Large Scale Central

Battery Voltage

General Discussion
#21

Greg,

Are you suggesting “RECHARGEABLE batteries” aren’t consumable; i.e., not intended to be used up and replaced?

Anyway I’m sure you’ll agree, battery life and or death begins the second the cells are assembled it’s inevitable and irreversible (this is true of any cell type). Lithium cells/batteries can totally degrade within a few years, even if rarely used or mildly charged.

The formation of a surface film layer of reactive products on the anode of Lithium cells is in play and is the predominate source of irreplaceable lithium ion losses during storage conditions.

Michael

#22

Michael, there is not doubt that you are right, but for most of us, good enough, is… well, good enough. Close enough for all practical purposes, if you will.

You see, most of us are “napkin builders.”

#23

My LiIon batteries are now 5 years old. I thought I had one fail but it was actually my charge jack. They sit in my unheated barn all year long. This past winter it was -17 summer gets to 95+. I haven’t noticed any change in difference for run time. I couldn’t be happier with them. Good enough for me I guess.

I mostly like the fact that i don’t have to care for the charging of them. I plug them in when i need to and then leave them until I need them. NiCad was the main reason I got out of RC cars, I would have to preplan my run time and start charging two hours earlier.

Terry

#24

No Michael, and as you know, we are normally eye to eye on about 100% of the stuff discussed between you and I.

I’m specifically reacting to (and I believe others were) “once you combine the chemicals the clock starts ticking.”

The majority of the aging is from the mostly, but not completely, reversable reactions that define the term “rechargeable”.

Your statement seemed to implicate that the mere combination of the materials to make a lithium-ion battery was a SIGNIFICANT part of the aging process. It is not.

The significant part of aging is the number and “depth” of the charge-discharge cycles. That’s all.

Clearly rechargeable batteries, if you need a “yes or no” answer, are consumables, because they EVENTUALLY wear out. (And I bristle at trying to make answers “binary” when there’s a lot more to the situation)

Hopefully that clearly establishes my opinion and position. Regards, Greg

Michael Glavin said:

Greg,

Are you suggesting “RECHARGEABLE batteries” aren’t consumable; i.e., not intended to be used up and replaced?

Anyway I’m sure you’ll agree, battery life and or death begins the second the cells are assembled it’s inevitable and irreversible (this is true of any cell type). Lithium cells/batteries can totally degrade within a few years, even if rarely used or mildly charged.

The formation of a surface film layer of reactive products on the anode of Lithium cells is in play and is the predominate source of irreplaceable lithium ion losses during storage conditions.

Michael

#25

Greg,

I am not an expert, that said I rely predominately on my experience and that of associates as well as what I garner from experts in the field. Its been several years since it mattered to me, accordingly I may offer thoughts and perspectives that are gleaned out of context due to memory and or my misunderstandings.

FWIW, I agree that D.O.D. can be a major player in Lithium’s short life cycle, perhaps even ‘significant’ as you note . However in the typical controlled environment of lithium ion applications D.O.D. is not as big an issue as heat with regard to cell degradation and or capacity loss.

When the chemicals are mixed the clock starts, weather or not its a ‘significant’ factor is known to those that have empirical data to suggest same. Back when I played heavily with Giant Scale RC Aircraft I had multiple battery sponsors and delved deeply into lithium ion technology in earnest in support of our needs. I was provided literally hundreds of Lithium ion batteries for test and evaluation from multiple OEM’s. Over the course of time I logged data for each and every battery I was in control of; many of the batteries saw little to no use after initial commissioning. The aged batteries with minimal cycles failed as often as those with many cycles in my experience (keep in mind a single cell failure delegates the battery to the trash bin). In any event the point I was making is cycle count does NOT tell the tale in its entirety…

I previously noted a chemical reactive surface layer builds up on the anode, this literally chokes the cells ability to pass ions. Formation of the surface film layer is the predominate source of ion losses of lithium ion batteries in storage. And yes higher cycle counts contribute greatly to the growth and thickness of the aforementioned reactive surface layer too. All this means that the desired reversible reactions of rechargeables becomes irreversible capacity loss regardless of cycle counts.

