General Li-ion safety

[Joe Talmadge]

Re: Feedback requested: Li Ion beginner primer

Those bags look like a nice insurance policy for the super cautious among us, if they really work. If you're using something like a Pila IBC, would you just shove the entire charger into the bag? Or are they made for chargers with leads instead of bays?

 

[samgab]

Re: Feedback requested: Li Ion beginner primer

Those bags look like a nice insurance policy for the super cautious among us, if they really work. If you're using something like a Pila IBC, would you just shove the entire charger into the bag? Or are they made for chargers with leads instead of bays?

They are really for RC guys, using hobby chargers, and who are charging at high rates, like 5A-10A. If you put a Pila charger or similar in the bag, you'd probably do more harm than good, because of heat. You'd be putting all the electronics in the bag, whereas they are designed to take RC battery packs where the electronics of the hobby charger remain out of the bag.

 

[45/70]

Re: Feedback requested: Li Ion beginner primer

Hi Joe. Your looking pretty good, I'd say. One thing that may be OK as it is, but most LiCo cells of 18650 size and larger have a maximum recommended charge rate of 0.7-0.8 C, or some even considerably less. You can probably get away with charging most of these cells at a 1C rate, but it's not good for them. You may want to work this point in somehow.

What exactly is supposed to happen when you try to charge a Li-Ion battery that has been over-drained?

Just to add something here. The biggest danger in over discharging cells is that at a voltage of around 1.5 Volts/cell, copper shunts can form within the cell, which as Joe mentioned, can cause the cell to short internally. These shunts may, or may not form, but the longer the cell is in a low voltage state, the more likely this may happen.

The scariest thing about these shunts is, while a short is probably more likely to occur when attempting to charge the cell, it could also happen at any time, while the device is in use, or even when not in use, such as in your pocket, or stored in a drawer. The other thing about these shunts is once they start to form, they continue to grow and the condition is irreversible. This results in a cell or battery that may seem fine one day, but may develop internal shorts the next day, after a week, or even months later. Of course, it's also possible that shunts never started to form, in which case, nothing will happen. The only way to tell for sure, is to disassemble the cell and look at it with an electron microscope.

With something like a cellphone, usually the built in protection circuitry will prevent the cell, or cells from being discharged to a low enough voltage to cause problems. If on the other hand, a battery is drained to the point where the protection circuitry has activated, and then the battery is not used for sometime, the voltage may drop lower. Then, there may be a problem.

It is important to remember, that the discharge graph of most any cell drops like a rock at a certain point. In the case of Li-Ion cells, this point is very close to the cutoff voltage of most protection circuits. So, while self discharge of Li-Ion chemistry cells is very low, it doesn't take much for the voltage to drop significantly, once you're headed over the cliff.

Dave

 

[Joe Talmadge]

Re: Feedback requested: Li Ion beginner primer

gotcha on the correction about 18650s, I'll update that

 

[Jackasper]

Re: Feedback requested: Li Ion beginner primer

Very good info. Thanks for taking the time to write this up. It never hurts to have a DMM to keep tabs on voltages both before and after charging. It's so difficult to know exactly where your voltages are with most cradle/bay style chargers. Relying on the protection circuit, like you mentioned, is never a good idea. By having a meter handy, it saves alot of guesswork.

 

[HKJ]

Re: Feedback requested: Li Ion beginner primer

Thanks guys, lots of good comments, I'll start reflecting some of them. I like the idea of a graph in the charging section. HJK, do you own that graphic you just posted, and if so, do I have permission to include it in the guide with an attribution to you?

Yes, it is my own and you can use it. The graph is from charging a CalliesKustom 3100 mAh cell.

 

[Joe Talmadge]

Re: Feedback requested: Li Ion beginner primer

Very good info. Thanks for taking the time to write this up. It never hurts to have a DMM to keep tabs on voltages both before and after charging. It's so difficult to know exactly where your voltages are with most cradle/bay style chargers. Relying on the protection circuit, like you mentioned, is never a good idea. By having a meter handy, it saves alot of guesswork.

True .. are there standard recommendations for inexpensive multimeters for beginners, or is quality such that most will do?

An alternative question: my only way to measure voltage is using the voltmeter that's part of my Cottonpickers charger. Any reason that that's not enough?


HJK: thanks, added the graph

 

[Joe Talmadge]

Re: Feedback requested: Li Ion beginner primer

I added a slightly more detailed section on charging, A BIT MORE DETAIL ON CHARGING

 

[N162E]

Re: New section added 12/26/11: Li Ion beginner primer

12/26/11: Added A BIT MORE DETAIL ON CHARGING, after the charging section

There are multiple battery chemistries for Li Ion batteries. I am going to almost solely discuss LiCo, but there are other chemistries popular in lights such as IMR and Lifepo4. I will contrast with IMR occasionally.

