So I’ve been looking at possible 12v solutions, inverters, batteries, and solar/wind. The inverters are reasonable and the batteries aren’t bad. The problem is getting enough solar or wind generation to make up for what you use. I have a generator and it will run anything I put on it but the main problem is fuel and the second is noise. I’ve never used it but discovered today that my genny has a 12v 10Amp output. My understanding would be that if I ran it for two hours connected to 1 12v battery it would put back approximately 20Amps into that battery. I’m going to check with the manufactorer on Monday and see if I can run the 12v @ 10Amp and use the other 220v/110v outputs as I would normally. My thinking is:
Run the genny 2 - 3 hours a day to pump water from well (220v), run fridge/freezer as cold as possible, anything else that draws a big load. At the same time charge up a 12v battery.
Then keep the fridge cool by cycling fan and some compressor time(.19 and 1.53 amps respectively). Depending on how much the fridge has to run, there might be some amps left for lights, fan for sleeping (.24 amps), etc etc.
Is my thinking correct here?
Nopower, most of the gensets I’ve seen will allow you to use the 110/220 at the same time as the 12 volt charging system. So yes, that should work.
Your problem will come when you start taking the amps out of your battery. You will be putting 10 amps in for 2–3 hours (ie 25 amp/hrs) plus whatever your 110v battery charger will put in. Lets say you have a 15amp charger. You’d be putting in an additional 37.5 amps/hrs. Together, you could put in a little over 60 amp/hrs over 2 hours. That’s probably too much juice, too fast, for most deep cycle batteries. You’d better assume you are charging a bank of at least 2 batteries.
Now, on the takeaway side, you list an amp draw of .19 and 1.53 amps. But, I have to assume this is at 110 volts, unless you are using a marine/RV refrigeration unit. As you are storing juice at 12 volts, you’d need an inverter to convert the 12 volts to 110 for the freezer fan and compressor.
When you use an inverter to go back to 110 volts, you lose some efficiency in the conversion. Additionally, you need to provide roughtly 1.5 amps at 110 volts. You have to multiply the amps at 110 volts x about 10 to get the number amps pulled from the battery.
So you’ll be drawing, while the freezer is running, about 15 amp/hrs from the batteries. You put in 60, so you’d have about 4 hours of compressor time before you start running a deficeit.
Depending on the amount of time the compressor/fan actually runs each hour will determine whether this will work. I’d look at ways to insulate the freezer, to cut down this run time.
If you can get the compressor running time down to 10–15% of the time, you might have a few amps left.
Hope this helps.
Fla-Medic. See that. Go out for a few hours to mow the lawn and someone shoves you out of the way and takes your job.
Well done though.
Ahh, I didn’t even think about using a 110 charger to charge at the same time as the 12v. Some maybe I get two batteries (or maybe two sets of 2?) and charge one from the 12v @10amps for 3 hours and charge the other one from 110v @ 15 amps. Then I could run an inverter off one (or a set) for the 110v apps and run a 12v fan, some 12v lights of the other batt (or set).
I just picked up a fridge/freezer thermometer from ebay that you can set high/low alarms on. I’m going to test my fridge to see how long I have to run it per day to keep it at an acceptable temp. The Kill-a-Watt will monitor how many watts it is using in a certain time period.
OK…one more hopeful suggestion from me, I promise this will be the last. We have been round and round this whole power situation. Generators are fine for regular power outages, but we have listed quite a few reasons why they are not the perfect solution for lengthy SIP. How about a little generator specifically for the purpose of recharging a battery bank. Something that will just chug along, sipping gas and not making a big racket. I haven’t seen anything ready made on the market. Maybe it would be possible to cobble something together?
You mean maybe like something with a propeller on it that the wind can turn so it doesn’t make much noise and doesn’t need any gas?
One of those would be nice, but it won’t work at my house. I’m still looking for that illusive solution that doesn’t exist.
that was me at 21:38…I switched accounts on Billy’s Wonderful Operating System.
Hillbilly Bill - I have a Honda EI2000i. When set to economy mode it throttles down and is supposed to go up to 15 hours per tank of 1.1 gallons. With it outside, about 20 feet from my wife sitting in the house (doors and window closed) and watching TV, she was not aware it was running. In ecomony mode, if more power is needed, it speeds up. At full power level, a tank is suppose to go 4 hours. 1600 watts; 2000 watts surge (it can run at 2000 watts for up to 30 minutes if I remember correctly). Maybe the Honda 1000 would be quiter and use less gas.
