Inverter

Will2020
Will2020 Solar Expert Posts: 62 ✭✭✭✭
I'm looking for an inverter that will run a laptop, as well as power tools. I will be using this inverter from my work truck for now, but I want one that will last.

Do I need the square wave? Sine wave? What is the difference with the waves?

Comments

  • bryanl
    bryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: Inverter

    The difference in the waves is how they are constructed electronically. The ideal, based on the ideal AC generation system, is a smoothly changing voltage and current. This is known as a 'sine wave' because it looks like the plot of the trigonometric sin function. In practical terms, there is no such power available as loads, noise and other factors 'pollute' it.

    There are several methods to construct AC in an inverter from a DC power source. The simplest is to simply turn on and off the power. That creates a square wave. not smooth. From there, steps are added to smooth out the rise and fall of voltage and current. If you get enough steps, you end up with something that, for all intents and purposes, is the same as a sine wave.
    I want one that will last.
    This means you want one built with high quality components. That raises the price and, usually, when the cost is higher, more attention is paid to providing a smoother waveform. So what you want is a 'quality' inverter and not a cheap one.

    The reason folks get all in a twitter about sine vs other inverters is related to load factor and other AC issues. Some devices have power supplies that are very sensitive to the power they are supplied and need a smooth AC waveform to work properly (else they overheat or they break down from the way the voltage changes). These sorts of devices are few and far between these days and you'll usually see caveats on inverters about them if that inverter doesn't provide super smooth AC. Sometimes, non smooth AC can also increase losses in a device and that may generate heat or reduce efficiency.

    So get a good quality inverter sized to meet your power needs and don't worry much about the purity of its output. A modified sine wave from a good quality inverter should do just fine for your laptop or power tools. (IMHO)
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Inverter

    size for power tools depends on the power tools. a small electric hand drill would be ok on a 600w MSW but a circular saw cutting 3/4 plywood would need at least a 1000 MSW..
    Usually you can buy a bigger MSW than a true sine wave for same price.
    example but not real figures as dont know where you are
    600w true sine wave $200
    1000w MSW $200
    Most power tools work ok on a MSW inverter,, Well I have never had any problems doing it for many years,, everythink from angle grinders circular saws hammer drills..
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter

    Your best bet is probably to purchase a small (300 watt or so) TSW inverter and a second, big ol' 1,000-1,200-1,500 watt MSW inverter for the tools (and you need a good sized battery bank+wiring to supply the power needs).

    And you can buy a second 1,200 watt MSW inverter as a backup (same or different brand to see what works well for you) for the sales tax savings on a 1,200 watt TSW inverter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Will2020
    Will2020 Solar Expert Posts: 62 ✭✭✭✭
    Re: Inverter

    I'm thinking of getting this guy for my small electronics

    http://store.solar-electric.com/sa300wa12vos.html

    Does this have cables that I can tie in to the battery? Or does it have just a 12v plug?
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: Inverter

    It has tubular screw down terminals, but also comes with a cigarette lighter plug.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter

    Remember that a 300 watt inverter will draw around 30 amps--A lighter plug is good for around 10-15 Amps maximum.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Will2020
    Will2020 Solar Expert Posts: 62 ✭✭✭✭
    Re: Inverter

    Is that continuos amps?

    So if I'm using 30 amps for 5 hours, that will be 150 amps drawn from the battery right?

    I just want something to run my laptop. On the ac adapter it says 1.5 amps, so I'm guessing this will pull 15 amps or 180 watts continuously.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter

    Power = voltage x current

    360 watts = 12 volts x 30 amps (typing on phone-short answer)

    30 amps x 5 hours = 150 amp*hours (not amps)

    1.5 amps x 120 volts = 180 VA (sometimes watts)

    Read about power factor correction else where here today.

    Power supply ratings are very difficult to use for off grid planning. Get a Kill-a-Watt meter to measure actual volts, amps, watts, va/power factor, and kWH numbers.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: Inverter

    Absolutely get the meter. My netbook adapter is rated 1 amp @ 12VDC, but when I monitored it with the Kill-a-Watt, it was drawing less than that. I also had two chargers and an 11watt LED light going, and the total draw was between 35-40 watts.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Inverter

    Another thing to keep in mind is alternator output.

    I used to run a 2000w MSW inverter hard-wired to my work truck's battery. For something small, no problem. For something medium, truck engine running.

    For anything big, like a 1/2" Hole Hawg or a Skil Saw - engine running and a brick on the throttle to keep the RPMs up to where the alternator was really putting out.

    A lot of alternators don't put out anything at idle speed. I had a good one on my truck and it would put out something even at idle, but not a lot. I had to really get it spinning to feed a 2000w inverter with any substantial load.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Inverter
    bmet wrote: »
    Absolutely get the meter. My netbook adapter is rated 1 amp @ 12VDC, but when I monitored it with the Kill-a-Watt, it was drawing less than that.

    Um...

    You mean less than 1a @ 120v no? Not 12v?

    Is there a Kill-A-Watt that measures 12v?
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: Inverter
    dwh wrote: »
    Um...

