16.4 Lithium (Lipo, Liio, Life) Batteries - ROBBE Power Peak C8 EQ-BID Notice D'utilisation

16.4 LITHIUM (LiPo, LiIo, LiFe) BATTERIES

GENERAL INFORMATION
There are various basic types of Lithium battery:
1. Lithium-Ion batteries containing fluid electrolyte, with a nominal voltage of 3.6 Volts.
This is the first generation of Lithium cell, and is not often used for modelling applica-
tions.
2. Lithium-Ion batteries containing fluid electrolyte, with a nominal voltage of 3.7 Volts.
This is the second generation of Lithium cell, and is housed in a metal can.
3. Lithium-Ion-Polymer batteries (LiPo) containing gel electrolyte, with a nominal voltage
of 3.7 Volts. This is the current generation of Lithium cell, and they have also become
known as Li-Po or Li-Poly batteries. The gel electrolyte results in a reduced pressure
build-up in the cell during charging and discharging, for which reason a foil housing is
adequate. This cell has rapidly become very popular for model purposes due to its low
weight and high energy density.
4. Lithium-Ferrum batteries (LiFe) with a nominal voltage of 3.3 Volts. These are the
latest generation of Lithium batteries, and are also known as A123 cells. Due to their
high maximum discharge rate and good energy density this type of battery will quickly
become popular for modelling applications
CAPACITY DIFFERENCES
If several cells are assembled to form a battery 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 discharge
capacity. The cell concerned will then be discharged more quickly, with the danger that it
will eventually be discharged below the permissible final discharge voltage.
Considerable differences in capacity can occur when external temperatures are very low.
For example, if a Li-Po pack is flown in an electric helicopter, the front cell will be cooled
very effectively 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 voltage.
To avoid the danger of permanent cell damage we recommend that Li-Po cells should only
be discharged down to a final discharge voltage of about 3 Volts. We recommend the MC
Balancer, No. 8636 (max. seven cells) or the MC Balancer 14S, No. 8643 (max. fourteen
cells) for this task, both of which monitor the individual cell voltages of a LiPo pack. It is
also essential that the cells are brought up to the same level when the pack is recharged.
Charging individual cells wired in parallel presents no problems, as the total current is dis-
tributed amongst the individual cells according to their voltage level.
We are unable to accept liability of any kind for damage caused by improper or
incompetent use of Lithium cells. Please observe the safety notes at all times.
Operating Instructions
Power Peak ® C8 EQ-BID
20
No.
8553