Whole Bunches – at 22:26 Hmmmm….that would be a really nice Christmas gift…
HBB - The more we all have discussed the idea of power sources, the more I have planned and wondered about the best thing to do for the event of an open ended major event. In such a case, anything which uses manufactured fuel, whether it be gasoline, kerosene, propane, used french frys oil, anything, will either eventually run out or be pilfered.
My original planning was how to get enough power to run my well pump periodically, and have enough power to run some lighting, some entertainment, my CPAP machine at night, and maybe a fan for the hot weather. This looked like a fairly major nattery bank, recharged by my generator, with either a small out of the way backup genny, or a large solar array, or, the best choice seemed to be wind power.
All of them expensive, to the tune of 2–3K minimum.
Rethinking the situation, I am now drifting in this direction:
Water will come by refitting the well with one of those manual pumps that can co-exist with the standard downhole mechanical and electrical stuff. They cost a little under 1K when fully kitted out, so I would look at the total cost of that end to be about 1.5K. Interestingly enough, about the same cost of just the batteries and hefty inverter to accomplish the same task. As long as someone can get out to the pump, water can get into the house (the pump can generate about 100PSI).
Almost all the rest can be run from about 60–75 watts of solar panel, which make no noise, can be pulled in at night, and can be used to charge 10–15 AH batteries which I already own in abundance.
Along the same lines, I would much rather use rechargeable AA and AAA cells in LED lights so that I can save my candles for those occasions when they are really needed. So I plan on using the 10 or so solar Malibu lights that I bought on special which each contain a pair of AA NiCads that they can charge during the day. I can either use them directly as light sources, or I can just use them as chargers during daylight hours and then pull the batteries.
it just occured to me how nice my very very long driveway would look wth solar accent lighting running along each side. If TSHTF, I can just pull them in and use them for another purpose.
If I look at the issue of how long a gas generator, or even a wind generator would remain in my posession during a really bad time, I lean more and more to a solar array that I can pull WAYYY into the house (not just the garage which is vulnerable). In this way, a major theft of gas or equipment does not leave us completely helpless. I could even stock a spare panel or two for the event one array gets hoisted.
Let’s harvest this topic and add to:
(I hope I’m getting the links right.)
Sorry: the first link should be:
lugon hides in a hole in the ground
Eccles, is there any reason why you want your solar array to be portable and not fixed to the roof?
What are the pros and cons of each? I am in the planning stages of getting a PV unit on the roof. Several options are up in the air <g>, basically bigger and more expensive or cheaper, smaller, but will not provide as much power. I am aiming at having 12 hours of useage for what I would consider mission critical items, but since we are a large family, it still adds up to quite a bit. But we can get government grant here, and that would help. However, I’m still not sure about the ‘putting-something-on-the-roof’ thing. So Mr Engineer Eccles, can you tell me what are the biggest down-sides of that? The upside (as compared to a portable system, is that they don’t get stolen, and you don’t have to move them around, maybe more durable?)
Also, what do you think of ground-source heating? It seems like a wonderful idea except you do need electrics to run the pumps. However, in the event of ONLY :-) intermittent failures, they seem to be quite efficient in heating the house via underfloor heating, which I already have.
What about charging a whole bank of batteries from the mains as backup? Would that be the easiest (for technically-challenged types) solution for energy storage, even though it wouldn’t be the cheapest or most environmentally friendly? I have a friend who lives in an apartment and he’s saying maybe he should do that and then get a small PV unit just in case power is down for prolonged periods.
On the subject of batteries, can you post some links or resources, if you have them, for how to choose inverters, how to figure out what you need, the differences between different types of batteries etc? For example, if someone wants 300AH in total, would it be better to have lots of small cells, some small, some big, or just one single battery? What are the different considerations that might affect choice of batteries, inverters and such.
OK, that’s far too many questions in one go. :-)
Much thanks and really appreciate your posts!
