I want to do a solar setup on my new TT. One big enough to run the A/C.I'm thinking of getting an inverter big enough to run the A/C, and just running the shore power cable to it when I'm camping. The problem I see with this is that the shore power charges the batteries which would eventually drain them. I need to know how to disconnect/turn off the battery charger when I'm using the inverter. ORIs there a better way of hooking up the A/C to an inverter?

rankhornjp wrote:I want to do a solar setup on my new TT. One big enough to run the A/C.I'm thinking of getting an inverter big enough to run the A/C, and just running the shore power cable to it when I'm camping. The problem I see with this is that the shore power charges the batteries which would eventually drain them. I need to know how to disconnect/turn off the battery charger when I'm using the inverter. ORIs there a better way of hooking up the A/C to an inverter?For most, it is not feasable. Start running the numbers to see why.

I guess you could run the AC with your batteries charged by solar but your asking a lot from your panels and batteries. Like the previous poster has said do the numbers first.As far as keeping your batteries from being charged from the converter/inverter just flip the converter breaker off. Just be sure that the converter is the only thing on that breaker. I had a some outlets on that breaker so I added another circuit breaker for them. I will be adding a relay to automate that procedure soon. So when it senses my inverter being on it will drop that panel breaker.Ron W.

Where we live you probably can only get to use the solar panels for 6-7 hours per day. The solar panels only works for you when in high sun. Out West of course this is longer but not much.The concept for me would be to increase your battery setup to run all the things you want to run and then use the solar panels to recharge the battery banks before the high sun goes away... You can recharge any battery bank from 50% to 90% charge state using smart mode charging in around three hours if you have enough DC current available. This however will require a very high DC CURRENT requirement at the initial re-charge start-up. Just after one hour however this high DC CURRENT requirement tapers down to a very usable solar panel output. Having 5-6 hours a day of solar energy in the high sun period would work great for you getting the batteries to at least their 90% charge state. This will happen a lot quicker depending on the charge state of the battery bank when you start charging.Using this concept then you have all the power needed 24/7 verses only a few hours a day..The ideal situation of course would be to have alot of Battery Bank and just use the solar panels to keep them topped off by not consuming alot of power from the batteries. This of course is hard to do unless you just want to run a couple of lights and a fan maybe...In my case I have very little power consumption during the day time and the 6PM to 11PM time period is where I consume most of my power consumption. Solar Panels during that time period would not be any use for me then.The obvious downside to anything solar is there is going to be days when it rains or is cloudy all day long which will require you have alternate way to keep the batteries re-charged. Being mobile almost dictates you have a usable generator source to keep the batteries charged when solar energy is not available. You only other free choices is wind generators, hydroelectric power, or fuel cells. Only the wind generators and fuel cells would be of any help when being mobile.Get some good advice from the guys on here that are setup to live in the RV's 24/7. There are a few on here that is making it work good for them but it takes a lot of planning and resources to be successful. I don't think You just can't throw up some solar panels and think you are going to solve all the encountered problems. In my case I have been doing this in baby steps. After 5-6 years of camping the off-road trails in my setup I feel I am very conscious now on what to expect when running off the battery banks and how to keep them re-charged without doing damage to them. I am just now starting to think about solar panels to keep me from having to run my 2KW Honda generator three hours each day to make it all work.IMO it is much more than just adding solar panels...Just some planning thoughts here...Roy Ken

rankhornjp wrote:I want to do a solar setup on my new TT. One big enough to run the A/C.Sure, wouldn't we all! :SCrunch the numbers, including the cost, and I have little doubt you'll realize just how impractical this is. :R

A typical 13.5 BTU RV air conditioner will draw 12-15 amps of current when operating (a bit more when starting for the instantaneous lock rotor draw). For the sake of this example lets say the AC draws 14 A on average. 14A at 120V = 140 A at 12V (probably a bit more considering inverter and wiring losses). A 12V typical RV Marine hybrid battery has a capacity of around 100AH at the 20 hr. rate. That is 5A/hr for 20 hr and the battery is completely discharged and wouldn't light a flashlight bulb, much less run an air conditioner. Since we would wish to use the battery on the second and following days, we would discharge it only 50%. That makes available 2.5 A for 20 hrs. Now we can buy some batteries...56 of them to operate the air conditioner for 20 hrs a day. But wait, you're going to have solar power available and that will recharge the batteries while the AC is on. How much will you need? To break even for the 20 hr run of the AC, you'll need to replace 2800 Amp Hours or 33,600 Watts. If you use 230-250W solar modules, you'd need 26 of them at typical insolation and typical controller/wiring losses. You would also need a big solar controller and some serious wiring to handle the 6700 W being harvested from the modules. I hope this example shows the impractibility of solar and typical AC use. There are a few members experimenting with low draw AC units and solar. They are using 5K window units and a minimum of 3 250W modules. The requisite battery bank is needed along with temperate weather to accomplish the task.

Running A/C on solar. | Good Sam Community

westend
Explorer
May 25, 2015
Huntindog wrote:
reed cundiff wrote:
Have done the math and it is practical.

