5 Replies Latest reply on Sep 29, 2016 8:36 AM by Intel Corporation

    Powering from battery

    tommises

      I am cross-posting from electronics.stackexchange.com.

       

      I have STK1AW32SC, which I am trying to power from a battery.

       

      The computer is powered via a Micro USB port. It comes with a wall power supply which has 5V 3A output. I measured the actual output to be 5.16V. The maximum power consumption I measured to be 1A in my application.

      Here is what my initial setup was for powering from a battery:

      [16V battery] -> [5V 3A out buck converter] -> [Intel Compute Stick]

       

      Using this setup resulted in bricking two computers. Each time, it happened while reconnecting the power supply. I hooked up an oscilloscope and observed voltage spikes when connecting the battery. To cope with this, I decided to add an electronic switch between the buck converter and the computer (Mini MOSFET Slide Switch with Reverse Voltage Protection SV from Pololu) and to make sure it is always open when connecting the battery.

       

      So, my second setup was:

      [16V battery] -> [5V 3A out buck converter] -> [MOSFET switch] -> [Intel Compute Stick]

       

      Below are pictures from the oscilloscope, the first two are for the first setup without the switch and the rest is for the second setup. So, it all seemed to look just fine. The actual converter output is around 5.28V which is just slightly more than 5.15V and there are no voltage spikes. At this point I decided to make the final test by connecting the battery and switching the switch on until the initial welcome screen was displayed and then switching back off. I planned to try 200 such cycles, and after 130 cycles Compute Stick died...

       

      combined.png

       

      So, I still must be doing something wrong, but have no idea what this could be at this point. As far as I can tell, all I have at this point is constant 5V power supply from the converter and I am just opening and closing the switch.

       

      Any ideas?

        • 1. Re: Powering from battery
          tommises

          I noticed a number of posts on this forum reporting bricked Compute Sticks even though the factory power supply was used. I followed the recommendation to press the power button for 3 seconds and my latest bricked computer came back to live! The two previous ones are still dead, presumably damaged by those voltage spikes. So, it looks like this product has some serious flaws related to power supply... disappointing. Hopefully, it keeps working going forward...

          • 2. Re: Powering from battery
            Intel Corporation
            This message was posted on behalf of Intel Corporation

            Hi Tommises,
             
            Please let me investigate and see what I can do for you from this site.
             
            Regards,
            Hellen.
             

            • 3. Re: Powering from battery
              rguevara

              Hi tommises,

               

              I am with Intel Customer Support and I just would like to let you know that we haven’t tested or validated any battery powering and therefore our contribution to this scenario is very limited.

              I encourage other community members to share their experience.


              Thanks,

              Ronny G

              • 4. Re: Powering from battery
                Pitrack_1

                Hi tommises,

                 

                Funnily enough I have been testing 5V power supply over USB lately. So here's a few items I can think of.

                 

                1) A power capacitor across the output should help alleviate the spike, and any sags perhaps caused by spikes in demand.

                 

                2) How much are your little 'buck' converters worth? Are they any good? If you've got a $200 PC, spend a bit more than $2 on the power supply which follow.

                     a) How gracefully does the buck handle changes in power demand? If it suddenly increases, e.g. you plug a USB3 device in, will there be a droop whilst it catches up? In which case you're likely to suffer a crash or even another 'brick' experience.

                     b) what's the ripple like?

                     c) Do they handle overcurrent demands gracefully?

                     d) Do they maintain voltage output up to their rating? I have quite a few cheap devices that don't measure up to their 5V 2A rating or anywhere near it. The voltage droops far before (crash/brick)

                 

                I have some 12V to 5V 4A DC-DC converters that are worth ~ say $20 each. They're industrial ones, I believe now out of production. But there should be a plethora of similar ones available. However I have tested 5 of them and found:

                a) They are at 5.00V +/-0.05V with only one at 4.95V

                b) They all maintain voltage up to the 4A easily

                c) They have an "overhead" of 20% i.e. they will run 5V up to 5A no problem (I test for say a minute)  whatsoever. Testing done on an electronic load tester.

                d) No heatsink required. They only get mildy warm.

                e) They are larger than a simple "buck" a circuit board 105x50mm.

                f) Can't remember but I think input is tolerant up to 18V

                g) I think they are at least 80% efficient

                h) If you wish to look them up they are model PP25-12-5 using a module from Densei Lambda, supplier in Australia was Amtex, now under heliosps (see this link for some specs)

                3) I haven't tested the Intel Power supply, but I will now- if I can take of the power from the plug effectively without damaging it.

                 

                4) USB cable (and connector) quality is critical. And this actually is what my testing was all about- to be able to charge 5V 2A devices at 5V 2A. Cheap aftermarket cables will exhibit considerable resistance increasing with current and this leads to voltage drop (crash/brick). The brand name cables from USB high current charging devices, e.g. Asus, Samsung, Apple all are much better as they have thicker wire for the power wires. For example, at ~1A I couldn't get better than 4.6V through a cheap cable, and 4V at 2A. The Asus cable was ~4.9V at 2A. The Microsoft cable will have to support the 3A so you're probably better off cannibalising one of those power supplies for the cable to power your device.

                 

                5) 5V vs 5.16V and voltage drop. Was the 5.16V open circuit? And see point 4 above, if under load the 5.16V may be to allow some voltage drop in the cable under heavy load.

                 

                6) Also what is your instrument calibration? To be honest ours aren't directly calibrated however I have cross-checked voltages on several Fluke multimeters against the load tester and they were all in agreement within +/-0.02V at 5V DC.

                 

                Regards,

                 

                Patrick.

                • 5. Re: Powering from battery
                  Intel Corporation
                  This message was posted on behalf of Intel Corporation

                  Hi Pitrack_1,
                   
                  Thanks for this great information.
                   
                  Best Regards,
                  Hellen.