RCR123 pairing in Fenix P3D question.

[abvidledUK]

I've just run some unprotected 800mah RCR123's all same manufacturer, nearly new, few cycles each. Through my P3D's (3) all at the same time.

After charging and resting, 24 hours, in preparation for the arrival of the P3D's, they all were approx the same voltage under "light" load from my digital battery tester.

They were grouped into two's of similar voltage. Placed into P3D's

Discharged in the P3D's until the low voltage flickering occurred. voltages measured again.

The P3D's all ran 65 mins, before flickering started, within a few seconds of each other.

This time there was a wide variation in discharged loaded voltages, up to one volt max difference in any pair. 1.9v - 2.9v

1.36v, 1.65v, 1.85v, 1.9v, 1.9v, & 2.9v measured immediately after removing from P3D's.

They did recover quite quickly to over 3v per cell, within a few minutes.


My question, should I pair them up as per their discharged voltage, rather than charged voltage. I think I should do this.

The advice will probably be to only use protected cells.

 

[DM51]

I'm sorry to have to tell you, but you have wrecked 5 out of 6 of these cells. They are all badly over-discharged. The 2.9v one should be salvageable, but the others probably won't be.

I assume these are resting voltages. Li-Ions should never go below 3.0v at rest, preferably not below 3.5v.

If you have a charger which can charge them at 0.1C (60mA) we can discuss the possibility of rescuing them.

If your charger can't do that, but can only charge at a higher rate, do not try putting them on charge as there is a serious possibility of the cells overheating and venting.

The 2.9v one is the only cell that might survive on a normal charger, but it would be better to get it up above 3.0v before you try that.

 

[abvidledUK]

I'm sorry to have to tell you, but you have wrecked 5 out of 6 of these cells. They are all badly over-discharged. The 2.9v one should be salvageable, but the others probably won't be.

I assume these are resting voltages. Li-Ions should never go below 3.0v at rest, preferably not below 3.5v.

If your charger can't do that, but can only charge at a higher rate, do not try putting them on charge as there is a serious possibility of the cells overheating and venting.

The 2.9v one is the only cell that might survive on a normal charger, but it would be better to get it up above 3.0v before you try that.

Understand what you are saying, but surely the P3D would in that case over discharge every RCR123 used in them, as the low voltage warning is the same.

Voltage measured immediately after removing from P3D's, not after resting at all.

 

[DM51]

Can you confirm these are resting voltages? You mention 'discharged loaded voltages' in your 1st post, but you don't say how you measured them under load.

If not measured under load, how long after you took them from the light were the voltages measured, i.e. how long had they been resting?

 

[abvidledUK]

Can you confirm these are resting voltages? You mention 'discharged loaded voltages' in your 1st post, but you don't say how you measured them under load.

If not measured under load, how long after you took them from the light were the voltages measured, i.e. how long had they been resting?

I wrote my reply to this question before you had written it !!

We must have had the same thought at the same time, see previous post of mine.

This is the tester I use, works for me, comparatively

http://www.tradeeasy.com/supplier/2...ital-battery-tester-for-12-12v-batteries.html

 

[DM51]

If you have left them for 15+ mins, they should have achieved a resting voltage, so you could measure them again now.

The 2.9v one should have bumped back up and be OK. Maybe the 1.9v ones too, although typically the difference will be 0.5v (depending on the load).

If any are still below 3.0v, they HAVE been damaged, and you will need to be careful with them. The lower they are, the worse the damage and the less likely it will be that they can be recovered.

 

[abvidledUK]

If you have left them for 15+ mins, they should have achieved a resting voltage, so you could measure them again now.

The 2.9v one should have bumped back up and be OK. Maybe the 1.9v ones too, although typically the difference will be 0.5v (depending on the load).

If any are still below 3.0v, they HAVE been damaged, and you will need to be careful with them. The lower they are, the worse the damage and the less likely it will be that they can be recovered.

You reminded me, I can only charge 2 x 2 at a time, so two of the cells had been resting, waiting to be charged, and as luck would have it, they were the 1.36v and the 2.9v cells ! (I number all my rechargeable cells)

Surprise, surprise, after 4 hours resting, the 1.36v cell now measures 3.14v, and the 2.9v cell now measures 3.37v, before being charged.