Older son is off-grid
Daughter has 6 to 7 kW and gets $50 and more back each month from El Paso Electric (one of the few power companies that encourages solar) even in heat of summer (Las Cruces, NM)
Brother-in-law has around 4 kW in Albuquerque.
Younger son has no solar since his house is entirely shaded with older trees.

We have been off-grid (land power) and generator for two years except for one instance.

Do the math. It is a real act and not merely a meme. You could put 750 to 1000 W on a small TT.

Reed and Elaine

Do the math again without the federal/state subsidies and mandates.
No electric company willingly pays a customer for their using solar.
And the landscape is changing. As power companies see more solar use, they are fighting their subsidizing it, and they have the support of non solar users in this fight, as they are the ones ultimately paying the tab.
Right, up to a point, i.e. In my State the power utility made an agreement with the State that if they could store their used radioactive waste, in casks, and on site, they would produce their energy with 25% from alternative energy within 25 years. That bill has now become due for the utility. Three years ago, there was no one at the customer service level that could help me about installing PV at my home. Today, a home owner contract is in place, laws are being changed as to utility payments from users, and the utility is trying to bank the carbon credits from users of PV. Any direct rebates for purchasing PV are eroding and this is typical of other States that led the way. AFAIK, the federal tax credits for alternative energy still exist.

More info here:Dsire
JiminDenver
Explorer II
May 25, 2015
you are right, you see the utilities are fighting Solar, well residential solar. you think you're paying for those subsidies, Wait till you see your bill go up when the utilities start putting up their own arrays and adding the equipment cost to your bill. They don't care that residents pay 10s of thousands and won't see a return for decades. They see it no different than building a new power plant and getting you to foot the bill while getting free power to sell you forever.
reed_cundiff
Explorer
May 25, 2015
The math is for off-grid as I noted for two of the four users. El Paso Electric is quite happy for relief from power surges during hot days in west Texas and southern NM.

Of course most electric companies are not happy with anything cutting into their profit. They may gain support from non-solar users through salacious advertising. The Koch Brothers are involved as might be expected. The power companies in Arizona and Oklahoma are working overtime on this.
Huntindog
Explorer
May 25, 2015
reed cundiff wrote:
Have done the math and it is practical.

Older son is off-grid
Daughter has 6 to 7 kW and gets $50 and more back each month from El Paso Electric (one of the few power companies that encourages solar) even in heat of summer (Las Cruces, NM)
Brother-in-law has around 4 kW in Albuquerque.
Younger son has no solar since his house is entirely shaded with older trees.

We have been off-grid (land power) and generator for two years except for one instance.

Do the math. It is a real act and not merely a meme. You could put 750 to 1000 W on a small TT.

Reed and Elaine

Do the math again without the federal/state subsidies and mandates.
No electric company willingly pays a customer for their using solar.
And the landscape is changing. As power companies see more solar use, they are fighting their subsidizing it, and they have the support of non solar users in this fight, as they are the ones ultimately paying the tab.
reed_cundiff
Explorer
May 25, 2015
Careful, the Chihuahua is looking at everyone's cards.
cmcdar
Explorer
May 25, 2015
Reed,

Actually, moving air will cool you as the cooling effect is due to evaporation. Having that MOVING AIR be COOL is a plus.

Also, from experience, having a rousing card game with the table in a kiddie pool so your feet are in the water while playing is both FUN and COOLING.
reed_cundiff
Explorer
May 25, 2015
As noted in earlier post, have over 7 kW-hr of usable electricity with LFP. Total weight of the four batteries (each is 4 x 3.4 V CALB cells) is 254# (116 kg). They are expensive but that is a choice we made to be totally solar autonomous. There is room and weight allowance in front bay for two more 12 V (nominal) batteries (this would be 10.5 kW-hrs usable) but it would be expensive and Elaine does not go for it.

Might go with those 435 W panels if we were to do it over again; however, son buys the 235 W panels in multiple pallet loads so there is a cost differential. We could probably put six of those 435 panels on roof.

From Wikipedia:
"...A ton of refrigeration (commonly abbreviated as TR) is a unit of power used in some countries (especially in North America) to describe the heat-extraction capacity of refrigeration and air conditioning equipment. It is defined as the heat of fusion absorbed by melting 1 short ton (2,000 lb; 0.893 long tons; 0.907 t) of pure ice at 0 °C (32 °F) in 24 hours.[1][2] It is equivalent to the consumption of one ton of ice per day and originated during the transition from stored natural ice to mechanical refrigeration.

A refrigeration ton is approximately equivalent to 12,000 BTU/h or 3.517 kW,\..."

You will need a lot of ice in that ice box air conditioner, but it certainly beats nothing.

Reed and Elaine
2oldman
Explorer II
May 25, 2015
op?
cmcdar
Explorer
May 25, 2015
Add about 65 lbs. per battery as well...
sushidog
Explorer
May 25, 2015
Sun E-20 solar modules are over 20% efficient, meaning they produce a lot of power for a small footprint. Their 435 watt panels are only 81.36 inches long by 41.18 inches wide. 4 panels (1740 watts) could easily be mounted on just about any RV adding only 224lbs to the roof for all this power.

Chip

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