75 replies to this topic

[Ned Pepper's chaps]

My wife and I intend to ween ourselves off 120V appliances as well as fossil fuels. I am currently looking at our options for solar power to charge battery banks as well as dreaming about the utilization of so-called subtle energies. We have already seen that our light requirements are easily met with 12V lamps, other things however, not so much. I was wondering if anyone else is already using only 12V full time and what sort of sacrifices it's required of them.

[Kirk]

Most people who operate "off grid" do so by using batteries for storage and an inverter to supply 120V-ac power for things not capable of running on 12V-dc power.

[Ned Pepper's chaps]

What sort of load can that type of setup sustain? Also, how many batteries would one need to have a workable sized bank?

[Mastercraft]

The no fuel use thing is more well suited to a permanent living arrangement typically in a real moderate climate. A super insulated, super high thermal mass, house can be designed with windows positioned for passive heat collection in the winter and shading in the summer. Wood stove for heat.....need a truck and chain saw to collect the wood and get it home.
I am unaware of an acceptable "no fuel use" solution for air conditioning. Getting a 12V source (battery bank and inverter) to pump water from a 400' well is also a bit of a challenge. If you want pressurized water (50 psi and 10 gal / minute) that will be a challenge for the 12V battery bank and inverter as well. I suppose, in a permanent arrangement, you could position your well and storage tank about 110 feet above your point of use (up the mountain) and get 50 psi gravity feed water.

I hear there are some folks who are fueling their homes and cars with sea weed in DC.

[David & Lorna Schinske]

Go to the solar websites. There you will find worksheets to size your solar panels and your battery banks. You would need to pull a cargo trailer full of batteries to power an air conditioner.

[Ned Pepper's chaps]

It's not looking good for an air conditioner. That will be fine if I end up back in the Rockies, but I'm really hoping that I find my way here in Oregon. The wife is more inclined to need air conditioning. I'm fairly certain that wherever we end up it'll be in the mountains. One of the criteria for land is it must be on some water of some sort. Perhaps filling a holding tank and pressurizing that with air would work? I doubt 50psi would be feasible that way, but our water pressure now is crap, at least in the shower and that's where pressure counts the most. I told the wife earlier we should start looking out for a good deal on a gang of deep cycle batteries. Buy 10 or 15 at one time, all brand new, same kind and all. I tore out the bed today and hauled the mattress to the local dump, so the bedroom repurposing adventure has officially begun. We use the sofa bed in the living area since getting in and out the small space to the bed is a pain. The plan is to buy a nicer sofa bed (we found one we like at camping world already) and convert the back room into a utility area. I plan to use some of that area for a battery house since it will be easy to vent back there. I also want to move the bathroom sink and perhaps install a larger shower, but the shower is just a maybe as we've gotten used to the small sized one already. All my electronics gear should be here within the week and I'll need a place to solder and tinker, so a desk, foldaway perhaps, is also in order.

So many projects and mods, so little time. I'd be lying if I said I didn't love it, though. The kids think we are off our nut, they totally don't get it. Me, on the other hand, I don't get why everyone doesn't want to live in an RV. I miss my house sometimes, my lathe and brewery, but this so much better. I've not been this optimistic or content in my entire life.

[Technomadia]

In our last RV (a 17' fiberglass egg) we attempted to go entirely 12v and propane. We had 200w of solar on the roof and a 225 aH AGM battery bank. All the lights were converted to LED, and we tracked down 12v power adapters for our Macbook Pros. Our trailer's server, a Mac Mini, our CradlePoint Router and cellular Amplifier were also powered by 12v. It worked pretty well, but the reliability of the 12v laptop chargers was not suitable - we ended up rendering them useless within a few months. So we did end up utilizing our 1500w inverter more often than we would have liked. We even converter our Honda 2000 generator to run off propane, which could run our A.C.

The other downsides with 12v is lack of choice with some devices - such as screens (TVs or monitors) and entertainment systems. If those are of interest to you. They are available - but not always the latest in technology.