Using the above tester I use for comparative purposes.

PS, the other 4 went through their charging cycle ok, no probs, no overheating, no funny smells.


So, back to my question, should I pair them up, as per their discharged, rested voltages ?

or perhaps even their just out of P3D voltages ?

 

[DM51]

So you are safe with them. As long as they rebound above 3.0v, they are OK, although >3.5v would be better.

I think however that from now on you should most emphatically NOT rely on the P3D low-voltage flicker to warn you to recharge the cells.

You say the run-time before the flicker is ~65 mins. Next time, I suggest you should pull them at 45 mins and test the resting voltages. If they are in the range 3.6v-3.7v, you have the lowest point at which to recharge them for longest life. You can recharge Li-Ions as often as you like – they don't suffer from 'memory' effect, and prefer to be topped up rather than run to empty.

And to answer your question: I would personally pair mine for life, so each pair has exactly the same history. As soon as 1 cell of a pair starts to fail, and doesn't hold a charge of >4.0v, you should get rid of it and use the other one in single-cell applications. You should not see such large voltage discrepancies after use if you keep them from running too low.

 

[abvidledUK]

You say the run-time before the flicker is ~65 mins. Next time, I suggest you should pull them at 45 mins and test the resting voltages. If they are in the range 3.6v-3.7v, you have the lowest point at which to recharge them for longest life.

And to answer your question: I would personally pair mine for life, so each pair has exactly the same history.

In real life, I would recharge the cells after each use, it is doubtful that they would be discharged to the point of flickering.

Like you, I tend to pair for life, just want the initial pairing to be as good as possible. The cells, 7a, 7b, 8a, 8b etc have already been paired for a few cycles, running tests now to see how they compare discharged, rested, charged.

I'm just running 2x P3D's with other RCR123's, I'll pull them as you suggest at 45 mins, and compare, as above.

 

[mdocod]

but surely the P3D would in that case over discharge every RCR123 used in them, as the low voltage warning is the same.

The LOW BATTERY INDICATION on a P3D was (as I understand it) intended to warn the user when a pair of PRIMARY CR123s are getting low so you can use the remaining power wisely, it was never implemented with the intent of preventing the over-discharge of li-ion cells. The Low indication probably starts to kick in when input voltage under a load drops down around 4-4.5V, which would mean an average 2-2.25V per cell, which is WAY to low for li-ion cells.

In reality, you never want li-ion cells to be loaded to anything less than ~3.0V(ideally higher), In your case, you most certainly dragged the voltage of the cells far too low. I would personally be cautious of those cells.

This is an interesting case, as it is the first case I am aware of that points to the possibility that the function of the P3D could be misinterpreted as being for li-ion cells. Which could lead an uninformed user to an explosive event.

 

[SilverFox]

Hello AbvidledUK,

When you over discharge a Li-Ion cell, the electrolyte dissolves some of the electrode material. This results in contaminated electrolyte and reduced capacity because of the reduced size of the electrode. The longer the cell remains in a over discharged condition, the more damage.

Charging cells with contaminated electrolyte results in higher cell temperatures during charging, and if the temperatures get high enough, rapid venting and flame. This probably won't occur at the rates you are charging at, but if you keep track of cell temperatures during charging, you should be able to see an increase in temperature even when charging at low charge rates.

Quality cells like LG, Sanyo, Sony, and Panasonic, seem to be able to handle a few cycles of this with minimal damage, but even they will begin to heat up during subsequent charging. It is best to avoid over discharging.

Back to your original question... Match Li-Ion cells in a fully charged state. They will often be out of balance when discharged, then go back into perfect balance upon charging. Part of the reason for limiting the discharge is to account for these differences when the cells are in a discharged state.

Tom

 

[abvidledUK]

The advice from all, including Trevor @ Fenix Store, is not to use RCR123's to the point of low voltage flickering warning.

The flickering is really only designed for primary CR123's indication.

Advice also is to only use protected RCR123's, as the P3D can utilise voltages down to 2v per cell, at which point RCR123 becomes damaged / dangerous.

So, I'll not do that then.

Only done it once.

CR123's in my P3D's from now on, until I get some protected RCR123's, AW recommended by everyone.

Thanks all for the clarification I was after.