How long would I charge an 18650

[kobebeef24]

Sorry, I'm new and I don't know much about flashlights/batteries. But I recently ordered an ultrafire 3.7v charger and trustfire 18650 2400 mah black/orange protected batteries. I'm wondering how long I would have to charge these for. Would it be dangerous if I left it in there too long, and how would I know if it's fully charged? any feedback would be appreciated. thanks. :huh:

 

[Black Rose]

I'm assuming you are referring to the WF-139 charger.

It supposedly at 450 mA and will terminate when the cell is fully charged.
It should charge for no more than 4 to 6 hours I believe, depending on the charge state of the batteries.

When dealing with Li-Ion cells you should have a DMM as part of your kit.

Here is a general guide on how "full" a Li-Ion cell is.

Resting voltages (no load connected) are a good indicator of state of charge. These figures are approximate:
4.2V = 100%
4.1V = about 90%
4.0V = about 80%
3.9V = about 60%
3.8V = about 40%
3.7V = about 20%
3.6V = empty
<3.5V = over-discharged

 

[VidPro]

because li-ion chargers are supposed to terminate on voltage there is no real problem leaving it on the chargers.
the problem comes when a charger reacts differently then expected, a component comes loose, a microcontroller fails (computer boots) or it just doesnt follow the proper rules.

so usually its all fine and dandy, then one day you come home and big red trucks are in front of this blob of charred ruin. And then you realise its the neighbors house who wasnt being overly cautious.