# KWH, 12v batteries and a dull evening...

Discussion in 'Homesteading Questions' started by comfortablynumb, Oct 7, 2006.

1. ### comfortablynumbWell-Known Member

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All my work is done for the day, I made \$200 and scored a free rototiller to rehab and resell later. So I have earned my bread for a few days. Then something horrible happened... I started to think.... and scribble and play with a calculator. :help:

I have been rethinking the electric usage thing, because I was charging up a car battery and got to wondering how much 12v light I could string the house with, run the light circuit on 12v car batteries and keep them charged with cheap \$20 solar car battery chargers. I figured, one battery, one charger, and this would light a string of nice bright parking light type bulbs for a good long while a day, I figured about 6 hrs a day. I wont bore you with that math but I was surprised, that a good sized common car battery will indeed keep a half dozen really bright 12v bulbs lit for 6 hrs before they begin to dim. Halfway good sunshine would recharge the batteries, and presto free evening light for a small investment. I may still do it just for those blackouts or tight months where a spare 5 dollars would make a difference. For now its not worth my investing the cash in itâ¦ but I think I may make ONE circuit and one charger, just to test the working theory. Then I got to thinking, a trickle charger actually puts out more and more reliable steady charge than a cheap solar battery charger panelâ¦ I wondered what does a trickle charger use? So I plugged it into a kill-o-watt meterâ¦ 22 watts draw. Skip the math, thatâs only 5 cents to charge the battery for 24 hours. In fact, one could leave a maintainer charger, running on 22 watts, 24/7, in the circuit, and it would only cost a nickel a day for a long string of maybe 5 lights. If you can cope with dimly lit rooms, its brighter than an oil lamp. Thatâs only \$1.50 cents a month, per battery, to keep topped off, maybe less if you donât use the lights that often.

A cheap solar charger is \$30, thatâs 20 months of charging on the grid! The more I think about it the more it sounds like a good idea..
Lets assume, in my caseâ¦ I need about 20 little 12v bulbs (bright ones, like a back up light) to supply all my dark spots with a happy pool of light. If each room has a switch to turn on and off, I think I can make due with 2 large batteries. (big truck batteries) now to keep a 22 watt maintainer running on each thatâs \$3 a month. This will keep me lit up for about 6 hrs every night. If they shut off my power, at least I can have light! And when I drive somewhere, put the battery in the bed of the truck hooked to a splitter and charge it for free while I run around, worst case scenario. At best, I am going to pay the power plant \$3 to light my whole house, each month.
Its an interesting theory.
This leaves me with no hot water, or Tv, or computer. BUT lets think, we can skin that cat two ways; buy a 750 watt inverter at wal mart (about 30 bucks) and bada bing, I can recharge my laptop, my cell phone, and since my Tv and sat receiver takes only 100 watts, even watch a little tv every eve. Hot water, well I got a gas stoveâ¦. Or the wood stove. Iâm not that desperate yet or that gung ho, but itâs a good thing to have already thought over.
So for \$3 to \$5 a month, I could recharge my battery bank, have tv, light and a computer. If I am willing to watch a 4â tv screen, I have a really nice color TV for camping that runs on12v.
But I did more figuring and until I get this theory in practice, I had to figure again, the cost of a KWH. They raised mine a whole penny! Now I have to pay total cost, aa whole 7.5 cents a kilowatt hour. What can you do for a measly 7.5 cents? I was surprised actually. Using the trusty kill-o-watt meter, I checked all my stuff, and did some figuresâ¦ based on my cost of power.
A shop light fixture on the bulbs says it uses 40wx2= 80 watts, but the meter sez it draws 60 watts. So based on a 60 watt figure I got some interesting numbers to cope with. Skipping the math you can do yourself, you can run a 60 watt shop light for Â½ of a penny an hour, or .11 cents for a 24hr day. You have to admit, this is cheap, considering you could use oil lamps or 12v car batteries. So for about 3 cents, you can run a shop light (60 watts of florescent light) for 8 hours, the same as it costs to pay to charge one battery for 24 hours. I have 7 shop lights total, I use them less than 6 hr a day (night, actually) so my power use, for a whole house full of light comes to a whopping \$5.50 a month. For a 6 hr eve of nice bright light, I think thatâs a bargain. Looking back at the math, it will take \$3 to \$5 a month to maintain a 12v battery system, plugged into the grid, just to keep the same areas lit. assuming you have no solar panels, the battery idea has only one real upside; youll have light and useable 110 power with an inverter, when the power goes off. Use a big deep cycle battery, and a 220v inverter you can pump your well water for a short burst a day, maybe get 30 or so gal before the power drops and the deep cycle needs recharged. For the cost of the inverter, and the big deep cycle battery, this is a great idea to set up on your well system; power blacks out, unplug the well and plug it into the 220 inverterâ¦. Same AC power, the well wont know the differenceâ¦ for a limited time, till your battery weakens. At least, you have way to get water out of the well. Invest in a solar panel and a controller box, and bada bing, charge it the next sunny day.

