Better small TSW inverter for continuous operation?

RandomJoe
RandomJoe Solar Expert Posts: 472 ✭✭✭
I am considering adding my new computer (15" Macbook Pro with 24" Cinema display - sweet! 8) ) to my solar system. I was amazed just how low-power the whole setup is, and have plenty of capacity for it. The display has a built-in power adapter for the laptop, so I need to feed the display with 120V.

With that in mind, are there any caveats to running one of the smaller inverters (150 to 300W max) 24/7? I would probably turn it off when I'm not using the computer, but it would definitely see a LOT of continuous runtime. I will be getting a pure-sine, I have a couple Samlex units now which have done just fine but of course I don't use them constantly.

Reading the FAQ from NAWS, they list by "quality" several manufacturers with Exeltech on top, and Samlex on the bottom so...? Is there a substantial difference in going with the Exeltech for this application, or would the Samlex be sufficient? Any opinions on the other brands?

Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    I have a morningstar suresine 300 that has been going 24/7 for nearly three years. I do turn it off when I leave home for more than a day or so, but other than that, I don't even bother to switch it off from sleep mode as it draws so little power. Some times I wonder if it is good for it to pulse on and off while searching, over night every night, but like I said, it has worked just fine.

    T
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Better small TSW inverter for continuous operation?

    That's a good point, I hadn't thought about one with sleep mode. The smaller Samlex ones don't have that feature - just an on/off switch on the front. Didn't think anything that small would have sleep, I'll have to check for that as well.

    Plugged the setup into the KaW again, to verify I remembered the numbers right, and yep - even adding the desk lamps (CFL) would hardly tax a 150W inverter! :p With the battery charged, laptop running and both screens (15" laptop and 24" monitor) going the total draw is 52W / 54VA! Wow! This has a Core 2 Duo processor, and in comparison my desktop C2D system I put together a few years ago with roughly the same screen space (but in three "square" monitors instead of two "cinema" ones) tops the scale at 300W idle!

    Just the laptop alone is a miserly 20W, but the power factor goes to pieces - 52VA! Still, won't complain too much there. The "carputer" Atom-based (slow!) system I have on my battery bank now pulls 25W without any screen!

    Charging a 50% discharged battery adds about 50-60W to the total, so even then I think I'll top out around 100-120W. Okay, perhaps a 300W inverter for "breathing room"! ;)
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Better small TSW inverter for continuous operation?
    RandomJoe wrote: »
    Okay, perhaps a 300W inverter for "breathing room"! ;)

    There's even more breathing room than that, since the SureSine is rated at 300w continuous, and 600w surge.
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Better small TSW inverter for continuous operation?

    I was about to make a comment about the relative uselessness of surge ratings, but had the Morningstar manual onscreen too and checked the specs - wow! 15 *minutes* at 600W! That's sweet. Yet another major difference from the Samlex units, which are double-rated for only a few cycles - not too useful!

    I think that Morningstar is definitely going to be a good choice. I'm already getting some wild ideas... Like, if I used the laptop portable and ran the battery down, rather than recharge off the battery bank put a relay on the remote enable of the inverter and switch on when the charge controller goes to absorb or float! :D

    Ah, new toys... Such fun! :cool:
  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    Re: Better small TSW inverter for continuous operation?

    Ran a 600 watt 24/7 for 1 year. Now have a 1100 watt that also runs 24/7. If you do run a inverter with a fan. Check it every 6 months. The fan on the 600 watt failed. I found was not working during my monthly check.

    OT: Also just got a 24" LED display with a 13" Macbook Pro. Sad part is paid less for this setup than I did for my 15" Macbook Pro two years ago.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    We run the whole house off the Suresine including a Mac book and a Mac book pro 15". If we are having good weather, we just run them plugged in, and then let them sleep. If we work at night we work off the internal battery, and then charge when the house battery begins to amp down after lunch. From a dead battery, with the display on energy saving mode, I think the Mac book draws ~50 watts.

    The suresine also has no fan, and is one of if not the most efficient small inverters. My only complaint is that it induces some small RF noise on the AM band, but since I don't really ever listen to AM it doesn't bother me.

    Good luck,

    Tony
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Better small TSW inverter for continuous operation?
    icarus wrote: »
    My only complaint is that it induces some small RF noise on the AM band, but since I don't really ever listen to AM it doesn't bother me.

    Hm. Wonder how bad that is... I'm a ham radio operator, and already get enough noise off the FM-80 charge controller! Don't need to add any more. I haven't noticed any with the Samlex units yet, but then I haven't really looked either...

    Always something!

