ROBBE POWER PEAK Infinity 2 LI Manual De Instrucciones Adicionales página 9

Temperature range:
Charging: -> 0° ... +45°C
Discharging -> -20° ... +60°C
Temperature behaviour
Lithium cells feature a pronounced tempera-
ture index which means that the full nominal
capacity is not available at very low and very
high temperatures.
Temperature curve
The external cell temperature should not
exceed certain limits during charging (45°C)
and discharging (60°C), otherwise the cell will
be damaged, with a permanent loss of capa-
city.
If the limit values are exceeded for a pro-
tracted period, the cell will be ruined, and
may explode and start a fire.
Variations in capacity
If several cells are assembled to form a bat-
tery which is then discharged at a fairly high
current, the cells will heat up to different
extents as the cell or cells on the inside are
unable to dissipate heat effectively.
This results in changes to the cells' internal
resistance, which in turn reduces their disch-
arge capacity. The cell concerned will then be
discharged more quickly, with the danger
that it will eventually be discharged below the
permissible final charge voltage of 2.5 Volts.
Considerable differences in capacity can
occur when external temperatures are very
low.
Supplementary operating instructions
POWER PEAK Infinity 2 LI
Temperature °C
9
For example, if a Li-Poly pack is flown in an
electric helicopter, the front cell will be
greatly cooled by the normal airflow, while
the inner cells become significantly warmer.
The colder cell will lose effective capacity,
with the danger that it will be discharged
below the permissible final discharge vol-
tage.
To avoid the danger of permanent cell
damage we recommend that Li-Poly cells
should only be discharged down to a final
discharge voltage of about 3 Volts.
Storage
Li-Poly cells feature an extremely low rate of
self-discharge (approx. 0.2% per day), and
can therefore be stored for long periods wit-
hout problems.
However, before a protracted period of sto-
rage they should be charged up to about 50
- 80% capacity, and they should be topped
up again after about 4 - 6 months.
Memory effect, cell capacity
Li-Poly cells do not suffer from the memory
(lazy battery) effect, so the standard proce-
dure with NC and NiMH batteries of dischar-
ging before recharging (cycle charging) is not
necessary.
Indeed, it is actually better to avoid dischar-
ging the cells before recharging.
Each charge process reduces the capacity of
the Li-Poly pack slightly, so this would lead
to an unnecessary loss of capacity.
Assembling battery packs
Li-Poly cells can be wired together in series
or parallel in order to increase pack voltage
or capacity, but this does present problems
due to variations in charge voltage and capa-
city.
For this reason it is important to use
selected cells exclusively if they are to be
wired together to form a battery.
Order No.
8294Li/D