Unprotected Rechargeables, any danger using them below suggested voltage if...

[ky70]

...they will never to be used again.

Hello folks,

I understand that there is a risk of damaging an unprotected battery if it is over discharged or over charged (which both could lead to other dangers). But I'm curious to know if there is any danger in allowing an unprotected battery to fully discharge in a flashlight and then never use it again? If I have a unprotected cell in my flashlight and I'm in an emergency situation where I need more runtime, is there any risk in letting the flashlight completely drain the battery IF I never re-use the battery after this full depletion?

Thanks!

 

[John_Galt]

Re: Unprotected Rechargeables...any danger in using them below suggested voltage?

Super-discharging (my phrase) a Li-ion will damage it internally, greatly increasing the risk of a fire venting episode while recharging. If you were to never use it again, you should be ok.

I believe Novatac's operate on this principal. The automatic cell protection kicks in for all but the lowest output level, the idea being that in an emergency situation, having light is more important than saving a rechargeable cell.

 

[McAllan]

Re: Unprotected Rechargeables...any danger in using them below suggested voltage?

The typical LiIon, LiCo (ordinary 3.7 v), yes. Don't do it. It's a bad idea.

A LiFePO4 (~3.2 v) which is typically unprotected will be no greater danger. You however need a a good charger which charges with a very low current below a certain point (2-2.2 v if I remember correct) if the cell is to be treated most optimal. Not a good idea as it really wears the cell but shouldn't result in an increased danger.
The charger kit I bought from ELV (still need some cells ) fulfills this criteria.

LiMn (high current 3.6 v) I can't speak for.

 

[Brian321]

Im not sure i can answer your question,

But FWIW, I can tell you if i am in an emergency situation where my life is in danger if i turn my light off, I think ill take my chances and leave it on, That last thing ill be worried about is my light blowing up.

Now if your in an emergency where your life is not in danger, why not try and make due with what you got and try to save what you got. If your in the city or a town you never know when or where you might find batteries or flashlights. Besides if your not in danger you could just go to sleep when it gets dark or start a fire for light if your stranded in the woods etc.

Just my opinion.

Brian

 

[ky70]

Thanks for the replies. What I'm hoping to determine is if there is any danger in overdischarging an unprotected cell that you would never use again. My thinking is that the danger is in reusing or recharging the cell but not with the initial discharge...is that correct?

 

[45/70]

Hi ky.

When you run a single Li-Ion cell, there is no danger if you run the cell to zero Volts. A lot of people do this before recycling them, to prevent possible shorting out of the cells in the recycling bag, or whatever.

Now, if you go to charge a cell that has been discharged to below the recommended level, you are correct, this is when you could run into problems. There is no guarantee of a problem, especially if the cell is/was in good condition and spent very little time in the over discharged state, but it is not recommended to try to charge a cell that has been over discharged, as the cell has been damaged to an unknown degree and could become unstable.

Li-Ion cells that are used in series are a different story. Cells in series should not be over discharged beyond the recommended level, and cells used in this way should be matched so that they discharge evenly. As you are probably aware, reverse charging of lithium cells is almost a guaranteed problem however, I've heard that a well matched set of Li-Ion cells are likely less of a threat than lithium primary cells in this situation. That doesn't mean I would try it though!

Dave

 

[ky70]

Hi ky.

When you run a single Li-Ion cell, there is no danger if you run the cell to zero Volts. A lot of people do this before recycling them, to prevent possible shorting out of the cells in the recycling bag, or whatever.

Thanks Dave for the clarification.

Now, if you go to charge a cell that has been discharged to below the recommended level, you are correct, this is when you could run into problems. There is no guarantee of a problem, especially if the cell is/was in good condition and spent very little time in the over discharged state, but it is not recommended to try to charge a cell that has been over discharged, as the cell has been damaged to an unknown degree and could become unstable.

Li-Ion cells that are used in series are a different story. Cells in series should not be over discharged beyond the recommended level, and cells used in this way should be matched so that they discharge evenly. As you are probably aware, reverse charging of lithium cells is almost a guaranteed problem however, I've heard that a well matched set of Li-Ion cells are likely less of a threat than lithium primary cells in this situation. That doesn't mean I would try it though!

Dave

Thank you Dave for the clarification. Regarding using Lions (or primaries) in series, from everything I've read I don't trust the multiple Li-on setup in a light so I only buy lights that will operate on a single Li-on battery.

 

[McAllan]

...they will never to be used again.

Wonder if I missed that or it was edited in after I made my reply :thinking:

Anyway as 45/70 says it's no danger discharging them down till zero. As long as there's no danger of cell reversal (as in a single cell light).

I agree with 45/70 that deep discharging them before recycling them is a good idea. Especially when speaking about those loose cells - protected or not - which we are using in flashlights since they by accident can have their wrapping pierced in the recycle bin - perhaps even the bin you have at home before delivering them to a recycle bin/station. Regarding protected cells you however need to remove/bypass the protection cirquit in order to fully discharge the cell. You can do it with a resistor or a suitable incan bulb.

I also still stand by my comment regarding LiFePO4. No problem recharging them with the right charger - or you could do it manually with some resistors in series to limit current into the cell - you have to know how to treat it though for optimal result.

 

[ky70]

Quote:
Originally Posted by ky70
...they will never to be used again.

Wonder if I missed that or it was edited in after I made my reply :thinking:

Anyway as 45/70 says it's no danger discharging them down till zero. As long as there's no danger of cell reversal (as in a single cell light).

I agree with 45/70 that deep discharging them before recycling them is a good idea. Especially when speaking about those loose cells - protected or not - which we are using in flashlights since they by accident can have their wrapping pierced in the recycle bin - perhaps even the bin you have at home before delivering them to a recycle bin/station. Regarding protected cells you however need to remove/bypass the protection cirquit in order to fully discharge the cell. You can do it with a resistor or a suitable incan bulb.

I also still stand by my comment regarding LiFePO4. No problem recharging them with the right charger - or you could do it manually with some resistors in series to limit current into the cell - you have to know how to treat it though for optimal result.

Thanks McAllan for your input. I added that text in bold to the top of my post after reading your reply as I noticed that you didn't catch in my original text that I said, "...and then never use it again", "...IF I never re-use the battery after this full depletion"

Thanks for the note about the LifeP04 cells. I do have a couple of those so that is good to know.