> #1 =A0 What factors limit the lifetime of Lithium batteries ?

Cycle life.

Battery mechanical structure changes as storage is depleted of Lithium
metal and battery mechanically flexes itself to death. 300 cycles
often claimed. Some brave souls say 500. Not going to very top on
charge helps. LiFePO4 gets 2000+ cycles by having a structure whose
size/stability is not dependant on amount of li metal in store at any
time. Cost is lower capacity.

18650 LiIon get 2000 - 2500 mAh. High end can be suspect. Some claim
3000 mAh +. Walk carefully away with hands in sight. LiFePO4 is about
1200 mAh.

Calendar life.

Cell starts to electrochemically degrade from 1st use. Lofe unknown
and will vary but maybe 3 years.
LiFePO4 not known to have a calendar life limit. It may hav but I've
never seen it mentioned.

> #2 =A0What is the #1 factor limiting energy storage ?

Amount if Li metal that can be effectively crammed into space without
getting very short lifetime.
LiFePO4 is a better bet $ wise if absolute  energy densities  are not
a major issue.

Surprisingly, modern NimH energy density is about as good as many LiIon.

LiPo =3D Lithium polymer are variants on LiIon theme and probably
similar life etc.
YMMV.


                Russell McMahon

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