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However, before a protracted period of sto-
rage they should be charged up to about
50 - 80% capacity
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 disch-
arging before recharging (cycle charging,
cell balancing) 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
capacity.
For this reason it is important to use
selected cells exclusively if they are to be
wired together to form a battery.
Charging battery packs
Integrated charge protection circuit
Each Li-poly cell usually contains a voltage
monitor module to protect it from overchar-
ging, deep-discharging or excessive cur-
rents.
However, for modelling applications it is
usual to draw high load currents, which
means that the monitor module would very
often be tripped to protect the cells. For
this very reason most battery packs do not
include this feature.
The lack of the protective circuit can gene-
rate problems in the charging of series-
wired Li-poly cells. As mentioned earlier,
individual cells in the pack may well have
slightly different charge states and volta-
ges.
Supplementary Instructions
POWER PEAK MAXAMP LI
10
In this case the overall final charge voltage
is not distributed evenly amongst the indivi-
dual cells, with the result that cells featuring
higher voltage can easily be overcharged.
To avoid this, the individual cells must be
brought up to the final charge voltage of
4.2 (or 4.1) Volts.
For packs containing 1 ... 5 cells this can
be achieved by using the robbe Equalizer,
No. 8446.
Charging parallel-wired cells does not pre-
sent problems, as the total charge current
is distributed to the individual cells accor-
ding to their voltage.
We wish to point out expressly at this
point that, in the interests of safety, Li-
poly batteries may only be charged using
the MAXAMP Li charger if each individual
cell is fitted with a voltage monitor
module.
We accept absolutely no liability for
damage caused by incorrect or incompe-
tent handling of the cells.
Please be sure to read and observe the
safety notes regarding the handling of Li-
poly cells; you will find them at the end of
these instructions.
The charge process
Lithium-Ion batteries are charged using the
constant voltage method.
For this reason the final charge voltage is
pre-set on the charger according to the
number of cells in the pack.
During the initial charge phase the battery
voltage rises slowly to the maximum value
of 4.1 or 4.2 V / cell. In this phase the
MAXAMP Li charger ensures that the
charge current remains constantly at the
pre-set value. At a charge current of 1C and
with a discharged battery this initial phase
lasts about 50 to 60 minutes, during which
time about 80% of full battery capacity is
charged in.
Order No.
8121
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