Re: Battery chargers, inverters, engine generators-parameter
Davydd said:
Anxiously awaiting your real life test results that seems only you understand what needs to be reported. Wouldn't it be nice if some E-Trekkers would do the same beyond dwelling on running an AC? We are getting a B built without propane or generator but solar, large inverter and multiple batteries yet to be determined. My gut and experience tells me you'll have success. If I can brew my morning coffee, use the microwave/convection oven and induction cooktop routinely every day and never have to debate or worry whether I need an electrical hookup I'll be a happy camper.
Overkill or not, diesel idle controversy or not I will have the second alternator high idle option. If I use it no more than I have used my propane generator the last 4 years (13.9 hours) I doubt I'll ever have warranty issues many seem to be concerned about.
As we are slowly progressing through finding out how this stuff works, or doesn't work so well, together, it has bee pretty obvious to us that many of the old standards that we all have heard and accepted may not be all that accurate. I wouldn't go to the extremes that Handybob does in criticizing the entire world of rv electrical systems, but I do think there are some major issues.
Most of the issues have been discussed at various places around here and elsewhere, and I think I am getting closer to having some final opinions, which are just opinions, and need to be either get final testing, or be proved or disproved by the industry over time. Just a quick runup of things as we see them with our system and use, and from what others say and do.
* Throw out any and all discussions of running air conditioning on batteries. Even if you can run for "X" number of hours, you pull the batteries down so far that recovery is a very long process. If you need air conditioning when shore power is not available, you need a generator. If you are OK having that be an engine generator, you obviously need to run the van engine, so at that point you may as well use the van engine air conditioner and skip the coach air conditioning except when on shore power. I think Roadtrek really muddied up this whole issue with the initial claims for the e-trek, and way too many folks are still seeing the old claims on the internet, or getting them from less than stellar salesman. There are way too many way overly optimistic ideas of what to expect from the various systems.
* I like the idea of having some sort of a very large engine generator, although I think that the best system for most would turn out to simply be a very large single, or dual normal sized, alternator. Roadtrek appears to have their engine generator on the e-trek running at 24 volts, to a dedicated 24 volt battery bank, which runs the inverter at 24 volts also, I think. While more efficient in transporting high wattages, the 24 volts requires all kinds of other ballancers, etc. Without the continuos high draw of the air condtioning through the inverter, the 24 volts probably is more trouble than it is worth. The one thing in the engine generator area that I have not really seen much of anything about is the use of 12 volt to 12 volt multistep chargers with them. I find it very interesting that folks will carefully be sure they have a multistep converter/charger in their RV, that is putting out maybe 40-60 amps to the batteries, but then will not hesitate to hit the same batteries with a constant, and often poorly regulated voltage, from a big alternator, that could be well over 100 or even 200 amps. My guess is that the 12 volt to 12 volt chargers will become more standard as engine generation takes off. We address this with a manual separator cutoff switch, but that would not be the solution for many folks, I think, and it is not best solution either. I think the engine generators are very useful for recovering big battery banks, if you drive enough. For us, the biggest benefit should be to be able run the microwave or hairdryer without draining the batteries too much. Using the engine generator for the short shots should be able to stay within even the most restrictive MB rules, if there are drives every couple of days. It is the running of air conditioning that really bumps off the MB rules as it is many hours beyond the recommended.
* The, probably overly, discussed topic of the ability of the currently available chargers to get you batteries full. IMO, pretty much all of them have some issues. I think in the future you will see most of the higher end ones with more progammability, with charge completions based on ending amps, not just timers. They will be programmed to your battery style, size, age, etc, and not one size fits all like they are now. Temperature compensation is absolutely essential if you are trying to charge accurately.
* Automatic switching beween charging systems will be needed, I think. A system with a shore charge, solar charger, engine charger could seemlessly only use the one that is the most desierable at the time. From what we have seen so far, it would be very difficult to have the individual chargers not interfere with each other, unless shut off when they are not the one you want to be charging with.
