How not to make fire spinning safer

I had a friend ask me to look at someone’s LED fans they got to do dancing/long exposure photographs/artsy stuff with. They weren’t working well and I was asked to take a look at them. My conclusion was that I could probably salvage them, but I ended up replacing basically all the guts to do it. Here’s what I ended up doing.

The heart of the fans were these controllers, from what I can tell they’re gutted versions of these “RGBZONE 1m USB DC 5V RF Wireless Remote LED Controller” from amazon. Not a terrible choice. RF remote means you don’t have to expose an IR receiver when packaging them, 5v meaning they don’t need a huge boost converter like 12v ones, and it’s just RGB, not addressable so you can bend the LED strip whatever way is convenient and don’t have to worry about the chaser direction for effects. That’s where the good ideas stop, however.

Soldered to the power input of this module, through a switch (actually bravo, someone might actually try it without this and they’d really be in trouble), is a raw 18650 lithium cell salvaged from some laptop. The voltage rage of the battery would be between 3.7 and 4.2 volts, not really ideal for powering this 5v device, but if everything else worked I might give it a pass. On top of that there’s no protection circuit on the battery, that means you are free to discharge it lower than 3.7v and (probably not in this application) draw way too much current from it if there’s a short. This is not good, maybe that’s why the modules aren’t working, perhaps the charger doesn’t detect the battery anymore and won’t attempt to charge it. But wait, where is the charger?

This is also… not good. In parallel with the battery is soldered a barrel jack. No protection, not even a diode, just a standard barrel jack that most people have drawers full of adapters that will fit (most at 12v!). The creator of this has packaged the cheapest lithium charge circuit module in the world in the middle of a usb cable and put two barrel jacks on the output. That’s right, you’re supposed to hook both of your fans up to this at once to charge both lithium batteries in parallel. Never mind if one is full and the other’s empty, as soon as you plug both in you’ll get many amps flowing straight from one to the other while they equalize. There’s that unconstrained current flow I mentioned earlier. All this stuff is wired up with tiny solid core 24 gauge wire that looks like it’s out of some ethernet cable (except the colors are different) and it’s wrapped in a roll and a half of electrical tape. How do I save this?

Well, individual protection circuits for one. I packaged the lithium cells with their own protection board, but these boards have some other features as well. In addition to charging from 5v, and protection features, there’s a LED bargraph fuel gauge (which is of questionable usefulness in this application), a button so I can turn off the output without a switch in the circuit (unused, since the target audience already knows how to work the current setup), but most of all a 5v boost converter on the output to keep the LED strip happy. Oh, and I had to buy new LED modules too as the original ones wouldn’t pair with the remotes anymore (damaged somehow? not sure if I can blame the original design for this).

I can’t promise that the boards I picked are flawless, but they did ‘check all the boxes’. The last thing I did was build a high-current charging cable. A barrel jack and thick gauge cable pulled from a power supply soldered directly to a USB-A plug and hot glued up. I had tried to use a different salvage USB cable end, but it was so thin it was restricting the charging speed. I put a splitter at the end of that and both fans charged perfectly from that.

This is what it looks like all wired in, I don’t have any pictures of it all together but if I get some I’ll add them here. The moral of the story is if you’re going to hack some electronics together and sell them for real money, try to do it a little safer than the alternative of literally grabbing things already on fire. I can’t say for certain that it would have been anything but broken, but if you look around you can find an army of chicken littles claiming that lithium batteries are just waiting for any excuse to murder you, your whole family, and everyone you love and an inadequately protected cell is all the reason it needs. At least now I expect that if they have an issue they’ll come back to me for a checkup.