The storage and risk of Li-po & Li-ion batteries

[Erfolg]

Although my intention is not to be confrontational or argumentative, I am, and will seek to shed some light on the Lithium batteries we use. This will only happen with contributions by more knowledgeable people than me.
 

I see the greatest threat to a sensible discussion are arguments of the type which equate to “how many angels can stand on the head of a pin” also the units used are not technically correct (typically it should have been expressed in slugs, not Newtons type debates).

From a little reading I have concluded that Li-ion and Li-poly are of the same type of battery. That is using broadly similar electro chemistry. Just as a wet cell Pb battery is similar if of the Pb/acid or Pb/gel type.

From my understanding there are two conceptual differences.

The first is the “separator”, in the case of the Li-poly, this takes the form of a flexible porous polymer membrane with the anode and cathode bonded to opposite sides.  In the case of what we typically call Li-ion, the separator is still porous, but the anode and cathode are mechanically held against the separator, typically by a hard case.

The electro chemistry being intrinsically similar, by that I mean susceptible to the same issues, at our practical level, for us this is principally fire or explosion. I have seen on this web site that the Li-ion being put forward as intrinsically safer. I am not sure that this is true. As examples can be quoted regarding Sony lap top fires and some mobile phones, which were of the type called Li-ion.

I can anticipate that some are already reaching for the key board, but before they do, I would suggest that any additional circuits designed to control; and limit the consequence of the risk for one version of a group of batteries does not change the underlying issues or chemistry.

From limited reading, there does seem to be a limit to life, this appears to be driven by electron charge and temperature. But can be just a couple of years, which fits with my own experiences. This area of useful life is yet another area of discussion. But many regard this to be  80% of rated capacity, and thousands of cycles, within a designated period (not infinity as I had thought). The change or attenuation/reduction is a consequence to changes to internal resistance.

From reading I have come to accept that to maximise life it is necessarily to:

a)      a)    Minimise charge, this appears to be approx50%.

b)      b)    Store at a low temperature above freezing (Arrhenius diffusion principle).

These conditions are not the same, as when seeking to extract energy from a battery.

Regarding safety, these appear to be of an order that is similar to many other types, do not discharge intentionally at a rate which is greater than rated (shorting being an extreme  issue). Do not over charge. Conceptually this is similar to not providing an ignition source to a venting Pb cell or overcharging a Nicad. All can lead to either an explosion or damage. All are safe if operated with due care.

Now what is needed is a sensible debate to confirm, modify or refute my proposition.

Please discuss is no more than 20* 10^10 words

 

Erfolg

[Ultymate]

I keep mine in the models on the dining table right next to my two petrol cans

[Peter Beeney]

   I put mine in the petrol cans. After all, it does say, ' place in a metal container......'

[Tim Mackey]

Yeh thats about right Erfolg...now go out and fly something.

Less than 20 words.

[Erfolg]

Timbo

 

Strange you should mention flying.

 

Before writing the note, I had just charged one battery, a second was on charge AND THEN the snow came down, the wind was blowing a gale.

 

I sulkily, sat down, went Boo, Hooo , Hooo, when will this atrocious weather end.

 

Still there is Friday I hope!

 

Then again I have Do 335  and Cassutts to finish, plus a Graupner Nemesis to make a proper start.

 

Plus my Coastguard Heli to get prepared for Friday night.

 

My God, so much to do

 

Again being serious, the storage at a low temperature is new to me.

 

Erfolg 

[Tim Mackey]

Well with respect Erfolg, I did, I think, cover that and pretty much everything else needed as far as storage and use of all the popular battery chemistries - in my articles last year - which is also now shown on the forum here.