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#2
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I'm trying to learn about inverters, and how to put a
system together. I want to use it pretty much just for my refrigerator (about 800W), and my TV/VCR etc. It seems like it would be cheaper to get two less powerful inverters, than one powerful one. So far getting two of the 1200W for $120 each at: http://store.worldstart.com/customer...=16468&cat=307 seems like the best deal for me. That would leave me plenty of head room--especially on the TV circuit--for including other things. Does anyone know of a better deal? How do I figure what size batteries to use? Should I keep the batteries separate for each inverter, or is it better to connect two or more batteries and go from there? If so, how to connect the batteries together, and then how to go from there to the inverters? I'm lead to believe that any inverters I can afford would produce a square wave instead of a sine wave. How to know what influence that would have on my TV's performance? The TV works great using the Generac 4000W generator I'm using now. Can I expect it to be different using the inverter? Thanks for any help! |
#3
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If your refrigerator is a dual voltage, AC/DC unit you might check into running
it directly off of DC rather than inverting DC to AC. (Most of these dual voltage units only run on DC anyway........there's a transformer that converts either 12 V DC or 120 V AC to 9V DC). And your are correct. The limitation will be the size of the battery bank. Three times the amp hours the application requires is a good guideline. Double because you want to avoid discharging most batteries beyond 50% and the rest because you will recover the capacity between 50 and about 80 percent pretty quickly but getting all the way up to a full charge might take more charging time than you have available. We run a small color TV/VCR off a square wave inverter, without any significant problems. More sensitive electronics will appreciate a sine wave. |
#4
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I have a 33 ft sailboat with 2 house batteries on the usual 1-2-both
and off switch. I also have a separates strater batterie which is independent ans makes sure that I can always start the engine even if the house batteries are empty. I installed a 1500 W (2000 peak) sine wave inverter which I bought for less t6han $150. This runs the TV, VCR, Microwave, toaster, coffeemaker etc. I can only run one of these items at a time. I have had no problems with the modified sine wave But the toaster uses 1200 Watt. At 12 volts this is more than 100 amps. So I used No 2 wire to connect the inverter to the switch. I soldered the connetions to make sure. I always use both house batteries because drawing 100 Amps from one battery is very high. The 110 V side of the inverter is connected to via a selector switch to the 110V system on the boat so that all the outlets are live. The selectro switch makes sure that the 110 V system on board is fed from the inverter or the shore power, but not both. The toaster and the coffemaker only runs maybe 15 minutes per breakfast. So the usage is only 100*15/60=25 amp hours. My batteries are 100 amp hours each so this is no problem. I have 3 ways to recharge the batteries. One is by solar panel. When I leave the boat after a weekend the solar panel will recharge the batteries during the time I am away. This is what usually happens.The second is when I run under engine, then I have a switch which parallels the house battery to the starter battery so that the alternator recharges both the strater battery and the house batteries. The third is with a battery charger from shore power. With this system I have lots of power for everything, but of course I cannot have a hair dryer, fridge or heater except when I am on shore power. |
#5
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wrote in :
I'm trying to learn about inverters, and how to put a system together. I want to use it pretty much just for my refrigerator (about 800W), and my TV/VCR etc. It seems like it would be cheaper to get two less powerful inverters, than one powerful one. So far getting two of the 1200W for $120 each at: Ahhh...one of my favorite subjects.... Powerful inverters are now dirt cheap to produce with great profit margins, especially in marine stores where they command amazing prices.....but, alas, read on. http://store.worldstart.com/customer...=16468&cat=307 seems like the best deal for me. That would leave me plenty of head room--especially on the TV circuit--for including other things. Does anyone know of a better deal? Oh, no problem at all getting the OUTPUT POWER to run just about any 115VAC product you can buy. POWERFUL INVERTERS are real cheap with the digital switching technology of today.....but, alas, read on. How do I figure what size batteries to use? Should I keep the batteries separate for each inverter, or is it better to connect two or more batteries and go from there? If so, how to connect the batteries together, and then how to go from there to the inverters? Oh, oh. The slick salesman in the yacht club shirt, tan yachtie shorts and expensive deck shoes didn't talk to you about BATTERIES actually powering it, did they? NOT. Let's use your load specs and have a look..... Power isn't produced by inverters...it's converted at a small cost of efficiency...over 90% in today's technology. Let's look at 800 watts, you example, at the top. Discount the fridge doesn't run 24/7 while we look. How long it runs depends on how often you open the door and how hot it is in the boat. Volts X Amps = Watts, so Amps = Watts/Volts...whether it's at 115VAC or 12VDC. The important part is the 12V side. 800 watts divided by 12V = over 66A, about what the boat's starter draws after the engine starts cranking over. There's the problem.....How long can we crank a starter before the battery goes dead? Days?...no. Hours?....no. Minutes?...we getting warmer. Seconds?...ah, there it is. It's about ampere-hours, and how batteries are rated..... First, put starting batteries out of your mind. Starting batteries will produce a LOT of current for a few SECONDS, then they are dead....as any boater already knows...