AW 123 - weak?

[crofty]

My P3D just switched itself off, immediately thought great broke after just 2 months :thumbsdow
So I checked the voltages and one reads 3.29 and the other 3.09. After a charge it worked again, thankfully :twothumbs

When I charging them on the Pila the first one will go to 4.17 and you can press the button and it`ll charge a bit more, the second one will go to 4.17 aswell but wont charge anymore when you press the button.

So is one of these cells duff or is it just weaker than the other and are they matched enough to be used together? Should I charge often to minimise reverse charging or return/replace the weaker one?

TIA

 

[Marduke]

Those voltages are pretty low to be running the cells down. I highly recommend to charge them prior to getting that low if you can help it.

 

[crofty]

Yeah I wasn`t expecting them to be that low tbo. I hadn`t long charged them, maybe one is getting low prematurely and draining the other. I`ll have to keep a closer eye on them.

 

[Patriot]

At least they're still charging to the correct voltage and the charger seems to be working well also.

 

[crofty]

Patriot36, yep the charger being ok is something, it`s just this one cell is dropping off considerably more than the other.

I`ve monitored the voltages over the weekend during general use, nothing to heavy. v`s have stayed pretty much identical throughout with one cell being consistently 0.01v behind the other.

This is where it gets interesting. Today I checked the v`s, 3.75 and 3.76 respectivly. So I set my P3D to high and leave it on, about 10 mins later it goes off.

Pull batts out imediatly and one reads 0v and the other 3.60. After about 10seconds the 0v turns to 3v, I guess the cuircuit tripped and reset. Half an hour on they now read 3.28v and 3.65v.

So after only a few days of light use one cell goes so low the protection kicks in (so glad they are protected :duck:)

The cells are new and have had 2-3 cycles max, the runtime before now has been a lot better than 2 days and they`ve never been overdischarged.

IMO this one cell is faulty, the short runtime is to short for it to just be a weak cell and the low voltage is extreme.

But what do you experts say? If it`s just weak then it`s a case of buying another that is hopefully better matched, but if it`s faulty then it`s a case of trying for a replacement. So I`m keen to hear your expert opinions

TIA

 

[Black Rose]

I am not an expert on the RCR123 cells, but it sounds like you have a faulty cell. Good thing it's protected, or you likely would have had a reverse charge situation

I would contact AW or the vendor you bought it from if you didn't get it directly from AW.

 

[mdocod]

First off, don't worry about the 4.17V charge termination on the Pila, this is going to be pretty normal for the Pila when used on RCR123 size cells as it's lowest current output of the constant voltage stage is designed around the higher capacity of 17500 and larger cells. It's going to terminate slightly premature on small RCR123 size cells. Consider it a blessing rather than a vice as it means your cells will never be overcharged. There is nothing wrong, especially if they are still holding ~4.17V the next day.

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There is probably nothing wrong with your cells... allow me to explain:

When A LiCo cell approaches the point of being completely drained, the cell voltage starts to fall off very rapidly...

first click here:
http://www.candlepowerforums.com/vb/showthread.php?t=117117

have a glance at a few charts and get a feel for the way li-ion discharges...

If you see what I see, you see that the cell voltage runs a steady decline from ~4V down to around ~3.4V (all depending on load and cell size, so the numbers can vary some) under a load and then suddenly the cell voltage drops RAPIDLY to about 2.5V where tests are terminated, or where many cells would cut-off naturally with their built in protection.

All cells have some minor variation in capacity, but that variation can show up as HUGE voltage differences towards the end of a simulntanious discharge, because one cell will start to fall on it's face a few seconds before the other cell, causing it to drop in voltage rapidly, right down to ~2.5V where the protection kicks in and shuts down the circuit... while your other cell is still reading 3.6V...

The reality is that if you took that other cell, and ran it for about another ~10 seconds by itself in another circuit or something, it too would drop all the way down to ~2.5V under a load, and barely bounce back to ~3V open circuit. The fact is, that if your cells are staying within 0.01V of each-other through most of the normal portion of the discharge (which you have indicated) (where both cells are above 3.6V open circuit) then they are matched reasonably close in capacity and there is nothing abnormal going on here.

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This is where it gets interesting. Today I checked the v`s, 3.75 and 3.76 respectivly. So I set my P3D to high and leave it on, about 10 mins later it goes off.

remember, 4.20V is 100%, 3.6V is basically dead. 3.75V open circuit means you had maybe 20% charge remaining, (give or take). So you got 10 minutes out of it... but I don't know what load the P3D runs at on "high" and are you sure it was "high" and not "turbo?" Assuming "turbo" that seems about right I think...

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The only way to really tell for sure if your cells are "duds" would be to do a discharge test from a full. They should deliver in the ballpark of 550mAH if they are in reasonable condition.

