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L.R.A

PowerBank has a project power supply - minimum current?

18 posts in this topic

Hi guys!

I have a little problem here. So I want to make a robot with 2 servo motors. To make it small and easy to use for the kids at the club, I want to use a power bank to power everything. Well I've heard some powerbanks have a minimum current before they shut down. I don't want to use a resistor or a pulsed load to keep the powerbank on if that's the case.

So I would like to know if anyone has had experience in using these powerbanks and knows it's good to use with just a microcontroler drawing power from it - the robot has servos but sometimes it can just be standing still.
I'm thinking of using this ones (they need to be about 100x25x25mm or less)
http://www.ebay.com/itm/USB-2600Mah-Portable-External-Battery-Charger-Power-Bank-for-Cell-Mobile-Phone-/141564208385?var=&hash=item20f5e26501:m:mjdVxgZQJgBThymbmYBeIUA


If anyone could help it would be greatly appreciated :)

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Hi @L.R.A

 

My experience is limited but I did try A USB charger with larger capacity a year or so ago. It would shut down when a MSP430 was looping and polling with no other activity. I pretty quickly turned to alkaline and lipo batteries in the 3 V range and didn't work with it any further. At that price you are not out a whole lot of money trying though.

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I've never had issues with a similarly looking power bank.

 

Haven't tried it in real low power scenarios, but it was happy to feed my AIS receiver at 17mA all day long.

L.R.A likes this

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This will be mostly for using Arduinos and Launchpads like the TM4C with Energia so if 17mA is good then no problem :)


Thank you very much. Then I might be able to order the whole bunch without having to ask for 1, test and then ask for the bunch

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The circuit seems to be pretty much the same for these ones. I don't think there will be any diference in this model relative to that protectiom. I asked a seller and he said there isn't such protection. So if it comes and there is, then I will ask for a refund based on that answer

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btw, anyone interested in this base (@@chicken, @Fmilburn)? I'm probably gonna make another version that has places to fit in the launchpads back female headers.
It's based on a project by adafruit, so the rest of the parts are there, I just made a different base.

 

open with adobe reader to look around.
It's 130x75mm in size. The powerbank box should be about 2cm of the ground. The powerbank box is 120x25x25mm
 

test.PDF

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I'm probably gonna order some for me too after september starts. Plus,of course, some for this project

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@@Fmilburn It arrived. Tested it and there seems to be a lower limit. I would estimate about 50mA. If you draw less than that it turns off... :(
It will work for this little robot, I could have an LED in it flashing too. But it's a shame, can't use it for a project that only has a bluetooth device, a MCU and a IMU.

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At the very least there should be a sense resistor. You can increase it but then you limit the maximum current before it cuts off.

If there is a voltage divider setting the minimum current, that would be awesome.

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@L.R.A

 

I ordered a different one which arrived last week. Unfortunately it did not work at all. I took it apart and the battery is dated 2013.04.16 so it had been sitting around a while.

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@L.R.A

 

I ordered a different one which arrived last week. Unfortunately it did not work at all. I took it apart and the battery is dated 2013.04.16 so it had been sitting around a while.

Seriously? what a bummer :/

 

I've been waiting for another before this one.... since august the 15th (this one that arrived was ordered august the 31st)... let's hope that one works. If it arrives. 

 

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I set my expectations low for these cheap no-name items.  That way I am not disappointed and sometimes pleasantly surprised.  The soldering is quite bad on this one and take a look at the pin on the right that was apparently shorted. No QA apparent at all.

 

post-45284-0-60354100-1474072288_thumb.jpg

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So far I am pleasantly surprised as it is still going and already charged it (well it was not all they way discharged when it came).
I would post a video but it doesn't seem to support it.

How did you open yours? I want to look inside mine but not sure on how to open the case.
 

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It is not the same model as the ones in your original link.  It is in an aluminum tube and the top unscrews.  The little PCB inside has components on both sides - nicely soldered SMD parts on one side and hand soldered SMD on the other.  The hand soldered side is really bad.

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Why are you adverse from using a pulsed load resistor? Depending on the power bank, the pulse only needs to be once every 15 seconds. The average load will be in the <1 mA range.

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