In 110-degree weather, the air conditioner in our 19-foot Bambi will keep the interior as cool as we want.
Two weeks ago, when we came home from a week at Disneyland with our granddaughters, our home heat pump had broken down; and it was over 100 degrees inside our house. We spent the next day and a half "camping" in our Airstream, waiting for the a/c repair person to arrive. The daytime temperature was about 108 the next day, and my wife made me turn the a/c up because she was freezing. I don't recall the exact temperature inside our Bambi, but I think it was in the low- to mid-70's. I know some complain that their a/c won't keep it comfortable inside their Airstream. However, ours cools fine, perhaps because it is a smaller model and there isn't as much space to cool.
To be honest, we have only run our Bambi's a/c using generator power once; and that was when we first bought our two Hondas. I just wanted to make sure they would power the a/c. Since then, we haven't used the a/c on generator power again. In the summer, we usually visit friends in Tucson over a weekend, but stay in a campground with full hookups. And, when we camp, we head north to higher country; and Flagstaff usually has daytime highs of 80-85 degrees and overnight lows around 55-60. So, no a/c is needed. Plus, with the exception of taking our grandkids on a summer roadtrip to cooler climes, my wife and I do most of our camping between Halloween and tax day, when the weather in the southwest desert is beautiful.
As an aside, I think our batteries charge faster on generator power via the shore power cord (and converter). If I recall correctly, connecting a generator directly to the batteries via the 12-volt connectors on a Honda provides only 10 amps max. I'm not sure how much current the converter provides, but shore power (via the generator) allows us to use the other 110 VAC appliances while charging the batteries.
re: "this is significantly more usable capacity than has been estimated by previous posters" -- this is usually a clue that a bit more investigation is needed.
One of the first issues to consider is that not many trailers carry 540# of batteries.
The rule of thumb is 12 usable watt hours per pound. That'd come to 6480 watt hours of usable energy capacity. this is fairly close to the 5.4kWh spec and to be expected as the energy density of AGM's is a bit less than that of wet cells.
re: "Since these are AGM batteries, they can be safely located inside living areas." -- if you use code as the criterion for safety, this isn't the case. AGM batteries need a properly constructed, vented battery compartment as far as the relevant codes are concerned. This is a special concern if you don't have battery charging and maintaining equipment appropriate for AGM's.
The keys to all of this are:
1) You can adapt your lifestyle to whatever energy resources you have. What works for one may not be something suitable for another. The variance is quite wide.
2) solar is a low density power source which means you can't collect much with an RV and you need to be able to store sufficient energy to handle a couple of days reserve.
3) energy storage by batteries is limited in RV's primarily because of the weight. (the 30# propane tank holds 190 batteries worth of energy and you can drain the tank without causing tank aging)
I think we need to be careful about telling others that what works for us is good for them, too.
re: "If I recall correctly, connecting a generator directly to the batteries via the 12-volt connectors on a Honda provides only 10 amps max"
The fastest way to recharge the batteries is with an intelligent multiple stage battery charger. The genset 12v output is like a lot of converters in that it is quite dumb. It provides maybe 13.6v that is current limited and that is not optimum for battery charging.
One should also take note that a full and complete charge on a lead acid battery takes 12 hours or so. That is why many with solar will use a genset in the morning with a good battery charger to get the batteries up to 90% or so and then let solar finish the absorption stage.
As a word of caution, an RV often has a number of sensitive electrical loads (appliances, control boards, etc) attached. That is why RV converters that have multiple stage charging usually top out at 14.4v. An automotive charger may go quite a bit higher than that and that might not be good for the RV stuff. 14.4v isn't that much longer during the bulk stage and it is a bit easier on the batteries as well.
The charging and maintenance of batteries is also an issue. With most RV solar systems, you can't get enough current for a vigorous charge that helps keep sulfation down. Only recently have I seen any solar charge controllers that also provide a good maintenance mode providing sulfation inhibiting techniques.
While on the subject of safely installing and using AGM batteries - NO battery should be charged without a correctly matched charging system. AGMs have a different profile than even other types of lead-acid batteries, and they should not be mixed with other types or charged like other types. When Lithium batteries become practical for RV use, proper charging will be even more critical.
Speaking of that weight, it is extremely important that batteries be properly mounted and secured, and the terminals protected so that no metal will come in contact with them or short them.
Issues like these are the reason that, despite the fact that I'm an electrical engineer, I chose to have professionals install my system. DIY solar in an RV sounds like a safe bet, but there are a number of safety-related issues that require proper attention.
That said, I believe that the safety and maintenance issues associated with a properly installed solar power system are far less significant than those encountered using, transporting, and maintaining generators and their fuel. I think that both of them require lifestyle compromise (of different sorts) when using them dry camping or boondocking. In our case, the compromises are mainly mitigated by choosing appliances carefully - LED lights, 12V low-power TVs, 12V supplies for entertainment, computers and internet equipment, low-power microwave, efficient electric espresso maker (although we also have a stovetop one). With a large-ish (for an RV) solar power system, we are able to enjoy all of these amenities every day while camping.
