Question about "when" your Li-ion batteries are "dead"?

Fully charged Li-ion batteries are full when a volt meter tests 4.2v static charge at the terminals. And Li-ion batteries are supposed to be dead at 3v (some LiMn batteries @ 2.5v). However, batteries tend to sag under significant discharge and there is really no easy to know what the working voltage really is.

But when are the batteries "dead":
When the working voltage sags to 3v (or 2.5v)?
Or When measure of the static charge is 3v (or .5v)?

I call the batteries dead if they don't recharge anymore. You can throw them away or you can cut off the battery pcb and use it as non-protected batteries.

I meant, when is the battery considered depleted/empty/discharged/etc...

I did not mean, when is the battery no longer servicable

2.5~3Volt under no load, I would consider the battery flat.

LazyBeam;

Using the open-circuit voltage . . .

the cell is discharged greater than 95% at 3.5 VDC.

(per Sanyo discharge graphs)

LarryDFW

Yeah, no reason to take it lower than ~3.5V, but many cells can go down to 2.75V without sustaining damage.

BShanahan14rulz said:

Yeah, no reason to take it lower than ~3.5V, but many cells can go down to 2.75V without sustaining damage.

Click to expand...

A well-manufactured cell can go as low as 2.2 VDC . . .
and still have low Internal Resistance if charged properly at 1/10 C.

LarryDFW

I'm sorry but that ^^^ makes no sense at all.

This is interesting, i have one of those flat-top blue 18650 ultrafire 2400mAh (not protected) that fully charged is 4.2V but after some minutes of non-use it drops alone to ~3.3V.

Is this ok?, or is my battery damaged/wasted?, i use it for my 50mW greenie and i would say it performs well without any problem and last long time before it drops less than 3.1V. If i use a "healthy" protected battery with voltage between 3.7-4.2 on the same laser, i dont see any difference in power or anything, except that the warning led blinks like crazy

In the first week of use i waited till the warning led started to go dimmer so i could recharge the battery, multimeter reading was ~2.8V (text on battery says cut-off discharge is 2.75V) so i thought it was ok but my charger didnt work, indicator led was green as if it was full .

Took it off and after some minutes the voltage was back at >3.0V and it was then when my charger finally started to well...recharge the battery, i didnt have my multimeter in the first day when battery was brand new so i dunno if it was like this since the begining or was it after i discharged that got like this...

As i said above, despite this, battery seems to be and perform "ok", same as with protected batteries but wanna know if it is indeed damaged or even if its a threat to my laser? :undecided:

...fully charged is 4.2V but after some minutes of non-use it drops alone to ~3.3V.

Is this ok?,

Click to expand...

No, it's not.
Voltage should stay at ~4.2V for at least a week or so.

anselm said:

No, it's not.
Voltage should stay at ~4.2V for at least a week or so.

Click to expand...

I tot so, thats how my other batteries are and im going replace the battery anyways, but i wanna know how bad is to keep using it, would it damage the laser if keep using it?.

Written on battery you can read:

The voltage of full charge and cut-off discharge is 4.2V and 2.75V

Click to expand...

What exactly does this mean?, is still the battery dead or useless?, sorry if these are noob questions but im not too much into electronics

Thanks in advance

That just means when charging the protection circuit on the battery will automatically stop it from charging when voltage reaches 4.2, and when discharging it will cut off when voltage gets down to 2.75.

The battery probably won't hurt a laser but it is pretty much useless.

My unprotected 17670 cell reads, "The voltgae of full charge and cut-off discharge is 4.2V and 2.75V" Vague enough to either mean that the cell will do this automatically (it won't), or that those are the recommended voltage limits.

But yeah, as members before have posted, 4.2V dropping to 3.3V = bad cell. Recycle it. Do not recharge it. Use it if you have to.

Attempt to charge it (outdoors) and then promtly hit it with a sledgehammer.
Post the youtube video.