Wavecom GR64 GSM/GPRS Integrator's Manual page 46

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Li-Ion batteries have a higher ESR (compared to Ni-Cd or Ni-MH), although this
should not be a limiting factor for peak current delivery, any battery should be
capable of at least 50% greater than the GR64 demands (~3A peak)
To determine battery life, on a full charge, the following rule of thumb can be applied:
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Example 1 – – – – Standby time: Example 1 Example 1 Example 1
A 600mAh rated Li-Ion battery, from fully charged (around 4.2V) to the Wireless CPU
cut-off point (3.2V) will provide around 95% of its total charge capacity.
standby (idle) current of 18mA, the Wireless CPU will typically provide
Example 2 Example 2 – – – – Call time: Example 2 Example 2
An 1800mAh rated Li-Ion battery fully charged, transmitting maximum power on a
low-band (850/900MHz) channel may consume an average 320mA, therefore the
Wireless CPU would typically provide
Example 3 3 3 3 – – – – Typical Operation: Example
Example Example
A Wireless CPU performing periodic network data transfers and communicating
intervallic status information to its host would spend its non-active periods in sleep
mode. If the Wireless CPU spends 30 minutes each day on call (320mA), 30 second
each hour performing housekeeping, monitoring and status tasks (110mA), and
sleeps (2.1mA) during the intervening periods, an 1800mAh rated Li-Ion battery fully
charged would typically provide
CAUTION
GR64 Integrators Manual
Page: 46/104
monitor battery temperature during charging using a thermistor placed on or
near the battery wired to an ADC input on the Wireless CPU
Standby time = Battery Capacity (mAh) / Idle current (mA)
Call time (voice or data) = Battery Capacity (mAh) / Call current (mA)
Standby time: Standby time: Standby time:
600*0.95/18 = 32 hours standby time
Call time: Call time: Call time:
1800*0.95/320 = 5 hours 20 mins call time
Typical Operation:
Typical Operation: Typical Operation:
1800*0.95/([0.5hr*320]+[0.2hr*110]+[23.3hr*2.1]) = 7 days 6 hrs operation
The above examples are given for guidance, the actual battery life will
depend upon variables such as battery condition, number of previous
charge/discharge cycles, operating temperature, series resistance
between battery and the Wireless CPU, and manufacturing tolerances
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