Bigfoot Camper - Major Modifications I'm Considering...

[adamis]

So I've had my Bigfoot for several years now and have been generally pretty happy. In recent communication with another member here, I've thought once again about some major changes I have toyed around in the past. I thought I would spell them out here and see what others think about the idea.

1. I want to change out my AC unit. The current one I have sits 17" high off the roof and stands out like a sore thumb. It's also very noisy. My first thought was to go to a 12v DC unit. More common in the trucker world but starting to be more available due to the Sprinter camper craze. Expensive yes but lower profile and allows for running off batteries.

2. Alternative to changing out rooftop AC unit is eliminating it all together by combining it with the furnace. I do not know if there are ready made solutions out there but I have considered doing my own fabrication project to combine these two units together. The clear benefit is not having a huge AC unit on my roof anymore for trees to snag and I can either add another fan / vent in the opening left behind or just glassing it closed.

3. I currently have 200w of solar and a single 100AH LiFePo4 battery. I can easily add another 200w of solar, maybe even close to 400w if I eliminate the AC on the roof for a totall of 400w to 600w of solar. I have plenty of space to add another 300AH of LiFePo4 batteries. Going this route would allow me to run my AC on batteries which really is the ultimate goal really. Nothing fancy or unusual here.

4. Eliminate the generator and possibly 1 of 2 20lb propane bottles. Right now the generator is almost never used. It is bulky, loud, and heavy. Yes, convenient once in a while but with a much larger battery and solar setup I can't see how it would every be used. If I eliminated the generator I would consider finding a fiberglass shop to close off the outside access panel completely. I could then repurpose that space for better under counter / sink storage with full width drawers or something. Eliminating one of two propane bottles just frees up additional space and more weight savings. A single 20lb bottle should last at least one if not two weeks for just fridge and stove duty.

So those are the thoughts I am kicking around. Some of these paths are well traveled, others not so much. None of this is really necessary to improve our current camping lifestyle, much of it is for kicks and giggles. So with that, I'm putting it out to all you "seasoned" camper gurus for your own thoughts.

[CA_Traveler]

3 tons wrote:
CA traveler said, “5000 BTUs is equivalent to 1465W”…

By what method of calculation??

3 tons

By any actual energy conversion you choose.

As pointed out A/C BTUs are a marketing value and A/C efficiency is a factor reflecting actual AC energy (watts) usage.

There are online posts on actual BTU energy and A/C BTU conversion to watts.

[Grit_dog]

But everyone has dreams I suppose.
While I'm dreaming about hot women, cool cars and 5' of fresh powder in January, some people are dreaming of a camper that looks like a solar farm, volume discounts at Renogy and the ability to use their AC for 25% of the day without buying $5 worth of gas at the Kum n Go!

[Grit_dog]

JimK-NY wrote:

adamis wrote:
I am surprised there are so many skeptics when it comes to running AC off of solar.

This is not a matter of opinion or wishful thinking just do the math.

I for one, am not surprised that he is surprised....different conversation.
And then I really giggle when I think about RVing in N Idaho and NW MT and how the ole AC basically doesn't stop from about 8 am until 9 pm every day. And then it cools off enough to open the windows at night. And how that is less demanding than most anywhere else in the country in the middle of the summer. And how, "if you use it only 2 hours a day and it's not too hot and the sun is perfect and you dont do it more than 2 days in a row and if you buy a little dinky AC that only uses 700W, and and and and....."

AND if you're doing all that you don't really need AC, or if you do, you'll just be sweating your ____ off for 12 hours a day instead of 15!!

[adamis]

JimK-NY wrote:

adamis wrote:
I am surprised there are so many skeptics when it comes to running AC off of solar.

This is not a matter of opinion or wishful thinking just do the math. Pick an A/C unit you think will work. Look at the specs for the wattage. That will probably be in the 700 watt range. That will mean each 100 AH of battery will last you a bit less than 2 hours. You also need to look at the amount of power you can expect from how every many solar panels you think you can fit on your roof. I would recommend using this calculator: http://www.where-rv-now.com/Notes/Solar/index.php
Remember that will be the absolute max you can obtain. I would not count on more than about half that output to compensate for other uses and for occasional clouds and shade. Do the calculations yourself to see if your plans make sense. Again this is not a matter of opinion.

