Lost again in the battery charging Twilight Zone - what caused this?

[matrixshaman]

I guess I'm on a battery rampage today - I think this is a new and strange occurrence for a charger that I have used with many Li-Ions though. It seems to always go green (indicating fully charged) at right around 4.25-4.29 volts and that is with many different brands of cells and sizes including CR2's RCR123's and 18650's. It's a low current charger. I put a new RCR123 in it today (unprotected as many of my cells are) and it seemed it had been on for quite a while (still red light) so I pulled it to check the voltage. It was reading 4.46 volts and even after being off a few minutes was still at 4.42 volts. Yet this battery wasn't even a little warm to the touch. In fact a digital laser temperature reading gave only 72.1 degrees. This charger charges at 100ma and will read 4.87 volts open with no battery in it. I've just never seen it charge a battery that high without shutting off. Lost again in the battery twilight zone :thinking:

 

[LuxLuthor]

I'm not an expert on this...but my gut impression is "YIKES!"

 

[Curious_character]

All the data sheets for Li-Ion cells I've seen specify a charging voltage of 4.2 volts with very tight tolerance. The charging voltage will be lower when the charger is delivering its maximum, limited current, but 4.2 should be the charger voltage when it's delivering less current as the cell approaches and reaches full charge. I don't know what happens to a cell if you try charging it to a higher voltage, but it might not be pretty. I wouldn't use a charger that tries it.

c_c

 

[matrixshaman]

After reviewing a few places I got a couple chargers and batteries I believe this particular charger was made for protected cells - it was purchased with Delkin eFilm cells that say they are 3 volt - still not sure if they are protected but might be. If so I guess it's lucky I charge batteries in a steel tool box with the lid closed. Tried the same type cell that went to 4.46 on my other charger and it went green at 4.03 volts. This other charger has an open circuit voltage of 4.21 volts and IIRC most batteries have come off it at around 4.2 volts. Maybe I just caught this one sooner than most after going green but I still say I'm in the charger Twilight zone :tinfoil: :laughing:

 

[hank]

I think I read somewhere (this is not help, I'm just talking to myself) that protected cells need a higher voltage charger to deal with the protection circuit.

I know I read lots of places advice against mixing up cells and chargers.

I think what you did putting an unprotected cell on a charger set for protected cells is .... wrong.

Maybe I'm wrong. I wouldn't do that without much better advice than I can give.

 

[LuxLuthor]

After reviewing a few places I got a couple chargers and batteries I believe this particular charger was made for protected cells - it was purchased with Delkin eFilm cells that say they are 3 volt - still not sure if they are protected but might be. If so I guess it's lucky I charge batteries in a steel tool box with the lid closed. Tried the same type cell that went to 4.46 on my other charger and it went green at 4.03 volts. This other charger has an open circuit voltage of 4.21 volts and IIRC most batteries have come off it at around 4.2 volts. Maybe I just caught this one sooner than most after going green but I still say I'm in the charger Twilight zone :tinfoil: :laughing:

Matrixshaman, check this list of incidents with links below first posts. Somewhere are images and video of a metal box being exploded from the pressure...maybe on this forum page.

There is also information in this CPF thread.

 

[matrixshaman]

It's not sealed at all - just a loose tool box that would keep flames or small exploding parts from getting out into adjacent area - even a sudden burst of pressure would have no trouble inside this very loose fitting lid. Maybe one lesson here too is that batteries don't explode when cold - so maybe the higher voltage on this cell is not so much a problem as much as charging too high of current too fast.

 

[SilverFox]

Hello Matrixshaman,

Glad you were able to figure it out.

You have most likely damaged your cells through overcharging. Mark them and keep an eye on them. Usually the damage manifests itself in greatly reduced cycle life, but there is the possibility of lithium plating during the overcharge. Lithium plating can contribute to thermal runaway during subsequent charging.

Tom

 

[65535]

http://www.rcgroups.com/forums/showthread.php?t=355739 boom!

 

[matrixshaman]

That was a LiPo pack being charged at 15 amps. I don't even charge my car battery at that much. What I am getting very interested in now is whether anyone has studied very low current charging to higher voltages on Lithium Ion versus higher current charging to lower voltage and the effects on the lifespan of cells. My feeling is that HEAT is the big culprit in damaging cells rather than a slightly higher voltage. Voltage may do it too but I'm sure heat causes a lot of damage in a cell that is essentially a chemical reaction being reversed with voltage. When things get hot chemistry changes.

 

[matrixshaman]

I think I read somewhere (this is not help, I'm just talking to myself) that protected cells need a higher voltage charger to deal with the protection circuit.