    Is this noise that you can hear from anywhere in the house, or just if the radio is near the inverter?
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?
    RandomJoe wrote: »
    Hm. Wonder how bad that is... I'm a ham radio operator, and already get enough noise off the FM-80 charge controller! Don't need to add any more. I haven't noticed any with the Samlex units yet, but then I haven't really looked either...

    Always something!

    Is this noise that you can hear from anywhere in the house, or just if the radio is near the inverter?


    BTW, if you want to go HF mobile, don't jump for a hybrid vehicle or even just electric... They are notorious for EMI and hard to clean up... But, evidently fixable with a LOT of work. I'm enjoying HF lately but ONLY in the mobile at the moment. (Not because of any inverter or charge controller though)

    boB
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    The reality is that the CFLs make way more noise than the inverter. Bill wrote a piece a long time ago about how to kill the interference. Mine is much better now that we are in the new house. Like I said, I don't listen to AM broadcast band any way.

    Tony

    Ps the old "house" was ~ 300 sq ft, with everything in one room. The inverter was ~15' from the radio. The new one is ~ 600 sq ft, and the inverter is~ 25' from the radio. I just went over and tested it. It is a 60 hrz buzz that gets deeper the lower in the band you go, crisper the higher you go. It is an automotive type radio with both a tall omni directional vertical antenna as well as a directional Yagi on an A/B switch. It buzzes just the same on either antenna. (The radio is 12vdc, and its's wiring shares some wiring paths as the 120 vac, a no-no as far as radio noise is concerned so I am told.

    T
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Better small TSW inverter for continuous operation?

    If CFLs are noisier than it is, I doubt I'll have a problem! I do have some very noisy (old) fluorescent strips in the kitchen, but all my CFLs (nothing special - Commercial Electric and nVision from Home Depot) don't bother me on HF.

    I'll find out soon enough anyway - went ahead and ordered the Suresine. I finally remembered to dig the Samlex 300W inverter out of the work truck, so am currently running off that. I ought to fire up the HF rig and see if I hear this one just to know...

    With the DC meter on the input to the inverter, I have found with just the laptop on (where I had the lousy power factor) the DC in is incredibly "spiky". Constantly bouncing all over from 1.8A to 4A. Add the separate screen in, and the input current settles out significantly, only fluctuates about 100 mA.
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: Better small TSW inverter for continuous operation?

    Did I read somewhere that you should wind the two input inverter wires around each other to decrease noise? Or am I remembering something else all together?

    Tim
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    I believe that was one suggestion I got from Bill or Neil. I tried it, and it didn't seem to help. I also cased the inverter in foil, and that didn't help either. Then I cased it in copper screen, that didn't do much either.

    As I said, I just don't listen to AM.

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    do understand that the suggestions made by me or anybody else to combat the interference that i or the suggestions are not the problem. the problem is the devices are not being engineered to not radiate interfering components. the art of reducing interference can stump even the best of the experts at times and some times only a small reduction is possible after all efforts are done that the average guy without equipment to measure it would not see as the interference, still being there, is all they know.
    twisting the wires can help in preventing long wave resonances from occurring, but there aren't any guarantees on elimination of interferences. bad connections and corrosion can amplify interference to wild proportions too, but the source of the problem is the products themselves.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Better small TSW inverter for continuous operation?

    But--yes, twisting wires is one method used to help to prevent broadcasting noise (and prevent picking up interference too)...

    Basically, it is the opposite of a "loop antenna"... Instead of a Loop of Wire which makes a nice directional antenna, the twisted wire keeps the "differential" magnetic energy in the wires (if you look at a Cat 5 Ethernet cable, you will see that the pairs of wires are twisted every 1 inch or so--keeps the high frequencies "in the cable" instead of broad casting).

    However, what Niel said is true too--If the company that makes the product does not work hard at preventing electromagnetic interference, it is very difficult to do anything on the outside of the box to minimize the interference generated...

    For example, twisting wire will reduce "balanced" currents from broadcasting (i.e., for every impulse going out the + wire, there is an equal and opposite impulse coming back on the - wire). This reduces differential noise.

    However, there is also common mode noise... Basically, the signal is between ground and the wire (or bundle of wires) going out--this is just like a radio transmitter. All of the current is going out all the wires at the same time (like all + wires in the previous example). And a separate current is in the "ground" plane (metal frame of car, in the earth itself, etc.)... "Twisting" all of the "+" wires together does not change a thing--because the same current is going the same direction in all of the wires (no canceling current in the "-" direction--that is taking a different path).

    Also, interference is very frequency specific... AM noise (like Tony talked about) is "low frequency" (from an FCC Class A/B point of view) is below ~30 MHz... That is hard to kill.

    Then there is the range of ~30 MHz to 200 MHz--for computers, most of that energy comes out the cables (common mode and differential mode noise). Cable routing, ferrite beads, etc. can help here.

