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Old 06-14-2015, 06:51 AM   #15
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UK ... why did you say you run the microwave and water heater on electric at the same time as you are running your generator? What is the significance of that? THANKS
I can answer thatÖ

A couple of reasons spring to mind, first that the microwave doesn't even work from inverter power, so you either need to run the generator or have shore power to use the microwave at all. Also, the best time to run any of your heavy-load appliances is when you're running the generator, so they're not draining the batteries.

Second, your 2.5kw/20amp generator doesn't always put out 2.5kw. Actual power output is dependent upon rpms, so the more you load up the generator, the more efficient it is. Within reason. The sweet spot on the torque and horsepower curves, to get the maximum electricity output per unit of propane input, is somewhere between 50% and 75% of the generator's rated load. Meaning you want to have a load of somewhere between 10amps and 15amps including battery charging.

It doesn't have to be microwave and water heater. You could run your generator in the hottest part of the day to power your air conditioner instead. Or any combination of appliances that gives you a load somewhere between 10amps and 15amps.
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Old 06-14-2015, 08:27 AM   #16
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I thought it had something to do w/ your second paragraph, but wasn't too clear on that. Thanks for your helpful clarification.
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Old 04-19-2016, 08:00 PM   #17
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Looking for some advice. For our '16 GT we have boondocked on numerous occasions. With wise battery management we can get 16 - 20 hours before we need to charge. I've found that the chassis 220 amp alternator is far more effecient at charging the house batteries than the Gen and alot quieter (this was actually suggested by an AS Regional Sales rep). So that is my method versus the genset. I recognize that MB does not recommend long idle times so I try to work in a fast idle on occasion.

I would like to have the capability of at least a couple days without having to charge and accomplishing this plug&play versus the major solar upgrades discussed elsewhere in the Forum. In researching batteries and loads, I've come up with the following scenarios. Does anyone know of any downsides to switching to LiFePO4? I know I may have to modify the battery boxes, but that appears relatively easy. See my scenarios and battery options below.
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Old 04-19-2016, 08:28 PM   #18
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Lewster can probably answer this best as he's mentioned it previously but from what I can recall, you have to protect them from freezing. But they may have mitigated that since then.
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Old 04-19-2016, 08:55 PM   #19
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Thanks, the batteries I'm looking at are good to -20 degrees C
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Old 04-19-2016, 09:08 PM   #20
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I have long wondered about charging house batteries with the engine. The Magnum charger and my Blue Sky Energy MPPT controller both have sophisticated charging strategies designed for Lifeline AGM batteries. On the other hand the Mercedes alternator is designed to charge the lead-acid chassis battery. AGM coach battery charging is an afterthought through the BIM. So... am I better off charging the coach batteries 'the wrong way' through a poorly controlled engine alternator , or not charging them at all? Hobsons' choice I guess.
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Old 04-20-2016, 06:25 AM   #21
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I often charge thru the engine while boondocking, then plugging a charger into the dash for the iPad, phone, etc.

15 minutes or so of the engine running tops everything off.

I wouldn't be too intent on not having to charge during a several day boondocking, instead accepting the limitations of your batteries and just running your engine or generator for awhile at least every other day.

A small thing, in the great scheme.

Just my opinion.


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Old 04-20-2016, 07:13 AM   #22
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FWIW, and for the benefit of other owners including T1N owners, engine charging has not proven to be effective in many cases (it's discussed in more detail in other threads). For reasons that are not clear, our alternator often raises the battery by only 5% per hour. There's no way we can keep up with a boondocking drain by running our engine.

Has anyone ever added solar and then later stated that they regretted spending the time and money? Ever, in the history of the Class B universe? I kick myself because my husband and I didn't do our 300 watt DIY project a year earlier than we did (but we had other projects going on). By investing about an additional 5% of the original purchase price of our (8-year-old used) Interstate, we got 400% more enjoyment out of its vastly increased versatility. And we went high-end on our products because my husband enjoys the novelty of developing cutting-edge applications where possible - solar could be added far more cheaply than our project. Everyone has their viewpoints, but to me, this is a no-brainer.
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Old 04-20-2016, 08:01 AM   #23
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One of the benefits, for me, of having an older Interstate is that I don't have a gauge that gives me percentages of charge on my batteries.

Color me ignorant, but I am glad to not have that.

Between driving between sites, and running the generator or engine when not driving, we have not had a problem keeping up with the limited draw on the battery during low-use boondocking.

Nor does battery wear seem to be excessive.

Just more than one way to skin a cat....depends on what you're doing and how you do it.


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Old 04-20-2016, 08:35 AM   #24
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Everyone has their viewpoints, but to me, this is a no-brainer.
Nope. If it was a no-brainer, Airstream would do it themselves.

It doesn't take a rocket scientist, or even an engineer, to figure out that off-grid camping requires solar panel wattage at least equal to house battery amp-hours to have a reasonable expectation of keeping the batteries charged through solar alone, if you start with the assumptions that: (1) you can only use half the amp-hour rating daily (50% discharge) and (2) will only get about 6 hours of "good" sunlight on an average day on flat solar panels laid horizontally. The rest is simple math.
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Old 04-20-2016, 09:45 AM   #25
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Nope. If it was a no-brainer, Airstream would do it themselves.

....
I don't think I agree for the simple reason that Airstream likely has a dual line of thinking on this issue, but their lines of thinking do not reflect decision trees invoked by boondocking (some of this repeats previous thread content):

(1) They are making a semi-reasonable assumption that a lot of buyers are going to travel from hook-up to hook-up and therefore would have little use for the type of solar that could allow them to remain off-grid for more than a period of hours.

(2) They are probably also gambling on the fact that the balance of buyers, the would-be boondockers, are not going to know the difference at the point of sale. They will see a small solar panel standard installation and assume they're good to go. By previous forum accounts, sometimes those installations do meet the needs of the traveler. But often not (because of parasitic draws or usage patterns or weather patterns or whatever other factors). By the time it dawns on those owners what are the natural limitations of what they bought, it's too late for buyer's remorse and they'll probably just bite the bullet and upgrade it themselves, no skin off Airstream's nose.

My point was, for would-be boondockers, even occasional boondockers, I think it's a no-brainer, especially for owners like my husband and I whose rigs were born without any solar to start with. A bit more cash enables a vast number of additional travel scenarios.
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Old 04-20-2016, 09:52 AM   #26
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(1) They are making a semi-reasonable assumption that a lot of buyers are going to travel from hook-up to hook-up and therefore would have little use for the type of solar that could allow them to remain off-grid for more than a period of hours.
And yet a generator comes as standard equipment. I'd gladly trade the generator for an equal weight of additional house batteries and solar panels.
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Old 04-20-2016, 09:56 AM   #27
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from my own experience, the sub-standard base package of inferior panels, wiring, controller, and installation ... made the solar a negative rather than a positive. I had to upgrade all 3 of those. It would have been better if they had started with nothing. Not sure why (other than making their assembly line simpler) they don't give us some solar upgrade options when we're ordering a van. That alone might cause me to go to Advanced or someone else next time.
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Old 04-20-2016, 10:11 AM   #28
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For reasons that are not clear, our alternator often raises the battery by only 5% per hour.
Have you had your alternator checked? That sounds like a very slow charge rate, especially if you still have one house battery.
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