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[avanti]

What is incredible? That I actually reported some use and observation and not opinion?

Since you asked:
What is incredible is that you accuse me of being an "armchair expert" in response to a post on a system that I personally researched, installed, instrumented, observed and tweaked. Can you say the same? Or are your repeated rants simply mouthing what you were told by an upfitter, whom you believe to be infallible? When the party line of that upfitter changes, your story conveniently changes to match. When the persistence of the Internet makes these changes evident, you fall back to you other favorite epithet "Internet jockey", trying to imply that skill in uncovering your inconsistencies is somehow bad. Throughout it all, you spout tiresome statistics about how many miles you drive, while unsubtly accuse others (and me in particular) of not doing the same when, in fact, you have absolutely no data on that topic, since I rarely choose to share it.

I posted what I did to correct a piece of poor advice. You responded with an ad hominem attack, along with pointless and banal observations ("Balmar temp sensors can and do fail"), more unsupported and incorrect claims ("That Nations alternator was not designed for continuous high output use") and outright trolling ("See my amusement? I use my B").

You asked me to stop referencing you on this list and I have done so. But I will correct your factually incorrect claims. It would be constructive if you would extend the same courtesy and stop attacking individuals. I have referred to you in this post only because you attacked me personally and because you solicited a reply.

Finally, you can skip your "glad you got that off your chest--go lick your wounds" snideness. We have all heard it before.

 

[avanti]

Then add the statement - "Thus the thought of shore power hooking up is just a nuisance." Is all this worth avoiding a plug to the van, and another to the power post at the Campsite? (I know there's more to it, but I'm keeping it basic.)

There are really three levels of aspiration wrt power in a B-van (1) be resigned to always using a hookup; (2) support limited dry camping/boondocking; and (3) try to "have it all" and support all van systems independent of shore power. The costs grow exponentially as you progress along that path.

#1 is trivial. You don't really need much of anything other than some wiring and outlets to accomplish it. You could even totally eliminate a coach battery, although few setups go that far. The cost is negligible.

#2 is where coach batteries, chargers, solar and small inverters come into play. Traditionally, rigs came with a single small battery and a so-called "converter/charger" that produced 12VDC from 120VAC shore power and also charged the coach battery when plugged in. This is enough to keep your furnace running all night, power your water pump, plus a few lights, and maybe limited TV viewing. Cost of materials is a few hundred dollars--more if you want some solar to extend battery life. A small, inexpensive inverter will let you charge your laptop and phones. No microwave or A/C without hookups, though. If you want that, you typically get a gas or diesel genset--several thousand dollars installed.

#3 is where the big bucks come in. Running your microwave from coach batteries requires a large, expensive inverter and more battery. Running an A/C for any useful interval requires MUCH more battery. But, if you have huge batteries, you need a way to charge them. The options are (a) shore power; (b) a genset; (c) your van's alternator; and/or (d) a second engine alternator. Of these, the second engine alternator is the most capable, and is very convenient if you drive more than you stay put. Putting together a large inverter-based system will start at maybe $4-5K and go up from there. A second engine alternator costs around $2K installed (roughly the same as a conventional genset, but with different advantages and disadvantages).

This is just a quick overview--hope it helps a bit.

 

[markopolo-ClassB]

That's a good general overview.

I'd add #2.5 - utilizing a low cost inverter and having 1 or 2 coach batteries and being able to power a microwave oven, low wattage travel hair dryer, low wattage toaster, low wattage coffee maker etc.

I think more than a few of us got to that stage or a bit better and never saw a great need to improve much on that for camping.

With one battery you'd have to run the engine for microwave oven use for example. Wilton was the first person I recall explaining to folks how to do this: http://www.classbforum.com/forums/f8/wiltons-1000-watt-xantrex-inverter-for-a-roadtrek-67.html - that was over a decade ago. :thumbup:

He chose to use the engine battery while running the engine to power a microwave oven through an inverter. He very likely had the first engine generator rig.

The next thing folks seemed to be doing related to this was having two house batteries and low cost inverter to power the microwave oven and running it from your house batteries. That was a bit hit and miss it seemed based on the age and brand of your batteries and the size of the inverter etc. I added a second battery to the RT I had in '05 and a $75 inverter off ebay and it powered the microwave oven no problem. Not everyone was lucky on the first try though using lower cost stuff.

As Avanti points out running the air conditioner off batteries is where the costs really climb. E-treks cost a fair bit of money and they seem to get around 5 hours or so air conditioner run time and they have 8 batteries.

