As we’re heading down the path of technology (and “much money”) we thought we’d take-up the "over-the-top" side to this discussion.
First, we reflect on our somewhat limited background, that being, our CaRV. The CaRV includes a single, huge 245AH AGM “coach” battery weighing-in at a mere 165 pounds. The battery supplies, principally, our backseat, top access Whynton 12vdc/120vac refrigerator, computers and other toys, and a small pile of LED campsite lights. A 120 volt receptacle in the bumper connects directly to the refrigerator and to a ‘smart charger’. The frig is powered, firstly, from the rear coach battery but automatically switches to 120v when shore power is present. The smart charger automatically assumes a ‘charging role’ (of the coach battery), again, when shore power is present. There is a solenoid operationally connected to the ignition switch which automatically interconnects the vehicle and coach electrical systems when the engine in running. A separate switch allows us to disconnect this automatic ‘tie’ as may be required.
With such a large AGM battery we had originally intended on a large sine wave inverter - - but then reality struck. 245AHs really isn’t that large, particularly if you consider the ‘wisdom’ of not fully draining lead-acid technology - - this wisdom suggests targeting a maximum discharge of 50%. So, at best - - if one doesn’t want to further diminish the longevity of their AGMs - - we’re down to less than 125 AH - - that’s a mere 1500 WattHours. Are we really going to run a microwave, electric or induction stove top with only 1500 WHs? We scrapped the large sine wave inverter for a cheapo Walmart non-sine replacement that functions only to charge small cell, camera, and computer batteries (and, from time to time, it powers our Ubiquiti internet modem/antenna and router - - more on this another time).
We had no solar. But the combination of “drive time charging” and the not infrequent use of shore power proved more than sufficient for our comparatively minimal electrical demands - - mostly that 5 amp refrigerator (which drew power only when the compressor was going . . . average draw was half that) and those notoriously low-power LED lights.
With the “ProMaster Decision” came our desire to completely revamp our thoughts and reliance on electricity. We call the new approach “all electric” which implies having lots of available and alternative electricity and doing-away with LP. We really don’t have anything against LP - - it’s just another system to install and maintain and refill. If it can be avoided as an unexpected advantage of the “electric decision”, why not? There are many good cooktop alternatives to LP - - and we’re going to adopt a combination of straight electrical burners (in connection with an exterior galley/cooking experience - - remember, we’re tent campers just taking our first steps into the world of RVs) and induction cooking. As for heating, we’re not initially planning any, but believe we can accommodate this with our large electrical system and, of course, whenever we’re “on the grid” there’s more than sufficient energy for electric heat. And the refrigerator? There’s a growing trend away from 3-way frigs that can run on LP. The reasons are several including cost, reliability, ease of use (you don’t have to level your RV for an all electric frig) and, for us most importantly, efficiency. LP capable refrigerators are notoriously less efficient.
There is, to our understanding, no inexpensive way of going “all electric”. Anyone on a tight budget should probably hit the Ctrl-Alt-Del keys now. We justified the expense, in part, because we could afford to do so and - - contemplating what we might have spent for a ‘pre-manufactured’ conversion, it seemed that the savings justified a few splurges.
As an aside, we attach the following link to “TheFitRV” website. They have published a not-overly-technical video of their “all electric” system installed in a Winnebago Travato - - of ProMaster lineage.
http://www.thefitrv.com/rv-tips/our-generator-free-rv-lithium-battery-solar-alternator-and-inverter/
An all-electric solution practically assumes Lithium batteries (actually LiFePO4 or, in our case we think there’s a little magnesium in there, thus, LiFeMnPO4). Why? Lead-acid (or its descendents, like AGM) is just too large and heavy for the needed capacity. Our current new lithium batteries have a “sticker capacity” over twice our larger and heavier AGM batteries. But “sticker capacity” does not tell the whole story. As previously mentioned, the “wisdom” of lead-acid is never to discharge below 50%. So while the ‘sticker capacity’ of our AGMs is 245AH, we can really use only 125AH. Lithium, by contrast, can safely and regularly be discharged down to 10-20% - - this means, for the same weight and size, you can have nearly 4 times the effective amp-hour capacity. Yes, there were a variety of “worries” accompanying lithium (small things like fires and explosions), but LiFePO4 lithium chemistry isn’t the same as the exploding kind and, in any event, we’re convinced that the modern charge controllers will keep us safe (and maybe more importantly, keep those expensive batteries safe!).
Our all electric system will incorporate three charging systems: 1) shore power: 2) solar; and 3) a 2nd and large 280 amp alternator (amp or ampere permitted. “Amperage” is a 4-letter word to an EE). This alternator, importantly, can output nearly 150 amperes at idle and, in that statistic, is the real beauty. We used to carry a Honda 1KW generator in our CaRV. This little baby was quiet - - we could often run it, undetected, after campground ‘curfew’. But, we rarely used it and now leave it at home. However, with our new focus on “electricity”, everything changes. And that large alternator is key. We will be able to develop nearly 2 KW of power at engine idle. Why, then, would anyone want a separate clunky generator that is noisy, messy, smelly and takes up valuable space, when they can achieve the same end merely by idling their vehicle? We know of no rules against idling vehicles in campgrounds.
During “longer drive” periods, this is all that’s necessary to keep things “topped-off”. But during those more lazy ‘stay-in-the-same-spot’ for days experiences, or where you’re inviting the entire campground for a large dinner party (and need lots of cooking energy), the idling alternator saves the day.
Indeed, between the often available shore power, the large second alternator and the larger coach battery capacity of lithium - - that may be all that’s necessary. But we decided to add several solar panels. These, alone, won’t supply a full diet of high energy consumption but; when coupled to large coach lithiums, will stretch the need for shore or other supplemental power for days.
We’ve done much research in this area. And while we don’t have the credibility of those who have actual “done-it” experience, we stand prepared to answer (or bluff) any inquiries.
Winston
