Help! I desperately need an education - LiIon Batteries and Chargers

[Atomic_Chicken]

Greetings!

This is a difficult post to write, because I have so many questions. I'll start with an overview, then ask a few specifics.

First off, I am badly in need of an education with regard to Lithium Ion batteries. I am interested in this from a technical and electronic/testing standpoint, not a "myself as an end-user" standpoint. I use Lithium primary cells in all my lights, for several reasons - chief of which is that I want my lights to ALWAYS GO ON when I press the switch, and have as good a runtime as possible even if I haven't touched the light in months. However... with the Aviatrix project in full-swing, I'd like to do some runtime tests using LiIon batteries so I can publish the results alongside Lithium primary cells in the specifications pages, and give potential customers advice and information should they choose to use LiIon batteries in their Aviatrix modded A2s. Once again, I emphasize: I am NOT very interested in using LiIon for my own day-to-day use, I'm interested mainly from a technical/electronic standpoint for testing and marketing purposes.

Here is what I know about LiIon batteries: LiIon 123 cells come in two flavors - protected and unprotected. Protected cells have internal circuitry which cuts off the battery from the external device in the event of overcharging, or over-depletion of the cell below it's minimum voltage. LiIon cells can be damaged to the point of no longer taking a charge if they are depleted below their minimum voltage. LiIon cells can burst into flames if they are overcharged. These two reasons are why protected cells exist. The drawbacks are that protected cells do not have as high a mAH capacity as unprotected cells, and protected cells are often larger in diameter than unprotected making them mechanically incompatible with some lights. Special chargers are required to charge both unprotected as well as protected LiIon batteries - the grocery store chargers for NiMH batteries won't work. Both unprotected and protected LiIon cells output higher voltages than primary Lithium batteries (up to 4.25V, if I understand correctly). Finally, there are versions of LiIon cells that are the same diameter as primary Lithium CR123 cells, but they are longer and meant to be used in place of a pair of CR123s (sometimes with an added lengthening spacer) - and power a light with LESS voltage than a normal pair of CR123's but with higher mAH capacity.

That is the extent of my knowledge of LiIon rechargeable CR123-replacement batteries.

Question 1 - Do I have all of the above correct, or have I misunderstood something(s)?

Question 2 - Is there a special designation system that can be used to tell which cells are protected, and which aren't, by looking at the part number? So far, I'm a bit confused by the various mfg.'s part numbers.

Question 3 - How do LiIon batteries compare to primary Lithium batteries in terms of power capacity (mAH)?

Question 4 - If I buy a bunch of different LiIon (protected as well as unprotected) batteries for various runtime and compatibility tests for current and future Aviatrix (Surefire A2 Aviator mod) models, what is a GOOD battery charger to buy that will support them all? Is there something out there that would allow me to "tweak" the settings and over/undercharge or fast-charge the batteries so I can do testing under a variety of conditions? Something with a timer or voltage monitoring for charging unprotected cells? Maybe something that will charge 4 or 8 batteries at a time? Cost is important, but not critical - I can budget several hundred dollars for this if really necessary, but I'd prefer something sub-$100 if it still provides flexibility and good charging options.

Question 5 - Browsing through this forum late last night, I came upon one of CPF user "AW"'s posts, where he was talking about a "New Version" R123A protected cell with 750mAH capacity. He listed the diameter of these batteries as 16.6mm. I measured the inside tube diameter of two of my Surefire Aviators, one was 16.69mm and the other was 16.70mm. Based on this, I ordered a few of these batteries and his $15 charger - thinking that if nothing else, I could "get my feet wet" with LiIon technology and maybe have something to sell/trade later if they didn't perform well for mechanical fit or testing. Did I make a mistake? Are those decent protected LiIon cells?

Question 6 - Is there any other information, threads, books, etc. that you can recommend to help me obtain the thorough overview of LiIon battery technology that I am seeking?

Question 7 - What are the most popular, best performing, and best priced LiIon CR123 replacement batteries available? Note that I'm not asking for a single battery that fills all 3, but if there are 3 different batteries that fall into those 3 categories, I'd like to know about each of them.

Question 8 - Are there any issues or problems I need to be aware of when using LiIon batteries as a pair in series configuration?

Question 9 - Are there any other questions I should be asking?

Thanks in advance, and best wishes!
Bawko

 

[cd-card-biz]

Hi A_C,

Sorry if you already know about this online resource, but it is a great reference:

www.batteryuniversity.com

Also, FWIW - a very knowledgeable group with Li-Ion technlolgy is the RC (radio control) groups. They typically use the programmable chargers like the Triton2 and Triton Jr. ( http://www.electrifly.com/charger.html )

Also, there is a thread here on CPF regarding balanced charging of multiple Li-Ion cells.

Hope this is of some value. And, I don't think I am alone when I say how much we appreciate your passion for the Aviatrix project!

Best,
Bill

 

[kavvika]

I suppose I can answer questions 3 and 7. Typically, 3v lithium primary batteries have a capacity within 100mAh of 1300mAH. The exception is Radio Shack's CR123A's. They are rated around 800mAH, IIRC. And they are priced higher than Duracells or energizers at Walmart. Ultrafire RCR123A are overrated and testing shows they contain about 700mAH, even though they claim 900mAh. AW's batteries are, IMO, top of the line and he does not overrate their capacity. They are 750mAH, like you mentioned. I trust the protection circuit in AW's rechargables, and if a cell is protected it will explicitly say so in the description. If the description does not say protected, it is not, and I would stay away unless you know what you're doing.