If people want to camp where AC is "required" 24 hours per day, there really is no practical option other than shore power. Everything we do in an RV is a compromise, however. If someone is the type who is only happy with all the comforts of home - home is probably where they should be. Both solar and generators are imperfect solutions.
My view is that the tradeoff goes something like this:
Generator Pros: More total power available per day, lower purchase price.
Generator Cons: Setup/teardown/transport required for each use, noise, maintenance, pollution.
Solar Pros: Virtually maintenance free, silent, clean, no setup/teardown/transport hassle.
Solar Cons: Cost, less total power available per day.
This is assuming a properly-sized, professionally designed and installed solar system.
The Lifeline page has those batteries at 90# ea. That is about 1.5x to 2x the weight of the battery usually encountered in Airstreams which also only use 2 batteries as OEM. 80# is still within the nominal error range for battery measures, though.
Rule of thumb is to have at least 1 watt of solar per pound of battery. with a quarter ton of battery, that is hard to do on a typical trailer.
Good point re safety but I have seen one note that there are 2300 battery accidents every year. What got my attention was that a good portion of them (40% I think) were due to handling heavy batteries.
As far as setup and teardown, I have both a trailer and a B-Van with installed gensets that only need a button push to start. The safety is arguably a bit better than with batteries as well except for the amount of stored energy.
For a nice battery bank, see Sean's Odyssey blog. He recently replaced the 8D's in his class A and figures batteries average out to a cost of $1000/year for him.
The lesson for me is that most of the pro or con depends upon how you configure your rig and how you use it.
re: "This is assuming a properly-sized, professionally designed and installed solar system." -- if you read these forums and others, you'll find that even "professionally designed and installed" can leave a lot of gaps. Part of the reason is the inherent limitations of an RV and another part is cost many are willing to pay.
What amazes me is the number of folks with 60 watt solar added to their RV and trying to find happiness ....
That is right in there with folks looking for a magic bullet with 'improvements' that are inside the error margins of the pertinent measurements or that think a usable solar system is not expensive.
Yep, I thought they were 90# also, but when I went to that page I linked it said 82. I figured my age was kicking in.
We have about 400W of solar, and are thinking of adding another 100w at some point, but haven't run into the need. It sounds like we are near your rule of thumb.
On the issue of battery longevity, check out the specs and test results on the difference in battery life vs depth of cycle. That is part of the reason we went with such a large array. We have never discharged ours to less than 59% of capacity despite some long stints with little sun. Normally, we stay above 90%. I'll report back what kind of life we get. So far, zero failures but it's only been 18 months.
For us, the weight isn't a big factor. With full tanks and all our junk, we are still far below all the limits and our tongue weight only increased slightly. AM Solar did a very nice job constructing the battery area an wiring and securing everything.
Following up on your comment on people with 60w solar... I do think those are useful in some cases:
If you store the RV outside, it's a decent way to maintain batteries while in storage (assuming you have a good charge controller.).
If you mainly use your RV in "glorified tent" mode it could certainly extend the time you could run things like lights. You could run a bunch of LEDs pretty much indefinitely. It's when you add things like a heater that you'll be disappointed.
re: "On the issue of battery longevity, check out the specs and test results on the difference in battery life vs depth of cycle." -- This one gets to be an interesting analysis. What I have found is that cycle life just isn't an issue for most RVers.
Consider that the batteries we have commonly available at retail for RV and auto range in lab cycle tests from about 200 to 800 cycles to the 80% of original capacity. Compare that to the number of weekends in a typical 5 year battery life. Also consider that you need a charge cycle of at least 12 hours and an RV needs a reserve of at least two or three days nominal use.
The you can consider the cycle depth versus cycle life curves and find that the 50% instead of 20% SoC doubles or triples the cycle life. When coupled with the nominal RV reserve, the cycle depth is often much less than that that which doubles or triples cycle life again.
Another issue is that most RVers aren't really aware when their battery bank only has 80% of its original capacity - this is like the folks that don't figure out its time to replace the starting battery until if fails with sub zero temperatures.
Then you can get into the factors that influence available battery capacity by 10% or more.
re: "on people with 60w solar... I do think those are useful in some cases" -- me, too. But the comment was somewhat satirical in regards to people looking to solve all their energy needs with dreams.
It's lifestyle balance and it always amazes me what folks find suits them - from the big class A's at 20 tons to those who sleep in the back seat of a sedan. I think it is really a blessing that there are so many choices that we can each choose what best suits us.
If you don't require AC, solar is the quiet and seamless solution once you've cleared the initial cost and installation. How many panels you'll need is a function of your energy appetite. In my opinion, 40w is enough if you are extremely frugal, 200w seams to suit most boondockers, and 500-600w is probably the outer limit of what the most consumptive boondocker might need. The autonomy and peacefulness of solar is liberating ... just add water and you are ready to go. Some say continue to wait for technology and price to evolve ... I say now is a great time to embrace as much solar as your budget allows.