(c; Let's look at some common deep cycle batteries made for this kind of service. A common deep cycle battery, the size of a large car battery, is rated at 130 AH (ampere-hours), usually at a 20 hour rate (we take 20 hours to discharge it). In reality, if you drain the battery over 50% of that, the battery will soon be useless, so you have 65AH of "power" available. Geez, that battery will only produce 66 amps for ONE HOUR?!! Well, no, it will only produce 66A for a lot LESS than one hour because we didn't discharge it over a 20 hour period, giving the chemical reaction time to eat away at the lead plates in an orderly fashion. No, as you can see, this isn't going to work, no matter how we're wishing it. We need 66A of 12V power for a couple of days, not an hour! 66A x 48 hours = 3,168 ampere-hours! WOW! The biggest 6V golf cart battery, the big tall one they want $179 for, is only 700AH and we need TWO of them in series to get 12V! 3,168 AH is gonna take BANKS of these monsters to get 800 watts for TWO days! That guy in the Sperry Docksiders never said anything about this problem, eh? Back in the days of the diesel submarine, the battery banks were made of 2 volt, lead-acid cells that were 6,280 AH capacity, which we could draw 3,168 AH out of without destroying them, easy! Each CELL was about 4' wide, 7' high and 3' deep. We'll need 6 of them to get 12V. Where we gonna put 'em? Can we FLOAT 'EM?!! Each cell weighed about a ton or so....(sigh) Oh, oh. Now we're gonna have to RECHARGE THEM!..... Whatever battery bank you use, it must be RECHARGED, FREQUENTLY if it is to survive for any length of time. Batteries are NOT instant-charging capacitors. The chemical reaction takes LONGER to recharge one AH than it did to discharge them. You're also limited by the size of your ALTERNATOR's output capacity to produce amps....lots of amps. So, if you're a power boater running the engine all day, this is no problem. The engine's running, anyways. Ragbaggers take a dim view of running the engine to recharge big battery banks. My captain is one of them. He thinks a battery should recharge in 20 minutes....(c; To put 3000 AH back INTO the battery banks, we're going to have to put in MORE than 3000 AH because lead acid batteries are AWFUL inefficient places to store electrons....slowly. I'm lead to believe that any inverters I can afford would produce a square wave instead of a sine wave. How to know what influence that would have on my TV's performance? The TV works great using the Generac 4000W generator I'm using now. Can I expect it to be different using the inverter? No longer true. You can buy a 4KW synthesized sinewave inverter for under $1000, easy. I paid $109 for a 500W Tripplite. Sinewave inverter power is CHEAP and EASY to build with our computer technology. All we need now is a 5000 AH battery the size of a starting battery that can produce 500 AMPS for 10 hours without being destroyed in the process. It's why there are NO BATTERY POWERED CARS on your street charging in 2 hours from the plug in the garage. It's just not practical at this time because of the battery power problem..... The power stored in a 10 gallon diesel or gas tank to run the Generac would be the size of your garage stored in lead-acid batteries and weigh 20 tons.....Genset is still the answer.... Larry NOTHING is funnier than a boater with a new 4KW inverter carrying his electric heater down the dock with a big smile on his face....(c; |
#6
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The best answer for a fridge is propane but that can be troublesome on a boat I
guess. I have one for the house, in case of emergency and I got it from a guy who had it on a boat. |
#7
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Larry's discussion has some very good information. I have a couple of
questions: 1) Why are you running refrigeration through an inverter? 2) Why, with the choices available today, are you running a TV through an inverter? I have a (one) 1,000 watt inverter for my 110 volt stuff, and just about the only thing I run is the microwave oven. Marine refrigeration is either dual power (110/12) or cold plate (engine driven), lcd tvs are 12 volt (4 amp draw) If you are running 110 volt appliances you are not being very efficient. Opinions, please. Jim wrote: I'm trying to learn about inverters, and how to put a system together. I want to use it pretty much just for my refrigerator (about 800W), and my TV/VCR etc. It seems like it would be cheaper to get two less powerful inverters, than one powerful one. So far getting two of the 1200W for $120 each at: http://store.worldstart.com/customer...=16468&cat=307 seems like the best deal for me. That would leave me plenty of head room--especially on the TV circuit--for including other things. Does anyone know of a better deal? How do I figure what size batteries to use? Should I keep the batteries separate for each inverter, or is it better to connect two or more batteries and go from there? If so, how to connect the batteries together, and then how to go from there to the inverters? I'm lead to believe that any inverters I can afford would produce a square wave instead of a sine wave. How to know what influence that would have on my TV's performance? The TV works great using the Generac 4000W generator I'm using now. Can I expect it to be different using the inverter? Thanks for any help! |
#8
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A toaster and a coffee maker? Off an inverter? WHY WOULD YOU DO THAT????
