Noob 18650 Safety Concerns

[BigT504]

I just bought a Thrunite Catapult. This is my first light using 18650's nad have been reading a lot about the batteries but I am still a little confused on things.

Let me start by saying I have a set of AW2600mah batteries coming. Tonight though, I opened a battery pack off of a no longer working laptop, and pulled 6 18650 cells out of it. The are flat tops and say "ICR18650-22e Samsung SDI 732" on the battery. They are light green. They all had a voltage between 4.0-4.1 and charged up to 4.19 on the WF-139 charger. They seem to work in my cheapy Ultrafire wf501-b light, but I do not want to damage my Catapult.

1. Are these bare, unprotected, or protected cells? AFter reading I think they are bare but I'm unsure. Is it safe to use two of these in the Catapult?

2. If a flashlight has a low voltage cut off (IE Catapult at 2.7volts), do you really need a protected cell?

Any helpful info for a noob to 18650 batteries would be great. :thinking:

 

[alfreddajero]

Dont know much about that light, but since it already has a voltage cutoff for the battery then you can use the 18650......but protected cells do offer a much better protection.

 

[BigT504]

So since the lights have a voltage cutoff, the proctected cells are just an additional from of protection from over discharging? Is there any danger to using two unprotected cells or will the voltage cutoff still protect both cells?

 

[Steve in SoCal]

In case you haven't read it here is a thread going over the basics of rechargeable batteries. http://www.candlepowerforums.com/vb/showthread.php?t=161536

As you probably know, most CPF members use AW or Pila rechargeable batteries. Per AW, Li-co battery voltage levels of the various states of discharge are listed below (I believe this is not under load). In comparison your flashlight cutoff of (2.7v under load?) seems a little low. Experts please chime in.

LiIon Battery Charge Status

4.2V – 100%
4.1V – 87%
4.0V – 75%
3.9V – 55%
3.8V – 30%
3.5V – 0%

 

[BigT504]

Yeah that was an excellent thread. I was wondering the same thing about the 2.7?

 

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1. Are these bare, unprotected, or protected cells? AFter reading I think they are bare but I'm unsure. Is it safe to use two of these in the Catapult?

All cells recovered from laptop packs are unprotected.

2. If a flashlight has a low voltage cut off (IE Catapult at 2.7volts), do you really need a protected cell?

Technically, no. This assumes though, that you have a matched pair of cells, ie. their discharge performance is identical. The safest route to go, is to use protected cells.

I might add, that routinely discharging Li-Ion cells to 2.7 Volts under load, will shorten their life considerably. It's best to stop the discharge somewhere around the point where, when the cell(s) are rested a few minutes, the open circuit (OC) voltage reads upwards of 3.6-3.7 Volts. This point in the discharge, will of course, vary with different light applications, depending on the current draw of the light.

Any helpful info for a noob to 18650 batteries would be great. :thinking:

I suppose you've already done this, but reading the "stickies" at the top of this forum is a good place to start, if you're new to Li-Ion cells.

Dave