Lithium ion powered fan question

[230RN]

I got a small 3-speed cordless fan for around $14 which perfectly satisfies a need to quietly ciculate a little extra air under my laptop.

It is driven by a lithium ion batterywhich is rechargeable by connecting the fan to a USB charging station or a USB port on the laptop. The cable used is an "80CM USB."

Product Code is 8 56770 00590  1

Distributed by Spark Innovators Corp

A single pushbutton control gives on, off, low, medum, and high speeds.  There is a power on light and a charging light which blinks while recharging and glows steady when fully charged.

Can I keep the charging cable plugged in to the computer (or  line-to-USB charging device) at all times, or do I have to be aware of the charge state while it's plugged in and unplug it when fully charged?   In my ignorance, I'm leery of anything with lithium in it, including hydrogen bombs, but especially lithium batteries.

Terry, 230RN

[Hawkmoon]

I'm hardly an expert, but I share your reticence about lithium-ion batteries. I'm pretty certain that I've read in multiple sources that they don't like to be overcharged. It's probably okay to keep it plugged in while you're computing, but not when you're away from the computer.

[dogmush]

While that is a cheap, likely from China, so anything is possible  the changing light depending on the state of charge tells me there is definitely a charge controller in there.

That's become pretty standard in all lithium batteries anyway, because you need something to balance the loads across the cells as well as monitor over charge and over temp conditions.

So probably the charge controller monitors cell voltage as well as incoming voltage and shuts off current to the cells when they hit full, and doesn't turn it on again to charge until they hit 95(ish)%.  So you should be safe.  That's kinda how most of them work these days.

The only way to be 100% sure is to open it and run down what particular OTS controller is in it though.

[230RN]

OK, that's what I was hoping, dogmush, so thanks.  I'll operate on that premise.

I had heard recently that the drone and R/C plane pilots keep their Li batteries in steel .50 BMG ammo boxes for fear of explosions and fires.  Don't know if that was CURINF or even ACCINF, but I didn't want any surprises with lithium as in the Castle Bravo hydrogen bomb tests.  (I guess that joke was a bit of a stretch in the OP.)

The instruction "manual" was a bit sparse.

Terry, 230RN

REF (wiki on Castle Bravo hydrogen bomb test to save folks the trouble of looking it up):

Detonated on March 1, 1954, the [Castle Bravo] device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon.[1][2] Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving lithium-7, which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll. At the time, it was the most powerful artificial explosion in history.
https://en.wikipedia.org/wiki/Castle_Bravo

But as I said, the joke was kind of strained.

[230RN]

"While that is a cheap, likely from China, so anything is possible  the changing light depending on the state of charge tells me there is definitely a charge controller in there. "
 
Confirming that by subsequent observation of behavior.

One thing I didn't think of right away is that charging from the computer USB port stops when I hibernate it or shut it down, although the fan itself doesn't stop since it's running off the battery at that point.

Duh. 

One of those "obvious in hindsight" things.

No problem, I used to have to manually shut off the previous noisy 110V fan anyhow.

Terry