Why bother with an inverter? DC electricty works just fine.

- Forums - Register/Sign Up - Reply - Search - Statistics -

Small Cabin Forum / Off-Grid Living / Why bother with an inverter? DC electricty works just fine.


Author	Message
Jess Member	# Posted: 10 Apr 2020 10:05am Reply Hey yall! We've got a unique set-up on our off-grid farm I'd like to share with everyone, and see if anyone else has figured out something similar. So we're down in Virginia, USA and we use solar energy to meet most of our needs. Because PV panels produce DC electricity, we just forgo the inverter and run our systems on DC. One less thing that can break and needs to be replaced sooner or latef! The only thing that we use our batteries for is lights and charging phones, laptops and our wifi hotspot. Our batteries are not lithium or lead... they're nickel iron, which are extremely durable and can last decades. They are also nontoxic. They can handle deep discharges and other misuse without lasting injuries. Using nickel iron batteries and forgoing the inverter means almost zero maintenance costs. Appliances like our grain grinder, freezer, hot plate, seed blower and our tools like drill press or saw run directly off the solar panel. No inverter, no battery, just a switch. We just run them during the daytime. This works for DC motors and universal motors. We call this daylight drive. Using daylight drive means that much less energy needs to be stored in our batteries, and instead of one big system, we have a lot of smaller independent systems.This is much, much more failproof then conventional off-grid systems. Thats the electrical side of things. Here is our website for more about that: livingenergylights.com However, the first priority before electrical storage is reducing energy usage, and then thermal storage. We have a straw bale house and a solar thermal heating system, which is a daylight drive air-based radiant slab system. We also use a solar hot water heater, and a very very big storage tank. Our water pump is daylight drive as well. That means we pump a lot of water and heat a lot of water when the sun comes out, and it stays hot through the night and through cloudy spells. Energy storage is key! More on that at our farm's website: livingenergyfarm.org Anyone else come up with something similar? We don't know anyone else who has, which is a shame. It works great. Never had the lights go out in ten years!

SE Ohio Member	# Posted: 10 Apr 2020 12:10pm Reply Hello Mess, Interesting first post. I notice both links go to your sales sites. That is very helpful as many of us here are unaware that we can search the internet to shop for our cabin needs. Your info is well, spam-tacular! Thanks for using this site for your personal marketing purposes. Signed, Spammenomore

Brettny Member	# Posted: 10 Apr 2020 02:24pm Reply Definitely spam. But why run an inverter? Dc appliances are expensive. Dc is usually low voltage thus you cant make long runs with it without major voltage loss vs the same size wire and 120/240v...so in the end it's easier and cheaper to just run an inverter.

Jess Member	# Posted: 10 Apr 2020 06:33pm Reply Hello sorry if I broke any rules! Inverters are not worth it. Something like 90% of the electricty we use is high voltage, 180v or 90v DC directly off our solar rack used to run our motors. At 180v DC the wiring is the same as househould wiring. A DC motor can handle enormous amounts of voltage variation, like 500%. An inverter can't and will shut off with very a small amount of voltage change. DC motors never shut off, they just slow down as the voltage drops. The same is with DC lighting. If there are two many loads on the system, the lights will just start to dim. Because inverters can't handle voltage change and shut off they are the weakest link in a conventional offgrid system.

toyota_mdt_tech Member	# Posted: 10 Apr 2020 08:19pm Reply Inverters shutting off is what protects electronics from low voltage or brown outs. Its a safety feature, it was overloaded. Maybe a larger inverter? Then you can wire cabin for 110V/220V and run it on battery via an inverter. Higher voltages means smaller wires needed to do same work.

ICC Member	# Posted: 10 Apr 2020 08:26pm - Edited by: ICC Reply Jess, Many of my kitchen appliances and workshop tools, have labels that specify AC only (120 or 240 VAC) or specify a voltage along with 60Hz, or in some cases 50/60 Hz. So, keeping in mind that new devices come with a warranty, how does one use those devices on DC without the need to hack them somehow, which would void the warranty?

Brettny Member	# Posted: 10 Apr 2020 09:12pm Reply So I should skip the inverter and buy all new appliances and this will save us money? Where do I buy a refrigerator that runs on 180v DC?

