[0:00] It’s summer and it’s been getting hot…
[0:02] I’ve got this little desk fan, which is handy for keeping the office a little bit cooler,
[0:05] but its not rechargeable and uses a lot of batteries.
[0:08] I’ve also got a couple of these power banks which were given out for free at a conference
[0:12] I attended a few years ago.
[0:13] It’s time for a bit of hack.
[0:14] I’m not sure what the actual capacity of the power bank is, but it claims to be 2200mAH.
[0:22] The power bank comes apart pretty easily, we just unpeel the front sticker and then
[0:25] undo these screws.
[0:26] You can then just push the contents out of the metal tube.
[0:28] Inside we’ve got the PCB with the USB connector and a 18650 battery.
[0:33] It’s a pretty compact PCB, after watching a lot of Big Clive tear-downs I was initially
[0:38] concerned that I couldn’t see any sign of a charging chip or battery protection circuitry.
[0:42] The chip is an MP3402A - initially I struggled to find any information on it, but I was able
[0:49] to find some Chinese data.
[0:50] Fortunately Google speaks a bit of Chinese and it’s turned it into pretty readable English.
[0:55] It turns out this little IC does everything, battery charging, battery protection, and
[0:59] boosting the battery voltage to 5V - it just needs a few passive components.
[1:02] It’s a amazing how simple power banks are - and these ones are quite a few years old.
[1:07] Shoehorning the 18650 cell and charging circuit into the fan was pretty easy.
[1:12] The base has a lot of empty space and has even more once the batteries are removed.
[1:16] I had to trim a bit of plastic and there is a small imperceptible bulge once the case
[1:20] is closed.
[1:21] To hook things up, I just removed the battery clips and joined the wires onto an old USB
[1:25] cable that I’d hacked up for a previous project.
[1:27] I could have soldered the wires directly onto the board, but since I had this cable I thought
[1:31] I would save my eyesight.
[1:32] At some point I’ll upgrade this hack so that the charging point is a bit more easy to access,
[1:37] at the moment you need to take off the battery cover to charge it up.
[1:40] The existing PCB does have a power jack and initially, I was thinking of using this to
[1:44] provide power for the charger, but slightly worryingly the power jack is connected directly
[1:48] to the battery terminals so I’d need to do a bit of work to make that safe.
[1:51] At that point though, it’s probably worth replacing the whole circuit board with a custom
[1:55] one.
[1:56] All in all though, quite a nice little mash up of a free a power bank and a fan.
[1:58] I get 5-6 hours of runtime from the single cell which is not too bad.
[2:02] It’s worth picking up these free power banks as they are great source of components.
[2:06] Thanks for watching
[2:07] I’ll see you next time!