Lithium Ion Charging Safety?

[belmaktor]

I recently purchased a laser from Lazerer and I also ordered an Ultrafire 18650 battery (3000 mAh) and a charger along with it. I have read about how lithium ion batteries can explode if not handled correctly. I am worried because the charger only cost $3 and I want to be sure it is safe. Here are some questions I have.

1. Is this charger safe and reliable? If so can I leave it unattended? If I cannot leave it unattended, what is involved in attending it?

2. How do I know when it is time to charge the battery? I have read that overdrawing it can cause problems.

3. How long does this battery take to charge?

Thanks!

 

[Hemlock_Mike]

1. Is it a protected cell?
2. Use your DMM to test the cell after use. If it is getting dim and/or the voltage is
under ~3.5 V, I'd charge it.
3. Most chargers shut down at 4.2 Volts. Always be around it. If the cell gets hot,
take it outside. (I did that only once!)

HMike

 

[LarryDFW]

belmaktor;

Mike has the correct info.

Ultrafire cells are known for overheating
(I have experienced about 20% failure rate myself) .

Overheating cells are dangerous.

Check them frequently on your charger,

throw away any that get uncomfortably hot to the bare hand.

Use only U.L. listed cells in the future.

LarryDFW

 

[belmaktor]

Thanks for the advice. I have since charged it once overnight in the same room I was sleeping in. I stuck a metal trash can under it and set my alarm every 2 hours to check on it and it never heated up significantly so I think it is fine.

 

[RyanElectro]

Thanks for the advice. I have since charged it once overnight in the same room I was sleeping in. I stuck a metal trash can under it and set my alarm every 2 hours to check on it and it never heated up significantly so I think it is fine.

That's intense. Glad you have taken much safety precautions. You don't wanna end up waking up with a hole in the wall lool.

Oh and if your voltage is low, your laser will flicker on and off and you will definitely notice it lose power. So, I wouldn't be so worried about over-discharging it because unless you're an idiot who keeps trying to turn a flickering laser on and off, you'll be fine. It's VERY noticeable.

 

[rhd]

And hey, if all else fails, make your own charger

This design is a 24 channel lithium ion charger that I just had 20x copies of made. Each channel has two current settings (selectable with a dip switch), it's own LED status monitor, and attaches via a header (allowing for multiple cable types).

It basically requires a 5V 20A power supply brick to actually operate, and the PCB is 10 x 10 cm. It can actually split in half and yield two independent 12 channel 10 x 5 cm PCBs instead.

But if it works as expected, it will mean a whole lot less closet-clutter

 

[HIMNL9]

I solved the problem of unattended lithium battery charge process in a different way ..... made my own charger

It's nothing special, no microcontroller nor special ICs ..... it's simply a constant-current/limited-voltage system with a thermal shutdown add-on ..... a precise voltage regulator keeps the output voltage at 4V maximum, and with a current regulator you can set the current from 1/4 to 1/10 of the cell capacity ..... it's slow, ofcourse, but there is absolutely no risk of overcharge, and the NTC in contact with the cell disconnect all if the battery is damaged and for any reason go over 45 - 50 C.

 

[LarryDFW]

HIMNL9;

Sounds like a nice design with the NTC temp sensor
( the UltraFires need one).

I would charge to at least 4.15 VDC if you can set the voltage precisely.

Manufacturers quote 4.25 VDC as a max for production chargers.

I like to set my charger's voltage to the exact voltage also,

as I have done on the 4.35 VDC new chargers.

LarryDFW

P.S. RHD - Nice job on the 24 channel charger.
I could of used 24 channels a few times for large orders.
I usually charge about 8 or 16 cells at a time
with a 5 amp digital supply.