Jess Member	# Posted: 11 Apr 2020 10:40am Reply Quoting: toyota_mdt_tech Inverters shutting off is what protects electronics from low voltage or brown outs. A DC system does not need to be protected from low voltage. We disconnected our battery set from the PV panels for four days recently to run some tests and our lights didn't go out. Four days with no energy source! Lights will just get dimmer but voltage drops will not damage the DC system. Quoting: toyota_mdt_tech Then you can wire cabin for 110V/220V and run it on battery via an inverter. Higher voltages means smaller wires needed to do same work. No need! Our lighting circuit off the battery is 12v, but voltage drop doesn't matter because the lights are only 3 or 7 watts, so it's too small to have any effect. All of our other motors are connected directly to solar panels at high voltage DC (180 or 90v) so no problems with voltage drops either. The fridge runs off a nominal 24v panel though. Quoting: ICC Many of my kitchen appliances and workshop tools, have labels that specify AC only (120 or 240 VAC) or specify a voltage along with 60Hz, or in some cases 50/60 Hz. So, keeping in mind that new devices come with a warranty, how does one use those devices on DC without the need to hack them somehow, which would void the warranty? Some AC appliances have universal motors. Usually it's appliances you can pick up, like a blender even though it specifies AC it is probably a universal motor and will run fine on 90-120v DC. A washing machine will probably not run on DC. Right now I don't think there is a high quality DC washing machine on the market, which is a crying shame. There are crappy RV ones but they're expensive and not well made. We use an old repurposed cement mixer to wash clothes, ha! We're trying to source high quality appliances, with brushless motors so they'll last, but we're still working on it. We found a great fan. But back to kitchen appliances. We were experimenting with blenders, just buying them from the thrift store and found that about 80% of them will work with AC. The only problem is that DC electricity will arc and melt an AC switch so you can either wire it and bypass the switch or you can plug it into a heavy duty external switch. But don't mess around with that high voltage stuff unless you know what you're doing. But yeah, you could mess up your appliance and not get the warranty. We have some videos showing how we do this stuff. if you are still interested I can send you some links. Quoting: Brettny So I should skip the inverter and buy all new appliances and this will save us money? In the long run it will. If you've already invested in a conventional off grid system then you could convert piece by piece to a DC system. The DC system we run has near zero maintenance costs, because we don't use an inverter and because our batteries are nickel iron, which last a lifetime. We actually have an old one from the 50s that still works at about 50% capacity. It's an old miner's lamp battery haha. It can still light up a room for a few hours. Quoting: Brettny Where do I buy a refrigerator that runs on 180v DC? We bought a SunDanzer fridge that can handle voltage swings from about 10 to 50. We hook it up to a nominal 24v pv panel, but you could do 12v too. We've had it for a couple of years and it works great. It even got struck by lightening, but we were able to fix it since it's such a well-made machine. Just put the panel near the fridge, so voltage drop won't be an issue.

cspot Member	# Posted: 11 Apr 2020 11:06am Reply Looking at that fridge it is basically double the cost of a regular 120V fridge. I don't see where the $$savings are by not running an inverter and then being able to run what you want. I currently run a simple 12V system at my cabin (recreational use), but if I wanted to up any in use or lived there full time it would be worth it to go to an inverter. I simply take my generator with me now if I have to run anything 120V like tools.

SE Ohio Member	# Posted: 11 Apr 2020 11:12am Reply Nice to see this thread has become a lot more interesting than a simple sales pitch! SE Ohio

paulz Member	# Posted: 11 Apr 2020 12:39pm Reply Speaking of inverters, I have been wondering, without finding the other thread, and after realizing I should have a true sign wave inverter.. Do generators put out full sign wave power? I will be running my new drive in movie projector off a genny most likely, don't want to blow it up. I maybe could run it off my inverter but it is not a full sign wave, plus the projector draws almost 10 amps.

ICC Member	# Posted: 11 Apr 2020 01:39pm - Edited by: ICC Reply Quoting: Jess We were experimenting with blenders, just buying them from the thrift store and found that about 80% of them will work with AC. The only problem is that DC electricity will arc and melt an AC switch so you can either wire it and bypass the switch or you can plug it into a heavy duty external switch. That is what I thought. One would need to hack many things in some way in order to run on DC. And many devices are no go without a hack of some kind. That is not really very user friendly to non technical people. No thank you. My old place that I sold to a friend is still going fine after 14 years running the same pair of stacked Outback VFX inverters and it is "plug 'n' play". I use Schneider in the new place and expect great things from them too. Also a "plug 'n' play" home and shop. I get to choose the exact fridge I want (LG inverter fridge), in the style and color I want. The new saws in the shop still have the remainder of their 2 year warranties and their variable speed controls runs at the speed I set without wandering as would/could happen with your approach. Just a FYI; I began tinkering with solar power 20+ years ago out in the boonies here. I went through the DC only stage and eventually it easier to do what I want with AC. Part of that is due to the fact that our world is designed around AC. Now, IF our world was designed to operate directly off DC mains, things would undoubtedly be different, easier.