There are things that the stove does very well, and uses no electricity. I don't care if it works, it's... not efficient use of your batteries. Rolf wrote: I have a 33 ft sailboat with 2 house batteries on the usual 1-2-both and off switch. I also have a separates strater batterie which is independent ans makes sure that I can always start the engine even if the house batteries are empty. I installed a 1500 W (2000 peak) sine wave inverter which I bought for less t6han $150. This runs the TV, VCR, Microwave, toaster, coffeemaker etc. I can only run one of these items at a time. I have had no problems with the modified sine wave But the toaster uses 1200 Watt. At 12 volts this is more than 100 amps. So I used No 2 wire to connect the inverter to the switch. I soldered the connetions to make sure. I always use both house batteries because drawing 100 Amps from one battery is very high. The 110 V side of the inverter is connected to via a selector switch to the 110V system on the boat so that all the outlets are live. The selectro switch makes sure that the 110 V system on board is fed from the inverter or the shore power, but not both. The toaster and the coffemaker only runs maybe 15 minutes per breakfast. So the usage is only 100*15/60=25 amp hours. My batteries are 100 amp hours each so this is no problem. I have 3 ways to recharge the batteries. One is by solar panel. When I leave the boat after a weekend the solar panel will recharge the batteries during the time I am away. This is what usually happens.The second is when I run under engine, then I have a switch which parallels the house battery to the starter battery so that the alternator recharges both the strater battery and the house batteries. The third is with a battery charger from shore power. With this system I have lots of power for everything, but of course I cannot have a hair dryer, fridge or heater except when I am on shore power. |
#9
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The best answer for a fridge is propane but that can be troublesome on a boat
I guess. Propane refrigerators are no longer offered for marine use. You may still be able to buy one for an RV. |
#10
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because he's a power boater and don't know these things
On Mon, 05 Jul 2004 20:20:43 GMT, Jim wrote: Larry's discussion has some very good information. I have a couple of questions: 1) Why are you running refrigeration through an inverter? 2) Why, with the choices available today, are you running a TV through an inverter? I have a (one) 1,000 watt inverter for my 110 volt stuff, and just about the only thing I run is the microwave oven. Marine refrigeration is either dual power (110/12) or cold plate (engine driven), lcd tvs are 12 volt (4 amp draw) If you are running 110 volt appliances you are not being very efficient. Opinions, please. Jim wrote: I'm trying to learn about inverters, and how to put a system together. I want to use it pretty much just for my refrigerator (about 800W), and my TV/VCR etc. It seems like it would be cheaper to get two less powerful inverters, than one powerful one. So far getting two of the 1200W for $120 each at: http://store.worldstart.com/customer...=16468&cat=307 seems like the best deal for me. That would leave me plenty of head room--especially on the TV circuit--for including other things. Does anyone know of a better deal? How do I figure what size batteries to use? Should I keep the batteries separate for each inverter, or is it better to connect two or more batteries and go from there? If so, how to connect the batteries together, and then how to go from there to the inverters? I'm lead to believe that any inverters I can afford would produce a square wave instead of a sine wave. How to know what influence that would have on my TV's performance? The TV works great using the Generac 4000W generator I'm using now. Can I expect it to be different using the inverter? Thanks for any help! |
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