Eccles, my humble apologies. Chalk it up to pre-pandemic stress. I saw nopower’s post, and it just sat there, unanswered, for 30 minutes. Wild imaginings ran thru my head, wondering why you had not solved this weighty problem. I envisioned all sorts of terrible calamities, and prayed none were true. Then, after 40 agonizing minutes, I resolved to pick up the gauntlet, and try as best I could to answer in your stead. To carry on bravely, albeit with a heavy heart. And to do so in your honor.
It was with great joy that I discovered later that disaster had not befallen you, and you were simply temporarily otherwise engaged. My heart leapt. My concerns were vanquished. A lesson learned my friend. The meds don’t work unless I take them every day. ;)
LOL, it’s good to be back on the wiki. <g>
anon-5:18
“ground source heating” as in geo-thermal? or hot water radiant?
No Power,
Get a healthy converter like the PD9160A with the “Charge Wizard” and use that to charge your batteries from the genset while running it for other purposes, we do it all the time when camping. It’s all a matter of amp hours in to the batteries! 60 amps into the batteries is less than 1kw, we use either the 4kw built in to the MH or a little Kipor 1000ti outboard, both work just fine.
Yeah I was looking at chargers last night after reading the follow ups. I still think getting a propane tank and converting my generator is what I am going to end up doing since it would require alot of solar/wind to power what I need. With a 500 (400 actual) gallon propane tank, I figure I can run 2 hours a day for 90 days. So if in those two hours I can put enough charge into several sets of batteries to give me some power the rest of the day I think I would be fine. Honestly, the fridge/freezer isn’t going to run for 90 days because it will be out of food in a week or two but it would be nice to freeze bottles of water to keep a cooler cold for that time.
The other thing I have to consider is that my preps are 80% hurricane and 20% panflu. So if a hurricane hits, I can crank the generator to 10 hours a day since I know I can get the propane filled in a couple of weeks.
anon_22, My power company says that they are gridtied compatible and I’m going to call them on Monday and see if they have any incentives or programs for alt energy. I saw a chart on one of the alt energy websites showing that if you took out a loan to setup your whole house system it would be a huge savings over 20 years because the loan amount would stay roughly the same but the cost of energy will continue to rise sharply.
Food and drinking water were the easy part of prep, this is where it gets more difficult.
As for the ideas of not using a generator because someone will hear it and steal it. I have to admit that I have been pretty laxed on home security/defense. That has changed as part of my prep. I’m better securing my doors, putting alarms on my doors/windows, and planning on how to secure my perimeter and gates to keep people from entering my backyard. I’m also stocking up on lethal and non-lethal personal protection. I don’t like the argument that you shouldn’t have something because someone might steal it. And I don’t think if you have a large array of PV on your roof, people will be up there removing them and hauling them away (atleast hopefully not while you are there to stop them). If you plan on possibly leaving your house, then I would suggest you have a more travel friendly form of power production.
Don’t forget to allow for surge capacity needed by motors when they start up. You need to ck the specs of any motor and it will tell you the start up amps it needs for a short period. If you don’t plan for that you will ruin your batteries and may start a fire or have a small boom! It is better to over design in this area. There will be no fire trucks coming to your house at the height of this problem. My apologies to those who do this better than I do…I am not worthy. Grin.
anon_22;
IMHO, PV panels that have 20 year warranty are pricey enough that they would attract thieves when you are away, even on a 2 storey roof top. Telescoping step ladders that collapse to fit into the trunk of a small car are widely available. It only take 10 minutes to steal your panel. With a crew of 3 (2 on roof top and one on the ground, I can imagine it takes half an hour or less to steal your array of say 6 x 150W. The PV array also acts like a bill board - I am well prepared, when TSHTF come and rob me.
I bought cheaper 5 year warranty portable 15W panels to charge 20Ah battery. I am betting that prices for PV panels, just like TFT panels, will drop significantly in a few years as manufacturing volume increases. I am planning to test mounting onto a removable frame that fit inside 2/3rd of my south facing windows. I know I am supposed to mount it about 45 degrees outside and I won’t get the efficiency if the panel is vertical - but I don’t have to worry about it being stolen. How much efficiency do I lose if it’s vertical?