ICC Member	# Posted: 11 Apr 2020 02:01pm - Edited by: ICC Reply Quoting: paulz Do generators put out full sign wave power? FYI, it is sine, not sign, though the two words sound the same. Virtually all generators with a 120 VAC or 240 VAC rated output produce sine wave AC power. That is the nature of spinning magnets and copper wire as used in an AC generator. Where many generators of the construction variety fall down is in speed control. The increase and decrease of engine speed as the load changes causes the AC frequency and voltage to vary. Call that "dirty" power. That can play havoc with electronics. A good inverter generator starts off with DC output and inverts that to AC with an onboard inverter. I know Honda and Yamaha produce very stable power. Call that "clean" power. Not sure about other brands. Some devices run fine on either, others are more particular.

Nobadays Member	# Posted: 11 Apr 2020 02:14pm Reply Quoting: ICC A good inverter generator starts off with DC output and inverts that to DC with an onboard inverter. Pretty sure ICC meant, ....starts off with DC output and inverts that to AC .....

paulz Member	# Posted: 11 Apr 2020 02:23pm Reply Quoting: ICC FYI, it is sine, not sign, though the two words sound the same. I knew that! Also probly knew that it would be full sine, given the basics of it. Too many projects going on.. Thanks!

ICC Member	# Posted: 11 Apr 2020 02:37pm Reply Quoting: Nobadays Pretty sure ICC meant, ....starts off with DC output and inverts that to AC ..... Yes, you read better than I proof-read. Thanks. I corrected my original.

Ontario lakeside Member	# Posted: 11 Apr 2020 04:32pm Reply We arn out cabin off 12v for two years but now we have a battery inverter setup. Equipment prices have fallen a lot and for most people its easer and safer to use 110.

Jess Member	# Posted: 11 Apr 2020 07:27pm Reply Quoting: cspot Looking at that fridge it is basically double the cost of a regular 120V fridge. Yup true but this fridge will last for decades. If you buy a cheap fridge it's going to break and It'll be badly insulated and be a big old drain on your system. If you run a cheap fridge through your batteries and an inverter, it just means you need a bigger battery set to keep a badly insulated box cold. It's just a waste of energy and in the long term a waste of money. This daylight drive fridge doesn't need a battery or inverter... so that means your battery set can be smaller and because it's an independent system if something fails with your batteries, your fridge is fine. Does no one else think it's very strange and inefficient that in conventional off grid systems the PV panel makes DC electricity, that electricity is stored in a battery, it is converted into AC with an inverter and then it's used to chill a badly insulated fridge? Instead The PV panel can connect right to the fridge, and the electrical energy can be stored thermally with all the insulation! This uses radically less resources and energy! Quoting: Ontario lakeside We arn out cabin off 12v for two years but now we have a battery inverter setup. Equipment prices have fallen a lot and for most people its easer and safer to use 110. So if you were trying to run heavy loads off of 12v DC that would be very bad. But we only light lights and charge cellphones and laptops and run a fan off our 12v system. Appliances, shop tools etc we use high voltage electricty that does not go through the batteries. We call it daylight drive. Now I'll respond to ICC's comment: So it's true that certain things about our system are funky. Like hacking appliances since reliable DC appliances aren't on the market (yet...). But because we have near zero maintenance costs it's much more accessible to a whole lot of people around the world, especially at the community level. You mention your two inverters that work well, but I mean those are two expenses that we just don't have. And you mention the inverters give you the freedom to chose the color and style of your fridge. If that is important to you and you have the money for that then yeah there's not really anything that our system can offer you. I mean, what's great about our systems is they're so cheap and accessible to those that would find conventional offgrid living prohibitively expensive. That and our systems never fail. We did a few projects on the Dine (Navajo) and Hopi reservations this past year, where lots and lots of people live off grid not by choice but just because it costs tens of thousands of dollars to get power poles to their homes. So many people there have broken solar equipment laying in their yard because they can't afford the maintenance cost, replacing batteries and inverters etc... All in all, If one forgos the inverter, uses nickle iron batteries and runs the essentials like a fridge and water pump on daylight drive, you and your family or community have almost zero maintenance costs for the rest of your life.

