Inverters

System
System Posts: 2,511 admin
Hi, I'm new here, but have a question. And just on a side note I have been an electrician for about 25 years so I "get" most of the electrical stuff, but one thing that has been racking my brain.

Why use an inverter and not just 10 12 volt batteries wired together? 10X12volt = 120 volts right? or for 240 volt loads 20 batteries?

Batteries should be fairly easy to come by, but the other question is can I use auto batteries or marine lead acid batteries? most of them have a pretty high amp hour rating.

Just some questions that I would love to have some answers to, preferably with some sort of explanation so I can wrap this hard head around it.

THANKS!

BTW, I'm probably going to do a solar/wind combination...

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Inverters

    Welcome to the forum.

    If you're going to do a solar/wind system you'd better learn about a lot of stuff.
    First up would be the difference between Alternating Current (as used in household wiring) and Direct Current (as sourced from batteries) and how many things that will run on one won't run on the other.

    Some inverters take a 'low' DC battery Voltage ( 12, 24, or 48 Volts) and convert it into standard household 120 Volts AC (or 240 Volts). Some inverters are Grid Tie type; they take power directly from the solar panels and 'back feed' the household wiring. Some are 'hybrid' and can sell back to the grid while having battery power for emergency back-up.

    You do not want to use automotive or Marine/RV batteries for RE; they aren't up to the continual deep cycling that off-grid systems function with. There are specific deep cycle batteries for this purpose.

    Please take some time to read through the FAQ section: http://forum.solar-electric.com/forumdisplay.php?f=14
    There's tons of information and resources in there and you can probably find lots of "preliminary" answers which will lead you to ask more specific questions. :D
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Inverters

    ITfitz98 you have been an electrician for 25 years and you nave not yet discovered batteries dont come in AC.? and only in DC . ?????????/:confused:
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverters

    Technically, there are a fair number of devices that can run on 120 VDC (brushed drill motors, many power factor corrected computer power supplies, etc.).

    However, the several big issues with 120 VDC... One is that it sustains an arc very well (DC switches/relays must be built much heavier than their AC cousins).

    Also, from a shock hazard point of view--DC tends to be worse (causes a gripping action and a person is much less likely to release themselves with DC shock).

    Some of the other smaller issues--Electrolysis and corrosion from the unidirectional nature of DC. For DC distribution systems, they are positive grounded to prevent corrosion of water pipes and other metal buried in the ground.

    As near as I can tell why you do not see Solar RE with 120 VDC or higher battery banks is the issue that UL/NRTL tends to say that >60 VDC is a hazardous voltage and you need to treat is like 120/240/etc. So--that is my guess why the standard "high voltage" for DC power systems is 48 VDC (about 60 VDC when charging the battery bank).

    You will find high voltage battery UPS systems--but they seem to be, mostly, dedicated to commercially built and maintained computer rooms--not very common outside of that environment (at least from the little I have seen).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Inverters
    john p wrote: »
    ITfitz98 you have been an electrician for 25 years and you nave not yet discovered batteries dont come in AC.? and only in DC . ?????????/:confused:

    Ok, I'm a dumbass. I the whole AC/DC thing didnt even click in my little pee brain....dont know what I was thinking, but apparently it wasnt about AC versus DC.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverters
    itfitz98 wrote: »
    Ok, I'm a dumbass. I the whole AC/DC thing didnt even click in my little pee brain....dont know what I was thinking, but apparently it wasnt about AC versus DC.
    itfitz98, welcome to the form. Unfortunately a few responses you get here can be (intentionally or not) rather undiplomatic, so to get the most from the form, concentrate on the information, otherwise they'll get under your skin and drive you away like they did me. I was away for a couple of years because of it. There are some really great and helpful people here, and they make it one of the very best and most knowledgeable forms you'll find anywhere. Best of luck with your possible future projects.
  • Frxddy
    Frxddy Solar Expert Posts: 113 ✭✭✭✭
    Re: Inverters

    Wind power: I have been there, done that. I own a perfectly functioning turbine that I do not use. The reason? Not enough wind at my location. I hired a guy to do a wind study and learned a very expensive lesson, that is, a wind study can not be done from a walk around and a computer program showing average winds in your area. If you are seriously considering wind power, please listen to this one thing. The ONLY way to calculate the wind power at your location is to install a temporary tower and put a recording anemometer (wind meter) at the height of your propose tower and watch it for a year.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverters
    Frxddy wrote: »
    Wind power: I have been there, done that. I own a perfectly functioning turbine that I do not use. The reason? Not enough wind at my location. I hired a guy to do a wind study and learned a very expensive lesson, that is, a wind study can not be done from a walk around and a computer program showing average winds in your area. If you are seriously considering wind power, please listen to this one thing. The ONLY way to calculate the wind power at your location is to install a temporary tower and put a recording anemometer (wind meter) at the height of your propose tower and watch it for a year.

    Agree totally. The alternator from my former wind turbine has been in constant use for the last couple of years - - - - on my micro hydro turbine. From all the dealer for the wind turbine told me, as well as all info from the manufacturer, my wonderful wind turbine was to have supplied all my electrical needs, including even some electric heat. HA! What a pile of horse poop! Except for the visual beauty of it spinning against the sky, it was basically useless! With solar, very few indeed, are the days when I don't get at least some useable power, while with the wind turbine, very few indeed were the days when I got any useable power at all! Basically the only times it produced power was during tropical storms that came up the east coast in the fall.
  • System2
    System2 Posts: 6,290 admin
    Re: Inverters

    So where is it that you use your hydro?

    And I was thinking of a wind/solar combination to harness as much as I could. I would love to be completely off grid, but for some reason my wife seems to think thats stupid.

    So I was doing some math today and was looking at my chop saw. It has a 15 amp motor in it, which equates out to 1.8kw at 120 volt if my math is correct. So just to run that saw I would need an inverter capable of 1800 watts. I guess my question is how much wattage is needed to run a whole house of average size. and I mean everything, fridge, washer, dryer, 4 tv's, xbox, home theater system, extra freezer in the garage.

    And really people dont piss me off with their smart ass comments, I am on a boating forum where it is actually expected and if you dont there must be something wrong with you.