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    Inverters - 12volt to mains power 240v

    Anyone know which type of inverter is best for laptops?

    Pure sine wave or modified sign wave.

    I need to have 8 amps, 12 volt available from the inverter. What size is recommended? 300watt? 600w? 1,000w?

    #2
    Re: Inverters - 12volt to mains power 240v

    Pure sine wave is preferred for anything, but it's usually more expensive than modified sine wave.

    The power supply/adapter that comes with the laptop is most likely to work fine with modified sine wave... but some power supplies do have issues with this type of generated AC current.

    The inverters usually give you the power in VA ... the actual power is about 80% .. so if it's 300VA, the maximum it would handle would be about 200 watts. A 600VA would handle about 450w and so on.

    Laptops usually come with a 19v 4-6A adapter, for a total of about 120w maximum, but they don't use this much all the time, in fact they usually hover at around 40-50 watts.

    I don't understand the first part of the last line.... the inverter would generate 220-240v up to whatever current is specified by its VA rating. From that point, the power supply/adapter will generate those 12v or whatever the laptop needs.

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      #3
      Re: Inverters - 12volt to mains power 240v

      You may want to look for something like this instead:
      http://www.ebay.com/itm/DC-12V-19V-4...item43b66500a2

      Why convert 12VDC to 240VAC to feed the laptop adapter and then convert it back down to 19VDC to feed the laptop.
      Never stop learning
      Basic LCD TV and Monitor troubleshooting guides.
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      Inverter testing using old CFL:
      http://www.badcaps.net/forum/showthr...er+testing+cfl

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        #4
        Re: Inverters - 12volt to mains power 240v

        yeah thats more efficient solution.
        is this for car or boat? you can get DC/DC Converter laptop adapters that plug direct into a 12v cigarette lighter. http://www.powerstream.com/ADC-HP.htm
        capacitor lab yachtmati techmati

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          #5
          Re: Inverters - 12volt to mains power 240v

          My home is solar powered on a very small battery bank. I have 4x 6 volts 105 amp/hr in parallel giving the 12 volts. I measured the current of all the parts of the system at 12 volts.
          Satellite modem 3.6amps
          Wireless router 0.8 amps
          Printer 1.6amps
          Computer 2amps
          Total 8amps

          I've used those variable DC-DC units in the past using 12volt to 19 volts.Two in fact, both ended up failing. They may have improved since as I found that they can be bought specifically for the brand of laptop it would be used on.

          I could try using them again, one for modem which requires 24 volts and a 19 volts for the laptop. The wireless router is already 12 volts. The printer is not that essential.
          I must add here I currently use a petrol generator to use the internet and wish not to have to.
          We found a pure sine wave inverter yesterday and wondered if our meager system and our power needs could be handled by this one... http://wallcann.com/1000W-12V-Power-...8Zed_3055.html

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            #6
            Re: Inverters - 12volt to mains power 240v

            Rather than having multiple 12v to something dc-dc converters, you're better off using such inverter for everything in the house. The 12v to 19v dc-dc converters will be 60-80% efficient while a 230v to 19v laptop adapter may be 85-90% efficient.

            Not sure how you measured the amps... are all those devices using the same voltage? Because if they're not using the same voltage the total of 8 Amps is meaningless.

            Most hardware already has some dc-dc converter inside but they're using standard wall bricks that output 7.5v,9v or 12v because they're easy to source from a 3rd party manufacturer. I'm not recommending you risk it without knowing for sure how the internals are, just saying some devices that say they need 7.5v DC or 9V DC may actually work just as well with 12v DC.

            I don't like that inverter, but I generally don't like obscure brands of equipment. Seems too lightweight and small to actually do 1000w with 2000w peak and also be pure sine wave.

            I wouldn't know what to recommend though, don't have much experience with inverters. I personally would probably buy and hack an online ups with pure sine wave output to run from battery 24/7.

            Comment


              #7
              Re: Inverters - 12volt to mains power 240v

              Originally posted by mariushm View Post
              Not sure how you measured the amps... are all those devices using the same voltage? Because if they're not using the same voltage the total of 8 Amps is meaningless.



              I don't like that inverter, but I generally don't like obscure brands of equipment. Seems too lightweight and small to actually do 1000w with 2000w peak and also be pure sine wave.
              I measured the amperage by plugging each items 240 volt plug into a 300 watt square wave inverter that whistles and carries on. I quickly checked my houses 12 volt regulator that shows amperage usage.
              So if this 8 amps is a correct total reading then are you saying 1,000watt inverter can't handle it?
              I'm really not conversant with how to calculate power usage. 12v x 8 amps would be 96 watts so how do you calculate this with 240 volts and the 1,000watts?
              Would I need something larger than 1,000w inverter?