Nobadays Member	# Posted: 11 Apr 2020 08:36pm Reply Jess... this seems to work for you, sweet! But I'm not convinced "hacking" electric motors and running them off DC power is for the every day user. I feel sorry for the Dine people when they plug something into their new power source and the magic smoke escapes. I feel you are wrong to state traditional solar systems like most of us here run are more wasteful or less cost effective. It would be hard to convince me that AC shop equipment will live a long life when run on high voltage DC current. Switches will melt down, brushes and armatures designed for alternating current will run hotter and will fail prematurely. You have paid 3 times what I paid for my energy star Magic Chef 10cuft fridge. It uses less than 8 watts of energy per day (based on the reported 312kw/year), that is not wasteful. Nickel iron batteries... in your application, yes probably fine but they will not charge quickly or discharge quickly so using them for a traditional off-grid energy system is probably not advisable. You state they contain no toxins... that is not really correct, the fluid in the batteries are toxic at the levels in the cells... yes it can be diluted to safe levels. Isn't the solution to pollution dilution? If anyone is interested...HERE the down side of nickel iron batteries. Not trying to shoot you down... really... but there are more ways to skin a cat... and yes I do eat meat.

Jess Member	# Posted: 12 Apr 2020 08:26pm Reply Nobadays, sorry about the cat meat thing. You have my sympathy. I hear road kill squirrel tastes better. But on a more serious note, my family has been doing residential and commercial construction and energy systems for 30 years. We helped start Living Energy Farm after we had helped numerous of our friends build off-grid system. NONE of those systems are still operational. They cost $1000 - $2000 per year in battery replacement costs (primarily) as well as replacing inverters and what not over time. You are flat wrong about our shop equipment. We are running DC brush motors for a fully tooled shop, including metal cutting bandsaw, lathe, drill press, multiple grinders, compressors. We cut firewood and run agricultural equipment with our DC motors. Those machines will run all day every day for the rest of your life at near zero cost. In 10 years we have replaced brushes on a couple of motors, cheap and easy. Generator costs are huge compared to our system. Your inverter systems allow you to remain obedient to the people who sell you consumer junk. We could live for decades without any help from the rest of the industrial world pretty happily. That link you refer to about nickel iron batteries is propaganda that serves to keep you buying their equipment that fails. To be specific: Cost: same as lithium, higher than lead-acid, but your annual cost is much, much lower. We have been running our first set for 10 years, and it's at 120% capacity. Energy density: Yes, it's low. These are stationary batteries, not laptop batteries. We have a nickel iron set that is over 70 years old and still operational. Ventilation: Just not an issue on a small battery set. They run nickel irons in massive sets in ships. Some rich people hook up large sets to inverters. No comment on that. Small sets vent naturally with no problem. Watering: Website says you have to water them weekly. That's a bald faced lie. Once a month would be conservative. The system we are using now involves opening a valve and counting to ten. Real hard... You know, I didn't know didly about nickel irons until someone gave me that ancient one 10 years ago. In a normal inverter setup, they would probably be okay. In the context of our system, they boarder on miraculous. You can draw them down and down and down and they don't go out on a DC system. Combined with the daylight drive systems, you end up with an overall package that provides a huge amount of service at near nil ongoing costs. The pernicious aspect of the domination of consumerism in solar technology is that the 2.2 billion people who don't have reliable electricity on planet Earth are stuck with junk because that's what the market sells. World Bank data (gogla.org) tracks the now rapid expansion of off-grid equipment in Africa and Asia. The average life expectancy of all that equipment is 3 years. Honestly, we are asking your help. If rich Americans would start switching to durable equipment, then we would create a market for it. The environmental benefits would be huge. And a couple of billion people would then start to gain access to good equipment because we created a market for. That's what happened with cell phones. We are hoping we can make that happen with daylight drive and nickel iron batteries. Ten people, ten years, all the energy we need at near zero cost, with an original investment of less than 200 watts per person. This thing works. Really it does. We get to take hot showers, watch movies at night. Cut steel and wood during the day, and earn a living to boot. The world needs this technology to spread. The youtube link if you want to see it.

Nobadays Member	# Posted: 12 Apr 2020 08:54pm Reply Thank you for your reply.

mj1angier Member	# Posted: 12 Apr 2020 09:24pm Reply I get the feeling they are selling more than a power system.

Brettny Member	# Posted: 13 Apr 2020 09:28am Reply Lol yes I get that feeling too.