CRAZY THOUGHT TO EXPLORE - may not be feasible: Theoretically, I might even be able to get the effect of the 45 degree installation by setting up mirror or aluminum (or even foil on plywood backing?) reflector at 22.5 degree from horizontal, sloping down towards the house, installed about 16 inches outside and away from the window to allow snow to slide down. At 22.5 degrees, the reflector would be 2.55 times the size of the panel, and may collect more sunlight. This is possible only if the second floor is several feet recessed from the main floor e.g. above a garage. Any engineer care to comment?
I went to a cottage life show and talked to several alternative energy exhibitors. I heard the shortest payback is solar hot water supplemental heater (claimed as 5 years), especially if you have hot water floor heating. This is only a little more expensive than solar pool heating, but for drinking water. Installed on the roof, no one will bother stealing it. Not sure how this would work when you don’t have running water.
Correction:
reflector is 2.6 (not 2.55) times size of PV panel.
hvac, ground source heating = geothermal. Most efficient use is I think underfloor heating/cooling and hot water supply.
ANON-YYZ,
we’re talking about probably 1kW of PV panels so I don’t think that’s anything that I can move around. Also, I’m in the UK and you get quite good grants from the government for these grid-connected permanent systems. Portable systems without grants costing the same probably produces less than 1/3 power.
I was worried about the grid connection cos that means the whole thing shuts down if the grid goes down, but I am told that there is a switch/controller thing which can, after a short interval, isolate the grid side and switch the inverter back on so that you can get AC out of your battery banks.
Everything is still at the planning stage and I’m trying to learn as fast as I can :-)
Your reflector idea is interesting. My physics is way old but if I were to make a guess i would say it might work although whether 22.5 degree plus reflector is more than a carefully adjusted 45 degree is debatable.
Engineers please comment?!!!
YOu know one upside to this pandemic threat is it probably moves a lot of people into sustainable living. Lots of people including myself understand the need and agree in principle but keep putting things off as there is always some other priority.
So things i am looking at: solar, geothermal, hybrid cars, biodiesel.
nopower,
See my comments about grants in the UK and getting a grid-connected system that can be disconnected at will.
As for generator noise, I have the same concern as my neighbours are quite close. However, I have converted the generator to use bottled propane. I have a very spacious 3car garage, and I am thinking I might experiment with running it inside with the garage doors all open say 1 ft at the bottom. There’s also a door on the opposite side, so if I keep that open another 1 ft, and maybe turn on a couple of fans, maybe the CO2 accumulation won’t be a problem but the noise is probably going to be a lot less. Also, my garage is very cluttered at the moment, lots of free standing wire shelves with all that food and water and toilet papaer, so I am thinking standing the generator in the middle of a bunch of such shelves (with a clear space, of course) might dampen the noise as well. If not, I might get some accoustic panels and stand them around the thing.
I was thinking of putting a small generator in a well insulated shed in the back yard. The exhaust would be run through some automotive type mufflers and then up a pipe that goes out the roof. I may need to put the mufflers in parallel to keep back pressure down, but I’m betting I can make the thing pretty darn near silent. If I just run it during the wee hours of the AM, I should be able to charge batteries for use later.
AVanarts,
You may have a problem with the functioning of the gen if your exhaust is too long.
Also, wee hours of AM is when it is quietest and any noise more obvious, especially if people are extra-vigilant for reasons of safety during a power outage.
It may be better to run it at say 7pm when everyone is inside trying to get dinner going with no power.
anon_22 – at 13:03
Geometry, really. Draw a horizontal line. Then draw a line through it at 45 degrees to make an X. The slanted line is the sun ray. The horizontal line is the reflected sun ray. Finally draw a line splitting the 45 degree in half - this is the reflector. The sun ray comes in at 45 degree pass horizontal which is 22.5 degree above the reflector. This is reflected to go horizontal and therefore perpendicular to the vertically mounted panel.
Anon_22 - Please excuse my delay in getting back to you (She who must be obeyed had weekend anti-vegetation duty for me).
Aside from the security issue of panels, I was looking at the efficiency of fixed vs movable panels. In the spacecraft industry, we had solar panel drives on the vehicles to track the sun. the reason for this is that solar energy, coming from a quasi-point source is expressed in energy per square meter in the plane normal to the incidence line. Any deviation of the panel from the normal to the incidence angle causes a fall-off in recoverable energy which varies as the cosine of the angular deviation.
