Cheapest Power Bank Review (with Schematic)

Test and teardown of the cheapest power bank ever – the 80 cent (incl. shipping) power bank from Ebay. Of course, you have to insert your own 3.7V Li-Ion 18650 cell into it :). What did you expect for 80 cents :)? It works well for loads up to 1A. At 1A the output voltage is 4.94V. At 1.1A the voltage drops to 4.56V and at 1.25A it shuts down. It charges the battery to about 4.2V and discharges it down to 3.1V. While charging, the power bank draws 0.78A from a 5V supply. Red blinking LED indicates charging. Steady red light indicates fully charged battery. Blue light indicates a load. When there’s about 10% of capacity remaining, the blue LED starts blinking. The power bank is controlled by MP3401A chip and there are just few other components (3 capacitors, 1.5uH inductor and 2 LEDs). The battery space is little bit too short, but you still can insert the battery. The only problem is that there’s no fuse in series with the battery. If the chip fails short, the battery will be shorted. In extreme case, this may lead to fire.


funny sunny says:

Please can you give link of buying it please

Neil Ahmad says:

My only question is how can i tell if my powerbank is full?

Adrian Andronache says:

I bought also one of these before seeing your video. They are okay, but as you observed, the batt compartment is really short. The chip used does not accept both charge&discharge simultaneously.

Some Random Guy With A Channel On YouTube says:

I bought one like one of these for $4.20 at my local dollarama and I couldn’t be happier it’s only *temporary* though

Penurious Sierra says:

I used a little hack that allows these things to accept protected cells so they don’t go nuclear that easily.
Remove the little pillar behind the positive contact with snips (including the tiny wall behind it) and flatten the contact with flat nose pliers (make sure not to snap the contacts or rip it from the circuit like I did). Now it can accept protected cells!

Ijaz aslam says:

I’m not really into electronics, but these videos are really interesting. Keep it up!

bb says:

Hi Diode, could you suggest way to make a backup power for ADSL router (power through)? It uses 9v, 0.6A. It won’t work with xiaomi 10Ah powerbank, even though I tried it without, and with 3 types of voltage boosters. They just cant hold the voltage. I am thinking of buying two of this small bastards that support power through, and connect them in series, but I don’t even know what kind supports being charged while they are charging the device, which is crucial for this kind of use. Xiaomi can do that, but I can’t order one more, because reliable stores don’t send it to my country anymore. I’m sure that a ninja like you have some solution for crappy problem like this 🙂

Jaspal Rana says:

Battery not charging please help me

paul barbara says:

Bought one for 2 euros after half charging it I started smelling something burning and in less than a second, a circuit part behind the small USB exploded. I just used it less than 2 minutes with a 5volt Samsung charger

Jimbo says:

Please post ebay links to the items you purchase to take apart. Great vid.

Yu Kauwai says:

if I only want to regulate the 3.7V battery to 5V DC output, should I connect the pin 4 to the GND?

Titanfall Tyler says:

So wait basically you can charge those batteries? Right?…..

Barry Greengrass says:

In your video you say it doesn’t have a fuse, please can you tell me whereabouts I can put a fuse wire? My circuit board is exactly the same as yours and has the same number on it TXT-XS-151224

#ff00cf Is my fav color says:

Hey guys do you notice the ic heats up when charging…. Kinda need your feed back lol

zx8401ztv says:

Well it is cheap, and it appears to control the charging fine, so it should be safe :-).
The boost converter seems to run out of steam, i would pay more for a better version, if i needed one.
Is it possible the battery you used was a bit duff?

migsven surfing says:

A lot for 80 cents. Thanks for the video.

Bartosz Olszewski says:

I’m buying one right now it’s excellent power bank

Georges Obeid says:

Great job man keep doing great video like this one

Gavin Davies says:

I think the power bank is designed for non-protected cell. As non-protected cells, do not have circuit board on the top, they are slightly shorter.

They sell these power banks in pound world with a battery for well 1 pound, if you live in the UK.

John Kelleher says:

Interesting. How about a link to the product?

ReEgo says:

to je frajer!strašně dobře mluvíš”!!

Emrldy says:

It doesn’t have reverse polarity protection when inserting the battery, I found that out the hard way 🙂

MrJohhhnnnyyy says:

Not bad for 80 cents, I would say. By the way, 1.5mH seems too high, maybe it is 1.5uH. These things operate at pretty darn high frequencies, 1.5uH seems more realistic. On top of that, you need a boat load of turns to get that inductance on this tiny core. Good videos, though, I didn’t know they’re down to 80 cents 🙂

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