Certa Power Inverter Modified Sine Wave 1000W / 2000W 12V-240V $51.99 + Delivery (Was $299.99) @ Kogan

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• 

  Villainous on 17/05/2020 - 13:57

  +7

  …"powering the most-sensitive of appliances."

  I wouldn't trust that being modified sine wave.

  • 

    tonyjzx on 17/05/2020 - 13:58

    +4

    yeah this was never $299

    its a cheap inverter for powering laptops or something that has something between your expensive item and the wall

  • 

    OverBought on 17/05/2020 - 14:12

    -5

    This^^

    I powered my work laptop off a modified sine wave inverter… and AC transformer power supply was buzzing and crackling.

    Still, I didn't care because it was a work laptop so work can just replace the power supply for me. That will teach them to send me on-call to remote places.

    • 

      Zaddo on 17/05/2020 - 15:23

      +3

      I hope one of your work mates points out your post to your boss. If you don't like your job, get another one. Being petty and not looking after the resources your work provides you to do your job is childish.

      • 

        tonyjzx on 17/05/2020 - 15:32

        Work probably provided the inverter lol…

        No one takes cares of work equipment.

        • 

          OverBought on 17/05/2020 - 21:38

          +2

          @tonyjzx: Actually, work did provide the cheapo cigarette lighter powered inverter.

          And then when I complained they said just use it, because it's worked for all the other on-callers before me.

          But yeah, neg away people.

      • 

        OverBought on 17/05/2020 - 21:41

        +2

        I hope so too. Because we've told our boss that it can't be good for the laptop and we don't feel safe.

        But yeah nah, it's a work laptop and can be written off every rear.

  • 

    Russ on 17/05/2020 - 17:24

    +2

    I wouldn't trust that being modified sine wave.

    For the majority of mains-powered hand drills, the speed control won't work with "modified sine wave", which is actually a square wave. The drill will be full-speed or stopped.

    • 

      Switchblade88 on 17/05/2020 - 22:21

      -1

      So… people have tools are old enough that you need a CORDED drill into an inverter, which is presumably running off a car battery?

      You're not going to BELIEVE the advances made in recent years!

      • 

        Russ on 18/05/2020 - 01:24

        +2

        Mains-powered tools still have their place. Try drilling more than a few dozen holes in concrete, and you'll be wanting a mains-powered drill. An inverter like the one in this deal makes it possible at a worksite without power, and with less maintenance than using a portable generator.

        You could use cordless power tools with a couple of batteries, charging one while using the other. But the most you'll get out of the charger, plugged into a car's cigarette lighter, is 120 Watts.

        The biggest Ryobi battery pack I can see at Bunnings is 9Ah 18V, which equals 162 Watt-hours. A car battery has about 420 Watt-hours, which gives you about 360 Watt-hours after taking the efficiency of the inverter into account. So the car battery has more than twice the power, and at lower cost than the Ryobi battery. And larger batteries are available too.

        A small hand trolley, like this one, makes the battery+inverter much more convenient to use. Mount the car battery at the bottom: https://www.ozbargain.com.au/node/434808

        Another advantage is that you can leave your drop saw, drill and nail gun plugged in, and alternate between them as needed, all using a single battery.

        • 

          DannyBoy on 24/05/2020 - 01:36

          @Russ: A portable battery/inverter setup is something I have wanted to do for ages more now but ended up going all cordless Ryobi 18v.

          The cordless SDS is a great investment if you intend doing a lot of small to medium masonry jobs

• 

  sputmayer on 17/05/2020 - 14:01

  Dick Smith ha it at the same price

  • 

    raydragon on 17/05/2020 - 14:04

    +4

    well not surprising seeing Kogan owns the Dick Smith Brand now… :)

  • 

    mycosys on 17/05/2020 - 14:09

    +2

    Dick Smith is the same store

• 

  dmbminaret on 17/05/2020 - 15:16

  $69.99/$64.99 now

  • 

    tonyjzx on 17/05/2020 - 15:36

    are they doing a bezos and increasing price once they see demand go up?

  • 

    hitman48 on 17/05/2020 - 15:40

    +1

    price goes down once you put in your cart

  • 

    mhecker on 17/05/2020 - 20:48

    Price reduced by 25% during checkout.

• 

  xcornx on 17/05/2020 - 15:41

  +3

  as nice as these little units are and they work, but be aware of the load you put on. If you want to run 1000W/240V continuous, that leaves you on the 12V side with somewhat between 80A and 90A (get the right cable sizes, or something will burn).

