Say I have a 2016 era laptop, and I travel back in time something like 20-70 years, but forgot to bring my power cable. How can I jerry-rig a power plug? Sure, including adapter / surge protection is better, but what is something to at least give me power so I could use my laptop?

The best answer will likely differ depending on how far back I actually go, e.g. 20 years vs. 50 years, but all suggestions are welcome.

**Edit: Ok, I'll be more specific. Is this feasible for an ordinary person to do without extensive knowledge of electronics? I.e. how easy is it for someone to put together a cable that they can plug into a wall with one end, and plug into their laptop with the other end, and not completely destroy the laptop?

Besides just going to some store or consulting someone with knowledge in electronics, I'm wondering specifically how the time traveler can do this. For instance, I wouldn't have an idea of how to do this without damaging my electronics, which is why I think this is a reasonable question to ask for specifics.

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    $\begingroup$ Watch movies that are 70 years old. You see they had wires and electric outlets, and presumably components such as resisters and voltage meters to use in building these devices. What’s the problem? $\endgroup$ – JDługosz Sep 1 '16 at 1:14
  • $\begingroup$ If you have the power brick, you can just directly wire it into mains. $\endgroup$ – Journeyman Geek Sep 1 '16 at 3:48

Take a look at the bottom of your laptop. It should list the voltage it's expecting. Mine says 19.5v 3.3A.

Luckily, AC to DC power converters have existed as long as electricity has been around. You'd go into Yee Olde electronics supply store and buy a bench power supply. Turn the dial to the correct voltage and amperage and you're half way there.

The hard part is the plug. For now you should be able to just stick the bare wires into the port. According to this it's probably negative on the outside, but since you can't afford to mess up you'd probably want to test with a multimeter. The guy who sells you the bench power supply can probably help if you can come up with a plausible cover for what your little box is for.

  • $\begingroup$ It's a light box. It has wire inside that glows when electricity is passed through it. It also has buttons that change what bits of light are lit up. $\endgroup$ – wizzwizz4 Sep 10 '17 at 19:07

Depends on the Laptop

This really depends on the laptop. If it just needs a stable DC supply, that can be done, but if it requires an activation signal as a brand-lock-in annoyance, then you are in for a lot more difficulty!

DC supplies

How you would produce a moderately high current regulated DC supply would depend a bit on era. In the solid state one, semiconductor diode regulators and transistorized regulation yields a fairly straightforward and practical design, albeit with a much heavier power transformer than the tiny high frequency ones used in today's switching supplies. Probably you can find something suitable for borrowing in an existing product (though perhaps not a consumer one). In an earlier era you may need more complicated rectification schemes, and high power low voltage filter capacitance will have to come from a very large array of low value capacitors. You may well end up with an AC operated motor driving a DC generator.

Lead Acid Cells

Another option to consider would be storage batteries. For example, one and a half "12v" car batteries starts to put you into the right range, and you are mostly targeting an era when car batteries would have been a maintainable array of individual cells held in a common crate, so getting a series connection of nine of them (one full battery, and 3 of the 6 cells in another) should not be hard. You can either charge the battery before use, or possibly use it as a bit of a stabilizer/regulator while connected to a power source.

Emulate the Battery Pack

If you do have a laptop which requires a brand-specific activation signal from the power supply, an option might be to disassemble the battery pack and try to emulate that, probably with some different number of contemporary chemistry battery cells, rather than provide the DC input. You may need to put some thought into emulating the output of a thermistor or other sensors. If the battery has an on-board management IC, you'll have to hope you can somehow generate conditions that satisfy it. Presumably you will shut the laptop down and charge your replacement battery independently of it.

The USB Tragedy

Once powered your computer will be usable as a manually interfaced data processing machine. A relay team of typists could accept input and produce output, but this will limit utilization of this unique-in-the-world resource. Back in the day when hardware serial and parallel ports were present, building an interface widgit with vacuum tube technology to collect inputs from and channel output to dozens of proto-teletypes would have been possible, but with the "legacy-free" switch to USB, not really. About the best that could be done if you decide to donate your services to a larger organization would be some kind of electro-mechanical speed typer to submit input jobs, and perhaps a film camera for capturing output ones for distribution back to the submitters.

Preserve it

It may be a good idea to remove the lower case of the laptop and build it into a console providing more and better filtered cooling air than the tiny ordinary fan can. If the keyboard fails constructing a replacement is actually fairly possible (which gives another input idea, but one whose risk may not be justified before the need). If the hard drive goes, you are in for a lot more trouble. With a PATA interface and the lucky accident of having brought printed documentation you might get somewhere towards constructing a replacement with 1970's digital logic or 1960's research-lab capabilities, with SATA you are out of luck, unless you want to have a go at emulating the bios flash.

While it will be painstaking, while the machine works you'll probably want to do a hex dump of the bios, boot sector, etc and photograph every page for preservation.

Better an older laptop

For many of the reasons threaded trough this, you'll be best off with a laptop from the 1990's or even the 1980's. It won't be as absolutely powerful as a modern one, but still many orders of magnitude beyond any contemporary alternative in your destination time. More importantly, it will be more maintainable and interfaceable. The battery pack will be built around simpler NiCd or NiMH cells, the power input won't require an activation signal, the disk interface will be one old technologies could emulate and there will be I/O ports within the realm of interfacing, etc.

  • $\begingroup$ If you arrive before the spreadsheet was common then you could use spreadsheets to take over the world much more efficiently than "electro-mechanical speed" typing. $\endgroup$ – Erik Aug 18 '17 at 16:02

70 years is tough, but anytime within 40-45 years (1970s to present) you just need to visit a Radio Shack and you'll be able to put something together. I'm not sure what the equivalent retail places for countries other than the US are.

Worst comes to worse, befriend an electrician or a ham radio operator, and they'll be able to build you something.


Should really ask this in a electronics stack. However I'll answer it.

Its ridiculous to try to make a fitting male part to place into the laptop adapter. So the best thing to do is to remove the adapter and connect/solder wires running DC current straight into the motherboard. Whether they can do that as well as sending a appropriate voltage and not destroy it in the process of all this, your guy will need to know some electronics.

You can go back whatever amount of time as long as it can produce that right voltage and wires.

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    $\begingroup$ Why is it ridiculous? Lathes are not exactly new technology, and probably more commonly found in private possession in the time period of interest than today. $\endgroup$ – Chris Stratton Sep 24 '16 at 15:04
  • $\begingroup$ @ChrisStratton Now that you mentioned that, I realise its not. I wonder which one is easier for the person who doesn't know electronics. $\endgroup$ – Necessity Sep 24 '16 at 15:54
  • $\begingroup$ A power connector doesn't require electronic knowledge beyond the "everyone knows" concern to establish the two desired contacts without shorting them together; it does require a competent garage machinist. Soldering to the mainboard requires some skill and practice at similar work in an electronics context to bring awareness of what a disaster it would be to use acid flux (as jewelry, stained glass, or plumbing practice would), but doesn't really require much understanding of the circuitry either. $\endgroup$ – Chris Stratton Sep 24 '16 at 16:00

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