User Manual

GM862-QUAD / PY Hardware User Guide

1vv0300748 Rev. 5 - 20/09/07

When the charging current falls below a certain fraction of the fast charge current value, then the

battery is considered fully charged, the final charge stops and eventually starts the maintenance.

The pulsed charge process has no voltage regulation, instead the charge continues with pulses.

Usually the pulse charge works in the following manner: the charge is stopped for some time, let's say

few hundreds of ms, then the battery voltage will be measured and when it drops below its maximum

value a fixed time length charging pulse is issued. As the battery approaches its full charge the off

time will become longer, hence the duty-cycle of the pulses will decrease. The battery is considered

fully charged when the pulse duty-cycle is less than a threshold value, typically 10%, the pulse charge

stops and eventually the maintenance starts.

The last phase is not properly a charging phase, since the battery at this point is fully charged and the

process may stop after the final charge. The maintenance charge provides an additional charging

process to compensate for the charge leak typical of a Li-Ion battery. It is done by issuing pulses with

a fixed time length, again few hundreds of ms, and a duty-cycle around 5% or less.

This last phase is not implemented in the GM862-QUAD / PY internal charging algorithm, so that the

battery once charged is left discharging down to a certain threshold so that it is cycled from full charge

to slight discharge even if the battery charger is always inserted. This guarantees that anyway the

remaining charge in the battery is a good percentage and that the battery is not damaged by keeping it

always fully charged (Li-Ion rechargeable battery usually deteriorates when kept fully charged).

Last but not least, in some applications it is highly desired that the charging process restarts when the

battery is discharged and its voltage drops below a certain threshold, GM862-QUAD / PY internal

charger does it.

As you can see, the charging process is not a trivial task to be done; moreover all these operations

should start only if battery temperature is inside a charging range, usually 5°C - 45°C.

The GM862-QUAD / PY measures the temperature of its internal component, in order to satisfy this

last requirement, it's not exactly the same as the battery temperature but in common application the

two temperature should not differ too much and the charging temperature range should be

guaranteed.

NOTE: In this particular application the battery charger input current must be limited to less than 1A. Using a

current limited wall adapter as the power source can do this.

For your convenience in the EVK there's also a current unlimited input, where the input source is not limited in

current and the drawn current is limited to about 0,5A by a MOSFET in the EVK.

The external battery charger is suggested in applications where the total consumption is higher than the current

provided by the GM862-QUAD / PY module.

NOTE: For all the threshold voltages, inside the GM862-QUAD / PY all threshold are fixed in order to maximize Li-Ion

battery performances and do not need to be changed.

NOTE: In this application the battery charger input current must be limited to less than 400mA. This can be done by

using a current limited wall adapter as the power source.

NOTE: When starting the charger from Module powered off the startup will be in CFUN4; to activate the

normal mode a command AT+CFUN=1 has to be provided. This is also possible using the POWER ON.

There is also the possibility to activate the normal mode using the

ON_OFF* signal.

In this case, when HW powering off the module with the same line (ON_OFF*) and having the charger still

connected, the module will go back to CFUN4.