INFORMATION ONLY
The table below gives an indcation of the relative costof various
rechargeable battery technologies based on both initial capital cost and
cycle life.
Key point of interest is liable to be the low cost per cycle compared to eg
NimH.

No single set of figures will give a comparison which is valid in all cases,
and comparative results will vary with time, quality, application, battery
size, environment and more. But this chart gives a simple comparative
starting point could be useful.

Comparsion here is with Sealed Lead Acid (SLA) which is the industry
standard for other than small storage systems. At a glance it looks as
though they are probably promoting LiFePO4 batteries - and not withoutcause.
Notable points from the table (with some extra input) are -

- Lowest lifetime cost from traditional batteries - usually not a
viableoption nowadays.

- Per cycle LiFePO4 is about 4 x cheaper than SLA and 5 x cheaper than NimH.
(Initial cost is higher than NimH but lifetimes are much greater).

- SLA is about 25% cheaper than NimH (and has lower capital cost than NimH -
so lower cycle life is also implied).

- Lithium batteries other than LiFePO4 have 50% to 100% higher costs than
NimH. Advantages are high energy density (mass and volume) and ease of
management in very simple systems.

- Worst upper temperature range is shared by traditional Lithium and SLA.
They say 50C for NimH but more like 40C is more common.

- They say 200 cycles for SLA - more can be got by using less of the
capacity. They say >2000 cycles for LiFePO4 but people are getting > 3000
cycles with care and some reduction in capacity.

You can get AA x LiFePO4 cells but they are liable to be of low
energydensity compared to larger
cellss - PERHAPS getting down to NimH energy density. Not suitable for
direct use existing 1 cell or 3 cell NimH based lights. Wiring
rearrangements and/or circuit changes needed.




  Chemistry Voltage  Energy Density  Working Temp.  Cycle Life  Safety E
nvironmental Cost based on cycle life x wh of SLA  LiFePO4 3.2V >120
wh/kg  -0-60
=B0C  >2000 Safe Good

0.15-0.25

 lower than SLA
 Lead acid 2.0V > 35wh/kg  -20 - 40=B0C >200 Safe Not good 1 NiCd 1.2V >
40wh/kg  -20 - 50 =B0C >1000 Safe Bad 0.7 NiMH 1.2V  >80 wh/kg  -20 - 50 =
=B0C
 >500 Safe Good 1.2-1.4 LiMnxNiyCozO2 3.7V >160 wh/kg  -20 - 40 =B0C  >500 =
Unsafe
without PCB or PCM, better than LiCo OK 1.5-2.0 LiCoO2 3.7V >200 wh/kg  -20
- 60 =B0C  > 500 UnSafe without PCB or PCM OK 1.5-2.0

>From here http://www.batteryspace.com/li-ionsinglecell.aspx


Russell
-- =

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