Michael

#26

I have to disagree on one point, you ARE an expert, with all the real, empirical knowledge you have combined with your research, you are stuck my friend!

:wink:

Greg

#27

Does the high discharge rates involved in aircraft batteries affect their usable life? Remember, the discharge rates that we use are geologic compared to the average aircraft battery.

#28

Steve,

RC aircraft use batteries for flight systems and propulsion. As a rule propulsion is much more demanding. That said we recorded discharge numbers up to 26 amps for micro-seconds in 40% scale 40lb. aerobats with 14 digital servos in demanding flight conditions albeit this was not atypical. Moving forward servos became more powerful, gear trains were more robust and power distribution systems were desirable. The high power requirements were unbeknownst to modelers at the time.

Most servos utilized were ‘dumb’ digitals or analog and worked with what ever power was available without issue for the most part (JR-Futaba-Airtronics). Subsequent to Hitec’s programmable digital servo release; modelers began to report issues. We found the Hitec’s were for lack of better description were realizing a "brown-out’ and would reboot the micro-processor when the voltage dipped below 3.0V as I recall (essentially causing the servo to go to sleep momentarily). To give this assertion some gravity, most modelers were using 6.0v NiCad batteries in the 1000mAh range or so if memory serves me (2001). Many of us with larger aircraft gravitated toward dual receiver’s/batteries and light weight Tadiran 800mAh Lithium metal batteries to share the load with the atypical tin plated low quality switches/connectors/extensions/wyes and such typical of the time (this was inadequate yet state of the art). Herein we realized a robust power distribution system together with quality gold plated connectors and higher amperage batteries were a must… Onboard flight recording equipment came to fruition and as noted earlier the power demands of the flight systems was indeed substantial. Intelligent servo power interfaces came to the market with many desirable attributes, about the same time Lithium Ions were introduced and later found to be sorely lacking. 2000mAh cells in 2S1P configuration were the first, requiring voltage regulators, later 2S2P series-parallel batteries packs @ 4000mAh each were common in pairs thereof. These batteries got the job done in most circumstances and offered the highly sough after lighter physical weight as compared to NiCad’s and then NiMH technologies.

Sorry for running on…

If in fact high current demands are sustained and commonplace heat soak becomes a factor and yes this will effect a lithium ion batteries life cycle. Heat is the enemy; heat is realized when charging, discharging and or under sustained loads. Excessive flight loads are momentary yet uncommon with a properly set-up model (another common problem was improper linkage geometry, binding and excessive noise or chattering).

Your more likely than not to damage a lithium battery by medium to fast charging and high discharge rates which warms the cell as compared to running the typical G scale train. Storing batteries in high ambient temperature’s is undesirable as are low temperatures. As alluded to earlier D.O.D. (depth of discharge) plays a role too. All the above is responsible for cell degradation or capacity losses. And remember I suggested batteries failed at pretty even rate regardless of use or being shelf queens.

Best case scenario:
Store in cooler environment.
Charge to 4.1v @ C/2. (capacity/2)
Minimize discharge or run time to prevent dropping the voltage to the prerequisite threshold (D.O.D.)
Exposing the batteries to elevated temperatures is undesirable, even sitting on the rails…
Batteries grow old and fade sitting on the shelf, might as well burn them down on the rails.

If it ever applied; use it or loose it apply fits this technology.

Michael

#29

Greg,

Them is kind words at the least. :slight_smile:

Michael

#30

I meant them too!.. “book learning” helps form the basis for knowledge, that combined with investigation and real experience is what makes real knowledge.

Interesting side note when I was researching recently, did not realize that dendrite formation was the main issue in early lithium metal batteries… I had some of them until recently, the original “Molicell” … I did overcharge one (it did have dendrite damage/internal short)… went off like a roman candle, AA size with a 4" flame… impressive.

Regards, Greg