I know I read lots of places advice against mixing up cells and chargers.

I think what you did putting an unprotected cell on a charger set for protected cells is .... wrong.

Maybe I'm wrong. I wouldn't do that without much better advice than I can give.

hank - thanks for mentioning that - I had that in the back of my mind and am glad you brought it up.

 

[VidPro]

After reviewing a few places I got a couple chargers and batteries I believe this particular charger was made for protected cells - :

which would have used the protection on the cell for a cutoff . at that slow rate, they might make it to 4.4V before popping, but if they stink, or are at 0V then you should dispose of them.
an "open" li-ion has a specific (TOXIC) stench that comes out of it, that indicates it is open.
any good "CAN" cell will open up with nary a sound, and no flames or anything fun or spectacular. a li-poly will begin to puff up, when SLOWLY overcharged.
most can cells destroyed by overcharge, dont make forum headlines for spectacular displays.

if they are open you can smell it from a distance, it will be like a weird smell, that you cant figure its origin, then you remember what ya did, and over there is some guilty battery.

also the discoloration and oxidation of a location the battery is in, might be an indication that the battery is open, and stuff is exuding out of the top vents. Like on the bottom of a battery its in series with, on the chargers tabs, at the head of a flashlight, on the top tabs on a charger.

a Cheap "open" battery can continue to function, only the above clues might give it away. that and its slowly becomming unusable.
a Good "open" battery should disconnect at the same time, revealing itself quite noticably by being a big 0.
(so that is why its important to know , that there is not always an obvious indication)

 

[LuxLuthor]

Somewhat unrelated, I was out using a 14.4V battery pack in Mad MaxaBeam's MaxBlaster (Torch clone), when after about 2 minutes there was a loud "POP" and concussive impact from the light before it went dead. Initially, I figured the bulb blew up, but when I got home it was fine.

One of the twelve 2/3A Intellect batteries blew as this was the first time I used it...but no obvious damage was visible when looking at the black vinyl shrink wrap, which in retrospect was reassuring...since it was about as loud as a small (Ladyfinger) firecracker. After a fresh change of shorts, I was as good as new, and of course Mad MaxaBeam replaced it without question.

 

[OceanView]

I believe this particular charger was made for protected cells - it was purchased with Delkin eFilm cells that say they are 3 volt - still not sure if they are protected but might be.

Just checking a point you made, but you're saying the charger was meant for 3.0 V cells? Chargers for those regulated cells are different than your standard 3.7 V Li-ion cells, aren't they? Or, at least require a different charging setting from 3.7 V cells, I thought.

 

[matrixshaman]

I was lead to believe they were 3.0 volt batteries when I bought them but I still don't know for sure. I guess I could load test them but I don't think they actually are and maybe they are protected not regulated. They have almost no real info on their web site. These were the first RCR's I bought and didn't know much about them - just that they were advertised as 3 volt instead of 3.6 volt. I believe they come off the charger around 4.2 volts though so I'm thinking they are probably just protected if even that. I bought 2 and they both still seem to work well. I'm not sure if a charger for a 'regulated' cell is actually different but they may be. It would seem the regulation will occur under load and that a standard Li-Ion charger could charge them if the regulator was built so incoming current bypassed the regulator. I guess I get a bit frustrated seeing places sell batteries that say they can be charged ONLY with their charger. And their charger is usually $$$ and since I've built chargers from scratch I know most chargers are very cheap to build. So I have been making the assumption (maybe incorrectly) that they are just trying to make most of their profit on the chargers. Nothing against people making profit but if I can get around buying a charger I don't really need then I will do that. However I've obviously discovered a few things here that make it clear that unless you are babysitting cells and checking the voltage every so often that it can be important in some cases to have a charger that is at least more or less compatible with the battery being charged.

 

[65535]

Lithium Batteries are basically the same, when they go they go, doesn't really matter how slow or fast you charge them once they hit the critical value; temp, voltage, they go.

 

[hank]

Check AW's several and very long threads, someone will have a pointer (sorry, rushing); I am pretty sure that's where I got the idea that the 3v protected cells actually match up with a _higher_ voltage charger than the 3.7v unprotected cells require, because the higher voltage is needed with the protection circuit. Do not trust me on this, I could have it utterly wrong. But I'm sure there's real concern about mixing up cells and chargers and there are some combinations that lead to, as the nuclear power plant engineers call it, "rapid energetic disassembly with collateral damage" a.k.a. "things jump up and go boom" events.

 

[Tronic]

Here is a very good post from Markcm about the different 3.0V RCR123 charger.

Yes, there are some charger that charge up to 4.4V (or higher).
Dont use this charger for charging your "normal" liion battery!!!