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Ongoing tests/discussion about the various ways to power a laptop (requiring more than standard 12v DC supply) Made a post in the "best laptop for RV" topic, but want to expand on the power supply end of the process more than the laptop itself. Not interested in laptop specs, how energy efficient, how much power, or latest o.s etc they have. Just the power supply and what fulltime offgrid community might be doing to get around the "conversion" factor. Years ago (before laptops were so cheap) we built a "12v" computer system with a mini-itx motherboard and 12v flat screen monitor. A nifty DC-DC ATX pin adapter was used to convert the 12vDC to the various lower voltages needed for the motherboard (12v, 6v, 3v, etc). None of the volts were over 12v and so it was pretty simple. Prob not as effecient as it sounds with all the resistance, but there was no need for an inverter nor DC stepup to attain 19v. Earlier laptops used 12v DC jacks (internal batteries were prob 9v). We ran one directly off a camper battery/solar for 3 months in the winter of 1996. I believe it was a Toshiba? Might not have even had windows95! Nowadays laptops typically require 19 volt inputs and we are forced to do some kind of conversion for our system to work on 12v battery bank. For myself, a small 300W inverter along with the laptop's AC/DC converter brick has worked decent enough, but the process is not the most effecient. 12DC converted to AC (via inverter), converted back to 19v DC (via the laptop ac/dc power brick) and then charge up a 12v internal battery pack! And Stephen mentioned that the laptop screen requires its own AC and so the laptop does its own internal DC-AC converting as well! For those that just want to plug into their car battery for limited use, the market is flooded with all sorts of DC-DC step up converters. Maybe a tad more efficient than inversion (tests will show). And so will be investigating this route here soon. The question tho would seem is it possible to run a "19v" computer without DC-DC stepup nor Inverter-Converter? Quoting my post: After doing a little research on the internet, I have found several posts describing ppl able to get their 18-20V laptops working with car battery voltage. In all the instances, the users reported that while the computer "ran", but their laptop batteries did not charge. Maybe this was their own particular model or perhaps they were actually powering via the batteries and not realizing it.Many of us aren't looking for a "portable" computer and don't care if the batteries aren't being charged. In fact, best would be for the internal batteries to be removed for an off-grid application such as an RV. None of the laptops used in our household connected to 110AC have battery packs! And we've used the laptop in the RV off the inverter/power brick batteryless as well. (obviously "backup work" in case of power failure isn't a concern). So if you could get laptop to run as described with12v input into the 19v jack, then that would prob be the end of this discussion. But I couldn't get any of the different test machines to run this way. And so what about the internal battery pack itself? Unfortunately the computer's battery pack is a little more sophisticated than that (or so it seems). There are several voltages and signals being sent to the motherboard via different battery cell serial/parallel configurations. Looks like about 3 different voltages and 4 connections to the battery configuration. Now, it might be possible to recreate those voltages, but haven't came across any info or hobbyist who has tried thisWhich brings up another option: External battery packs. These batteries boast much larger capacity and can "extend" your battery usage. But the kicker is they hook up to the 19v DC jack and thus start "charging" your dead 12v internal batteries thus equalizing the 2 battery banks. Dumb idea. A backup battery pack should plug into the internal battery compartment, not the laptop charging port! Or at the least disconnect your internal batteries. And how does one go about recharging a 19V external battery pack in a 12v system such as an RV? These are simply meant as extended "portable" solutions. But we're not interested in portability. Instead, this external battery pack should be another "internal" 12v battery pack. In our case a bank of 12v deep cycle batteries with hundreds of Amp hours of use! So that's where we are. My inverter/converter brick is working fine and have plenty of solar/amp storage, but it is a nagging itch to bypass all the necessary conversion. Some say they were able to bypass the internal "charging" by connecting a lower 12v directly to the 19vDC jack. I couldn't get mine to work. I think a better approach would be to fool the laptop into thinking it's internal 12v battery pack was actually supplying the power NOT the 19v "charging" jack. ???? ... to be continued.