In our bus, we're going a different route - we're optimizing for 110, but via our battery bank & inverter for extended off-grid. It's an on going project for us - but we will eventually have the roof lined with solar. Our battery bank is Lithium Ion - we have a 500 aH bank currently (which is roughly 400 usable), which can run one of our air conditioners for 3 hours. We intend to double the bank soon. Lithium is newer stuff and a pricey upfront cost, but does start to make this sort of power system feasible without needing to 'pull a cargo trailer'. Our entire bank only weighs 145 lbs and is tiny in comparison to a comparable lead acid bank that would deliver the same usable capacity.

We have a series on our blog about our research into LFP at http://www.technomadia.com/lithium.

As far as what is 'workable' for a battery bank size and solar set up - you should conduct a full energy analysis of your needs, and go from there.

- Cherie

Edited by Technomadia, 24 March 2012 - 09:36 PM.

[Ned Pepper's chaps]

Thanks Cherie, I'll check your blog out. I'm afraid to even look at how much lithium batteries that size cost, but I can see how lead/acid would not even compare. At this point I don't speak the lingo or anything, I have no idea what is what. My education in this is just beginning, but I like to learn.

[Dugggg]

With a big enough inverter, you can even run big things like a microwave and hair dryer---for reasonably short periods. Don't go overboard with lead acid batteries---the bank must be small enough for your solar panels to fully charge them at least every other day.

[Stanley P. Miller]

Try here to start, http://homepower.com/home/ Then deciding what you need is the key, without knowing how much power you'll need you can't build an efficient system. The Sandia National Laboratory used to have some really excellent solar books that will take months to read but leave you knowing a lot about system design. They also had non PV material, start here: http://energy.sandia.gov/?page_id=2886

[Ned Pepper's chaps]

Cherie, you guys are geeks, awesome

I had a quick question. I was looking at charger/inverter bundles that did not include batteries. Would I need a special charger for the lithium batteries?

Thanks for the link, Stanley!

Edited by AreVee?, 24 March 2012 - 11:48 PM.

[Technomadia]

Cherie, you guys are geeks, awesome

I had a quick question. I was looking at charger/inverter bundles that did not include batteries. Would I need a special charger for the lithium batteries?

As lithium is a newer technology in the RVing world, most inverters don't have charging profiles for them. So most of us using them are improvising a bit. Unless you're electrical savvy we don't recommend approaching lithium quite yet - as we hope they become more mainstream in the coming years. Chris has a post planned about our inverter and more about our setup, I just need to keep prodding him to follow up. Stay tuned.

- Cherie

[Ned Pepper's chaps]

I can handle altering an inverter, you answered my question with a single word, profile.

I guess I need to do an energy audit first to see what we use currently and go from there. Inverters are kinda high and I have no idea, yet, how much inverter we should buy.

Thanks for the info, it's been inspirational.

[Ned Pepper's chaps]

With a big enough inverter, you can even run big things like a microwave and hair dryer---for reasonably short periods. Don't go overboard with lead acid batteries---the bank must be small enough for your solar panels to fully charge them at least every other day.

Considering your signature, I'd say you know what you're talking about. How big is your bank?

[Jack Mayer]

You need to conduct an energy audit to see what "ballpark" you are in. Then consider lifestyle compromises. It is the rare individual that does not have to make compromises to live totally off-grid. IMO using 12-volt only is not the way to look at it. I would look at it from an off-grid perspective, but there is not good reason to not use an inverter. You will find it far more convenient in selecting normal household, energy efficient appliances/ goodies. You can take a look at my website for technical details that should provide you some food for thought. Feel free to ask questions.

[Kirk]

As to the size of inverters and the number of batteries, you can supply enough 120V power to operate anything if you have a big enough budget and the weight carrying capacity to haul everything. The new motorhomes from companies like Newell, Marathon, and Prevost are now using all 120V-ac appliances that come right from the home market. They even have an electric cook stove and convection over, which they power via inverters from batteries. But these are also $1million plus RVs!