    Above ~200 MHz, it is typically the "slots" in the chassis where the emissions come from. Metal Clips, screws, and even copper tape (for testing) will kill this noise. Basically, it is 1/4 wave length "slot antenna" we are usually trying to kill. And up to 1 GHz, the slots cannot be more than ~1" in length before they start to cause problems (at the higher frequencies).

    -Bill

    PS: Typically, it is very difficult to kill "AM Radio" noise--but it usually does not travel far... Moving the source of the noise or the antenna of the receiver 10-20 feet (plus or minus) apart is enough to reduce the noise (unless you are in an area far from AM stations)... Using directional antenna may help (point away from your noise source and towards the station).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    Niel,

    I wasn't meaning to imply that your (or Bill's) advice was not good, but rather like so many things, the solutions are not always easy as you both suggest.

    In my case, I can't move the inverter farther from the radio,, in ~500 sq ft.

    T
  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    sorry to be slightly OT but what you guys are talking about triggers a long time question i have (non solar related).

    in my study i have a computer w/ speakers. no other electronics for many many dozen feet. but i live in a townhouse and the study is next to the neighbor's shared wall - dont know what he has on his side

    all i know is many times, when my computer is on, my speakers would have noise - its picking up radio or tv (i cant tell which) very clearly but faintly. what is that a result of? more importantly where is it coming from and how do *I* fix the problem w/out disturbing my neighbor.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    mshen11,
    that sounds like radio frequency interference from a transmitter, but i can't be sure without hearing it for myself. make very sure the wires are clean and well connected and even move the wires around a bit to see if it lessens the interference. does it increase when you touch the wires or connection points for the speakers? if you have excess wire try coiling it at the speaker end of things. adding inductance with ferrites at that same point may help too.
    http://store.solar-electric.com/nosufefi.html
    if it's already coiled then try straightening it to see if the interference lessens thus changing its resonant point. adding a .001uf ceramic cap across each of the audio leads and to ground from each lead may help too. (note here that high power amps may need higher voltage caps) you just have to play around with it, but some speakers tend to be more prone than others and may not ever stop being interfered with.
    also note that some stereos are junk and it's getting in through the stereo. if it gets louder by turning up the volume then get rid of the stereo imho.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Better small TSW inverter for continuous operation?

    Amplified speakers by any chance?
  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    they are cheap computer speakers - about 10 years old... $30 or $50 when bought new.

    not sure what you mean by "wires are clean". theres no damage to it. in the 10 years only when i moved to this place 2 years ago did i know of this problem w/ this speaker. very bizzare. and its not all the time (right now i cant reproduce the problem - next time it does ill do the tests you ask). and yes the wires are well connected and yes the wires are long - much longer than i need to use them and i did not coil the extra length
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Better small TSW inverter for continuous operation?

    Does it sound like a broadcast radio or TV station? Do you know if there is a transmitter site nearby? A friend used to live about a mile or two from an AM radio station's transmitter site and he could listen to that station on just about anything in his apartment! :p Cheap telephones and computer speakers being the most common. But he even had a water pipe receiving the station once, at a corroded fitting.

    I have a set of computer speakers in the garage that make noise if I leave them on when I talk on HF (usually only 10 meters) - sounds like a garbled voice (Charlie Brown's teacher?!), since I'm running sideband. They usually aren't on so I haven't bothered with trying to fix it.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    the problem may be the speakers themselves as rj pointed out and you weren't aware of this until a transmitter was nearby. by clean i mean good corrosion free connections using wire that has no breaks or weak areas from being walked on or other such abuse. putting a standard non-amplified speaker there will probably show no interference and lower volume unless the interference is making it in prior to the speaker wires which is sometimes possible.
    i tend to think it is a 2 way radio and could be a number of different sources from ham or cb to police, fire, and ambulances because broadcast radio and tv stations are on fairly constant with long hours of operation. more expensive shielded wires could also be used, but could cost more than some replacement speakers in some instances. as to replacing the speakers, now that can get sticky as you don't know which will have a problem or not so you may need to explain your problem and to be able to return the product based on if it becomes interfered with. you could go through many speakers this way.
  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    in recent months, i was informed i lived 2 miles from cable tv station which broadcasts (dont know what that means)

    wires are clean (per your definition). im going to write it off as cheap old speakers. it doesnt see much use anyways and im in the process (for the past few years) of trying to fade away desktops.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Better small TSW inverter for continuous operation?

    1> cable tv should not broadcast as they are not licensed to do so.
    2> do you have a straight speaker(nonamplified) or headphones to try and see if the interference is still there? if it isn't then the speakers are most likely at fault.