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Powering old laptops and other stuff with USB-C PD powerbanks

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First post, by adalbert

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Recently i had to replace the internals of my T3200SXC power supply and now it runs with modern DC-DC converters (Pololu) and laptop power brick instead of AC power. This is probably the first time that laptop got chance to get some real "portability", so I wondered if I could run it off battery. I have Mi Power Bank 3 Pro with PD output rated up to 45W, which is the peak power draw of that laptop with hard drive, audio and ethernet installed.

I bought some USB-C PD power triggers ("PD23.0 PD decoy module", there are 9/12V and 15/20V versions), attached DC power jack and turned the laptop on. Because of high starting current (HDD spinning up) a low ESR capacitor attached (25V around 1000uF) to the cable is needed, or the powerbank would shut down.

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It works just fine with 15V or 20V setting with T3200SXC (again I have custom power supply here, later i will mabe put schematics somewhere) and 20V with PCD-5ND (pentium 90MHz). 12V version would probably be enough to run 386 and 486 mainboards with Pico PSU or similar adapters 😀 I was also able to run HP DeskJet 340 with 9V setting (beware of reverse polarity), soldering iron and bunch of other stuff.

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Note: using additional capacitor has a small drawback: powerbank won't turn on if there is short time between plugging it on and off, because capacitor stores the voltage and powerbank thinks it's being charged, or something like that. Maybe a very small resistor between the leads (100k or so) used to discharge the capacitor would help.

Last edited by adalbert on 2020-07-22, 16:19. Edited 2 times in total.

Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

Reply 2 of 5, by imi

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I've been toying with this idea before, how do you set the voltage on the PD trigger? and can you make sure it will always do the correct voltage... i.e. not put out 20V when set to 15V? ^^

Reply 3 of 5, by adalbert

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imi wrote on 2020-07-22, 17:21:

I've been toying with this idea before, how do you set the voltage on the PD trigger?

There is a tiny switch on the side. It toggles between 15V and 20V, or 9V - 12V. It is a mechanical switch, so it "remembers" the setting. There are two versions of adapters and each toggles only between two voltages (9/12, 15/20).

imi wrote on 2020-07-22, 17:21:

can you make sure it will always do the correct voltage... i.e. not put out 20V when set to 15V?

There is an LED which tells the voltage. Red = 5V, green = 9V, blue = 12V, purple = 15V, white ("cool" white) = 20V. At least in model I'm using. If the switch is broken, it will probably default to lower voltage but this is my guess after looking on the circuit (switch seems to be shorting two traces to make higher voltage, open = lower voltage), I can't confirm that. PD cannot deliver more than 20V by design, so you won't get more than that.

If you connect that to unsupported power bank (5V USB), you get 5 volts and red light. If you connect 20V model to PD output which provides only 12V, you get 12V and blue light. If you connect 15V model to PD output which provides only 12V or 20V, but no 15V, you also get 12V.

20V is the safest option and should work with hardware requiring 19-22V. With lower voltages it's best to double check that they are correct.

There are also tiny fixed voltage adapters available. But they probably don't have LED.

Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

Reply 4 of 5, by imi

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I just remember reading that the USB-C power delivery is very flaky sometimes communicating voltages between devices ^^

unfortunately most of the variants I found only have a momentary switch and no toggle apparently.

Reply 5 of 5, by adalbert

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These are the ones I used, i just soldered screw terminals: https://aliexpress.com/item/4000124858649.html
fixed voltage (I didn't test it) https://aliexpress.com/item/4000124529027.html

If you want to be really safe and possibly waste some power and money 😜 you can use 15V PD module and step up/step down converter like this one, it will always work https://www.pololu.com/product/2573

Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg

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