Eric

 

[crofty]

Black, tend to agree with you there.

modcod, thanks interesting about the voltages dropping off dramaticaly towards the end of charge, I didn`t know that. Taking that into consideration it would seem there is nothing wrong with this cell, however, 2 days runtime vs about 2 weeks with the same usage pattern is a big differance.

Not worried about the termination, just pointing out that one cell is able to hold more charge after the initial termination while the other one won`t btw that wasn`t true for the previous charges, only since this one cell has started underperforming has it stopped taking "extra" charge.

I go by this chart I found here somewhere (props to the maker )
4.2 volts 100%
4.1 about 90%
4.0 about 80%
3.9 about 60%
3.8 about 40%
3.7 about 20%
3.6 empty for practical purposes
<3.5 = over-discharged

It was definatly on high. Turbo gets to hot for my comfort level after just a few mins.

A discharge test sounds like a shure fire way to confirm my suspicions. What do I need?

 

[mdocod]

Before you do anything, do this simple test:
Charge the cells on your IBC, remove cells from charger when finished, take a voltage reading, come back in an hour or 2 and take another voltage reading. If the cells are below 4.00V they are shot, if they are below 4.10V then they are definitely showing some effects of aging.

Is it possible that those cells were close to dead in your flashlight for an extended period of time?

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To do a discharge test, you need to figure out how much current the P3D is pulling from the cells on whatever mode you want to run the test in. (high would probably be a good place to test).

I'm not totally familiar with how the P3D works, so... I'm assuming that if you were to have the bezel slightly loose, and you were to use a wire to complete the circuit across the back of the light (from the cell to the body) leaving the tailcap out of the circuit, it would turn on in high....???

If that is true, then you should use a multi-meter set to the 10A or 20A setting to take a current measurement through the circuit (from body to cell) with the cells charged to ~3.9V (so you get a middle of the road reading, as it will change through the discharge).

Then charge the cells to ~4.20V, then do a runtime test on whatever mode you were able to take a current reading on.

Take however long it runs, multiplied by the current tested, and that's the rough amp hour capacity of the cell. Remember to convert minutes to fractions of an hour. (IE: 59 minutes = 0.9833 hour).

Eric

 

[PhantomPhoton]

I've had something similar happen to my newest pair (6+ months old bought from Lighthound) of AW RCR123s as well. They were in my 6P driving my M60. One started flaking out and not charging as high as it's mate. So I tested them in single CR123 lights. The weak one couldn't hold a high current for very long without shutting down. The mate performed fine. I discharged them at low current to 3.5V then tried a fresh charge and the same thing happened. I recycled the one as its no use to me if it can't hold a 1C current.

I seem to have a similar situation developing with my pair of (original run) AW C cells as well. I use a completely different charger for these guys, so I don't think its my old 139. I just don't like running most Li Ions in series now. All my single 18650 lights have cells which are doing just fine.

 

[jirik_cz]

If you see what I see, you see that the cell voltage runs a steady decline from ~4V down to around ~3.4V (all depending on load and cell size, so the numbers can vary some) under a load and then suddenly the cell voltage drops RAPIDLY to about 2.5V where tests are terminated, or where many cells would cut-off naturally with their built in protection.

All cells have some minor variation in capacity, but that variation can show up as HUGE voltage differences towards the end of a simulntanious discharge, because one cell will start to fall on it's face a few seconds before the other cell, causing it to drop in voltage rapidly, right down to ~2.5V where the protection kicks in and shuts down the circuit... while your other cell is still reading 3.6V...

I completely agree with this. There is nothing wrong with the cells. That is just common behavior.

 

[crofty]

Well I did the simple test and the voltage didn`t drop. I`ll likely do the discharge test one day but what I`ve done for now is use the AW spacers as a dummy cell and ran the cells one at a time on high.

The weaker one ran for half an hour less so I guess most of you are right and the cell isn`t faulty, just a bit weaker.

The depleted after 2 days bit is still puzzling me but maybe I used it more than I thought.

Thanks all.

 

[mdocod]

The weaker one ran for half an hour less so I guess most of you are right and the cell isn`t faulty, just a bit weaker.

A half hour less than what?

A half hour less than 45 minutes would mean that the cell is only performing 1/3 as well as the other, a half hour less than 24 hours means like 2% difference.

 

[crofty]

3. which is about right because with 2 cells high should last 4.8 hours.

 

[Marduke]

3. which is about right because with 2 cells high should last 4.8 hours.

4.8 hours is with primary cells. RCR123's have less runtime. On high, expect about 2.5-3 hours with RCR123's

 

[mdocod]

that's not bad then, especially considering that it would be getting dimmer and dimmer towards the end, which means that extra 30 minutes is not representative of very much juice being used.

 

[crofty]

That`s even better then.