As a result, if you have a small (say 45W) array, you can go out in the morning and point it at the rising sun, then go out every 2 hours or so and manually track the sun. if the panels are fixed toa roof, then they achieve full efficieny at only one narrow time period per day. Thus, the smaller panles deliver as much usable power as a much larger (say 2X or 3X) array.
Since I was looking at this as emergency/disaster backup, the manual workload is acceptable to me.
The maths of what is going on is fascinating. if you wish, i can post them. otherwise, that is my explanation, san the normal Eccles Lecture.
Eccles – at 18:06
WOW
Definitely interested in the math if I can get 2–3X usable power. Please post.
“you can go out in the morning and point it at the rising sun, then go out every 2 hours or so and manually track the sun”
I think there are astronomical telescope mounts that rotate around an axis pointing to the north pole (or south pole for down under), some with elaborate clockwork (spring-wound or dc motor) that tracks the sun. Would that be feasible for a small panel/array? What about costs?
Any astronomer out there?
In the solar oven links, someone designed an oven that tracks the sun driven by a tiny DC motor in turn powered by a small solar panel atop the solar oven. A 45W PV array should be lighter than a solar oven with food in it.
Anon-YYZ:
I’ll be happy to work up a description of the math. What you should understand is that by 2–3X I don’t mean getting 135W from a 45W panel, but rather getting all 45W from a 45W panel instead of an effective 15–23W from it.
As for tracking the sun, my goals are modest. This isn’t like a telescope where you need arc-minute or arc-second accuracies. Since the sun moves at 15 degrees per hour across the sky, going out once every 2 hours to move the panel means that you have at most a 15 degree error. Since the COS of 15 degrees is 0.96, you maintain a better than 96 percent efficiency during the entire day.
I’ll put something together that won’t lose the bulk of the Wikians, but will teach something about why where your panel is pointed is important.
Eccles
thanks
Would love to see you post that too.
96% efficiency sounds really good. Can you also answer my questions about batteries and batteries specifically 1) just charging them from mains (see previous post) and 2) many small ones versus one big one 3) how to choose (or is there any) a inverter that can be used for small jobs and to start up something.
anon_22 - My brevity keeps getting me into deeper and deeper trouble. The 96 percent efficiency is based on the rated output of the panel which is actually based on an energy conversion efficiency of about 22%. Thus, what I was saying was that 96% of the energy which illuminates the panel would be available for conversion (at the 22% conversion efficiency).
As I said, the math can become rather involved, and I need to simplify it down so this is not a dissertation presentation. I am rather swamped for the next few days, so I can’t promise instantaneous answers, but I will present the material in an understandable manner.
As for choice of batteries. the first issue in sizing the batteries is what the load looks like. The larger the instantaneous current you will be requiring the battery to provide, the larger the battery you will want to maintain. Normally battery capacity is rated on the basis of a 20 hour discharge and a 10 hour discharge. The more slowly you discharge the battery (relative to its capacity) the more efficiently you can reclaim the stored energy. The faster you discharge the battery, the less of its stored charge you will actually be able to recover. Thus, for large jobs, bigger is better.
the question of having a bank of batteries is troublesome. the more batteries one hooks in parallel, the more likely one is to encounter the situation where one battery discharges more quickly than the others and then begins drawing current from them to feed itself and disrupts the orderly operation of the whole assemblage. in certain series-parallel configurations of multiple batteries, this can eventually reach a runaway situation and cause melt-down or explosion. So multiple battery configurations needs to approached prudently.
having a number of batteries charged from the main and ready to go is not a bad approach. i personally have 5 fully charged batteries sitting here now, should the need arise, and 3 as yet uncharged new batteries that can further be pressed into service. The question ultimately becomes the same as cans of gas (petrol). It doesn’t matter how many you have sittng in the shed all filled and ready to go, eventually the question comes up as to how you plan to refill them.
So, if you stock batteries that can support you for about 1 day each, and have several on hand, and also have a charing system that can refill them again in a day or less, then you will be able to maintain the desired level of operation. otherwise, you will eventually be overdrawn at the electron bank.
A final note in sizing batteries. Lead acid batteries react rather poorly to being completely discharged and then recharged. It really decreases the number of cycles to do that to them. So you should size your batteries such that you plan to recharge them by the time they get down to about 50% charge. You can take them deeper in an emergency, but you will need to realize that you don’t get to declare an emergency too many times before they pack it in.
http://www.uuhome.de/william.darden/
Quick and dirty explanation of batteries and some of there uses.