 

[SilverFox]

Hello Bawko,

Question 1, you have most of it right... The maximum voltage for a Li-Ion cells is usually given as 4.200 plus or minus 0.05 volts. Numerically, this works out to your listed 4.25 volts, but the intent is to charge to 4.200 volts, and there is just a little leeway.

The reason protected cells are slightly larger in diameter is because there is a ribbon wire connection between the plus terminal and the protection circuit, which usually is at the negative end of the cell. This extra ribbon wire adds a little to the diameter. The protection circuit also adds a little to the length of the cell.

The protection circuit can also limit the amount of current drawn from the cell. An incandescent lamp can start off as nearly a dead short until the lamp warms up. This is why you hear about people having to double and triple click a light to get it going. The current is too high for the cell when the lamp is cold.

The protection circuit is a back up safety device. It is best if you never activate it. This means using a charger that is designed for Li-Ion cells, shutting the light off before the battery is fully discharged, and sizing the battery properly for the current demands.

Question 2, The cell is either listed as protected, or it is not protected. If it is not specifically stated that it is protected, assume that it is a bare cell.

Question 3, I assume you are talking about CR123 comparisons. The R-CR123 cells usually have a higher voltage (3.7 volts nominal), but usually have around half the capacity (mAh). CR123 cells come in at around 1300 - 1500 mAh, and R-CR123 cells come in at around 600 - 650 mAh (even though they may be labeled higher).

Question 4, A good hobby charger will give you some flexibility, but the most flexible charger for Li-Ion cells is a well regulated power supply. Something similar to the Mastech HY3010E would be great, but you could get by with the HY1803D and still have lots of flexibility. Keep in mind that if you go with a regulated power supply for charging Li-ion cells, you will also need an accurate volt meter to set it up. The resolution on the power supplies is not accurate enough for Li-Ion charging.

Question 5, Some of those cells will snuggly fit into an A2, others won't. It is difficult getting the snug ones out.

Question 6, Sanyo and Panasonic both have excellent white papers on the use and care of Li-Ion cells. The best reference book is the Handbook of Batteries, and it is currently in the Third Edition. There are also lots of threads on Li-Ion cells in this section of CPF. One in particular has to do with parallel charging Li-Ion cells. There is also lots of good information in the threads about the charging cradle that LuxLuthor is working on.

Question 7, R-CR123 cells are a compromise. The best Li-Ion cells are the 18650 cells, but they don't fit in the A2. I have had good luck with MP and Powerizer R-CR123 cells, and have heard good things about the cells that AW is offering. Please note that both the MP and Powerizer cells are not protected.

With that said, these cells are the same as any other Li-Ion cell. If you run them too hard, or over discharge them, or store them completely charged, you will loose cycle life. If you over charge them, they may vent with flame. Protected cells may be damaged by hooking them up to a NiMh hobby charger, or by dropping them on the protection circuit.

Question 8, Always check the voltage of the cells. They should be equal in voltage. If they are equal in voltage starting off, you should have no problems. Don't mix capacities or brands. When you charge, charge individually, or in parallel. Don't charge in series, unless you arrange for using a balancer and install balancing taps.

Question 9, Safety is the biggest concern. After that comes cycle life and performance. Li-Ion cells should stay cool. They may warm up, but if they get hot, you are pushing them too hard. There seem to be two different chemical mixes of cells available. One seems to perform better than the other, but suffers from poor cycle life. The other has extended cycle life, but does not have the highest capacity. A Li-Ion cell should be recycled when it falls below 80% of its initial capacity.

To get the most life from a Li-Ion cell, limit the charge to 4.0 volts and limit the depth of discharge to 80% of the capacity the cell has when it is charged to 4.0 volts.

I frequently only charge to 4.1 volts for normal use, and do a full charge to 4.2 volts only when I know that I need the extra capacity. Although you are supposed to be able to discharge these cells down to around 2.5 volts under load, you will get better life from them if they rebound to around 3.4 volts, or higher, within 15 minutes of removing the load. Recharging often is far better than running them all the way down.

Storage is best with the cell at around 50% of full charge, in a cool place.

The final thing to keep in mind, this time around, is that Li-Ion cells corrode (or "rust") from the inside. This starts from the moment they are assembled. Fresh cells perform better, and even if the cell is never used, it will eventually die. Originally the cells had a 2-3 year life expectancy, now it is up to 5-7 years and there is hope that eventually they will be good for 15 years, and still be capable of over 80% of their initial capacity.

Tom

 

[LuxLuthor]

SilverFox is the man.

I would add that there is also some question that storing protected Li-Ion cells in the freezer may cause damage to the protection circuit (there is a thread on that). I think the biggest issue with rechargeable Li-Ion cells is safe charging. The protection circuit can be defeated by improper voltage being applied. There is a post here of a member selecting a higher number of cells voltage on the universal charger and exploding a cell (with pictures).

There is some good information on the RC Groups forum, but they tend to use LiPo (Lithium Polymer) battery packs which does not have the Li-Ion cell metal canisters. Otherwise the performance and care is similar. Recently, they began using the new nano-sized titanate electrode Lithium Ion cells, which were first found in Dewalt power tool 36V battery packs which they took apart.

It's too bad that the new Saphion phosphate based cathode Lithium Ion batteries are not available in a variety of sizes, because they resolve the dangers, and dramatically increase almost every aspect of performance and charging. They are starting to be adapted to RC racing/flying applications as in this A123 racing battery site.

This Wiki site has a lot of information you are looking for, as well as these new technologies, and additional links.