worry about until the furnace comes on in the cooler months.

In northern NY the coldest nights are in the teens by thanksgiving sometimes not coming above freezing during the day. That means a standard lp furnace would use over 1000 watts of power and since we only have just over 2 hours of peak sun. I will be lucky to get %25 of the rated output of my panels on a clear day. With 9 hours of day that’s 450 watts of output if you don’t count charging and battery inefficiencies. That puts me short by 550 watts just for the furnace. PConsider that we have many days of heavy overcast at this time of year 200wats just doesn’t cut it. One of the most popular ways to fix this problem is to move to Florida for the winter.

 

[timselectric]

If you travel east, at night. And west, during the day.
You'll have more sunlight to work with. Then, fuel will be the only concern. lol

 

[rmaddy]

That means a standard lp furnace would use over 1000 watts of power

Did you mean to say your propane furnace uses 1000 watt hours / day when it's cold? And that's in addition to a bunch of propane.

I guess that's one advantage of my little trailer. At the end of last year, when I was camped in similar cold weather, the furnace in my 7'x14' trailer used about 200-250Wh/day and a 20lb propane tank lasted about two weeks. The furnace only takes about 25W when the fan is blowing hot air.

 

[time2roll]

I think mine pulls about 8 amps on close to 75% duty cycle as temps get close to 0F. Been down to -10F and was burning 20+# of propane every 24 hours. I would expect to be utility powered in these conditions. my 1200w space heater running continuous too. Solar does about nothing in the shade of the pines with a layer of ice and a couple inches of snow.

 

[Bobert]

Did you mean to say your propane furnace uses 1000 watt hours / day when it's cold? And that's in addition to a bunch of propane.

I guess that's one advantage of my little trailer. At the end of last year, when I was camped in similar cold weather, the furnace in my 7'x14' trailer used about 200-250Wh/day and a 20lb propane tank lasted about two weeks. The furnace only takes about 25W when the fan is blowing hot air.

I have an older 40’ travel trailer with one slide. In the teens the furnace runs continuously at 30 ish it runs about half the time. That calculates to over 1000 watts per day. If the tanks freeze up the furnace will run continuously and put out almost no heat ( freezing the tank can happen when drawing 38,000 btu of lp out of a tank in the low teens) then the power draw is more like 1500 watts

 

[Murph]

I live in northern NY about the same distance north as upper peninsula border. The problem I have here is that I cannot get enough hours of sun in order to properly charge lead acid batteries. If the batteries are in the cold the problem becomes much worse. Think about it in late fall I could have my batteries at %80 by 10:00 in the morning and have an easy 5 hours to get them full by sundown. By thanksgiving the batteries would not reach %80 till noon and I only have a few hours of good sun left. I could almost never get the batteries to full charge. I had a ground mount array of 2100 watts. I seriously doubt you will be able to deploy enough portable solar to keep from ruining your batteries in the winter. I would suggest a generator of some sort for backup.

I do have a 4k watt generator and I was wondering about the sun for these northern states for solar as I am in WI. I am running 2 100 AH AGMs and can usually get 3 days with them only down to around 75% if I remember correctly.

 

[Zil]

As posted above. With a RV of any size, you can never have too much solar panel.
Portable? Get as much as you can store when they are not deployed.
Mounted? As much as you can fit on the roof plus more as portable if needed.