    You mean less than 1a @ 120v no? Not 12v?

    Is there a Kill-A-Watt that measures 12v?

    The netbook's AC adapter reads OUTPUT 1AMP@12VDC .

    The meter is on the output of my inverter, when the netbook is powered from it, the Kill-A-Watt fluctuates between 6-9 watts. However, since the frequency is no where close to 60Hz it probably isn't a reliable measurement.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Inverter

    if its a MSW inverter then you wont even go close to getting accurate reading on kill the watts meter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter

    John P,

    I thought the Kill-a-Watt was sort of OK on MSW. The first versions (years ago) would overheat the AC to DC conversion circuit for the internal electronics.

    You have compared them with a good RMS meter and found them wanting on MSW inverters? (I don't have any equipment to do the test myself--So I am not arguing with your observation--Just wanted a bit more detail).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Inverter

    BB they just dont read acurately as they take the peak of the reading to give the figure but with MSW inverters there reallly is no peak. so it appears to a killer watt meter that the voltage is about 170 ,, so its calculations are wrong ,, have tried a few different brands all same problem In fact its hard to get accurate readings using any means from a MSW inverter output,the only accurate way to measure the power consumption of a device powered by a MSW is to take the DC readings on the input side and take into account the inverters own power consumption with nothing connected..
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter

    Sorry to hear that--But, cannot expect a $25 meter to perform like a $x,xxx power analyzer.

    That would seem to indicate that their measurements on grid power with non-linear current (old computer power supplies with rectifier type input) is probably less than accurate too. :cry:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bryanl
    bryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: Inverter

    re: "Is there a Kill-A-Watt that measures 12v? "

    The 0Watts Up power meter can be handy for this. Its good for 4 to 60v and will handle 50 amps. Other than that, you'd need to look at the battery monitors like the Trimetric or other 'electron counters'.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Inverter

    BB what I should have also said was part of the problem is the MSW inverters them selves as there are so many "types " of ouputs.. from simple squarewave to some with 2 steps to some with 20 steps.. RMS meters from different manufacturesr handle reading the RMS value in different ways and it is also affected by the count that the meter takes.
    At work we have many types of meters to read such outputs and you would be supprised at the different readings you get..
    Even expensive power analyzers give different readings,its hard to know what to believe.
    That is why its by far the best way to measure the voltage and amps drawn by the inverter..less its own consumption..
  • Will2020
    Will2020 Solar Expert Posts: 62 ✭✭✭✭
    Re: Inverter

    They have Xantrex x power 1000 watt inverters on the net for around $100.

    Then there are Xantrex pro series 1000 watt for about $230-250

    Are the $100 dollar ones prone to failure?

    This converter is for a diesel truck with a big battery bank and will be used for power tools.

    I need a good reliable one in the 1000-1500 watt range that will last for years. It does not have to be Xantrex.

    Any suggestions?
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Inverter
    bmet wrote: »
    The netbook's AC adapter reads OUTPUT 1AMP@12VDC .

    The meter is on the output of my inverter, when the netbook is powered from it, the Kill-A-Watt fluctuates between 6-9 watts. However, since the frequency is no where close to 60Hz it probably isn't a reliable measurement.

    Ahh. You had me confused. On the one hand referring to the 12v (output side of the adapter) and on the other referring to the Kill-A-Watt (input side).

    For reference - looking at my netbook's adapter (Acer ZA3, Lite-On adapter) it says 1.58a, 19vdc on the output.

    In Linux, acpi reports 9w-13w consumption normally, 14w when charging the battery, so your 6w-9w seems to be about in the ballpark since your netbook obviously uses less power than mine (judging by the smaller adapter).
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter

    The XP series looks to be just a straight forward 12 volts in 120 VAC out inverter.

    The Pro Series above has a transfer switch (plug to shore power--Shore power on, shore power to outlet. Shore power off, DC to AC inverter power to outlet). So, it is a bit like a "UPS" without the internal battery charger.

    Also includes a digital head for with display.
    The Xantrex PRO Series Power Inverters are the perfect complement to generators when shore power is unavailable, to quietly and efficiently provide household power when needed. The PRO Series design is both user friendly and versatile. These power inverters feature a detachable, digital remote control to display precise inverter, AC source and battery status information from one convenient location. A built-in transfer switch automatically detects when generator or shore power status changes to ensure power is always available.
    Both 1000 and 1800 W models are designed for demanding RV and marine conditions. They meet FCC Class B regulations to eliminate interference potential with other electronics, while UL 458 certification means they meet strict RV and marine safety standards. Versatile enough to be mounted either horizontally or vertically, these inverters can be easily installed to fit into any compartment. Conformal coated boards also minimize the chance of problems from moist operating conditions.

    If you want just DC to AC power--the first inverter will probably do fine.

    If you have shore power / generator and the inverter is hardwired into your vehicle's chassis--The transfer switch is a nice to have item.

    I don't have any experience with these inverters (or other brands) other than the random small MSW or the Xantrex GT inverter on my home.

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