12V Power Supply for EliteDesk 705 G1

[Zambonikane]

Hi Everyone, 

I just purchased a refurbished EliteDesk 705 G1 that I was planning on using for running my astrophotography equipment.  I will often use this in far flung places away from city lights and therefore have everything running from a dedicated 12V deep cycle marine battery. I looked at the specifications of the included power supply (a brick similar/identical to a laptop charger) and picked up a 3rd party car charger/PSU with the expectation that I would be able to run the computer from it.  Well, as you can imagine, since I am here, this did not work. I am getting the correct voltage from it, but when I connect it to the EliteDesk, I get nothing.  I then cut off the barrel adapter from the AC power adapter thinking it was a poor fit that was keeping and I noticed a 3rd blue conductor.  I figure this is the signal wire that allows laptops to communicate with chargers.  Does anyone know of a 12v solution that would allow me to power the Elitedesk in the field?

Thank you in advance.

Mike

[DGroves]

as you have found out the EliteDesk 705 G1 talks to the power supply, using what is known as a one wire protocol in order to determine the attached power supply wattage, and if missing not to power or or charge

the official adapters for this unit were 65W 90W 120W depending on the installed options with 90/120 being the most common

it will take someone with knowledge in the field to be able to reverse engineer this protocol and adaptect it. Due to this i recommend you replace the system with a  pico or mini  ATX motherboard powered with a commercial 12 volt to 24 pin  adapter 

that matches your wattage needs

https://www.aaeon.com/en/c/pico-itx-boards

https://www.mini-box.com/picoPSU-150-XT

https://www.amazon.com/Motherboards-Mini-ITX-Internal-Components/s?rh=n%3A1048424%2Cp_n_feature_six_...