* Power use calculations and past history, I think, are going to get a few folks in trouble when the transition to a more sophisticated rig. Many will be coming out of an older unit with no solar, 75-200 AH of batteries, no engine generator, maybe a rv generator, propane frig, propane stove, propane heat. Those older rigs also don't have lots of multiple control and monitor panels that use some energy, or continuously running inverters. In an older style rig, you can run on 20 AH per day if you are careful, but if you base your new rig on that you may be very disappointed. A compressor frig, especially if you go bigger like most are now, will use something like 40-80 AH per day by itself. Throw in a couple of microwave runs off the batteries, maybe an electric cooktop run, entertainment system off the inverter, etc, and you could easily be looking at 200 AH per day. 200 watts of solar sounds like a lot to someone who uses 25 AH per day, but it won't cut it at 200 AH per day, as you could only get about 80 AH on a good day. Same thing with battery bank size. Folks will need to determine, relatively realistically, how long they would like to be off grid, and size appropriately, based on what their new, not past, usage is going to be. Davyyd's moving almost every day (if the drive is long enough) is going to be very different from our desire to be in a spot 3-5 days, with only short trips to trailheads, etc. I think on many of the newer rigs, their 200/250 watts of solar will barely cover the refrigerator for many folks. With solar, you also have to be willing to park in the sun, which will be kind of tough for us, as we like shady.
* Solar and battery sizing. IMO if you want to be able to be off grid for extended times, with some cushion for poor solar conditions, you would probably want to have 4-500 watts of solar and 4-500 AH of battery. That would give a reasonable amount of reserve power to get you through cloudy days, and enough charging to catch you back up, and give a reasonable amount of charge when cloudy. It also allows you to have enough solar to get your batteries full, and not short cycled, which is important. Currently, I think the manufacturers are concentrating too much on big battery banks, and putting in too little solar, and they need to match better. IMO, this is one thing that Handybob has exactly correct, and which he proved by reducing his battery bank size to better match his solar and getting much better results.
* I don't know how the propane will turn out. For gas rigs, I can't see it going away because of the heat and hot water, but diesels can use their fuel for that. Even with diesel, we would want it built in, maybe with a smaller tank, because we use a gas grill and stove multiple times a day, many days. The little bottles are horrible and wasteful, in our opinion, and wouldn't want to have a loose 20# bottle.
* Having most everthing as 12 volts is very desirable. If the inverter runs 24 hours a day to keep something running, it will cost you as much as 30+ AH per day, depending on the inverter.
In Davyyd's specific case as he describes, his electrical use would be the frig, micro, induction cooktop, lights fans for the furnace and water heater, and maybe 30-40 Apple chargers:mrgreen: Say 60 AH on the frig, 140 AH per hour on the micro and induction cooktop, lights/chargers/fans/tv/ another 40 AH. With 1/2 hour of cooking, he would be at 170AH a day. That would take about 400+ watts of solar to keep up with in less than stellar conditions. If he is willing, and the rules allow it, running the engine generator while the microwave or cooktop, will put him down to 100 AH a day. I would guess that it would take something in the 1.5+ hour range of driving to get a good refill of 170 AH of battery, with a big engine charger, as the batteries don't take as quickly as they near full, but I have no basis for that guess from real experience. From that I would say if he drives a couple hours a day, small solar will be OK. If he wants to sit longer off grid, and especially if he can't run the van for short spurts for the cooking, I think 400-500 watts of solar would be better. 400-500 AH of battery in either case. If he is counting on doing much/most of the charging while driving, a 12v to 12v multistep charger would be a very good idea, I think. Of course, there still would be the question of needing to hook up to shore power if he got into an area that air condtioning would be desired, if he gets the air conditioning at all. It is very possible that Advanced has all this covered and available already, as they seem to be more on the leading edge than most.
All and all, I think it is going to be very difficult for the manufacturers to build a one size fits all, mostly electric, mostly off grid, rig, and I don't know if RV sales types are really capable or interested enough to evaluate what a custome needs to make them more customer specific. It will be very interesting how that end of it shakes out.
Thom
