Cool Tiny USB Li-Ion chargers.

[samgab]

by Cottonpickers.
I like their new design, that has a 3D printed case, and multiple current selections, also the option to turn the screen on and off.
Here is a review of the new one:
http://www.candlepowerforums.com/vb/showthread.php?336422-Cottonpickers-Nona-Charger-Review

Here is the page where the maker discusses them:
http://www.cpfmarketplace.com/mp/showthread.php?240304-gt-FS-Cottonpickers-Chargers-incl-Worlds-smallest-Li-ion-charger-with-display

And here is a review of one of the simpler models with display and only 4 current settings:
http://www.lygte-info.dk/review/Review%20Charger%20CottonPickers%20DM+4Settings%20UK.html

They use (almost) proper CC/CV method. The almost is because the current starts to drop just before full 4.2V has been achieved, probably due to the algorithm of the microchip controller, or possibly due to the power output limitations of USB.
But it's a pretty cool little solution, for charging individual Li-ion cells such as 18650's or 10440's etc, I think.

[samgab]

Oh, and they use as a microcontroller, Linear Technology's LTC4054:

http://www.linear.com/product/LTC4054-4.2

http://cds.linear.com/docs/Datasheet/405442xf.pdf

Pretty neat little IC.

[T4P]

Fact of matter is, a Li-Ion cell will slowly complete charge near 4.2V because of rising internal resistance towards charging, and the microprocessor is there to detect the rising impedance