So I'm not sure what you are saying. As stated, people are already doing this. Now, I get that unless you have a very efficient AC or a lot of solar capacity, the battery will be tapped and at some point will run down to where it won't work. Depending on solar and battery capacity, this could happen in an hour or two, or day or two or week or two.

But it isn't a simple matter of saying AC unit requires 700w of power so you need 700w+ of solar. First, AC only draws that much power when compressor is running. With a duty cycle of 30% to 50% that is a significant reduction in power actually being used. There are also two speed units that have an eco mode to pull less power. 700w is peak power running at full blast. Maybe in Las Vegas in July will you be doing that but most of where we camp it's more in the 100 deg range. 99% of my camping have been in the 100 deg or less range.

The question isn't a matter of can it be done, that has been answered by many already doing it. The real question is, how long and what cost to make it effective for the vast majority of the individuals use scenarios. I feel confident that 600w of solar and 400AH of battery will work more than sufficiently for my needs.

[mkirsch]

3 tons wrote:
CA traveler said, “5000 BTUs is equivalent to 1465W”…

By what method of calculation??

3 tons

Per google:

1 BTU is equal to 0.293W.

That's just a straight conversion from one unit to the other, not an air conditioning system. From what I've seen looking around, window units use about 1/10 of their BTU rating in electrical Watts.

[JimK-NY]

adamis wrote:
I am surprised there are so many skeptics when it comes to running AC off of solar.

This is not a matter of opinion or wishful thinking just do the math. Pick an A/C unit you think will work. Look at the specs for the wattage. That will probably be in the 700 watt range. That will mean each 100 AH of battery will last you a bit less than 2 hours. You also need to look at the amount of power you can expect from how every many solar panels you think you can fit on your roof. I would recommend using this calculator: http://www.where-rv-now.com/Notes/Solar/index.php
Remember that will be the absolute max you can obtain. I would not count on more than about half that output to compensate for other uses and for occasional clouds and shade. Do the calculations yourself to see if your plans make sense. Again this is not a matter of opinion.

[JimK-NY]

adamis wrote:
I am surprised there are so many skeptics when it comes to running AC off of solar. There are many people who already done this in some form already. 3 tons I know specifically is doing it and his setup is very impressive.

With the right setup, 400 to 600 watts of solar and 400AH of battery will get the job done. Now, you might run into issues if you are doing it over multiple days, the solar might struggle to keep up over time but that is when you can bring out the Honda generator and run it for a few hours to top the batteries back up.

In regards to a window AC unit, I think they could be a great option if I was to go the route of trying to combine the furnace and AC into one "box" that goes in the current furnace location. I would probably look for a 7500BTU unit and this is definitely a skilled fabrication job but I'm not seeing any technical reasons it couldn't be done.

Wouldn't a combined AC/Furnance that fits under one dinette seat and vents out the side by much more desirable than having a large bulky unit on the roof?

[adamis]

What do you know, someone is already selling a combined AC / Furnace unit designed for basement installation.

https://www.truma.com/int/en/products/truma-air-conditioning/truma-saphir-comfort-rc



This unit is 25"x16"x12". That is well within the the space requirements to replace my current furnace. I am sure this thing isn't cheap but it is definitely going on my list to look into.

[jaycocreek]

JimK-NY wrote:
So your 200 watt panel put out a peak of 118 watts and a total of 850 watt hours, not 850 watts. That would run a very small, 300 watt, A/C for almost 3 hours. It would run a more typical small unit for about 1 hour and a medium size RV A/C for about 45 minutes. To make up for inefficiencies, a bit of cloudiness or shade and the use of panels mounted flat on the roof and some other minimal electrical use, I would think maybe a 1000 watts of panels would be about right. You would also need a minimum of 1000 AH of batteries which is about a dozen car sized batteries.

Hi Jim

That was just one day with a rigid panel not installed laying on a garbage can or the ladder rack..There will be shortly 400 watts of solar installed and 200 watts portable..I am confident it will run that AC unit and doubt I would need the portable panels..