              Comment


                #8
                Re: Inverters - 12volt to mains power 240v

                Voltage x Current equals consumption (watts)

                watts / voltage equals current. So 1000w/220v would be 4.55A

                Well, you would check each thing you would have to plug into the mains and see what the label on it says.

                For example, the wireless router may say 12V DC 1A maximum ... that means 12x1 = 12 watts of power. Assume the adapter is about 75% efficient, that means the adapter may pull up to 12w x 1.25 = 15 watts from the 220-240v socket when it's 100% used.

                This 15 watt is barely a few hundreds of an A at mains voltage ... 220v/15w = 14.6 mA or 0.15A

                So add all those watts from all the adapters and see what would be the peak wattage if all equipment in your house is maxed out.
                Then add about 20% reserve or more in case you buy some more stuff, and then get an inverter for that wattage, or one rated for a bit more wattage (better get more than be sorry in the future, but don't overdo it).

                What you actually did by plugging all was to see how much the inverter would pull from the batteries, and you determined it's 12v x 8 A = 96 watts.
                But this 96 watts includes the conversion inefficiencies inside the inverter.
                A 300w inverter may be 80% efficient at 100w load (30%) so your devices actually use around 80-85 watts (just fictional numbers, didn't do the math) and the inverter wastes around 10 watts inside to generate the AC voltage.

                A 1000w inverter however may be only 50% efficient at 100w load, so if your devices use 80-85 watts you may see 120-150 watts (again, bogus numbers, didn't do exact math) pulled from batteries, or 10-12A from 12v battery.

                So it makes more sense to get an inverter with the maximum watts closer to what you consume, let's say 500-600w. If you only use an average of 100 watts now, there's not much point to use a 1000w inverter because it would be very inefficient.

                (There's also an issue here with power factor correction and the fact that you used a square wave inverter, which is different than a pure sine wave and may change how the devices you plugged in operated but it gets too complicated even for me)

                Comment


                  #9
                  Re: Inverters - 12volt to mains power 240v

                  I appreciate the help and advise. It's always been a challenge.
                  So it seems the 600 watt range may best suit my circumstance.

                  I checked the power consumption of the adapters rated against 240 volts.
                  Satellite modem 1.8amps @ 240v
                  Wireless router 0.3 amps
                  Printer 333mA
                  Computer 1.2amps
                  Total 3.633 amps @240 = 871 watts ?

                  So with this wattage 871, if the printer is not being used and the laptop is running on it's own battery and only being topped up, the 600w inverter would suffice.

                  The next thing would be for me to find a brand that will last.
                  Any suggestions of brands that can handle the wear?

                  Comment


                    #10
                    Re: Inverters - 12volt to mains power 240v

                    What kind of satellite modem is this? I'm surprised it uses that much more power than your wireless router. At 240V, 1.8A is quite a bit of power (400W-ish) - that would get warm fast, and needs fans...

                    Even a computer at 1.2A @ 240V - do you have graphics accelerators in your machine? That's a lot of power, my i7 (which has no graphics accelerator) is about 120W when being hammerred, which would correspond to 0.5A @240V...

                    Comment


                      #11
                      Re: Inverters - 12volt to mains power 240v

                      I'm on the new NBN Australian system.
                      The satellite modem is a skyedge II.
                      The government gives people in Australia a free satellite system if their NBN rollout of fibre-optics will not be delivered. Basically people in the country areas. We still have to pay an ISP, in my case $45 / month for 3G/3G peak-use/ off plan at 6 mbps speed and a promise of 12 mbps.
                      I was surprised at the rating for the laptop. It's a recently bought net-pad a Acer Aspire one D270. My usage of it is pretty tame.

                      Comment


                        #12
                        Re: Inverters - 12volt to mains power 240v

                        No, it's impossible that the modem uses that much power. It's certainly not 1.8A @ 240v.

                        It may be a maximum of 24v @ 1.8A but more likely it's 9-12v @ 1.8A. Look in the back of the modem and see what it says around the DC jack connector. It should say the voltage or something.

                        My whole computer barely uses 200 watts so that modem would need a huge fans and cooling system if it were to dissipate 400 watts of electricity.

                        Comment


                          #13
                          Re: Inverters - 12volt to mains power 240v

                          The AC input on appliances is often the maximum input current, i.e. inrush or during start-up of the power supply, or at very low line voltages (85~90V.)
                          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                          Comment


                            #14
                            Re: Inverters - 12volt to mains power 240v

                            Originally posted by mariushm View Post
                            No, it's impossible that the modem uses that much power. It's certainly not 1.8A @ 240v.

                            It may be a maximum of 24v @ 1.8A but more likely it's 9-12v @ 1.8A. Look in the back of the modem and see what it says around the DC jack connector. It should say the voltage or something.

                            My whole computer barely uses 200 watts so that modem would need a huge fans and cooling system if it were to dissipate 400 watts of electricity.
                            I checked the DC in at the jack on the router and it indicates 24volts @ 3A max.

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