Lithium Batteries (Li-Ion / Lipoly) - ROBBE PROFI Notice D'utilisation

13.4 LITHIUM BATTERIES (LI AND LP)
General
There are different lithium battery types:
1. Lithium-ion batteries with liquid electrolyte and 3.6 volt
nominal voltage, which are the first generation of lithium
batteries, are not common in model construction.
2. Lithium-ion batteries with liquid electrolyte and 3.7 volt
nominal voltage, which are the second generation of lithium
batteries, with metal cup.
3. Lithium-ion polymer batteries with gel-formed electrolyte
and 3.7 volt nominal voltage which are the current genera-
tion of lithium batteries and are also called LiPoly. There is
less pressure in the cell during charging and discharging as
a result of the gel-type electrolyte which means that a foil
casing is sufficient. It has become common very quickly in
model construction because of its low weight and high
energy density.
Charge procedure
Lithium-ion batteries are charged with the constant voltage
procedure. The charge procedure is the same for all lithium
battery types, however the disconnect voltage is different
depending on the nominal voltage.
For this reason, the cell count is pre-selected on the charge
device from which the Profi Homecharger calculates the cor-
rect disconnect voltage.
During the first charge phase, the battery voltage increases
slowly to a maximum value of 4.1 / 4.2 V / cell.
In this phase, the charger ensures that the charge current
remains constant at the set value.
This first phase lasts about 50-60 minutes with a charge cur-
rent of 1C and a discharged battery. A battery capacity of
about 80-90 % is thereby charged.
Another 35-40 minutes are required for charging the residual
capacity. Once the lower current limit of about 10 % of the
specified charge current is reached then the charge device will
turn the charge process off.
With the currently permissible charge rates of 1C this means
that the entire charge process takes at least 90 minutes with a
discharged battery.
In general LiPoly batteries have the following specifications:
Charge rate
1C, means capacity value = charge current
- Example: LiPoly cells with 1500 mAh;
1C = 1500 mA (=1.5A) charge current
Discharge current
3-5 C, short-term also up to 10 C
Charge end voltage
Cells with nominal voltage 3.6 V = 4.1 volt
Cells with nominal voltage 3.7 V = 4.2 volt
This is automatically determined by the Profi Homecharger
Profi-Home-Charger
In the second
phase, the
charge current
sinks as the
voltage diffe-
rence between
the charger
and the battery
gets smaller
and smaller.
27
by setting the battery type and the cell count.
Charging battery packs
Integrated charge protection
Each cell usually has a voltage control module to protect the
LiPoly cells from overcharging, exhaustive discharging or too
high current.
Since mostly high load currents are discharged in the field of
model construction, this control module would very frequently
switch off to protect the cells. For this reason, it is not integra-
ted into most battery packs.
This fact causes problems when charging LiPoly cells swit-
ched in a row. As mentioned previously, the individual cells
have slightly different charge conditions and voltage positions.
The applied total charge end voltage distributes itself unevenly
over the individual cells, whereby cells with higher voltage
position can be overcharged.
To prevent this, the individual cells must be brought up to a
charge end voltage of 4.1 or 4.2 volt.
Charging of parallel switched individual cells is unproblema-
tic as the total current distributes itself to the individual cells
depending on the voltage position.
We would like to explicitly point out to you that, for reasons
of safety, LiPoly batteries can only be charged with the Profi
Homecharger if the individual cells are provided with a vol-
tage control module.
We assume no liability for damages resulting from improper
handling of the cells.
Battery temperature range
Charging -> 0°...+45°C
Discharging -> -20°...+60°C
Temperature behaviour
Lithium cells have a distinct temperature index whereby the
nominal capacity is not available with very low and high tem-
peratures.
Both when charging (45°C) and when discharging (60°C), the
max. external cell temperature may not be exceeded as other-
wise the cell will be damaged permanently in the form of capa-
city loss.
If it is exceeded for a longer period it is destroyed, can explode
or start to burn.
Order No.
8194
Temperature o C