How low is too low for AW RCR123 discharge

[Ray1968]

I use a couple of AW RCR123's in my E2DL. While using the light last night it shut off. I pulled the batteries out and checked them with a DMM and they read 3.01. After sitting on a shelf overnight they read 3.34. Now they're on the charger.

Isn't this a bit too low?

 

[DM51]

Li-Ion cells are effectively empty at 3.6V, and over-discharged at <3.5V. If they get that low, you should charge them again at the earliest opportunity, as they deteriorate in a discharged state.

It is best not to let them get below 3.7V.

 

[Ray1968]

Thanks for the info.

At what point, if any, will the protective circuit kick-in during discharge?

 

[DM51]

Unfortunately, protection circuits are set too low IMO, at ~2.7V. If the bulb/emitter is a heavy current load, the voltage will sag during use, and will then rebound to above 3.0V after the load is removed - in some cases to above 3.5V, which is OK.

However damage can be done when the load is a very light one, as the voltage sag will be much less and the cell will not rebound above 3.0V.

If the cell doesn't rebound above 3.0V, it may have been damaged and care should be taken when recharging it - the initial phase of the charge should be at 0.1C until it is >3.0V.

What all that means is that despite the safety net of having a protection circuit, you should not make a habit of relying on it.