Questionable Battery behavior

[crizyal]

I have 2 cheap no-name brand (top score) RCR123 batteries that I am using in a Surefire G2 with a Lumens Factory EO-9. I know that I will hear a few say that I shouldn't use unprotected Li-Ion batteries... I am will to risk it with this light and I do monitor the voltage regularly. That being said I have found that the light is dimming out significantly after about 10 minutes of intermittent use. The voltage on these cells are 4.04 and 4.02 after resting for 15 minutes. That tells me there should be approximately 80% charge left in these cells. I am wondering what is causing the dimming @ 80 %. Am I missing something? :shrug:

 

[SilverFox]

Hello Crizyal,

In addition to paying attention to resting voltage you also have to be aware of the voltage under load.

A dimming light indicates that the voltage under load is dropping. Your cells may be worn out.

Tom

 

[crizyal]

Thanks for the quick reply. Would these batteries be classified a high risk for venting with smoke and flames if they are close to the end of said life or could they still be used with caution?

 

[SilverFox]

Hello Crizyal,

If they were mine, I would check them out under lower load conditions. They may work fine there.

Tom

 

[crizyal]

That is a great idea. I do have an application that would be much lower drain. Thanks again:thumbsup:

 

[Black Rose]

Have you checked how many amps are being pulled from those cells with the EO-9?

It could simply be a case that the cells are being pushed too hard with the incan drop-in.

I am using a pair of Trustfire protected 16340 cells in a G2 with a 7.4V incan drop-in that pulls 1.4A (more than 2C) from the cells.

I've noticed that those cells will now only charge to 4.05v, even after only moderate use.

 

[crizyal]

I will check to see how much current draw the light is pulling from the batteries. Any Idea what the limit might be for standard rcr123s?

 

[SilverFox]

Hello Crizyal,

The "nominal" voltage for a Li-Ion cell is 3.7 volts. This means that half way through the discharge the voltage should read 3.7 volts. The higher the load, the lower the mid point voltage will read.

When designing a battery pack you try to have enough battery to maintain nominal voltage. This gives you good run time and long cycle life.

Tom