<i>20V is not a 'stock' DC/DC output voltage, so we're going to look for something roughly 24V and find something that has an adjustable sense line for reducing the output to 20V.</i><p>Note that the absolute voltage limit is likely due to 25V electrolytic capacitors in the input circuitry (find a schematic for a model that uses the "20V nominal" PSU and inspect it to be sure), so 24V should be OK as long as you're aware of how far the tolerance of the output of the PSU you're using can be. I suspect the fact that laptop PSUs seem to come in a wide variety of very-close voltages around 20V (I've seen 18.5, 19, 19.5, 20, 21, even 18.75 or 19.25) is more for vendor-lock-in reasons than anything else --- 19V is only 5% less than 20V, and a PSU rated at 20V may even end up at 19V or less under full load from resistive losses. Due to using DC-DC converters, a slightly higher voltage may even increase efficiency as there's less I^2R losses with the lower current that results.<p><i>I did check the stock laptop power supply and it came in at 20.4V, which was somewhat curious.</i><p>That's only 2% high, and if it was measured unloaded, I wouldn't be surprised.<p>I explained the reasons for the ~20V standard for laptops in this comment from almost a decade ago, and not that much has changed since: <a href="https://news.ycombinator.com/item?id=7594383" rel="nofollow">https://news.ycombinator.com/item?id=7594383</a>
DeWalt (and the other power tool brands) now offer USB-C PD adapters for their batteries, which might be even easier to assemble if you have a modern laptop that takes USB PD and have already invested in a power tool brand.<p><a href="https://www.theverge.com/23287770/dewalt-dcb094-usb-c-pd-charging-kit-review" rel="nofollow">https://www.theverge.com/23287770/dewalt-dcb094-usb-c-pd-cha...</a>
I really enjoy working remotely, like properly out in the woods. For whatever reason most of the 'desktop replacement' laptops refuse to use external USB-PD battery banks so I designed a quick in-line adapter around an industrial DC/DC converter. Its fairly quick to assemble and thought this might be of interest to some of you.
This is a great article with a lot of lovely detail and photos…and yet I was left wondering how the author actually connected it to the e-bike’s battery—was it directly? Via the bike’s charging port? I’d love to know more about the actual mechanics of _that_ and how they went about it because I’ve long wondered why these modern e-bikes don’t offer more ways to charge other devices from them (with a few exceptions in the Bosch lineup, with the ‘smart hub’ that they sell).
Why not use an adjustable buck converter? They are extremely cheap and smaller (but without an enclosure). 15A can be purchased for $12 - <a href="https://www.amazon.com/Diymore-Adjustable-Regulator-Converter-Constant/dp/B072BN43P8/" rel="nofollow">https://www.amazon.com/Diymore-Adjustable-Regulator-Converte...</a>
Made something similar that outputs 12V/24V to use an inverter for 220V appliances. Which also allows generic USBC adapterw for the car to work, which do a much wider range of voltages than just 20V (with the ducurrent limitation of max 100W/5A).<p>Mostly have been using it to charge Lipos for RC (cars and drones) on the go.
Nice and tidy indeed! Overall packaging looks robust and the threaded gland nuts push it over the top. Nicely done. Now I just have to stop playing around with the embedded 3D model and make one for my scooter :D
I've been looking at less portable remote working.<p>I gradually moved away from larger and larger battery banks to a more DIY flavor, using lifepo4 batteries and inverters:<p><a href="https://www.amazon.com/dp/B098QL2VBZ" rel="nofollow">https://www.amazon.com/dp/B098QL2VBZ</a><p><a href="https://www.amazon.com/dp/B09DQ35JV7" rel="nofollow">https://www.amazon.com/dp/B09DQ35JV7</a><p>So this is AC -> battery -> AC but your DC setup should work too, skipping charging. The lifepo4 batteries have enormous capacity for not too much money.
That DC/DC converter is quite large and expensive for the rated power, no? If you’ve got a stable low-impedance DC source, I imagine you could do a lot better following a TI application note :)<p>I picked up a very tiny 65W GaNFET usbC brick recently, I’ve been curious to see DIY projects put that technology to use. Marginally higher part cost but significantly better efficiency.
I am doing a similar thing but for a Mac Studio running Asahi Linux (13 W idle, 215 W max), since DC/DC was not an option I am using <a href="https://www.amazon.com/CAT-Professional-Station-Starter-Compressor/dp/B088RMSXD1" rel="nofollow">https://www.amazon.com/CAT-Professional-Station-Starter-Comp...</a> (200W max) which was half price at Costco. A power adapter that can also inflate tiers and jumpstart other veihicles.<p>Would anyone know if I can charge it while the computer is plugged? I usually assume that is a no / no, but if I were to try, could something explode?
> Checking against the datasheet, I came up with ~12.7k to get to 20.4V and the closest I had on hand was 13K<p>You can measure the 13kOhm resistors that you have and see if there is one with a better matching value. 12.7k is ~97-98% of 13k which is well inside the tolerance of your resistors (it says 5% on the bag).
What is the power loss to heat? I am thinking about using Rad Cycle batteries as a power source for my van (instead of a Jackery, Goalzero, etc) The batteries are 48V, 600Wh and I mostly just want to be able to convert to 5V up to 2.4amps. Is this possible and is this a dumb idea? Any pointers welcome.
I thought it was a "ride faster if you don't want your laptop to shut down and drop your call" kind of experiment, but it's more of a "let's run a laptop on a big battery from an e-bike", should have read the title more carefully.
Sort of off topic - But I think consumer UPS have fallen short. A) They stick with SLA and not something like LiFePO4 and B) They haven't fully embraced USB-PD.<p>A UPS with LiFePO4 and USB-PD should give you hours of backup power.