New to 18650 and have a couple of questions.

[JStraus]

Hello,

Yesterday I got the below sku's from DX:

Digital Li-Ion 18650 Battery Charger (SKU: 6105). Basic black 18650 only, two bays.

TrustFire Protected 18650 3.7V True 2400mAh Rechargeable Lithium Batteries (2-Pack) (SKU: 20392). Black with flames (foreshadowing?!)

I charged them at work where I could keep an eye on them and all worked just fine. I pulled them when the bays lit green.

I was using them in my new 502B light and seeing how long a battery would go. This light seems to just dim out over time with the high, med, and low just running lower as time went on.

Should I just stop using the light when it's getting pretty dim or will the protection in the battery just cut off? I gather that the protection is just an extra safety layer and I should just stop using the light, but I thought I'd ask.

Also, with the charger, Should I pull them as soon as I see green light, or wait a bit longer, or are they ok to leave on? If I have the charger set up in a safe and fireproof place would it be extra crazy stupid to leave them to charge while I sleep and pull in the morning?

EDIT: Also, is it ok to interrupt a charge? If I should not leave unattended, then is it ok to interrupt a charge and put batteries back on? I don't want to inadvertently overcharge.

Thanks to all for any advice. To be sure, I will stick to the paranoid end of things until I hear that said paranoia is unwarranted.

J

 

[Nil Einne]

I don't actually own any 18650 yet, but yes you should pull them as soon as you see a green light. With li-ion batteries, trickle charging is not recommended so what green should/usually means is that the charger has completed charging and in theory should stop completely but sadly many do not so you should do it by removing them manually. This doesn't mean if you go away for 30 minutes and come back and they are now green you should panic, unless the charger is majorly defective 30 minutes of trickle charging shouldn't be catastrophic. The protection in the battery will usually only kick in at 4.25V or higher. You don't actually want your cells getting that high. So you should never rely on it in the first instance.

Unless you're sure your charger properly cuts off charge upon completion/going green, it's not recommended you leave the cells in for long periods. While some early 6105 did so, some more recent ones don't seem to so there's a fair chance yours does not. If you have a multimeter you can test whether it properly cuts off. In the absence of that, I would recommend you put it on a timer. Set if for a bit longer then it should take to charge.

As for discharging, again do not rely on the protection circuitry. In fact you can see some testing from I think old4570 who found many even some AW cells don't even cut off at 2.75V. Many lights lack any sort of boost driver, and the forward voltage of white LEDs is usually in the 3.25-4V range so it is normal for the LED to dim when supplied from a single 18650 (or other li-ion) battery as the driver drops out of regulation since it can't boost the voltage so can't supply the necessary current to drive the LED. Most cells will have a point where the voltage starts to drop significantly, you're likely to notice this rapid drop in the light brightness and you should stop using the battery at this point. Ideally you'd also want to test the battery before charging and make sure it's at least 3V, definitely no lower then 2.75V.

Taking the cells out when they are half charged is mostly fine. In fact if a charger does a proper CC/CV (which again early 6105 did seem to but recent ones are less clear) then when the CC phase is complete (depending on the current and battery but usually after about an hour or so) the battery is actually quite a high percentage of its capacity (I think about 75% or so from memory). However if you do take the batteries out when only half charged you probably should discharge them a bit first before charging again or test them if you can and make sure the voltage is under 4V before charging. Certain chargers (I think the 6105 variants that are crappy is one of them) are I believe known to have problems charging half charged cells and may charge them too fast or too much.

 

[JStraus]

Perfect, thank you very much for taking the time to answer my questions!

I hope others in my boat find this to better understand the world of these kinds of batteries and chargers.

I have been looking and haven't seen anything as clear and concise!

Thanks again,

J

 

[Midnight Oil]

For urine-rich men:

http://www.candlepowerforums.com/vb/showthread.php?t=106242

http://www.candlepowerforums.com/vb/showthread.php?t=250934

http://www.candlepowerforums.com/vb/showthread.php?t=275610

http://www.candlepowerforums.com/vb/showthread.php?t=235164

http://www.candlepowerforums.com/vb/showthread.php?t=247543

Lots of useful stuff about Li-ion batteries and chargers.