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Blog On Using a USB Battery for a Portable Project Power Supply
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  • Author Author: jw0752
  • Date Created: 15 Oct 2018 3:25 AM Date Created
  • Views 3912 views
  • Likes 20 likes
  • Comments 28 comments
  • portable_power
  • usb_battery
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On Using a USB Battery for a Portable Project Power Supply

jw0752
jw0752
15 Oct 2018

Everyone is familiar with the USB Batteries that can be used to charge a cell phone and which can themselves be charged off a any standard USB port or charger. A while back I began using one type of these batteries to power some of my small projects and also I began to advocate their use to my friends for this purpose. Here are two of the many brands and types currently available.

 

image

 

For the rest of this Blog I will refer to them as "Black" and "Silver". My first experience with using these batteries for project power supplies was with Silver. Silver is typical in that it has a 3.7 volt Li-Ion cell at its heart which can be charged with a 5 volt charger and when off the charger and plugged into another device uses an internal boost DC to DC converter to deliver 5 volts output. When Silver is turned on and no load is present it will turn itself off after 60 seconds. When Silver is turned on under load it will maintain an on state as long as the load doesn't drop below 10 mA for more than 60 seconds. Its internal sensor sees loads less than 10 mA as no load and starts a shut down sequence. My experience with Silver as a power source for small projects has been excellent as I seldom build anything that operates at less than 10 mA.

 

It is our nature to generalize and true to my human nature I made the mistake of believing that all other types and brands of these devices would behave just like Silver.

 

Along came Black whose purpose was to power a small frequency counter kit that I built for a friend. Black it turns out is not like Silver. Black will automatically shut down after 18 seconds if it doesn't see a load. Further it turns out that the lower limit for the load that it can see is 75 mA. The small frequency counter did not draw anything near 75 mA and so every 18 seconds the battery needed to be turned back on which was not practical.

 

The other day in a Blog by fmilburn   -  Working Prototype of a Kelvin (4-Wire) Milliohm Meter  the discussion morphed into some comments about using this type of battery pack for his portable milliohm meter. It was noted that there is a  tendency for these batteries to shut off. In the discussion Frank mentioned that somewhere he had heard about a procedure to pulse the USB battery with a short moderate current load to keep it active.

 

I wanted to have the flexibility to use Black in future projects so I drew up a schematic and did some bench testing finally arrived at a bread board prototype:

 

image

 

Here is a schematic of this circuit:

 

image

This circuit has a quiescent current of 2.5 mA and produces a 3 millisecond load of 300 mA every ten seconds. Black which would normally turn off after 18 seconds with a load of less than 75 mA was perfectly happy to stay engaged and run for hours when attached to this circuit. The 10 second load pulse was within Black's 18 second window to shut down and apparently the 300 mA load was sufficient to restart the 18 second time limit.

 

While I hadn't had any problems with Silver I wanted to see if Silver would also respond to the pulsed load to reset its 60 second time out on loads of less than 10 mA. Unfortunately this was not to be. The (6) 300 mA loads that were put on Silver did not change its mind and after 60 seconds it promptly turned off.

 

I do not want to make the mistake of generalizing this situation again but I know there are at least 2 different situations when using USB batteries (Silver and Black) and I might extend this idea to say that there are likely many others. Here is my comparison of Silver and Black:

 

Battery Name       Model & Brand               Time to Shut Down (No Load)        Minimun Stay On Load             Does the Pulse Load Fix Work

 

Silver                XPB15031S  Unknown                      60 Seconds                                10 mA                                                 No

 

Black                 16WMS137  Shen Zhen                   18 Seconds                                 75 mA                                                 Yes

 

I am posting this blog in Test & Tools as I do not want it to belong to me but serve as a place were additional information on using USB batteries to power projects can be posted. If you have a USB battery, and are inclined to test it, any information you can supply would be appreciated. Short of loading the battery down with power wasting loads to keep them on what other schemes can we come up with? Is there a special magic circuit that will work to keep any USB battery engaged powering our small portable projects or will we have to design a specific remedy for each unique USB battery type?

 

Since the use of the USB battery technology can be a benefit to anyone wanting a convenient power source for small portable projects I welcome as many ideas and tested remedies as can be found.

 

 

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Top Comments

  • dougw
    dougw over 5 years ago +7
    Nice solution jw0752 . I have some units that look exactly like your silver unit except they are black - and they stay on indefinitely - until the power button is pressed again. There is a little blue…
  • Gough Lui
    Gough Lui over 5 years ago +7
    As an experienced power bank tester - I've come across a wide variation of types, but I haven't really taken the time to test the shut-off behaviour. I have found some that: Have high quiescent current…
  • genebren
    genebren over 5 years ago +7
    Very interesting investigation and work-around. I really enjoy seeing your process and approach in solving a problem. Here is another solution, you could build your own USB/battery source. In my development…
  • colporteur
    colporteur over 3 years ago

    The circuit is overhead (wasted energy) on a battery supported system. How much battery life is lost due to the circuit?

     

    I got a battery like your silver unit  in a swag bag. I wanted to know how long it would power a Pi3B+ running a GPD module. I can't recall the time the Pi ran, I want to say 8 hours but I was using another battery with a higher capacity so I may have switch the values. The battery life was sufficient to turn a Pi into a portal GPS recorder. Yeah, no need to purchase something just for testing.

     

    What would be the lost of uptime due to your circuit? I realize the keepalive is small but it is still lost energy.

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  • dubbie
    dubbie over 3 years ago in reply to botsmaker

    Bill,

     

    If the battery capacity is scaled up then it probably makes sense to scale up the triggering current as well. I have used a 2600 mAh pack that needs a 50 mA drain to keep going although the trigger is much less. So I currently 'waste' 50 mA in a resistive load but the system will still work for 50 hours and I can always recharge it.

     

    It would be nice if it only needed a 1 mA trigger and constant current as then it would last for 2600 hours but I can always use a LiPo battery for that sort of current drain.

     

    Dubbie

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  • jw0752
    jw0752 over 3 years ago in reply to botsmaker

    Hi Bill,

     

    Nice modification using the PICAXE. It is fun to put ones own spin on things. I am glad it worked out. The USB batteries are really convenient except for the load trigger.

     

    John

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  • botsmaker
    botsmaker over 3 years ago

    Today I made one using a Picaxe 08M2 for the timing and used it to pulse a 2N4401 transistor with a 10 ohm resistor. I needed to use a battery pack to power a Arduino Uno with Logger (it wants 20 ma). Works pretty good with 10 millisec pulses every 5 seconds. After building it, I could have just added the resistor and transistor to the Arduino shield circuit itself and have the program pulse the resistor for me. With the Picaxe, only a few lines of code are required.

     

    It seems the bigger the pack, the more load is required. I tried setting up the timing for my Powobest Solar Bank and couldn't get enough current to trigger it.  Gave up on it as it would waste too much power.

     

    Good project idea, glad you posted it.image

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  • dubbie
    dubbie over 3 years ago in reply to koudelad

    David,

     

    Will you be sharing this data? It sounds interesting.

     

    Dubbie

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