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