Just for kicks to occupy my head, I figured out that at my present power cost, one watt hour (one watt consumed for one hour) costs .00008 cents. So a 60 watt bulb costs Â½ a penny to run for one hour. A 40 watt bulb costs 1/3 of a penny for one hours light.

Broken down, its actually quite a bargain.
Until you start to use it for heat. I can heat a 12x24 room with a 1000 watt baseboard heater, and keep it about 60 degreesâ¦ a livable temperature. This works out to \$1.80 a day, or \$54 a month. WOW thatâs a lot. But \$54 will buy 21 gal of kerosene, at a gal a day in that same room I will be cold for 10 days out of a month. So by the numbers, the baseboard, compared to the kerosun heater, is a deal. Kerosun heater = 2.50 a day, 1000 watts of baseboard heat, \$1.80 a day. For the cost of the kerosene I could run two 1000 watt heatersâ¦. And have change left over.
But I burn wood so the heating is an emergency backup if I run out of wood. No worries there. Good numbers to know.
The power hog in the house is the hot water tank. The fridge only consumes \$4.00 of power a month. On paper, my Tv and sat uses 100 watts, if I left it on 12 hrs a day (yeah right) thatâs about \$4.50 a month. This new laptop uses significantly less power than the tower/monitor setup, drawing over 600 watts. Plugged into the power pack, the laptop uses only 65 wattsâ¦ and actually is a lot more powerful than my old 600 watt system was. The dryer uses only \$3 a month (Iâm single, based on 1 load a week). The washing machine with cold water uses .20 a load, with the water pump running to fill it lets say .25 cents a load. Thatâs a dollar a month. I figured out that the power it uses for one load, a deep cycle battery would run about one large load before it was spent. So if a small solar panel had a week to charge it upâ¦. You could, in theory, wash one load of clothes off grid, per week with a deep cycle battery and an inverter. Not a trolling motor battery, you need a big fork lift battery. The last for about 5 yrs, normal use. Depending on the draw, a smaller deep cycle might do the job, actually, depending on the amp hour ratingâ¦. Or you could chain more than one together to up the capacity.

2. ### comfortablynumbWell-Known Member

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If you look at it right, the grid power is actually pretty cheap for the luxury it provides. If you have the money, you get a lot of use for the cost. I think paired with a 12v circuit to run lights and the lighter draw stuff, making use of the tons of 12v appliances available for RVs and camping, it can be reduced quite a bit. The problem, having the cash to buy some deep cycle batteries, a few solar rechargers, and putting in the additional house wires to run the 12v leg. A wal mart 800 watt inverter is \$60, a deep cycle batteryâ¦. I have no clue what they cost. For a string of 12v lights a regular car battery would do fine if it is kept charged and not drained past 50% before you recharge it. The last deep cycle battery I got for my boat was cheap, like 39 bucks. The difference in a deep cycle and a reg car battery is the car battery will break down and die if drained and recharged over and over, a deep cycle wont. And a deep cycle usually has better amp hour ratings than a car battery.
Using the junk I have around here, I have a good start on rigging up a 12v system of lighting, to just about everywhere. I was searching online for various plans and ways to install a 12v solar/battery system, they all work on the idea one battery bank to run everything. To do that you need the batteries to be all the same, or it ruins the bank. My question is why not have one battery run one circuit? and have several circuits to run the house? One battery to run say, 2 rooms of lights. I only actually use 3 rooms regularly, and they are not very big nor do I need âbright lightsâ to work in them, and if I need it, there is 110v house lights to flip on when needed. So really, I could get away with 3 batteries, or 3 circuits of lights. All my rooms, and my barn lit up via battery power. So I will need to juice up 3 separate batteries, so what? When they start to fade, a 24 hr trickle charge and we are good to go. A battery maintainer on each one wont use a continuous 22 watts, which is even better.

I donât know if the bother is worth it, if I can run a shop light for 8 hours for a whole 3 or 4 cents.