[Jack Mayer]

The new motorhomes from companies like Newell, Marathon, and Prevost are now using all 120V-ac appliances that come right from the home market. They even have an electric cook stove and convection over, which they power via inverters from batteries. But these are also $1million plus RVs!

I have 1020 Ah of battery storage in my 2012 New Horizons. So I can run a lot of things. But not AC for long - actually not at all, the way my rig is wired. The coaches Kirk refers to also have large gensets, with autostart. So they may run off inverter for a little while, but the genset runs a lot, in most cases. They also have around 2000Ah of battery for the house - at least the ones I have seen do.

I've though of building an all electric coach, but in practice having a little propane makes things far easier. Especially when it comes to heating in a 5er. The large diesel coaches use diesel-fired hydronic heating. In a 5er we can use propane-fired hydronic heat. But diesel - although sometimes used in a 5er - is a stretch IMO. So having an all-electric 5er is difficult, for no real benefit.

[Stanley P. Miller]

Altering an inverter is not an easy task, you will have no access to the hardware documentation, source code or to reprogramming instructions making reverse engineering a daunting task. Any programming error may destroy the switching section of the inverter and without very expensive equipment they are not repairable, even the manufacturers tend to scrap old units rather than attempt repairs. Obtaining the proper matched parts to attempt a repair may be a problem too.

[David & Lorna Schinske]

It's not looking good for an air conditioner... The wife is more inclined to need air conditioning.... Perhaps filling a holding tank and pressurizing that with air would work? I doubt 50psi would be feasible that way, but our water pressure now is crap, at least in the shower and that's where pressure counts the most...

Since his heart attack last year (16 heart attacks over two days was a lovely Mum's Day present, doncha tink?) David feels the heat much more. Air conditioning helps. So we stay on shore power (also due to our business... refrigerators & freezer required). We will add a generator later on. If we can get our idea of a low power use "air chiller" to work, we can lower the drain that an AC unit would put on a generator. Possibly enough for a couple of solar panels to power. Not that we would. We simply do not have either the room for the battery bank needed nor do we have the deep pockets to buy PV panels just so we can use them once a year for a couple of days. There is no sense in our wasting huge amounts of $$ on something we would use rarely. Our power is included in our site rent and I would rather invest in a generator to use while traveling or during a power outage. We only wallydock overnight. A generator is more suited to us.

As for your water pressure. We had a Shurflo 2088 Classic (the 2.8gpm... they make a 3.5 gpm in the 2088 Classic series) and we showered just fine with it. We also used a hand held low flow shower head that used to be in our home shower back when we had a house. There seemed to be no difference between the two. For our bus conversion, I will use the slightly bigger 2088 Classic since we will be set up to only use water from the holding tank. The water here in NM is so full of lime/minerals (even city water) that we will filter & soften the water before it gets to anything in the bus. My filters knock the campground water pressure down so much that it would work better to filter/soften then store the water rather than filter/soften on demand. I also plan to put a washing machine and dishwasher in the bus as well (I hate washing dishes). This bus is our fulltime home and I can see no reason why I can't have it like my home. So the slightly higher GPM Shurflo should work. I do like the Shurflo 2088 Classic pumps. They have been very dependable for us. The pump on the food cart is circa early 80's. The pump in the Class C my daughter "inherited" from us was bought in 1980 before we left FL. It stayed in a box until the 1970's pump on the Class C pooped out on us while in TX (2009).

Get the 3.5 GPM 2088. Paired with a 2.5 to 3gpm low flow shower head (typical for shower heads even for brix-&-mortar homes) should work to your wife's satisfaction and I'm a person who does like their showers!

[Jack Mayer]

Lorna, on the topic of water quality.....

In your situation I would use a reverse osmosis setup and store the water in the fresh water tank....and then just always run off of that. You can set up sprinkler controls to turn the RO off/on at certain times if the noise bothers you. Some people do not like hearing it "make water".