SIM802 Hardware Design
3.5.2 Recommended battery pack
Following is the spec of recommended battery pack:
Table 8: Spec of recommended battery pack
Product name & type
BYD, Li-Ion, 3.7V, 580mAh
To obtain more information
Please contact :
BYD COMPANY LIMITED
Normal voltage
3.7V
Capacity
NORMAL 580mAh
Charge Voltage
4.200±0.049V
Max Charge Current
1.5C
Charge Method
CC / CV (Constant Current / Constant Voltage)
Max Discharge Current
1.5C (for continuous discharging mode)
Discharge Cut-off Voltage
2.75V/ cell
Internal resistance
Initial
≤
200m
Ω
After 400cycles
≤
270m
Ω
3.5.3 Implemented charging technique
The SIM802 include the function for battery charging. There are three pins in the connector
related with the battery charging function: VCHG, VBAT and BAT_TEMP pins. The VCHG Pin
is driven by an external voltage, system can use this Pin to detect a charger supply and provide
most charging current through SIM802 module to battery when charging is in fast charge state.
The VBAT give out charging current from SIM802 module to external battery. BAT_TEMP Pin
is for user to measure the battery temperature. Just let this Pin open if battery temperature
measuring is not your concern.
So it is very simple to implement charging technique, you need connect the charger to the VCHG
Pin and connect the battery to the VBAT Pin.
The SIM802 detect charger supply and the battery is present, battery charging will happen. If
there is no charger supply or no battery present the charging will not be enabled.
Normally, there are three main states in whole charging procedure.
z
DDLO charge and UVLO charge;
z
Fast charge;
z
Trickle charge;
DDLO charge and UVLO charge:
DDLO (deep discharge lock out) is the state of battery when its voltage is under 2.4V. And
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