Eccles thanks for your prompt response and useful answer. I am not in any rush so take your time.
Any advantage of gel batteries?
Corky thanks as well. Looks like a good site. I will check it out.
(For some strange reason the comma on my keyboard is not working so my sentences are coming out weird !!)
there was this idea to use a lemon as a battery - could that work for emergency communications? third-world? brainstorming.resiliencetechnology?
shime! wrong link again - linked to fluwikie2 and it’s fluwikie.com brainstorming.resiliencetechnology
Eccles – at 00:26 “So you should size your batteries such that you plan to recharge them by the time they get down to about 50% charge.”
OK, in the abscence of an expensive “goes inta” and “comes outa” meter array, which you have previously explained is not 100% accurate, how do you know you have reached the 50% mark? I’m sure there is a nifty matematical formula for this, but some of us need something that doesn’t require a whole lot of “cipherin”, as Jethro would say.
And do I understand you correctly in that it would be best to buy batteries such that you would use one at at a time and switch to another when the charge in that one is 50% depleted?
Being the resident electro-geek is a full-time job, no?
HBB- The 50% point is a target value, not cast in stone. As long as you get to it somewhere between 25 and 50% things will be about OK. You can use the terminal voltage of the batteries as a first approximation, especially if they are under the same load all the time.
If you have several batteries that can handle a day’s wirth of load, you hook two in parallel and then use them as a single larger battery, but I would fuse the positive leads of each one individually to insure that if a runaway condition occurs, then the fuse blows and stops the havoc.
And what’s wrong with being a full time electro-geek? I’ve been one my whole life, and I can tell you, it is an exciting existance. You get fame, glory, money and lots and lots of girls.
Eccles, if I wanted to put several batteries in parallel what size fuses should I use on the positive terminal?
and…where to get the heavy guage wire to do the connections? Or can you buy it “pre-fused”?
Jeesh Bill - Do I have to tell you everything? OK. Have Uncle jed call Ms. Hathaway down to the bank to get out enough money to then go to a supplier like MCM and then order from their web site.
Without knowing what your load is, I don’t know what guage wire you need, but, for instance here is a catalog listing for #4 guage wire in bulk. Link to the wire.
There are many ways to work such a size, including soldering or crimping connections onto the ends.
Avanarts - The fuse size depends on the battery capacity and the load you expect to draw. The fuse should probably be sized to accomodate 1.25 times your peak load. But it should also be no larger than about 5 times the amp-hour capacity of the battery. but these are just rule of thumb estimates. As they say in the car ads, YOUR mileage may vary
Eccles: Thanks! Ms Hathaway is even going to use her computer-doodad to get me some of that there wire. I want to get right on this, Ellie-May is worried about how she will blow dry her llama if the power is off. It don’t make no never mind to Granny, she never would switch from usin’ her woodstove to cook on! :-)
Auto Zone has #4 gauge wire with battery connectors on both ends.
Eccles, thanks. 1.25 times the peak load should be easy to calculate.
AVanarts - Ojne modification to that would be if you are planning on a small load, then the charging current at the beginning of charging may be sufficient to blow the fuses. My advice would be to watch things during the charge cycle to make sure you don’t blow the fuses with charging current. If you do, it would necessitate going to a higher value of fuse.
Make shure you ground your system well. We grounded at the wind gen, solar panels and the batt bank. We are still going to be screwed if lightning hits the wind gen as lightning arrestors are expensive and I have yet to install one.
Jon C - lightning arresters are expensive. But solar and wind power systems are expensive. And new houses are REAL expensive.
Very true. We had lightning today and I hope I don’t have crispy preps when I get home. I will be buying one soon. Hopfully soon enough. He He (Nervously)
For lots of good DIY wind power and (not so) DIY solar power info, check out the discussion forums http://www.fieldlines.com/section/homebrew .
Eccles – at 21:25 Very very series of informative posts.- reminds me of going to Quaker Meeting years ago and a wise old woman standing up and speaking to exactly what was on my mind. It had been unexpressed on my part. Thank you for being so switched on. The whole solar panel thing is at the front of my mind- and your thoughts are most welcome!! Ta
Old thread - Closed to increase Forum speed.