Electronics > Beginners
Can I charge my laptop with DC-DC boost converter
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grythumn:
If you're running off 12VDC, I'd look for a commercial car charger unit... some of them even have the right eeprom to charge the picky laptops. It's highly model specific, though.

A universal one like this:
https://www.amazon.com/Outtag-Universal-Charger-Detachable-Notebooks/dp/B071SDW4QG/

Or there are brand-specific ones available for a lot of laptops.

-R C
amyk:

--- Quote from: ejeffrey on June 06, 2018, 05:10:10 pm ---Many laptops use an EEPROM on the charger that is needed for correct operation.  In addition to implementing "lock in" on their chargers, it communicates the current rating to the laptop.  So the laptop may start by drawing a relatively small current, then after identification increase the charge rate.  If you don't have the proper ID, the laptop may charge slowly or not at all.

Here is a hackaday article about spoofing this for a dell charger.  They use the 1-wire protocol:

https://hackaday.com/2014/03/03/hacking-dell-laptop-charger-identification/

--- End quote ---
Others use a resistor on the sense pin to determine how much current to draw, similar to USB. Of course there are also the completely "dumb" ones that just take +/-. Inspecting the plug (and schematic, if available) will determine what type you have.
firehopper:
yeah most are around 3-5 amps at 18-19.5 volts, mine however is 19.5 volts at 12.3 amps
input is 100-240 volt at 3.5 amps rated 240 watts.


--- Quote from: IanMacdonald on May 28, 2018, 05:05:58 pm ---The majority of laptops require 19v at around 4A. Some rely on the PSU to limit the charging current, though most have their own charge regulator. Thus if you set it to limit at 4-5A you should be OK.

As mentioned, some form of OVP might be wise (crowbar, relay or similar) since the monetary value of the load is far more than the cost of the additional bit of circuitry. Might also be worth thinking in terms of reversed battery protection.

--- End quote ---
amyk:
The difference between 19.5 and 19 (less than 3%) is probably a sneaky attempt at vendor lock-in. You can find 18, 18.25, 18.4, 18.5, 18.6, 18.75, and a bunch of other voltages in that range, with no real reason for the distinction. Measure one of those loaded and unloaded, and you'll find the voltage changes again.

In practice, anything from just above the minimum input of the buck converters up to the voltage limit of the input caps (usually 25V) will be fine. Anyone who thinks a 20V adapter will damage a laptop originally supplied with a 19V adapter  is electrically illiterate.
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