User's Manual

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Note d’étude / Technical document : URD1– OTL 5665.1– 002 / 70 884 Edition 03
Document Sagem Communications Reproduction et divulgation interdites
Sagem Communications document. Reproduction and disclosure prohibited
Figure 17: Backup battery internally charged
The resistor R depends on the charging current value provided by the battery manufacturer.
The charging curve which is done by the HiloNC is given hereafter:
Figure 18: Charging curve of backup battery
3.9.4 Backup Battery technology recommended
3.9.4.1 Manganese Silicon Lithium-Ion rechargeable Battery
Sagem Communications does not recommend using this kind of technology because of the following drawbacks:
• The maximum discharge current is limited (Shall be compliant with the module characteristics).
• The over-discharge problem: most of the Lithium Ion rechargeable batteries are not able to recover their charge when their
voltage reaches a low-level voltage. To avoid this, it is necessary to add a safety component to disconnect the
backup .battery in case of over–discharge condition. In such a case, this implementation is too complicated (too much
components for that function).
• The charging current has to be regulated.
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Sagem Communications does not recommend using this kind of backup battery technology.
3.9.4.2 Capacitor battery
These kinds of backup battery have not the drawbacks of the Lithium Ion rechargeable battery.
As there are only capacitors:
• The maximum discharge current is generally bigger,
• There is no problem of over-discharge: the capacitor is able to recover its full charge even if its voltage has
previously fallen to 0V.
• There is no need to regulate the charging current.
VBACKUP
HiloNC
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