Tenergy RCR123A Problem

[42]

I've got a few Tenergy protected RCR123As that I've been testing in a P2D on turbo. The batteries are less than 18 months old, have less than 10 charge / discharge cycles on them and spent the last 12 months sitting fully charged and unused. Now I'm lucky if I get 10 minutes of use out of them before they shut down. :sick2:

Are these just defective batteries or am I doing something wrong?

 

[mdocod]

Few questions that will help me answer your question:

Are these the "3.0V" "900mAH" cells?

What charger are you using to charge them?

how much runtime did you get when they were new?

 

[skunksoup]

Not trying to steal the thread here but I was told you can only use the Tenergy charger with these batteries? (mine broke) Can I use my Pila charger for these? Have both 750 and 900's.

 

[42]

The batteries were the 3.7V type and I think they're the 900 mAH. I used the Tenergy charger first but after the dismal runtimes I switched to my Trustfire charger with no difference. If I remember correctly runtimes were roughly 35 - 45 minutes in the P2d on turbo.

Mark

 

[mdocod]

skunksoup,
If your cells are 3.7V type, then the Pila charger should be OK, it will not charge any of the "3.0V" cells correctly.

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42,
I'm sure you are already aware, that 3.7V cells are usually "overdriving" the P2D anywhere from a little to a lot, it's kind of the mercy of the Vf of the LED. I thought I remember reading somewhere that as LEDs age, their Vf can drop a little, this could cause more current to flow than used to when being direct driven by the RCR123. I doubt that is what is happening but I just want to point out anything that comes to mind. If you have a current meter it might be worth checking current across the tail-cap just to eliminate this unlikely possibility.

Storing li-ion in a state of full charge does cause an increase rate of cell aging. They should be stored for long periods at about 3.9V. Tends to be that higher quality brands of li-ion cell are the best at resisting the effects of aging. It would be my guess that the cells simply aged rapidly due to a combination of being stored at a full charge and the fact that tenergy is known for having a less than superior product when compared to other name brands.

[edit in] if you have a volt meter, please test the voltage that the cell is coming off the charger, and then test it again after the cells have rested for awhile and see what happens. If they are not holding above 4.0V then that is another indication of simply being heavily "aged" cells.

Eric

 

[42]

It's kind of hard to gauge the voltage fresh off the charger because the lights tend to slowly change from red to green as the batteries charge so there isn't a definite cutoff point.I took voltage readings and they tended to read between 3.6 and 3.8 volts and dropped about 0.1 v after a few hours. When they were new the batteries ran between 4.1 and 4.2 v.

I'm beginning to think the Tenergy cells were just a bad investment. I've got some AW cells on order and will make sure that I don't store them fully charged, though that practice won't help much during a power outage. Fortunately I've got a fairly decent amount of Titanium primaries squirreled away.

Mark

 

[mdocod]

...between 3.6 and 3.8 volts and dropped about 0.1 v after a few hours....

yep, they're dead! probably from storage, sorry about your loss

try storing at 4.10V instead of 4.20V if you want them on hand for emergencies, pull prematurely from the charger, or run em down a bit before storing them to get the 4.10V..., this will give you close to 90% of a full charge with a lot less "aging" effects. The AW cells in my experience hold up pretty good, I have some old "blue label" protected AWs (from like, 3+ years ago I'm guessing) that still hold around or above 4.10V after a charge. They have actually spent a lot of their life stored at full charge, so that's pretty good

Eric

 

[42]

Ok, since these cells are bad I decided to experiment a bit. I peeled the plastic cover off one of the batteries and found a plastic module about a quarter of an inch thick on the bottom which contained the protection circuitry. I removed this, added a spacer, and put the battery in the charger. It charged to 4.1V and only dropped to 4.08V an hour later. I popped it in the light that it only lasted 10 minutes in earlier and got 30 minutes before it ran down to 3V. Very odd.:shrug:

Eric, I'll take your advice and in the future run them down a bit before I put them away for extended storage.

Mark

 

[mdocod]

are you sure those aren't "3.0V cells?" that thing you removed from the cell- could it also be a voltage shunting device? 3.6-3.8V sounds about right for an open-circuit voltage reading on a voltage regulated "3.0V" li-ion cell.... and the fact that removing this circuit allows you to take 4.0+V readings now... all seems very strange to me...

Sorry to pry into the matter further, thinking their might be more to learn from this than appears to the naked eye

 

[MattK]

They are 3V cells - Tenergy never marketed a 3.7V RCR123A product.

mdocod - you're spot on, open circuit voltage on a voltage regulated cell will not be as high as on an unregulated cell.

Mark - please don't charge them in the Trustife charger - it's not the right term voltage and is potentially dangerous. I believe the shorter than expected runtimes are a result of premature aging from storage at full charge - it's just an aspect of the chemistry and no brand of cell is more or less resistant to this.

skunksoup - same goes for you, please charge only in the correct charger - the voltage and current are specific to the Cell/PCB design.

 

[mdocod]

I'm going to assume they are 3.0V cells at this point, I think MattK is correct here. I can't recall ever seeing a 3.7V Tenergy branded RCR123, but to be honest, products like this come and go so fast sometimes and pop up at few places online then disappear, I don't think there is any way to be 100% positive.

Assuming we are dealing with 3.0V cells, (3.7V cells with voltage reducing circuits built in). Then if the "bare" cell is holding ~4.08V then it sounds like it should still be within 90% or so of it's original capacity.

I'm wondering if the charger you are using isn't topping them up properly or something. Very strange to say the least. PLEASE to NOT charge your now "bare" cell in the tenergy charger, if it is a charger designed for "3.0V" cells it will charge to ~4.4V, and will very likely cause the bare cell to explode or vent in some violent way without any protection in place to stop it!

Eric

 

[mdocod]

Oh... another question... Is your current tenergy charger the same charger that you originally bought with those cells, or is it a replacement? (I might be sort of going somewhere with this, bare with me)

 

[42]

I recall the batteries charging to 4.1 - 4.2 volts using the Tenergy charger when I first bought them. I thought the batteries were 3.7v but I'll take everyone's word that they were 3.0v. I didn't see any readily apparent difference in charge time or the final capacity of the cells regardless of the charger I used. And yes, the Tenergy charger is the one that I bought with the batteries.

I'm aware of the dangers of rechargeable Lithium cells so I kept very close watch on the temperature while I was experimenting.

I'll just chalk this whole thing up to a learning experience.

The Tenergy cells are ready for the recycle bin and now I've got a pretty good idea how to keep my new AW rechargeables healthy.

Mark