The hot water heater is my largest power use, as far as I can figure, at @ 35 to 40 bucks a month. I might have to learn to do without hot water, and turn it on for one day a weekâ¦ that should use about \$1.50 a day, or \$6 a month.

Iâll have to try it out. I think I did once and forgot to write down how it went. Argh!

My power bill this month was \$54, no hot water on demand would lower that to \$15 or \$20â¦. In theory.

3. ### MELOCMaster Of My Domain

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there are lots of ways to heat water for cheap. if you burn wood, you have stovepipe you can run some copper tubing around. you could reclaim the cost of a few roles of tubing and a fitting to replace the valve for the bottom of the water heater with one winter's hot water heater electricity expense. thermosyphon is where it's at. hook the copper to the top of the water heater supply with a check valve on the cold supply and return the water to the heat coil on the stove pipe via the drain valve on the bottom. you may actually have more hot water than you can use. if so, install more coil as a radiator if sorts to shed heat on the way to the water heater.

in the warmer months you can build a big compost pile and have a coil of black plastic tubing in the middle of it thermosyphoning hot water to the water heater. i have links from mother earth news dealing with that.

i shy away from the outdoor solar hot water panels for fear of the system freezing at night.

this thermosyphon thing...i had an idea as i was reading your post. if you have a check valve on the well, i wonder if it is possible to thermosyphon water from the well into a holding tank via a hotwater solar panel?

4. ### hollymWell-Known Member

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Mother Earth News had directions one time for making a wood fired hot water heater using the tank from a regular one. It looked fairly simple.

Or you could get a couple of canning kettles and heat as needed. We've done that even after we got the 'lectric' a few times when I didn't get around to fixing the hot water heater right away. It's less of a pain than you think if you have running water.

Your idea sounds great! When I lived in Montana they had marine batteries at WalMart. We only had a few lights hooked up, but used to swap regular car batteries in and out of the car to keep them charged as a back up to our one marine. Solar of course is a better idea, but I'm not sure if they had trickle chargers back then? Or else I just didn't know about them.

hollym

5. ### comfortablynumbWell-Known Member

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a small solar panel is a trickle charger.

I am wondering if an on demand propane warer heater would be more econonmical in the long run.

anyone have one? how much water can one pound of propane heat on demand?

I might be able to score one of those on the cheap.

6. ### wyld thangGod Smacked Jesus FreakSupporter

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in our trailer we have two 6 volt batteries hooked together (to make 12 volts--sorry I'm not technical), they last longer than one 12 volt(almost twice as long). How would that figure into your calcs?

7. ### comfortablynumbWell-Known Member

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8. ### GrandmotherbearWell-Known MemberSupporter

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I am really interested in that 4 inch 12v camping TV...

9. ### comfortablynumbWell-Known Member

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mine?
someone gave that to me, and its the BEST picture on a tv i have ever seen. its unbelievable.
and its OLD. it has to be nearly 15 yrs old... or more.

it uses 12v from the car, 110v in the house or 8 D batteries.

a cool freebie.

10. ### mightyboobooWell-Known Member

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Cheap too,a couple years ago we got em for the kids for 39.99

BooBoo

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12. ### Judy in INWell-Known MemberSupporter

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CN,

When I first moved into my new place, I just flipped the breaker for the hot water heater a half hour before I wanted to take a shower. My light bill ran about \$20-\$24 dollars a month.

When DD moved in, I had to leave the hot water heater on all the time, because she uses the whole tank for her showers. Plus, she runs a fan 24/7 in her room. My bill shot up to \$84 the first month she was here, with a high of \$97 2 months ago.

I installed the Gray Box last month. It costs about \$30, and is just a timer you can set for your hot water heater. They carry them at Lowe's. It dropped my light bill by \$30, even with DD's habits. I have it set to come on for an hour twice a day. It makes a difference!

13. ### OzarkguyWell-Known Member

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Lots of good ideas here. Reminded me of THIS.

I totally agree with "If you look at it right, the grid power is actually pretty cheap for the luxury it provides". Just don't like to HAVE to use it. Even hooked up to grid, there's always a thought of disasters or power outages and the like.

Even this year with all the storms and some folks without power for a month. Sheesh.... at least a little t.v. and some lights would keep you in SOME degree of comfort.

Just F.Y.I. folks. I was in Home Depot last week and the LAST two generators in the store were being banded to a pallet for shipping. The guy wouldn't tell me where or why, but it reminded me "when you need it, there won't be any". Best prepare AHEAD of time.

gotta love those hills.....

Ozarkguy

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