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I have been playing around with achieving better power in my 30-year old RV. I want to create both AC and DC systems to provide power. This has essentially 3 routes from my battery to device:

  • Samlex 300W AC Pure Sine Wave Inverter. - Solid system.
  • 12v to 12v or lower (USB). This works great too, pretty standard setup.
  • Greater than 12v via Boost Converter for me and my wife's laptops. This is where we are having issues.

The issue seems to be voltage drop as the computer draws more power. Most of our electronics work fine, but my 'beast' of a laptop is troublesome. It works perfectly fine on the inverter with the power brick it came with (which is rated 19.5v, 9.23A). I am currently typing this on the laptop and i have a current meter hooked up, and its pulling 2A. The boost converter is rated for 600W and doesn't seem to break a sweat, its maybe a degree about room temp.

When it hits about 5A the boost converter cannot seem to keep up (im assuming just momentarily), and the laptop disconnects from my power system and goes to battery. I initially thought the voltage was dropping but I cannot confirm this. This feels like an issue that could be fixed by adding more capacitance? IE, just slap a big car audio-style capacitor between the computer and the boost converter? Is this even worth it? I wonder if I should just use the inverter for this laptop, since none of our other electronics have issues.

Also, I am not an EE, but I will do my best to follow along with the more technical answers.

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  • \$\begingroup\$ What voltage is the boost converter supplying with a current draw of 2A? What does the voltage drop to at 5A? Is the boost output voltage adjustable? \$\endgroup\$
    – Eamon
    Commented Apr 29, 2019 at 2:14
  • \$\begingroup\$ Most likely the Boost voltage Converter which also demands more input current to do this, drags the 12V below 8V. Verify. \$\endgroup\$ Commented Apr 29, 2019 at 2:25
  • \$\begingroup\$ The voltage supplied is 19.5v. It is adjustable via a pot. The input is a 250w switch mode power supply currently. I have tested both input and output values and the multimeter isn't confirming dramatic voltage drops on either end. I will update the question. \$\endgroup\$
    – Chris Hill
    Commented Apr 29, 2019 at 2:34
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    \$\begingroup\$ Bear in mind that a big cap on the output will look like a short circuit on startup, so the power supply might fold back and stop working. You may also need a current limiting resistor or maybe choke \$\endgroup\$ Commented Apr 30, 2019 at 10:41

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Your boost converter is not 600W.

It says

Output power: = Input voltage * 10A

in the eBay listing. Therefore, 10A*12V = 120W output power. The laptop you have can use up to 19.5V*9.23A = 175.37W of power. If it does, the boost converter can't keep up and limit its output so laptop will see voltage reduction and switch to internal battery.

Capacitors can help, but only if average load is lower than whatever boost converter can provide.

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  • \$\begingroup\$ Thank you Volodymyr, I completely missed this in the specs. Accepted. \$\endgroup\$
    – Chris Hill
    Commented Apr 30, 2019 at 15:43
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It's depends on what you mean when you write "When it hits about 5A". If the "hit" is very short, say up to 1/10 of a second (and in this case this can probably not be seen with an ammeter but with an oscilloscope), then a capacitor may help. If the "hit" is longer than that, this cannot be solved in this manner (unless you use really huge capacitors, which would cause other problems anyway).

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