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Forum Index : Electronics : Fish Out of Water
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew I'll admit; I'm a fish out of water here. I don't understand anything I know about electronics, so I just leave it alone, but I have a question that presumably belongs here: Does anyone know how to wire a switch (or switches) so I can leave several 12-volt storage batteries hooked up and switch from parallel to series without having to unbolt cables and switch stuff all over the place? Thanks. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5024 |
How many batteries do you want in series? Is it like switching a couple of batteries in parallel, giving 12 volts, to series, giving 24 volts? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
glen Kinda like that. What I want to do is charge several 12-volt batteries hooked in parallel and I'd like to then be able to merely flip a switch or two (or several!) and be able to utilize them in series for different applications. I'm probably not thinking correctly, but I was thinking that charging them in parallel, they would all accept the same (shared) amperage @ 12 - 15 volts. What I then wanted was to be able to throw the switch and have 120 volts d.c. available (10 twelve-volt batteries in series), thinking it might be easier to invert a higher voltage. Like I said, I'm a fish out of water when it comes to this electronics stuff, so if it appears I'm thinking with my butt, I likely am! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5024 |
If you can wait until I get home this evening I'll draw up a circuit, unless someone else beats me to it. But remember 120DC is just as lethal as 120AC. In fact its a lot more dangerous and you need to take special precautions. For example, a switch rated for 120v AC wont be safe at 120v DC. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Glen Okay; you don't have to twist my arm. You've just convinced me to leave it alone. I'll just use the batteries in parallel. My guess is if I use my inverter, which is rated for 12-volt d.c. it'll deliver enough amperage (like enough to run a microwave oven) without much trouble. Am I right in thinking if the amps are available, they are deliverable at 12 volts as well as 120 volts? I should probably Google "Electronics For Dummies", eh? 
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Mack The power is in watts, amps x volts = watts the advantage of higher voltage is there is less copper loss in the wires as the flow of amps is drastically reduced. eg: 12 volts x 200 amps =2400 watts high current requires large wires { very expensive| 120 volts x 20 amps =2400 watts smaller wires {less expensive} However as Glen said that DC is much more dangerous than AC at any given voltage above 36 volts as it causes the muscles to go into spasm lock up so as to speak, whereas AC makes muscles fibrillate, I think that's the word, a push pull action that tends to throw you off the power. When I was at college years ago a guy in my class died from dc shock, he used to wear a tie all the time, and the tie was one of those with metallic strips woven into it as was the fashion at the time, his tie went into the controller he was working on and it sent the muscles in his neck into spasm he died on the spot. So stick to safe voltages up to 48volts with due care and my favorite 24v as it is nearly fool proof unless you are in the bath. There is plenty of cheap inverters now for 24 volts and the wire size is a good compromise 1/4 battery cable is readily available at reasonable prices. By the way charging batteries of the same specs and age is OK in series as the amps flow evenly through both batteries because they are in series, just check the voltage of both batteries to make sure they are the same, if you have a desulphator across them it keeps the equalized much better. All the best Bob Foolin Around |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5024 |
Here's a circuit I've used before for switching two 12v batteries from parallel to series. Uses a single DPDT toggle switch, or relay. The contacts should be break before make, or you will get smoke. Most switches and relays are break before make, its only the specialty stuff thats make before break. 
Bobs advise on 24v is good. 24v might give you a tickle if you have wet fingers, but it cant hurt you, and 24v inverters are good value. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Thanks to all. I've been bitten enough by electricity to have a healthy respect for the stuff. I'm so cautious, I even retest 240-volt a.c. circuits that "I" have opened when changing out electric water heaters (I'm a plumber in real life). Even knowing things are off, i have a hard time sliding that little metal nut thingy over the bare ends of the wires when I have to change out the romex connector! When it comes to electricity, I think I'm perhaps somehow genetically related to that large, flightless bird, the chicken! I think I'll take both your advice and consider the 24-volt gig. This post goes into my "Thebackshed.com Saves" bookmark folder for sure! Thanks again. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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readyakira Senior Member  Joined: 17/07/2008 Location: United StatesPosts: 114 |
Definatly better to run lower voltage DC applications. I would rather get hit by 220ac then 60v dc Even a car battery can kill under the right circumstances. 24v inverters I would think are much much cheaper then 120vdc ones. The inverter will be close to your battery bank so wire cost should be minimal concern. As for switching 12/24v what kind of charge rate are you talking? What kind of discharge currents are you planning? A typical micro here in the states is 1000w which is 83.34amps @ 12vdc You can figure 90 with losses. that can make for a pretty hefty switch. It seems most people have talked that it is cheaper to design the whole system to one voltage then switch it around. (by one I mean one dc voltage and convert it to whatever ac you need.) I could be wrong as I am a newb to this as well. Don't you think Free/Renewable energy should be mandatory in new buildings? |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
readyakira Thanks for the advise. Just to let you know, I'm a "techno-dummy". Mechanical stuff I can do in my sleep. All the electronics and other stuff is a mystery -- on the order of smoke and mirrors as far as I'm concerned. Also, math eludes me. I keep way too much money in my checking account just so I don't have to pull my hair out trying to balance the damned thing every month; I just let it balance itself! I can add a column of figures 5 times and come up with 6 wrong answers. Math just isn't my thing. My son, on the other hand, is a PhD aeronautical Engineer, so maybe my math gene is just hidden, eh? At any rate, I'm very proficient at figuring out mechanical stuff and I can build from scratch anything I can get my mind around, so I'll stick to what I know and leave the heavy thinking to others. Excuse me for now; gotta go out and finish building my R/C Corflute-winged glider (Gordon -- eat your heart out!  ).
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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GreenD88 Senior Member Joined: 19/05/2009 Location: United StatesPosts: 104 |
lol I know what you mean, and it's the right thing to do every time because you don't know if the breaker is working right even though you switched it off. Then i usually put a twist connector covering the wires and pull each one out of the connector individually. Also nice to have a non contact Voltage sensor with you too if you have one. And always LOTO even if your the only one around could save your life if some idiot decides the breaker shouldn't be off. I havn't swapped out many electric water heaters but I have installed and worked on ALOT of Air conditioners. (LOTO = Lock out Tag Out) Licensed Master Plumber / EPA 608 Universal License / 410a Safety Certified / Medical Gas Brazer/Installer |
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| readyakira Senior Member Joined: 17/07/2008 Location: United StatesPosts: 114 |
got zapped by a 220v range once cuz the little lady living in the house noticed the breaker off and thought "this shouldn't be this way" and flipped it back on. Don't you think Free/Renewable energy should be mandatory in new buildings? |
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