is it safe to power an Arduino project from a power bank? - Page 1
Forum section: electronics / beginners

author: engineheat
author_rank: Frequent Contributor
timestamp: June 24, 2019, 01:25:49 pm
content: I got an Arduino project that need a constant source of power. Rather than dealing with batteries, I want to use a power bank like this:Better yet, I want to keep the power bank plugged in to the wall outlet using a wall charger like this:The USB wire coming out of the power bank, I can modify it and connect it to the 5V on the Arduino (Pro Mini 5V version). Is it safe to do so? The application uses a stepper motor that draws around 200mA and only runs intermittently.Thanks

author: johnkenyon
author_rank: Regular Contributor
timestamp: June 24, 2019, 01:48:24 pm
content: Many power banks will not permit charging (from a wall wart) at the same time as discharging into a load.Or put another way, either current flowing into the power bank, or flowing out of the power bank, but not at the same time...

author: Brumby
author_rank: Unknown
timestamp: June 24, 2019, 01:49:44 pm
content: There's nothing basically wrong. Just make sure you're not trying to pull too much current (which it seems you've got covered) and that the power bank can supply powerat the same timeas it is being charged - then you should be alright.Snap!Quote from: johnkenyon on June 24, 2019, 01:48:24 pmIf the plug pack is a SMPS style (very likely these days), just be aware of the possibility of some capacitive coupling from the mains showing up on your circuit. It shouldn't be dangerous, but it might interfere with operation if there are any high impedance parts of the circuit.If you haven't done it already, I'd also make sure you had some bulk capacitance in the appropriate place to cover any instantaneous demands from the stepper.

author: BillyD
author_rank: Regular Contributor
timestamp: June 24, 2019, 02:32:00 pm
content: Another consideration is that some power banks will shutdown/sleep unless you are drawing a certain current.I have one which uses a boost converter to deliver 5V, so naturally the converter only operates when needed.You have to wake it up by physically plugging something into one of the ports, or pressing a button if they're already plugged in.It stays awake as long as you're pulling a reasonable current, say charging up a phone, but goes back to sleep once the current draw drops below a certain threshold.One which behaves like this would not be suitable for a low current standby type application.

author: kjr18
author_rank: Regular Contributor
timestamp: June 24, 2019, 03:33:34 pm
content: The best way to do this would be to use something called ups module.something like this one[\url].

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 24, 2019, 03:35:34 pm
content: Quote from: BillyD on June 24, 2019, 02:32:00 pmI've had this exact issue when powering an AVR derived device with a power bank.

author: Wimberleytech
author_rank: Super Contributor
timestamp: June 24, 2019, 04:05:31 pm
content: Quote from: BillyD on June 24, 2019, 02:32:00 pmIndeed. I bought a bunch of Chinese 18650 power banks and removed the buck/boost circuit for one of my arduino projects. Great idea...almost. The good news is that the circuit could charge the battery from USB and then boost the 18650 to 5 volts for the arduino.The bad news is, the boost shut down if you were drawing less than 60mA. Since the project used a bunch of LED indicators, I had to just turn them all on during idle. Bummer.No way to know which power banks suffer from this, but I suspect that most do.

author: Brumby
author_rank: Unknown
timestamp: June 25, 2019, 03:29:52 am
content: Quote from: BillyD on June 24, 2019, 02:32:00 pmYes - I've come across this as well.If I remember correctly, for the unit I am thinking of, the shut down didn't happen immediately the current went low, but after a delay. If you do encounter this shutdown problem, then it I would suggest you try doing some current and timing experiments to find out if there is a combination which will keep power applied with minimal excess power drain. You could then add a routine to your Arduino to switch on some LEDs (for example) to create that drain.

author: garethw
author_rank: Regular Contributor
timestamp: June 25, 2019, 07:50:46 am
content: The Zendure powerbanks allow simultaneous powering/charging which i use regularly for my phone whilst at Uni.

author: engineheat
author_rank: Frequent Contributor
timestamp: June 25, 2019, 04:42:13 pm
content: If I power my project using a PowerBank only (without the wall connector), I wonder how long I can use it before need to recharge.Say I get a fully charged 20000mAh power bank. The Arduino will power a 2 x 16 LCD (no backlight) and start a count down process from 2 minutes. Once 2 min is up, a stepper motor (also powered using the power bank) take consumes 200 mA would run for 10 sec, and that's the end of the program. I will put the Arduino to sleep after this, and I assume the power bank will shut itself off after awhile with minimal current draw.Suppose the program runs once per day. A simplistic calculation shows that it would be years before I need to recharge the power bank. But I feel in reality it won't last nearly this long, is that correct? The battery will probably lose juice on its own and I might've overlooked some other sources of loss?

author: Brumby
author_rank: Unknown
timestamp: June 25, 2019, 10:52:26 pm
content: You will have some self-discharge to contend with, but it is nowhere near as bad with modern lithium ion tech as it was with NiCad and NiMH. Exactly how much you might need to allow for I will leave to others with better knowledge.The other thing I am curious about is you say you start a 2 minute countdown - but what event triggers this? A manual button press? A sensor? Another signal? I ask because there is a question hanging in the air.....Once your Arduino has done it's duty and is put to sleep, should the power bank also go to sleep - how will the Arduino ever get power again? Unless there is an external input or stimulus to get the power bank to turn on, the Arduino will not have any power to support a "sleep" mode from which it can wake up - it will simply be off.

author: engineheat
author_rank: Frequent Contributor
timestamp: June 26, 2019, 01:13:35 am
content: A person would press a button (or two) manually to start the program. The goal of the program is to merely have the stepper motor do something after a delay so the person wouldn't have to come back (or wait around) to do it manually. But the whole process would be initiated by a human at random times.So the fact that lots of power banks would shut itself off is actually good for me. Power banks usually have a button that one can turn it back on.

author: mdszy
author_rank: Unknown
timestamp: June 26, 2019, 03:08:59 am
content: I've tried using power banks to power my own projects, and have ran into the issue that other people have mentioned: power banks will shut down unless they receive a specific signal telling them to provide power.Not to shill for this company, I'm not associated with them in any way, but they make a power bank specifically made for powering electronics projects and will be always on whenever they're powered, constantly providing power.The company isVoltaic, and they have a line of always-on power banks.I've used them and quite like them.

author: ledtester
author_rank: Super Contributor
timestamp: June 26, 2019, 05:47:13 am
content: How about running the project directly off a single 18650 Li-ion battery? Both Arduinos and 2x16 LCD displays can be run at 3.3V so all you have to figure out is the stepper motor part.Update: Here's a DC-DC boost converter which can deliver >200 mA at 5V with shutdown capability:https://www.pololu.com/product/2562Update 2: Another option: just use a bank of 4 AA alkaline batteries.