Early in the day but I just checked my Bluetti charging with two 100 watt panel flat on the roof putting out 106 watts,then checked the 200 watt panel charging my two LFP batteries at 121 watts..Thats 227 watts coming in for a AC,early in the day meaning it's right on the 70% cycle of the 330 watts,and the solar will get better...

I have 400 watts of lifepo4 batteries all together plus the 55 or whatever of the bluetti LFP and 600 watts of solar now..I do not see a problem..

Infact maybe tomorrow I will run the AC off of the Bluetti 70(700 wh) with 200 watts of input(max) more like 180-190 and see how long it last..
Just for kicks and giggles..LOL

[adamis]

I am surprised there are so many skeptics when it comes to running AC off of solar. There are many people who already done this in some form already. 3 tons I know specifically is doing it and his setup is very impressive.

With the right setup, 400 to 600 watts of solar and 400AH of battery will get the job done. Now, you might run into issues if you are doing it over multiple days, the solar might struggle to keep up over time but that is when you can bring out the Honda generator and run it for a few hours to top the batteries back up.

In regards to a window AC unit, I think they could be a great option if I was to go the route of trying to combine the furnace and AC into one "box" that goes in the current furnace location. I would probably look for a 7500BTU unit and this is definitely a skilled fabrication job but I'm not seeing any technical reasons it couldn't be done.

Wouldn't a combined AC/Furnance that fits under one dinette seat and vents out the side by much more desirable than having a large bulky unit on the roof?

[Grit_dog]

JimK-NY wrote:
So your 200 watt panel put out a peak of 118 watts and a total of 850 watt hours, not 850 watts. That would run a very small, 300 watt, A/C for almost 3 hours. It would run a more typical small unit for about 1 hour and a medium size RV A/C for about 45 minutes. To make up for inefficiencies, a bit of cloudiness or shade and the use of panels mounted flat on the roof and some other minimal electrical use, I would think maybe a 1000 watts of panels would be about right. You would also need a minimum of 1000 AH of batteries which is about a dozen car sized batteries.

Just let him run with the story. With the better part of 2 grand sunk into 2 different glorified jump starter packs (Jackery and Bluetti), it's a fair assumption that understanding is lacking.

PS....this is like the inane EV threads (and the other 7 page solar/AC thread which only has about 50% containment and will likely continue to burn and spread in coming days, LOL) where people read too much marketing, then begin dreaming, then hoping, then defending their positions, as incorrect as they may be.

[JimK-NY]

So your 200 watt panel put out a peak of 118 watts and a total of 850 watt hours, not 850 watts. That would run a very small, 300 watt, A/C for almost 3 hours. It would run a more typical small unit for about 1 hour and a medium size RV A/C for about 45 minutes. To make up for inefficiencies, a bit of cloudiness or shade and the use of panels mounted flat on the roof and some other minimal electrical use, I would think maybe a 1000 watts of panels would be about right. You would also need a minimum of 1000 AH of batteries which is about a dozen car sized batteries.

[3_tons]

CA traveler said, “5000 BTUs is equivalent to 1465W”…

By what method of calculation??

3 tons

[jaycocreek]

JimK-NY wrote:

jaycocreek wrote:

Yesterday my 200 watt solar panel I have hanging on the ladder rack waiting for installation parts put out 850 watts

This makes no sense. A 200 watt solar panel is rated to produce 200 watts at the maximum; i.e., full sun and directly overhead. Efficiency also drops off at higher temperatures such as on the roof of an RV. Of course roof mounted panels are going to be at a severe angle away from the sun for most of the day, depending on the length of daylight and latitude.

Yesterday was 100% off the new 200 watt panel that is not installed on the roof yet,the others are different days and conditions with 2 100 watt panels..

[CA_Traveler]

mkirsch wrote:

CA Traveler wrote:

jaycocreek wrote:
My 5k window AC draws 330 watts with the compressor on and 59 watts with the fan on high..

5000 BTUs is equivalent to 1465W, so not sure your A/C size that only uses 330W. :h

Those are "marketing" BTUs. Same as your "3HP" household upright vacuum cleaner which runs off a common 15A 120V AC circuit.

Thanks for reminding me that efficiency values are involved in A/C ratings.