I vaguely recall a discussion on this board before the e-trek came out about running the A/C overnight on batteries. I think 10 batteries was suggested and best of luck getting those batteries recharged for use the following night.

That's all changed now - tons of discussion on larger alternators, dual alternators, lithium batteries etc. It all depends on what it is worth to you.

 

[Keyne]

So regarding 2.5... If you have an engine alternator, 2k inverter, and 2 AGM house batteries (eg typical none etrek RT setup I see for sale often); assuming you would need to run the engine generator to run the AC. Then with volt start it would cycle on and off periodically to keep the AC running? Would the engine be running basically full time because you don't have enough battery capacity to run AC without? Meaning you need to go to step 3 which is more etrek cost territory?

 

[booster]

So regarding 2.5... If you have an engine alternator, 2k inverter, and 2 AGM house batteries (eg typical none etrek RT setup I see for sale often); assuming you would need to run the engine generator to run the AC. Then with volt start it would cycle on and off periodically to keep the AC running? Would the engine be running basically full time because you don't have enough battery capacity to run AC without? Meaning you need to go to step 3 which is more etrek cost territory?

A poster on the Yahoo board with a Zion says that the engine has to run about 1/2 the time to keep the AC running with one 200ah module. Still an awful lot of run time.

 

[Keyne]

Agreed, that's a lot of time. I think a regular genny makes sense for our needs until/if our needs or experience changes to go for a more advanced setup. For us as a first RV a more standard generator probably makes most sense and provides more purchase alternatives vs an engine generator. That being said I wonder how often we would use AC without a hookup... For me it's not an issue but my wife would like it more which would lead to more use which leads to greater rationalization of a more expensive setup

 

[Davydd]

If you know your air conditioner draw which could be a variable depending on air temperature and desired cooling, your battery bank capacity and how much an under hood generator (alternator) can put out you should be able to calculate performance. I find it interesting that when people do calculations they seem to ignore there are other battery draws such as general use, lights, inverter, refrigerator, parasitic, etc. That also has to be in the equation. I assume 10 amps per hour for all that though it varies and is probably closer to 7 or 8. However, a compressor refrigerator is going to run the majority of the time in any temperatures that require air conditioning.

 

[Keyne]

Yes that is true for sure regarding performance but without owning one it has t been easy to get specs for all appliances (15 for AC I would assume?).

However it still could be a good option for an engine genny... Thinking more about it... If I know it's going to be a hot weekend (our use not full time) we would just choose a campground with electric hook up. Most likely boondocking here in New England wouldn't be something we would do (at least at first) that often, so the only other use of inverter would be charging devices and the occasional microwave (we would use the stove more). The fridge would be a consideration but of course 3 way vs electric is another topic all together. As recommended we need to map out our typical usage and plan accordingly; all the options sound interesting but only after thinking about how "we" would use it can we really decide... And we haven't thought that far yet. It's been fun learning about all this stuff.

By the way, our first RV rental (2007 Gulfstream Sprinter class is this weekend. Should be fun! Hiking and fly fishing is in the plan.

 

[markopolo-ClassB]

Much of the following has already be covered in the previous excellent replies but I'll post it anyway.

In between #2 & #3 there would be several variations that permit some running of the air conditioner. A dedicated generator like an Onan is limited only by fuel for runtime. If running the a/c off grid is the goal and you don't want a generator then bite the bullet and go for #3 type rigs.

I see those as 8 or so lead acid batteries rigs or 400 ah or greater lithium battery rigs. With those, the van engine won't have to run as much.

The AGM battery Roadtrek Zion without the Onan generator is a rig similar to what Keyne described. It has an auxiliary alternator though. It could run the a/c on batteries alone I suspect but it would be very short duration. You'd have to idle the van a lot if you spent a week where it was hot. I doubt many would choose to do that. It would be much more convenient to find a campground and plug in IMO (and as previously mentioned). A 200ah lithium powered Zion again would have limited a/c runtime on battery alone (see Booster's comment above). The van engine would have to run often if you spent a week where it was hot. You'd have to be cognizant of your remaining fuel so as to not run out of gas also. There's nothing to prevent that as far as I know.

A single alternator rig could power an A/C; mine can (very small A/C, OEM alternator), Booster's could (larger A/C, aftermarket alternator). I don't think anyone promotes it as an ideal thing to do though. Short duration stationary operation of an OEM alternator is one thing (like a microwave oven). Long duration (like running an air conditioner) stationary operation of an OEM alternator is not the same as they're not intended to run full out for long periods as far as I know.

 

[Davydd]

I kind of look at it like sailing or power boating.

