inverter question

bigcountrybigcountry Registered Users Posts: 22
I have a 4X4 trailer that i built a box in i have a sunforce 60 watt backup system on it plus a 15 watt panel 2 deep cycle batteries and a cobra 2500 watt inverter I use for me and my sons RC racing habit was wondering if i could use this setup to run 49" lcd tv and blueray player when power goes out

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: inverter question

    Welcome to the forum.

    Two questions:
    1). How large are the batteries in Amp hours & Volts?
    2). How much does the TV/DVD system draw?

    You can get an answer to the second one by running it through a Kill-A-Watt meter. It will record some actual Watt hour numbers for you. Don't be surprised if it's over 200 Watts. Also don't be surprised if changing the video settings causes a significant drop. I lowered the brightness on my 40" Toshiba and reduced consumption by 100 Watts.

    Then it's simple math: for every 100 Amp hours of battery capacity (@ system Voltage of 12?) you can get about 600 Watt hours of 120 VAC, less system losses. A reasonable and "safe" (for recharging) expectation might be 400 Watt hours. Depending on the draw of the TV set-up, that could be two hours of watching time per 100 Amp hours of battery. Just about one movie's worth! :D
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    Can i get one at homedepot or lowes? If not were might i find it.
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    I have seen Kill-a-Watt meters at Home Depot before...

    There are several models out there now...

    P4200 - Kill A Watt Wireless
    P4220 - Kill A Watt Wireless Sensor
    P4330 - Kill A Watt PS-10
    P4400 - Kill A Watt
    P4460 - Kill A Watt EZ
    P4470 - Save A Watt
    P4480 - Kill A Watt GT

    Hmmm... Until I looked, I did not even know there where that many models these days. :roll:

    If you are going to be working with some smaller DC loads (no inverter), here are a couple nice DC Amp*Hour/Watt*Hour meters.

    One thing to remember is that these meters only sample current/power once every second or so--They will not measure starting surges--which for electric motors can be ~5x the running current.

    So, you may need to take starting loads/surges into account when designing the rest of the power system (wiring, inverter, battery capacity, fuses/breakers, etc.).

    Also, there is the issue of TSW vs MSW (true sine wave vs modified square/sine wave) inverters. For electronics, small wall mount transformers, small battery chargers, some motors/appliances etc.... It is a good idea to spend the extra money for a TSW inverter.

    All About Inverters
    Choosing an inverter for water pumping

    Some people address the issue by purchasing a smaller TSW inverter for the "critical loads" and a large/cheap MSW inverter for larger loads (pumps, large motors, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: inverter question
    Also don't be surprised if changing the video settings causes a significant drop. I lowered the brightness on my 40" Toshiba and reduced consumption by 100 Watts.

    I second that, I dropped my 47" TV's useage by 100 watts by lowering the brightness, too. If your viewing room is much darker at night (upstairs and not down in a basement) you can lower it even more for night viewing. For emergency use like you are describing I'd pull all the blinds and take the TV as dark as is tolerable.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: inverter question

    And I hope you have something more than a 15 watt panel to recharge those batteries, otherwise this will be a one movie wonder and that will be the end of it.
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    I have a total of 80 watts worth of panels on top of the trailer. The trailer started out as my search and rescue trailer that we use for the search and rescue team of tampa Florida that we have thru the jeep club i am in.

    This is my first attempt at solar.
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    So to be able to run my tv off an inverter power it needs to be a pure sine wave inverter?

    What percentage over should the inverter be ?

    For example if the things i want to power hit 500 Watts total at start up do i just need a 500 watt inverter or larger cause i read about the different surge ratings.
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    The short answer is we really cannot tell how your TV will run on MSW vs TSW inverters...

    Roughly, about 80% of appliances seem to work OK on MSW inverters and about 10% will die an early death of some sort.

    Small wall mount transformers, small electronics, AA/D/etc. battery chargers, some tool chargers, some motors (refrigerators, etc.) will die an early death. Some timing circuits will not keep time correctly (run 2x as fast, etc.).

    My suggestion has been to get a smaller 300-600 watt good quality TSW inverter (the MorningStar 300 watt TSW 12 vdc inverter is one of the nicest 12 volt units out there). And use a big/cheap MSW for stuff that is less critical.

