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I was planning on buying a motorcycle battery or some other large battery to charge my laptop, but most of the batteries I found are 12v or lower, and I need around 20v to charge my laptop. Is there a way to trade off amperage to get more voltage? I would rather do that if I can instead of buying 2 batteries and getting a resistor to get the right voltage.

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closed as off-topic by The Photon, JYelton, Voltage Spike, Daniel Grillo, Warren Hill Aug 12 at 7:39

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – The Photon, JYelton, Voltage Spike, Daniel Grillo, Warren Hill
If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Sure is. It is called a switching converter. Ask a more specific question. Also, your resistor idea wont work very well. for multiple reasons. \$\endgroup\$ – DKNguyen Aug 6 at 1:08
  • \$\begingroup\$ you can use 3x 6V cells \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 6 at 1:40
  • \$\begingroup\$ a resistor could not be used to drop the voltage for the laptop ... are you aware that you asked a yes/no question? \$\endgroup\$ – jsotola Aug 6 at 4:50
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You can very likely find a pre-designed car adapter that is compatible with your laptop as an accessory. This can use a 12V battery as a source. Internally these adapters will use a step-up conversion to make the appropriate voltage for your device.

Here's an example: https://www.amazon.com/Universal-Charger-Adapter-ThinkPad-Computers/dp/B07FY9TXNV

EDIT: based on your additional info (135W @ 19V, Acer laptop), here are some suitable 12V-in chargers: https://powerstream.com/ADC-ACER.htm.

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  • \$\begingroup\$ I was actually looking for a battery because whenever I tried to charge from a car, it wouldn't charge consistently, and I checked the adapter and it worked fine on a different laptop but it wouldn't work with mine. I also tried a different adapter and it still wouldn't work right. \$\endgroup\$ – Samuel Joseph Aug 6 at 1:56
  • \$\begingroup\$ Maybe your laptop needed more current than the adapter could handle, or it was picky about its input somehow. Is there an OEM car charger for your laptop model? One obvious thing to check: is the plug making good contact? \$\endgroup\$ – hacktastical Aug 6 at 1:58
  • \$\begingroup\$ There is a universal laptop charger and it says it works with acer (I have an acer laptop) but I couldn't find one that was made specifically for my laptop. Is it possible that the car wouldn't be able to keep up with my laptop or is it most likely the adapter? \$\endgroup\$ – Samuel Joseph Aug 6 at 2:18
  • \$\begingroup\$ What does the wall (AC) charger claim for current? Some chargers are really huge (e.g., for a gaming laptop) so your aftermarket 12V one may not be beefy enough. \$\endgroup\$ – hacktastical Aug 6 at 2:21
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    \$\begingroup\$ That's a beast of a wall charger. I didn't immediately spot a 12V one that big. Maybe use a ~250W inverter to run the charger off the battery? I know it's a kludge but it would get the job done. \$\endgroup\$ – hacktastical Aug 6 at 2:57
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Absolutely, it's called a boost converter! Basically it uses a magnetic field to convert low voltage/high current into high voltage/low current. You can probably find a cheap module online with an adjustable output, for example a module made with the LM2596 IC could theoretically give you 40 watts (2 amp output).

Another consideration is that laptops are sometimes pretty smart and might have a 3rd small pin that lets them identify if the power supply is a legitimate source. You may have to spoof that signal or steal the communication module from an existing charger.

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