130w laptop charger through 100w car power inverter?

Discussion in 'Accessories' started by Kaitlyn2004, Aug 16, 2017.

  1. Kaitlyn2004

    Kaitlyn2004 Notebook Enthusiast

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    I've got a 100W power inverter for my car, and although I don't (yet!) have the Dell XPS 15, I believe the power adapter is 130W. Can I plug it into my 100W power inverter? Will it just charge slower, as if it was a 100W power adapter or will it damage the inverter/try to pull too much power?
     
  2. John Ratsey

    John Ratsey Moderately inquisitive Super Moderator

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    The charger will only draw the power that it needs to. If you are fully loading the CPU, fully loading the dGPU and recharging the battery all at the same time then the required power could well exceed 100W (and note that the power rating of the PSU is the DC output - at 85% to 90% efficiency then 130W could represent 150W drawing from the supply. If you aren't going to be doing all three of the above at the same time then you might be OK. One way to avoid overloading the inverter is to get a 90W Dell PSU plus a tip adapter. The computer will then recognise the 90W limit and avoid any overload.

    John
     
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  3. Fire_Child22

    Fire_Child22 Notebook Guru

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    Instead of looking at the power adapter, you gotta look at the bottom of the laptop itself to see the max power draw.

    It will look something like this:

    [​IMG]

    In the above, to get the max power draw, take the 4.62A and multiply it by the Voltage of 19.5 to get a max Wattage draw of 89.7W.

    Note that most laptop power supplies should always exceed the laptops requirement, although not by much as AC to DC converters, Step down transformers and Inverters work best at close to 90% capacity in regards to efficiency (re heat output and energy loss).

    That will give you the best indication on the max power draw of the laptop and you can work backwards from there.

    Now as someone who used to work with engineers and sell inverters, it's best you check if the inverter is a pure sine wave inverter or not. Non pure sine wave inverters may work with some laptops however not all will.

    Now pending on the inverter, an over draw will blow it's external or internal fuse. So no big damage will occur to your laptop. However cheaper inverters may have a MOSFET or capacitor failure that can send a high voltage surge through to a device.

    The other risk of running inverters inside a vehicle is the inverter may be rated, but the socket it's installed into will only be 12v at 10A commonly. That's a max power draw of 120W. Some people chuck a 15A fuse inside their fuse box to counter this, however this is how you burn down a car as the wires aren't rated for the increased load and heat up and can catch fire.

    Now if the laptop is off and you want to charge it while moving, it's probably a safer option. Finally if you have access to a multi-meter with AMP reader that look like the below, you can get an AMP reading during various stages of operation. If you're on the edge of capacity, I'd say don't run it as the amp readers may not be 100% accurate reading via the clamp method.

    [​IMG]


    Hope this helps.
     
  4. Kaitlyn2004

    Kaitlyn2004 Notebook Enthusiast

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    Just came across this:
    https://finsix.com/

    It's a 65W charger, but how is theirs supposedly so much smaller+lighter while ALSO boasting a USB port?

    Looks like they have it in "universal laptop" and USB-C style (backordered...)
     
  5. Fire_Child22

    Fire_Child22 Notebook Guru

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    When you get your laptop, (you said it's on it's way?) then you need to check the laptop requirements before ordering that.

    65W may not be enough pending your model.
     
  6. Kaitlyn2004

    Kaitlyn2004 Notebook Enthusiast

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    Yeah, the XPS 15 wants/needs more to charge effectively... but I've heard it does charge with 60W? Especially if I have it sleeping/turned off, it should charge better. I recognize it may not do a good job/provide any charge at all if I am trying to charge it with 65W while using it
     
  7. t456

    t456 1977-09-05, 12:56:00 UTC Moderator

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    Yes, that sounds about right.

    A normal charge rate for a li-ion cell is 1A@~4V nominal, so 4W each. The XPS 15 has both 6-cell and 9-cell battery packs, so charging an unpowered system would take ~25W or ~40W of net power, respectively. Add 2x 10-15% conversion loss (also for the 19V->4V DC/DC by the laptop) and requested draw should be around 30-50W (my 6-cell uses 37W when solely charging). This is irrespective of the mAh capacity of each cell; these merely take longer to charge (and discharge, of course). So yes, looking purely at power consumption that inverter should work, but, as John has mentioned, if you'd also use it at the same time then it will even discharge the battery on a heavy work load, the system taking what it can from the DC port and the rest from the battery. Minor, light browsing and office work shouldn't be an issue. Mind that 'light browsing' ? YouTube et al; a modern browser will then activate the dGPU, which a power hog compared to the Intel HD.

    That DART thing looks nice, but one 65W adapter can be quite different from the next. It is possible to make them smaller by doing away with or using smaller versions of components that help ensure a 'clean' power supply (inductors are very large) and ditching internal heatsinks. Capacitors too; tantalum capacitors are noisy, but they also have the highest energy density, so if you're looking to make the smallest adapter possible then they'd be a 'good' choice. Here's an old, yet rather thorough review on a large bunch of adapters, measuring efficiency and voltage ripple:
    Round-up of 74 laptop power adapters: original or universal?
     
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  8. pitz

    pitz Notebook Deity

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    Just get the proper Dell car plug-in charger.

    ADP-90ND is the model number on mine.

    Rated for 90W.
     
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