L.R.A 78 Posted August 27, 2016 Share Posted August 27, 2016 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:mjdVxgZQJgBThymbmYBeIUAIf anyone could help it would be greatly appreciated Quote Link to post Share on other sites
Fmilburn 445 Posted August 28, 2016 Share Posted August 28, 2016 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. Quote Link to post Share on other sites
chicken 630 Posted August 28, 2016 Share Posted August 28, 2016 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 1 Quote Link to post Share on other sites
L.R.A 78 Posted August 28, 2016 Author Share Posted August 28, 2016 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 Quote Link to post Share on other sites
chicken 630 Posted August 28, 2016 Share Posted August 28, 2016 @L.R.A No warranties that they are the same inside though.. Quote Link to post Share on other sites
L.R.A 78 Posted August 28, 2016 Author Share Posted August 28, 2016 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 Quote Link to post Share on other sites
L.R.A 78 Posted August 28, 2016 Author Share Posted August 28, 2016 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 Quote Link to post Share on other sites
Fmilburn 445 Posted August 28, 2016 Share Posted August 28, 2016 I think I will order a couple now that I know they will work. Should be handy. Quote Link to post Share on other sites
L.R.A 78 Posted August 28, 2016 Author Share Posted August 28, 2016 I'm probably gonna order some for me too after september starts. Plus,of course, some for this project Quote Link to post Share on other sites
L.R.A 78 Posted September 16, 2016 Author Share Posted September 16, 2016 @@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. Quote Link to post Share on other sites
chicken 630 Posted September 16, 2016 Share Posted September 16, 2016 That's a shame :-( Maybe there's a way to hack it. Though it's probably all integrated into a single IC. Quote Link to post Share on other sites
L.R.A 78 Posted September 16, 2016 Author Share Posted September 16, 2016 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. Quote Link to post Share on other sites
Fmilburn 445 Posted September 16, 2016 Share Posted September 16, 2016 @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. Quote Link to post Share on other sites
L.R.A 78 Posted September 16, 2016 Author Share Posted September 16, 2016 @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. Quote Link to post Share on other sites
Fmilburn 445 Posted September 17, 2016 Share Posted September 17, 2016 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. Quote Link to post Share on other sites
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