    One suggestion would be to use a Kill-a-Watt meter, or equivalent, and measure the Watts and Amp (Power Factor, Volt*Amps is OK to log too--but not needed) on Grid (or TSW) power and MSW. If the Watts and Amps are relatively close in readings between the two power sources--you are probably OK running on MSW.

    If the Watts and/or Amps is 20% or greater--then you run the risk of early failure of the devices.

    Induction motors will use ~20%+ more power on MSW by the nature of the MSW waveform and how induction motors work. If the motor already runs hot/close to maximum power (some refrigerator compressors), then the extra 20% more power (that 20% is turned into all wasted heat) may be enough to push some devices over the edge.

    It is really hard to generalize--Some devices will fail soon (minutes-hours), and others may take months to eventually fail.

    In the end, 80 watts of solar panel is not going to give you very much power. Typically in good summer weather:
    • 80 watts * 5 hours of sun per day * 0.52 system eff = 208 Watt*Hours per day
    • 208 WH per day * 1/12 volts = 17.3 AH per day @ 12 volts
    A 500 watt load running from an AC inverter will last (roughly) on one day of charge:
    • 208 WH * 1/500 watts = 0.42 hours = 25 minutes per day
    To be honest, a small Honda (eu1000i or eu2000i; 900 watt or 1,600 watt) or Yamaha Inverter Generator will be a better deal for running the larger appliances.

    A gallon of gasoline will run 400-500 watt loads for ~9+ hours on the smaller gensets.

    Use the battery bank + solar for lights, water pump, radio, AA battery charger, etc... Unless you plan on using less loads or up sizing the solar array (assuming longer than 2-3 day trips).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: inverter question

    On this rare occasion I'm going to disagree with Bill about the need for pure sine wave. It is my opinion he has it backwards, as induction loads like AC motors are the things that really do not run well off MSW. Most electronics have really good power supplies that can take rather poor input power and clean it up well enough to run the equipment.

    That said, I still prefer pure sine for everything, including electronics. The prices have come down to the point where, in my opinion, MSW just doesn't make sense most of the time.

    As far as how much larger an inverter needs to be over the loads, the answer is "it depends". You should size it according to consistent loads with the capacity to handle peak loads. Don't count on surge ratings for anything, as they are short in duration and meant to compensate for the inevitable 'blips' in power consumption when things are turned on. There's quite a variety in those ratings too, both in terms of Watts and duration.

    So the first point would be that the inverter must be large enough to handle the maximum load. 500 Watts means at least a 600 Watt unit like this Exeltech: http://www.solar-electric.com/xp-600-12.html
    The second point would be the consistent loading. You obviously don't want to run any inverter at or near its peak power all the time. So if the average power is 300 Watts the 600 Watt unit is still fine. If it's closer to 450 Watts all the time you might want to "size up".
    The third point is; what can you get for the money? The 600 Watt Exeltech is $532. The 1100 Watt is $30 more. The thing to consider here is that the no load power use goes from 9 Watts to 20. So that extra 11 Watts has to be figured in to power consumption. Some other inverters will have lower stand-by consumption or "sleep mode" where they don't use much power at all while waiting for loads. This generally isn't found on smaller, inexpensive inverters.
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    Regarding Marc's comment...

    I was trying to say that a lightly loaded/low duty cycle induction motor can work "OK" on MSW. It will still waste power and get hotter vs running on a TSW inverter.

    However, it is always better to run one from a TSW inverter (if you can afford the high cost of a large TSW inverter).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: inverter question

    And we have to be fair and point out that not all MSW inverters are the same: some are barely better than square wave and some have many "steps" which are closer to sine wave. As well, different types of induction motor in different applications will work better or worse. Lots of variables.

    I just don't like MSW inverters for anything other than resistance loads. Even then ... :p

    There is also the option of using two sine wave inverters like the MS 300 if the loads can be so divided. That way one could be on all the time for lights and the other switched on as-needed to add in the TV or whatever. A sort of poor-man's stand-by mode. :roll:
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    Thanks for all the great info. I just found this site and it's been more informative in the week I've been on it then the six months I've been on another site.
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    Was also wondering how good central Florida is for solar electric at my house the son is blasting my house from 7am to 8pm every day.
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    I will suggest you start another thread for that question about Florida + AC.

