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BQ25606: deep-discharged battery

Moritz Schmidt
Prodigy 10 points
Part Number: BQ25606
Other Parts Discussed in Thread: BQ25601
deep-discharged battery
We have a current request regarding a 18650 Li-Ion battery.
The customer is afraid that deeply discharged LI batteries will be damaged by the BQ25606 battery charger. So that in worst case the batteries will start to burn.
Our reverse polarity protection circuit has a certain quiescent current (< 10uA), which deep discharges the cell over a long period of time.
So will the charge controller always try to charge the battery, or will it stop charging at a certain voltage?
Also:
>> Is there any possible to adjust the switch-off threshold of the Battery charger?
>>Is there a way to move the switching Point of Q4?
  • 0
    TI__Genius 11850 points

    Hi Moritz,

    The BQ25606 has trickle charge and pre-charge in order to safely charge deeply discharged batteries. Even if VBAT is zero, the BQ25606 will still trickle charge the battery. Here is a summary of the trickle charge, pre-charge, and fast charge modes:

    VBAT < VSHORT: The BQ25606 applies a 90 mA trickle charge.

    VSHORT < VBAT < BATLOWV: The BQ25606 applies a pre-charge current (5% of the fast charge current).

    VBAT > BATLOWV: The BQ25606 applies the full fast charge current to the battery.

    These thresholds are given in the EC table:

    I'm not sure what you mean in your last two questions.

    By "switch-off threshold," are you referring to the maximum charge voltage at which the BQ25606 will stop charging the battery? If so, then yes, this regulation voltage (VREG) can be set to either 4.2 V, 4.35 V, or 4.4 V using the VSET pin.

    By "switching point of Q4," are you referring to the voltage at which the BATFET transitions from LDO mode to fully on, as shown in Figure 14 below? We call this threshold SYS_MIN, but there is no way to adjust SYS_MIN on the BQ25606. However, the host-controlled BQ25601 does have a register which allows you to set SYS_MIN between 2.6 V and 3.7 V.