[Arm-netbook] Standardized Battery Pack Sizes?

[Wookey]

On 2017-09-27 15:42 +0100, Alexander Ross wrote:
> On 27/09/17 14:58, Christopher Havel wrote:
> > Typing on phone, please excuse top post.
> > 
> > Lithium ion cells are somewhat sedate, but cannot release as much current
> > at once as lithium polymer cells can. Lithium iron phosphate cells are
> > similarly sedare, but have capacities and discharge abilities more like
> > those of lithium polymer cells.
> arr didnt know about the quick and high current discharge of li-po vs
> li-ion. oh and thx for lifepo vs lipo too. thought lifepo could do high
> dischage but didnt know it was simular to lipo. oow i learnt some more

It's even more complicated than this. Li-ion can be almost as
high-discharge as Lipo cells, but there is a current/capacity tradoff
(more accurately a tradeoff between maximising capacity, or minimising
internal resistance). So powertools use 18650 li-ion cells which can
do 20 or 30A discharge, but these have 1.5Ah capacity, not 3Ah, which
good lower-discharge cells will have.

Compare the datasheets for 
LG INR18650-HB2 (high power 30A:, low capacity 1.5Ah)
https://www.nkon.nl/lg-hb2-1500mah-30a.html
and
Samsung ICR18650-29E (low power: 8.3A, high capacity: 2.9Ah)
https://www.nkon.nl/rechargeable/18650-size/samsung-icr18650-30a.html

'Lithium-ion' covers a multitude of slightly different battery
chemistries with different pros and cons (and
ages). lithium-manganese, lithium-cobalt (early 18650s), lithium iron
phosphate ('LFP', or 'LiFePO'), (both with and without ytterbium)
often in much larger-format cells, lithium nickel manganese cobalt
oxide: 'NMC', in many modern 18650s), and lithium nickel cobalt
aluminium ('NCA'). Many are interchangeable, but sometimes the
differences matter. LFP has significantly lower voltage (3.3 nominal
vs 3.6) and thus energy density. LiPos normally come in pouch format
and have a slightly higher charge voltage (4.2V vs 4.1V), both of
which features improve energy density, but are really the same set of
chemistries as Li-ion, but with a different electrolyte and
format). LFP won't catch fire. Lithium cobalt can, and is highly
exothermic if it does, which is one reason other chemsistries have
become more popular (and cobalt is now very expensive). Lipo's like to
burn too, but more modern chemistries (NMC, NCA) tend to be much safer.

And new things are happening in this area all the time, with some
exciting developments in glass combined electrolyte/separators.

https://en.wikipedia.org/wiki/Lithium-ion_battery
https://en.wikipedia.org/wiki/Lithium_polymer_battery

Wookey
-- 
Principal hats:  Linaro, Debian, Wookware, ARM
http://wookware.org/