Lithium 10440 behavior?

[Brock]

I have four UltraFire 10440 AAA cells and a nano charger and have been using them for about a year now in my LOD. I have recently noticed they drop off pretty quickly under load. One of them still runs 10+ minutes and one runs about 6 min and two of them run about 2 minutes. I rarely use the light in "high" mode, usually low actually, but I like having it avaiable.

So my real question is the nano charger killing them? I usually charge them or top them off nightly taking them out of the charger about an hour or so after turning green. It wasn't until recently I noticed them dying quickly.

Do I need a better charger or cells or was I charging them incorrectly? Or did I just use them up?

 

[Buck91]

Sounds like those cells are at the end of their life. How well do they hold voltage after a charge? If they aren't holding their fresh-charge voltage (about 4.2V) for at least a half hour I believe its a solid indication of used up cells.

Do a search for information on li-ion safety, there is a really good post somewhere.

 

[freedom2000]

Oh yes, it sounds really like an end of life for your cells....
I practice R/C and we really are not kind with the cells... after a few flights (30 or 50 not more) the lipo are out of order...
Same for the Li-ions...

JP

 

[45/70]

Hey Brock,

My experience with Nano chargers, and other relatively inexpensive chargers, is that after the light turns green, they continue to charge the cell at a slow rate. This isn't good for Li-Ions and can/will reduce their cycle life. If you, as you said, "topped off" your cells just about every night for a year, I supect that this may be at least part of the problem.

Just the same, maybe Tom or someone will have a more experienced opinion to offer.

Dave

 

[Brock]

They do hold voltage really well, I would leave a charged one at work and about every 3 months I would bring it home to charge it, and it was green right away. I had read that they should be taken out of the nano charger right away when it turns green.

So is there a better 10440 charger out there?

A better 10440 cell?

 

[45/70]

Well, if your cells seem to be holding a charge, then maybe the cells themselves are the problem. I have four UltraFire and two AW 10440's. AW's hold up to high levels better than the UltraFires in my LF2, and run longer as well. They also work well in my Extreme III's, however the UltraFires are too long to use in them.

As I understand it, the L0D draws more current with a 10440 than the LF2, so maybe that is the problem. Do you have any of AW's cells you could try?

Dave

 

[SilverFox]

Hello Brock,

My guess would be that the charger has caused reduced cycle life.

The proper way to charge a Li-Ion cell is to supply a constant current, not to exceed 1C, until the set voltage is reached. At that time, the current gradually tapers off as the voltage is held constant. When the current drops to around 0.1C, the charge is terminated.

I believe the Nano charger continues to taper the charge current off until it drops to 0 mA.

It has been reported that continuing to "trickle" charge after the charge rate drops to below around 0.1C will rob the cell of cycle life. It looks like your charger has worn out your cells.

Tom

 

[Brock]

Tom that is my guess as well, just wanted to make sure I wasn't just guessing

45/70 what charger are you using?

Maybe I sill stick with the Nano charger but make sure to take them out sooner.

 

[45/70]

45/70 what charger are you using?

Maybe I sill stick with the Nano charger but make sure to take them out sooner.

I am currently using a Nano as well. When I originally got the 6 10440's about a year ago, I went through two nano 10440 chargers. The first one lasted about a day and the second one somewhat less. In the meantime, I used a DSD, charging them two at a time to keep the charge rate under control (350mA/2=175mA).

Not too long ago, I bought another Nano 10440 charger, and it seems to work fine. When the led turns orange, the cell is at about 4.15 Volts, and when it turns green, 4.20 Volts. I always watch Li-Ion charging closely, however inevitably, I've let this one go maybe 15-30 minutes past green, and the cell was at 4.21Volts, not too bad.

I think Tom is right, that the cells are probably just used up, and probably due, in part, to the Nano. Still, I'd stay with it and just keep a closer eye on it. In the year or so that I've had my 4 UltraFire's and the 2 AW's, they still work quite well, although, as I pointed out, the AW's do demonstrate superior performance. Also at this time, after resting a day, the AW's come in at 4.18-4.19 Volts and the UltraFire's at about 4.11-4.13 Volts. I don't keep a record on these, but as far as I know, all six cells have seen about the same amount of use. I do keep them in rotation and also, in the fridge when not in use. I'm guessing they all have about 20-30 cycles down to 20-30% on average.

I'm not really plugging for AW (well, OK, maybe a little ), but his cells, to me anyway, are worth the extra cost when using in a high drain light.

Dave

 

[mudman cj]

I have similar experiences. I had two Ultrafire 10440s I was using with my Extreme III, but they are squashed be the performance of AW's 10440 cells at high currents. The Extreme III is even brighter than the L0D, and draws a similar current at 100%. Time until the battery can't hold 3.6V under this load on a brand new Ultrafire 10440 is maybe 7 minutes, while the AW cells hold it for about 12 minutes. Plus, the Ultrafires are not holding their charge as well as the AW cells, as noted by 45/70. I gave the Ultrafires away.