A question about li-ion batteries.

[OrionLonestar]

okay so i have been browsing over various posts in the modding forums, and have come across a bit of information regarding li-ion batteries and that one should be checking them regularly to help prevent them exploding on you..

okay, so i read up on my batteries protected ultrafire 14500's 3.6v 900mAh that i am using on my 3.7 box mod (until i can get another set and use my VV box for frequently). Anyways came across some information stating that after charge it should sit at around 4.11v after charge. Now ive charged each of the batteries about 5 times and each time at full charge when i check them the voltage on them seem to be increasing currently at 4.15v after charge. not that its a bad thing, I do understand that at least with car batteries (work for an auto parts store) that they can and frequently hold charges above their listed rating.

Now what i am curious to is alot of the information about overcharging. currently i am using a AD-103 multivolt charger from madvapes. At what point should one start to be concerned about a charger over charging my batteries which could increase risk of failure?

And no i am not worried about my charger at the moment, just looking for some information on what to be on the lookout for, or at least be pointed to more direct posts on the subject. there is just sooo much information available on the ecf and some of it is alittle harder to find.

 

[Sicarius]

Best sign of problems is the batteries feeling hot to the touch. they should not increase by more than 10 degrees over ambient.

The 4.15v is on the high side, but rated charging voltage is 4.2 on most Li batteries. If it comes off at higher than 4.2v then there may be problems.

It is best for Li batteries not to be fully charged (100%) as this leads to voltage stresses and reduced lifespan.

Ideal charging without a top line 2 stage charger is a regulated 4.1v for around 3 hrs. This should saturate the battery to around 90% capacity without voltage stress.

Hope it helps

 

[Deadite]

Also if you are using protected batteries the circuit will protect the battery from being overcharged and over discharged.
Things I look for are heat and over or under voltage once the charger says the battery is full. Heat and over voltage are more dangerous, under voltage just means the battery is at the end of its life cycle.
Here is some quick information on using battery chargers and what protection circuits are and do.
What is a Hobby Charger

 

[CraigHB]

Optimum terminal charging voltage for a 3.7V Li-Ion is 4.20 Volts. That's plus or minus 30mV so if it's 4.17 or 4.23 that's okay. Though, it's better to be a little under than a little over. Terminal charging voltage can be obtained by measuring the battery right after charging has completed.

Anything under 4.20 volts results in less charge than the cell's maximum capacity. For Li-Ions, charging is not linear with respect to voltage so there's a difference worthy of consideration between something like 4.1 and 4.2V. Going over 4.20 volts wears the cell prematurely.

You also have to consider the accuracy of your meter. That gets into a whole other discussion about the accuracy of meters and the confidence you can put in any particular meter. In this case, a quality meter is worth the investment.

Over-charging is the most likely cause of thermal runaway which is the technical term for a battery going up in flames. It's up to the charger to do its job correctly, but the protection is there to keep anything nasty from happening if the charger fails. The protection kicks in around 4.3V, but it takes somewhat more than that to cause a cell to go critical.

The next most likely cause is over-current which can happen due to a short circuit. Electrical shorts are not all that uncommon due to a faulty atomizer or faulty connector. Again, the protection circuitry keeps anything nasty from happening.

The protection is not designed to insulate the battery from any non-optimal condition, only to eliminate conditions that could cause thermal runaway or other cell failure. You never want to rely on the protection circuitry as a matter of routine.

Li-Ions loose charge capacity as they wear. Like any rechargeable battery, they wear from normal charging and discharging. A Li-Ion is considered worn out when it has 40% of its original charge capacity.

Li-Ions also wear over time just sitting on a shelf so it's best not to store them long term. Buy them as needed. It varies, but shelf life is usually at least 3 years and some are as high as 5 years. It depends on the exact chemistry.

A fully charged Li-Ion stored at room temperature loses as much as 20% of its charge capacity per year. For long term storage, shelf life can be increased by storing them with a half charge (which is 3.8V). Shelf life can be further increased by putting them in a refrigerator, but not a freezer. A freezer is too cold and damages them. A half charged Li-Ion in a refrigerator loses as little as 5% of its capacity per year.

Li-Ions can not be discharged below a threshold voltage. It varies depending on exact cell chemistry but it's always somewhere between 2 and 3V. Over-discharge damages them and if discharged deep enough, they won't recharge at all. That's why it's best to have some charge on them when storing long term. Manufacturers usually store them in their warehouses with a 40% charge.

 

[OrionLonestar]

Great information from everyone and thank you for taking the time to post it. i hope that someone else that is looking for this information will find this useful as well. i check my batteries every time they finish charging and average charge is about 4.13v and have not seen them go above 4.15v.

Like you said craig depending only on the "protection" circuit is not the wisest of ideas to do. which is why i check them (takes a whole 5 seconds to do) regularly. Thanks again all.

 

[CraigHB]

Welcome,

All of the charger chips I've used for my mods with built-in charging terminate very close to 4.19, within a few mV. I've built at least 10 of them by now with the same part number chip so I'd say that's out of 10. I have a few other chargers around and the cheapo round cell charger I have terminates at 4.17V, but I don't use it much. I mainly use the latter.

My wife uses the eGos so I have a number of those chargers. They've ranged between 4.16 and 4.20V. Though, with the eGo chargers, I can only measure voltage with no battery on them so I don't know if that's a true reflection of terminal charging voltage, best I can do with those anyway.

I have not yet encountered a charger that terminates over 4.20V, probably just by happenstance.