With a power boat, if you have fuel, you just aim and go with little management. In a B with a large battery bank, inverter and dual alternator, once you know your usage in given situations you just go with little need of management. You just have to maintain fuel in the tank.

With sailing you are constantly tacking and trimming sails to get somewhere. In a B that means turning on your engine or your Onan generator to activate something, turning an inverter on and off, switching fuel sources for a refrigerator, controlling electrical use by limiting use (turn off lights, TV, heater, etc. to get through a period of time.) In effect you are in constant planning and management. Sailing is a learned experience as is Class B energy management. You can go a week in the woods with a single house battery if you know how.

With either method, the limit is fuel, food and tanks as to how long you can last in a mode.

Personally, I decided, given a choice of which way to go, that sailing is a want, desire, challenge and satisfying achievement. Energy management in a B is a need, not a want. Energy management affects your decisions as to where you go next (i.e. tacking here and there.) The only plus is the satisfaction of achievement but at some worrisome, compromising, sacrificing cost.

Unlike sailing, a B is an internal combustion engine. There is no aesthetic achievement and satisfaction in that regard for me. Power boating gets you straight across the lake to do what you want to do.

 

[booster]

I would expand a little on davydd's and Marko's comments about AC running capabilities.

Davydd's is correct that you need to do a calculation about how much power you are going to use a day before deciding what system to get. The hard part is figuring that out when you don't have the van already. Davydd's non AC power consumption is really high compared to many of the rest of us at 6-10 amps, which would translate to as much as 200ah per day, and was substantially higher than his original calculations allowed for. Less fancy systems get easier to get closer, but it still is highly variable. We have not found our compressor frig to run even 50% in the high heat, which surprised us. In Zion last fall at 98* and the frig side of van facing south (our venting is outside, not inside), we still were using around 50ah per day for everything, including 3 fans running all day and DVDs at night, which is pretty typical for us. The frig probably took about 30ah of that so it was only 50% or less of the time, which is also what we thought we were seeing. Bigger frigs use more power, and some brands seem better on power use, and some not as good. If you can get along with the shortcomings of a 3 way frig, your power use drops a whole bunch, if you don't have other big use items.

Anyway you slice it, if the AC uses 100amps, and you can get about 200amps continuous out of the alternator (we are a bit under that with our non standalone version) the engine is going to have to run 1/2 the time. A big battery bank could give you more time between runs, but can't change the ratio. The only exception I can think of that could alter the equation, would be if you were at the van, not having it do it's own thing with Voltstart while you were gone, you could do a little manual trick to change the ratio to hours of AC runtime on batteries for every hour of idling. All you would need to do is shut off the coach AC while the engine is running so the entire 200 amps in the example go to the batteries and they get charged twice a quickly. Turn on the cab AC in the van to keep it cool inside (the cab air is likely at least twice as big as the coach AC). The only issue that might happen would be related to the extra load at idle of both the cab AC and big alternator at full output running at the same time.

Personally, I just don't see the running of AC off batteries as practical unless the runs are short enough, or the batteries and alternator big enough, to be covered by whatever driving you do. Short runs while hiking or at a restaurant or attraction type things. Having the van go on and off all day is just not what we want at our campsite, and I am sure the neighbors wouldn't either, whether allowed or not. I am afraid the whole discussion (not just here, but with the manufacturers also as they try to sell vans) of AC on batteries has been drifting back towards long period off grid AC without a standalone generator, which is kind of where the etrek stuff started, and it didn't appear to be very practical then, and still doesn't, IMO.

 

[Davydd]

I didn't even mention air conditioning in all my analysis but I have to agree with Booster. It is way oversold as a feature. A short restaurant stop, maybe with a pet on board. The other desire would be in a hot humid climate to simply dry out the inside of a B. That can be done in a couple of hours. Running continuously? Forget it. Maybe that Advanced RV Solar Womp with 800ah battery bank, 1,250 watts unimpeded from shade solar, split air conditioning systems and super insulated (as much as possible) windowless van can achieve that at Burning Man in the dry Nevada desert, but that is an extreme design.

If you need air conditioning seek and plug into shore power like normal people. There are plenty of campgrounds available both public and private. Running an engine in a stationary condition be it Onan or chassis to provide power is ridiculous especially in those serene, quiet, nobody around, beautiful off-grid places.

If you can stand to be outdoors and desire to you can design a B that can stabilize the inside temperature to match the outside. I know ours can. If you need to be cooped up inside with air conditioning then what difference does it make where you stop? Then seek shore power.