I always love "Beginner Primers" full of confusing acronyms.

 

[Joe Talmadge]

Re: New section added 12/26/11: Li Ion beginner primer

Heh, I see your point. That said, does knowing what "IMR" means really enhance readability and clarity of the document? I was reasoning that I'd just use the terms they'll be seeing as they do further research (and likely have seen already as they read through the forums), and knowing what the M in IMR stands for may not be as enlightening as knowing some of the characteristics of an IMR cell. A bunch of beginners on two forums seem to think this is clear as-is. I'm not necessarily being argumentative here, it would take me 60 seconds to whip up some definitions. I'm asking, if you're a beginner, does knowing what IMR stands for have any effect on the clarity of the document or its recommendations?

 

[HKJ]

Re: New section added 12/26/11: Li Ion beginner primer

Maybe you need to add something like:

Without the supported column, but with an explanation of the abilities of different chemistries.

 

[N162E]

Re: New section added 12/26/11: Li Ion beginner primer

Heh, I see your point. That said, does knowing what "IMR" means really enhance readability and clarity of the document?

Absolutly. When acronyms are used over and over again with no definition it makes for confusing and awkward reading. How hard is it to spell them out the first time around? What does Lico, IMR and life4pos or whatever stand for? I don't know and I've been here almost as long as you. I do applaud your importance placed on safety.

 

[Joe Talmadge]

Re: New section added 12/26/11: Li Ion beginner primer

OKay, will add some clarity to the different chemistries at the top, maybe in table form as HKJ suggestd

 

[N162E]

Re: New section added 12/26/11: Li Ion beginner primer

Maybe you need to add something like:

Without the supported column, but with an explanation of the abilities of different chemistries.

Specs are nice but, what do the abbreviations spell? ICR, IMR, IFR (Maybe Instrument Flight Rules) LICo2, LIMn and lifepo4.

 

[samgab]

Re: New section added 12/26/11: Li Ion beginner primer

Your own paraphrased version of these two tables might be helpful:

The information drawn from these tables was taken from the book: Batteries in a Portable World - A Handbook for Non-Engineers, 3rd Edition, by Isidor Buchmann

 

[HKJ]

Re: New section added 12/26/11: Li Ion beginner primer

Specs are nice but, what do the abbreviations spell? ICR, IMR, IFR (Maybe Instrument Flight Rules) LICo2, LIMn and lifepo4.

The ICR, IMR, IFR are not abbreviations, but a coded letter system, see http://www.candlepowerforums.com/vb/showthread.php?317698-Lithium-IMR-vs-ICR-vs-IFR for more explanation.
The LiCo.. etc. is standard chemical nomenclature, you can find them in a table of the periodic system.
Generally I do not believe that it matters what these names stands for, but more what is the ability of the cells behinds these names.

 

[N162E]

Re: New section added 12/26/11: Li Ion beginner primer

OKay, will add some clarity to the different chemistries at the top, maybe in table form as HKJ suggestd

TThank you Joe.

 

[N162E]

Re: New section added 12/26/11: Li Ion beginner primer

The ICR, IMR, IFR are not abbreviations, but a coded letter system, see http://www.candlepowerforums.com/vb/showthread.php?317698-Lithium-IMR-vs-ICR-vs-IFR for more explanation.
The LiCo.. etc. is standard chemical nomenclature, you can find them in a table of the periodic system.
Generally I do not believe that it matters what these names stands for, but more what is the ability of the cells behinds these names.

Maybe I'm just plain stupid, for sure not on a par with you genius' I guess I always thought that a "Beginners Primer" was supposed to answer questions not create them. You refer to the periodic table, I always thought that was elements, not mixtures or compounds.

 

[HKJ]

Re: New section added 12/26/11: Li Ion beginner primer

Maybe I'm just plain stupid, for sure not on a par with you genius' I guess I always thought that a "Beginners Primer" was supposed to answer questions not create them. You refer to the periodic table, I always thought that was elements, not mixtures or compounds.

I am not writing this primer, but just tries to fill in until Joe get it organized in the primer.
Look at the upper/lower case letters: Li, Co, Mn, Fe, all of them can be found in the periodic system, the number specifies how much of that elemental is used (It is a chemical formula). This specification does only cover the positive electrode (Cathode) in the battery, but getting into much more chemistry is way beyond a primer.

 

[Viper715]

Periodic table reference refers to the LiCo
If you separate it
Li=Lithium
Co=Cobalt
So you have a lithium cobalt battery chemistry.

Edit; beat me to it and better explanation.