    Short answers:
    1. Conservation, conservation, conservation.
    2. Check for insulation (~R40 or more for attic space, pile over A/C ducts). Double pane windows, etc.
    3. Check for proper A/C operation (not over/under charged, plugged filters, excessive oil in system, other A/C problems)
    4. Check for energy efficiency ratings for A/C system. There are some very good 26 SEER mini-split units (Fujitsu) that may be close to 2x the efficiency of the current system--Plus you can cool different rooms/zones to optimum temperature
    5. Check other appliances (fridge, computers, entertainment systems, etc.) for power usage. They can be inefficient (lots of extra power usage). Plus, that extra wasted energy needs to be moved outside by your A/C system (more costs).
    6. Measure power usage for major devices... If you don't know how much power you are using and where it is going--it is very difficult to "fix" anything.
    Solar Guppy (poster here) has a lot of experience with both solar power and Florida sun--He can give you a wealth of real-world solutions

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    What i was saying has nothing to do with air conditioning my house.

    It was geared towards will my panels do more on a production level in the state of Florida.

    Sorry if the question was portrayed wrong.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: inverter question
    bigcountry wrote: »
    What i was saying has nothing to do with air conditioning my house.

    It was geared towards will my panels do more on a production level in the state of Florida.

    Sorry if the question was portrayed wrong.

    As opposed to where?
    Lots of sun is good for production. Except that it comes with lots of heat, which is bad for production.
    In the Cariboo Winter temps are cold enough to make panels super-conduct. Unfortunately the daylight is so short you don't get much for it.
    You can't win for losing. :p

    You can use PV Watts http://www.nrel.gov/rredc/pvwatts/ to check out production potential in your area, but it doesn't have allowance for panel temperature.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: inverter question
    bigcountry wrote: »
    What i was saying has nothing to do with air conditioning my house.

    It was geared towards will my panels do more on a production level in the state of Florida.

    Sorry if the question was portrayed wrong.
    Like the man says, high altitude sun is good, heat is bad. You have both.

    Are you familiar with PVWatts?
    http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/
    http://www.nrel.gov/rredc/pvwatts/grid.html

    This program will give you a reasonable estimate of the output of a system, taking into account location, prevailing weather, and system size and orientation. Plug in a theoretical system and then move it around the country to compare how it would do in different places.
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    Solar Guppy finds that his systems produce more if they are pointed a bit East of South. The high afternoon temperatures and thunderstorms tend to reduce production later in the day (vs AM with clear skies and cool weather).

    You can play around with PV watts... It does take weather into account (not temperature). And you tend to have more sun in the winter than I do (San Francisco) and less in the summer (weather?). And it depends on your location (different weather patterns).

    You can get some idea from these various maps:

    http://www.windsun.com/Photovolaic_Systems/Solar_maps.htm

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: inverter question
    BB. wrote: »
    Solar Guppy finds that his systems produce more if they are pointed a bit East of South. -Bill

    Mine would also produce more if they were pointed a bit to the East of South. Reason being, my Eastern horizon is free of obstructions, while trees on a neighbors property block the last hour of the days sun during Spring and Fall. Winter not so much, as the sun is so far South that I'm getting 80% power within 10 minutes of the sun poking it's nose up off said horizon. And in Summer, the sun rises in the North East, behind the panels, and sets in the North West, also behind the panels.
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    Got a killawatt meter everything (50" LCD tv,cable box,blueray player, and Xbox, also home theater system ) I'm at 400 Watts with everything on.

    Side note how can i get a watt consumption on a ceiling fan and do ceiling fans need a pure sine wave. Inverter for it?
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    It is really difficult to say ABC will work and EFG will not on a MSW inverter...

    In reality, around 80% will work find, 10% will not (or actually fail), and the other 10%--who knows.

    With ceiling fans, they can have several different ways of controlling the fan's speed--Some which may work fine with MSW and others that may not.

    You can try using a Kill-a-Watt meter on a fan... Take the readings with TSW/Utility power, and take the same readings again on MSW inverter. If the current readings are about the same, then the fan will probably work OK. If the current or power(watts) is >120% greater on MSW, it may overheat and fail (this is a test I tell people to try on anything they want to connect to MSW inverters).