  • 

    Russ on 17/05/2020 - 17:18

    +3

    Actually it's likely to be a bit over 100A, as the inverter isn't 100% efficient, and you'll probably see a bit of voltage drop along the DC cables as well.

    You'll also want a battery rated for 100A-plus continuous discharge, the "Compatible with any 12V battery" claim is false. Draw 100-plus Amps continuous from anything smaller than a car battery, and you'll probably boil the electrolyte. I'm not even sure car batteries will take that sort of discharge, normally they get a ~900A discharge when starting the car, but that's only for a few seconds, so no significant heating occurs (it's like turning a kettle on for ten seconds).

    Pro tip: if you need some distance between the battery and whatever you're powering, keep the leads between the inverter and the battery short, and the mains cable can be long. Heavy-duty mains extension cables are better than ordinary ones, but be careful not to buy one with a 15A plug, it won't plug into the mains socket. The earth pin is larger on 15A plugs.

    Be aware that if you are drawing 100A from a lead-acid battery like a car battery, the battery will probably be gassing, and the gas is explosive if ignited. Make sure the battery is in open air, so the gas can dissipate, and there are no nearby sources of ignition. Hydrogen gas is explosive at almost any concentration in air.

    Also keep in mind that the average car battery is about 35Ah, so with this inverter at full power, you'll get at most 20 minutes before the battery goes flat. Even with the car engine running, so much of the 12V power is being supplied by the car, I think the average car only supplies about 50A (at most) to the battery. So the battery will still go flat, but a little slower.

    • 

      xcornx on 17/05/2020 - 20:01

      not denying what you're saying, I tested my unit at 1000W and it was drawing 83A. So that will fluctuate from unit to unit, I don't own the same, but similar. Keep the DC side short in wiring that's all I recommend.

      • 

        Russ on 17/05/2020 - 21:15

        +2

        1000W/12V gives 83.3A, so if you're measuring that, the unit would have to be 100% efficient. Which doesn't tally with the heatsinking fins on the case, the dual cooling fans on the rear of the unit, and the manual saying "The temperature of the shell will be high after operating the device for a long time, so do not touch it due to the risk of burns". So it must be less than 100% efficient.

        Either the input was higher than 12V (it could have been 13.8V if connected to a vehicle with the engine running), or the load lower than 1000W. What load were you using? If you were reading 1000W from the nameplate of an appliance, it's likely the actual power was lower. Nameplate power is a worst-case figure, only occurring at maximum input voltage and under maximum load.

        Jaycar's similar inverter says it has ">=82%" efficiency: https://www.jaycar.com.au/p/MI5140

        • 

          xcornx on 17/05/2020 - 21:26

          @Russ: ah well ok here we go, I used 2 x 500W Halogen lights, that gave me 83A on the 12 V side. Now we can argue that 500W halogen Lights might not have 500W as Ohmage/Resistence might be less or more. In this case OBVIOUSLY it was more, so somewhat less Watts. So if you want to argue, happy to show you all the parts and even the Clampmeter I've used. All I wanted to say, be aware what you are using. But than you clown came along.

          • 

            Switchblade88 on 17/05/2020 - 22:25

            @xcornx: NO need to be snarky, @Russ was right about everything he said.

            All you did was prove you didn't actually measure the wattage being drawn in your own experiment, and he rightly pointed that out.

            Once you've got accurate figures then the maths will work properly.

          • 

            Russ on 18/05/2020 - 01:31

            @xcornx: Halogen lamps are hugely non-linear. Assuming your lamps were rated for 240V, this inverter puts out 230V. Although that's only about 5% drop in voltage, it drops the power by about 15%, which would put the inverter at 85% efficiency - about the same as the Jaycar inverter I listed above.

            Here's a graph of power versus voltage for a halogen lamp, the rightmost curve gives 30% power drop at 90% of rated voltage, and 15% power drop at 95% of rated voltage:
            https://physics.stackexchange.com/questions/48513/what-does-…

            • 

              xcornx on 18/05/2020 - 08:01

              +1

              @Russ: my 2 Cent. You don't seem to get the point I was making - BE SAFE IN WHAT GEAR YOU USING. If you wanna crunch numbers, in theory that all sound's good, practice has a different language. (Original DC voltage to Transformed AC voltage + Power factor + Load + Clamp meter I was using) many variables. I don't need to tell you what happens if only 1 factor is 5% off, you can figure that. Happy days.

• 

  jimojr on 17/05/2020 - 15:51

  I got one $51.99 with Kogan First. How did you get it $48.74 ?

• 

  hd2002 on 17/05/2020 - 20:42

  showing as $69.99 now