C) Proper Handling Of Lipo Rechargeable Battery Packs - Reely SKY EC-135 Bedienungsanleitung

c) Proper handling of LiPo rechargeable battery packs
General information
Modern LiPo rechargeable battery packs ("LiPo" = Lithium Polymer) do not only have a clearly higher capacity than
NiMH or NiCd rechargeable battery packs but they also have a considerably lower weight. That is what makes this
type of battery pack interesting for the use in the field of model construction, for example.
Nevertheless, these battery packs might become useless due to total discharge, overcharge and overload.
Therefore, the following points should be noted when using this kind of rechargeable battery pack technology:
Dimensioning
The higher the current taken, the greater is the warming of the battery pack and the lower is the usable capacity.
The ideal operating temperature during discharging is between +20°C and +40°C and must not
exceed +60°C even under extreme load.
Danger of fire and explosion! Therefore, always ensure sufficient cooling in the model.
The maximum short-time current that can be loaded on the battery pack is stated in the technical data sheets or can
be read directly from the battery pack. The value "C" always refers to the capacity value of the respective battery
pack.
Example: A battery pack with a capacity of "100 mAh" and "0 C" can therefore be loaded with 100 mA x 0 =
4 A maximum.
However, the maximum permissible continuous current is clearly lower. If there are no precise manufacturer's speci-
fications, the battery pack should not be loaded with more than approx. 50% of the maximum permissible surge cur-
rent in the long run. In no case must the maximum permissible battery pack temperature of +60°C be exceeded.
Optimum charging of the rechargeable battery pack
A LiPo rechargeable battery pack has to be charged with a special current-/voltage-regulated battery charger.
This means: The charging current has to be limited to a value of 1 C at the beginning of the charging process.
A rechargeable battery pack with 100 mAh therefore has a charging current of .1 A max. When the maximum
permissible charging voltage of 4. V/cell has been reached, the voltage is kept constant and the charging current
decreases slowly. When the charging current has reached the lowest value, the battery pack is fully charged.
To ensure that no damaging excess voltages of more than 4. V/cell can develop when charging a seriesconnection
of individual cells within a rechargeable battery pack, the following electronic tools have to be used.
Use of a balancer
A balancer monitors the charging voltage of each single cell (in the case of multi-cell LiPo rechargeable battery
packs). If the voltage at one cell exceeds 4. V, either the cell is discharged or the charging process of the single
cell is stopped, depending on the type of balancer. This protects the single cell from overcharging.
Use of an equalizer
An equalizer equalises different voltage levels of the individual cells within the rechargeable battery pack already at
the beginning of the charging process. The individual voltages of the cells are thus absolutely identical during the
complete charging process.
Total discharge
Since a discharging below .5 V per cell leads to a permanent damaging of the rechargeable battery pack, this
total discharging is to be prevented at any rate. For safety reasons, programmable cruise controls/flight control
systems should be set in such a way that the undervoltage detection responds already at a voltage of 3.0 V per cell.
Alternatively, the optical undervoltage displays are also recommendable.
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No. 07010 / 0700