    Another issue with MSW is that sometimes appliances, light fixtures, etc. "buzz" on MSW power (has to do with the square wave's sharp edges).

    My suggestion, for an off-grid system that you need to be reliable (middle of no-where)--Use TSW, at least for "critical" and expensive components (laptops, cell phone chargers, A/V equipment, radios, wall transformers, etc.).

    You can get a bigger/cheaper MSW for larger equipment like hand tools (plug in saws, drills, big old pumps, etc.). Just watch the temperature of the motor and that they don't get too hot. Many times, devices that don't like MSW inverters will feel/smell hot before they fail.

    There are people here who have used MSW for years and are very happy. And there are folks here that have plugged in their Dewalt Tool battery charger and it went pop in minutes (that was a few years ago, supposedly the new chargers work on MSW now).

    If you are 1/2 way careful and diligent about conservation/power usage--You can probably work pretty well on a 300 watt or 600 watt TSW inverter (excluding refrigerator/freezer compressors and like).

    At my home that is four blocks from a Trader Joe's, Sears (large shopping mall), O'Rielly auto-parts, and a Central Computer (yea!--plus 5 minutes drive from Costco, Home Depot, and various ethnic markets)--I am perfectly OK trying MSW inverter on something... If it fails, other than cash out of pocket (or return to store)--I am not out anything much.

    If I was a 4 hour drive from the nearest point of resupply--I would only use a TSW inverter for my small loads. And I may use a MSW for corded power saws, drills, portable pump, etc.

    I am very sorry I don't have any better answers.:cry:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: inverter question
    bigcountry wrote: »
    Got a killawatt meter everything (50" LCD tv,cable box,blueray player, and Xbox, also home theater system ) I'm at 400 Watts with everything on.

    Side note how can i get a watt consumption on a ceiling fan...
    Take off the switchplate, get a clamp ammeter and measure the current in the conductor leading to the fan. P=IV. That's probably all that's going on behind the curtain in a Kill A Watt, anyway. I wish I'd thought of it.
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    The kill a watt does more than just measure current and voltage-It measures phase angles or other methods to obtain watts pf va, etc.

    How ever, it does not do a great job of estimating power, pf, etc. at $20-$30.

    But $1000-$10,000 test gear does not always agree either.

    Measuring with a current clamp/meter will give you worst case power measurements.

    For a motor multiplying by 0.67 x voltage x current will give you an ok wattage estimate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bluewickedburnerbluewickedburner Solar Expert Posts: 78 ✭✭✭✭
    Re: inverter question
    BB. wrote: »
    The kill a watt does more than just measure current and voltage-It measures phase angles or other methods to obtain watts pf va, etc.

    How ever, it does not do a great job of estimating power, pf, etc. at $20-$30.

    But $1000-$10,000 test gear does not always agree either.

    Measuring with a current clamp/meter will give you worst case power measurements.

    For a motor multiplying by 0.67 x voltage x current will give you an ok wattage estimate.

    -Bill

    I recently bought a Royobi device that is similar to the Kill-A-Watt and it calculates cost based on your current power costs. Its quite flexible and retains information so you can go from source to source, plug in your devices and get cumulative info.

    http://www.ryobitools.com/catalog/accessories/electronic_hand_tools/E49CM01
  • bigcountrybigcountry Registered Users Posts: 22
    Re: inverter question

    Thanks for all the info it is been great help.

    So what i am getting is that the safe side is to use a msw inverter on loads like lights in the house or free standing fans.

    Tsw inverters for more costly loads (tv,computer DVD players, home theater systems ) .
  • BB.BB. Super Moderators, Administrators Posts: 31,875 admin
    Re: inverter question

    Safe as in will not cause fires... Pretty much.

    Acceptable power from MSW inverter... Try it and see what happens. You may end up buying some replacement devices on occasion.

    And some CFL's appear to run OK on MSW, other CFL's are noisy or have problems starting/overheating. MSW peak voltage is ~20-30 volts less than TSW sine wave peak voltages--sometimes low "peak voltage" causes problems.

    In the end, you have a ~80% chance of being happy as long as you do not run small wall transformers and some laptop computer power cord bumps from MSW inverters.

    If you have a choice--buy "low tech" (like clothes washer with mechanical timer vs the fancy LED/LCD/Microprocessor controlled devices) when running MSW.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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